New information technologies are being introduced in all industrial sectors, albeit to varying extents. In some cases, the costs of computerizing production processes may constitute an impediment to innovation, particularly in small and medium-sized companies and in developing countries. Computers make possible the rapid collection, storage, processing and dissemination of large quantities of information. Their utility is further enhanced by their integration into computer networks, which allow resources to be shared (Young 1993).

Computerization exerts significant effects on the nature of employment and on working conditions. Beginning about the mid-1980s, it was recognized that workplace computerization may lead to changes in task structure and work organization, and by extension to work requirements, career planning and stress suffered by production and management personnel. Computerization may exert positive or negative effects on occupational health and safety. In some cases, the introduction of computers has rendered work more interesting and resulted in improvements in the work environment and reductions of workload. In others, however, the result of technological innovation has been an increase in the repetitive nature and intensity of tasks, a reduction of the margin for individual initiative and the isolation of the worker. Furthermore, several companies have been reported to increase the number of work shifts in an attempt to extract the largest possible economic benefit from their financial investment (ILO 1984).

As far as we have been able to determine, as of 1994 statistics on the worldwide use of computers are available from one source only—The Computer Industry Almanac (Juliussen and Petska-Juliussen 1994). In addition to statistics on the current international distribution of computer use, this publication also reports the results of retrospective and prospective analyses. The figures reported in the latest edition indicate that the number of computers is increasing exponentially, with the increase becoming particularly marked at the beginning of the 1980s, the point at which personal computers began to attain great popularity. Since 1987, total computer processing power, measured in terms of the number of million instructions per second executed (MIPS) has increased 14-fold, thanks to the development of new microprocessors (transistor components of microcomputers which perform arithmetical and logical calculations). By the end of 1993, total computing power attained 357 million MIPS.

Unfortunately, available statistics do not differentiate between computers used for work and personal purposes, and statistics are unavailable for some industrial sectors. These knowledge gaps are most likely due to methodological problems related to the collection of valid and reliable data. However, reports of the International Labour Organization’s tripartite sectoral committees contain relevant and comprehensive information on the nature and extent of the penetration of new technologies in various industrial sectors.

In 1986, 66 million computers were in use throughout the world. Three years later, there were more than 100 million, and by 1997, it is estimated that 275–300 million computers will be in use, with this number reaching 400 million by 2000. These predictions assume the widespread adoption of multimedia, information highway, voice recognition and virtual reality technologies. The Almanac’s authors consider that most televisions will be equipped with personal computers within ten years of publication, in order to simplify access to the information highway.

According to the Almanac, in 1993 the overall computer: population ratio in 43 countries in 5 continents was 3.1 per 100. It should however be noted that South Africa was the only African country reporting and that Mexico was the only Central American country reporting. As the statistics indicate, there is a very wide international variation in the extent of computerization, the computer:population ratio ranging from 0.07 per 100 to 28.7 per 100.

The computer:population ratio of less than 1 per 100 in developing countries reflects the generally low level of computerization prevailing there (table 1) (Juliussen and Petska-Juliussen 1994). Not only do these countries produce few computers and little software, but lack of financial resources may in some cases prevent them from importing these products. Moreover, their often rudimentary telephone and electrical utilities are often barriers to more widespread computer use. Finally, little linguistically and culturally appropriate software is available, and training in computer-related fields is often problematic (Young 1993).

Table 1. Distribution of computers in various regions of the world

Source: Juliussen and Petska-Juliussen 1994.

Computerization has significantly increased in the countries of the former Soviet Union since the end of the Cold War. The Russian Federation, for example, is estimated to have increased its stock of computers from 0.3 million in 1989 to 1.2 million in 1993.

The largest concentration of computers is found in the industrialized countries, especially in North America, Australia, Scandinavia and Great Britain (Juliussen and Petska-Juliussen 1994). It was principally in these countries that the first reports of visual display unit (VDU) operators’ fears regarding health risks appeared and the initial research aimed at determining the prevalence of health effects and identifying risk factors undertaken. The health problems studied fall into the following categories: visual and ocular problems, musculoskeletal problems, skin problems, reproductive problems, and stress.

It soon became evident that the health effects observed among VDU operators were dependent not only on screen characteristics and workstation layout, but also on the nature and structure of tasks, organization of work and manner in which the technology was introduced (ILO 1989). Several studies have reported a higher prevalence of symptoms among female VDU operators than among male operators. According to recent studies, this difference is more reflective of the fact that female operators typically have less control over their work than do their male counterparts than of true biological differences. This lack of control is thought to result in higher stress levels, which in turn result in increased symptom prevalence in female VDU operators.

VDUs were first introduced on a widespread basis in the tertiary sector, where they were used essentially for office work, more specifically data entry and word processing. We should not therefore be surprised that most studies of VDUs have focused on office workers. In industrialized countries, however, computerization has spread to the primary and secondary sectors. In addition, although VDUs were used almost exclusively by production workers, they have now penetrated to all organizational levels. In recent years, researchers have therefore begun to study a wider range of VDU users, in an attempt to overcome the lack of adequate scientific information on these situations.

Most computerized workstations are equipped with a VDU and a keyboard or mouse with which to transmit information and instructions to the computer. Software mediates information exchange between the operator and the computer and defines the format with which information is displayed on the screen. In order to establish the potential hazards associated with VDU use, it is first necessary to understand not only the characteristics of the VDU but also those of the other components of the work environment. In 1979, Çakir, Hart and Stewart published the first comprehensive analysis in this field.

It is useful to visualize the hardware used by VDU operators as nested components that interact with each other (IRSST 1984). These components include the terminal itself, the workstation (including work tools and furniture), the room in which the work is carried out, and the lighting. The second article in this chapter reviews the main characteristics of workstations and their lighting. Several recommendations aimed at optimizing working conditions while taking into account individual variations and variations in tasks and work organization are offered. Appropriate emphasis is placed on the importance of choosing equipment and furniture which allow flexible layouts. This flexibility is extremely important in light of international competition and rapidly evolving technological development that are constantly driving companies to introduce innovations and while simultaneously forcing them to adapt to the changes these innovations bring.

The next six articles discuss health problems studied in response to fears expressed by VDU operators. The relevant scientific literature is reviewed and the value and limitations of research results highlighted. Research in this field draws upon numerous disciplines, including epidemiology, ergonomics, medicine, engineering, psychology, physics and sociology. Given the complexity of the problems and more specifically their multifactorial nature, the necessary research has often been conducted by multidisciplinary research teams. Since the 1980s, these research efforts have been complemented by regularly organized international congresses such as Human-Computer Interaction and Work with Display Units, which provide an opportunity to disseminate research results and promote the exchange of information between researchers, VDU designers, VDU producers and VDU users.

The eighth article discusses human-computer interaction specifically. The principles and methods underlying the development and evaluation of interface tools are presented. This article will prove useful not only to production personnel but also those interested in the criteria used to select interface tools.

Finally, the ninth article reviews international ergonomic standards as of 1995, related to the design and layout of computerized workstations. These standards have been produced in order to eliminate the hazards to which VDU operators can be exposed in the course of their work. The standards provide guidelines to companies producing VDU components, employers responsible for the purchase and layout of workstations, and employees with decision-making responsibilities. They may also prove useful as tools with which to evaluate existing workstations and identify modifications required in order to optimize operators’ working conditions.

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Private Emergency Organization

Profit is the main objective of any industry. To achieve this objective, an efficient and alert management and continuity of production are essential. Any interruption in production, for any reason, will adversely affect profits. If the interruption is the result of a fire or explosion, it may be long and may cripple the industry.

Very often, a plea is taken that the property is insured and loss due to fire, if any, will be indemnified by the insurance company. It must be appreciated that insurance is only a device to spread the effect of the destruction brought by fire or explosion on as many people as possible. It cannot make good the national loss. Besides, insurance is no guarantee of continuity of production and elimination or minimization of consequential losses.

What is indicated, therefore, is that the management must gather complete information on the fire and explosion hazard, evaluate the loss potential and implement suitable measures to control the hazard, with a view to eliminating or minimizing the incidence of fire and explosion. This involves the setting up of a private emergency organization.

Emergency Planning

Such an organization must, as far as possible, be considered from the planning stage itself, and implemented progressively from the time of selection of site until production has started, and then continued thereafter.

Success of any emergency organization depends to a large extent on the overall participation of all workers and various echelons of the management. This fact must be borne in mind while planning the emergency organization.

The various aspects of emergency planning are mentioned below. For more details, a reference may be made to the US National Fire Protection Association (NFPA) Fire Protection Handbook or any other standard work on the subject (Cote 1991).

Stage 1

Initiate the emergency plan by doing the following:

1. Identify and evaluate fire and explosion hazards associated with the transportation, handling and storage of each raw material, intermediate and finished products and each industrial process, as well as work out detailed preventive measures to counteract the hazards with a view to eliminating or minimizing them.
2. Work out the requirements of fire protection installations and equipment, and determine the stages at which each is to be provided.
3. Prepare specifications for the fire protection installation and equipment.

Stage 2

Determine the following:

1. availability of adequate water supply for fire protection in addition to the requirements for processing and domestic use
2. susceptibility of site and natural hazards, such as floods, earthquakes, heavy rains, etc.
3. environments, i.e., the nature and extent of surrounding property and the exposure hazard involved in the event of a fire or explosion
4. existence of private (works) or public fire brigade(s), the distance at which such fire brigade(s) is (are) located and the suitability of the appliances available with them for the risk to be protected and whether they can be called upon to assist in an emergency
5. response from the assisting fire brigade(s) with particular reference to impediments, such as railway crossings, ferries, inadequate strength and (or) width of bridges in relation to the fire appliances, difficult traffic, etc.
6. socio-political environment , i.e., incidence of crime, and political activities leading to law-and-order problems.

Stage 3

Prepare the layout and building plans, and the specifications of construction material. Carry out the following tasks:

1. Limit the floor area of each shop, workplace, etc. by providing fire walls, fire doors, etc.
2. Specify the use of fire-resistant materials for construction of building or structure.
3. Ensure that steel columns and other structural members are not exposed.
4. Ensure adequate separation between building, structures and plant.
5. Plan installation of fire hydrants, sprinklers, etc. where necessary.
6. Ensure the provision of adequate access roads in the layout plan to enable fire appliances to reach all parts of the premises and all sources of water for fire-fighting.

Stage 4

During construction, do the following:

1. Acquaint the contractor and his or her employees with the fire risk management policies, and enforce compliance.
2. Thoroughly test all fire protection installations and equipment before acceptance.

Stage 5

If the size of the industry, its hazards or its out-of-the-way location is such that a full-time fire brigade must be available on the premises, then organize, equip and train the required full-time personnel. Also appoint a full-time fire officer.

Stage 6

To ensure full participation of all employees, do the following:

1. Train all personnel in the observance of precautionary measures in their day-to-day work and the action required of them upon an outbreak of fire or explosion. The training must include operation of fire-fighting equipment.
2. Ensure strict observance of fire precautions by all concerned personnel through periodic reviews.
3. Ensure regular inspection and maintenance of all fire protection systems and equipment. All defects must be rectified promptly.

Managing the emergency

To avoid confusion at the time of an actual emergency, it is essential that everyone in the organization knows the precise part that he (she) and others are expected to play during the emergency. A well-thought-out emergency plan must be prepared and promulgated for this purpose, and all concerned personnel must be made fully familiar with it. The plan must clearly and unambiguously lay down the responsibilities of all concerned and also specify a chain of command. As a minimum, the emergency plan should include the following:

1.      name of the industry

2.      address of the premises, with telephone number and a site plan

3.      purpose and objective of the emergency plan and effective date of its coming in force

4.      area covered, including a site plan

5.      emergency organization, indicating chain of command from the work manager on downwards

6.      fire protection systems, mobile appliances and portable equipment, with details

7.      details of assistance availability

8.      fire alarm and communication facilities

9.      action to be taken in an emergency. Include separately and unambiguously the action to be taken by:

• the person discovering the fire
• the private fire brigade on the premises
• head of the section involved in the emergency
• heads of other sections not actually involved in theemergency
• the security organization
• the fire officer, if any
• the works manager
• others

       10.     chain of command at the scene of incident. Consider all possible situations, and indicate clearly who is to assume command in each case, including the circumstances under which another organization is to be called in to assist.

11.      action after a fire. Indicate responsibility for:

• recommissioning or replenishing of all fire protectionsystems, equipment and water sources
• investigating the cause of fire or explosion
• preparation and submission of reports
• initiating remedial measures to prevent re-occurrence of similar emergency.

When a mutual assistance plan is in operation, copies of emergency plan must be supplied to all participating units in return for similar plans of their respective premises.

Evacuation Protocols

A situation necessitating the execution of the emergency plan may develop as a result of either an explosion or a fire.

Explosion may or may not be followed by fire, but in almost all cases, it produces a shattering effect, which may injure or kill personnel present in the vicinity and/or cause physical damage to property, depending upon the circumstances of each case. It may also cause shock and confusion and may necessitate the immediate shut-down of the manufacturing processes or a portion thereof, along with the sudden movement of a large number of people. If the situation is not controlled and guided in an orderly manner immediately, it may lead to panic and further loss of life and property.

Smoke given out by the burning material in a fire may involve other parts of the property and/or trap persons, necessitating an intensive, large-scale rescue operation/evacuation. In certain cases, large-scale evacuation may have to be undertaken when people are likely to get trapped or affected by fire.

In all cases in which large-scale sudden movement of personnel is involved, traffic problems are also created—particularly if public roads, streets or areas have to be used for this movement. If such problems are not anticipated and suitable action is not preplanned, traffic bottlenecks result, which hamper and retard fire extinguishment and rescue efforts.

Evacuation of a large number of persons—particularly from high-rise buildings—may also present problems. For successful evacuation, it is not only necessary that adequate and suitable means of escape are available, but also that the evacuation be effected speedily. Special attention should be given to the evacuation needs of disabled individuals.

Detailed evacuation procedures must, therefore, be included in the emergency plan. These must be frequently tested in the conduct of fire and evacuation drills, which may also involve traffic problems. All participating and concerned organizations and agencies must also be involved in these drills, at least periodically. After each exercise, a debriefing session must be held, during which all mistakes are pointed out and explained. Action must also be taken to prevent repetition of the same mistakes in future exercises and actual incidents by removing all difficulties and reviewing the emergency plan as necessary.

Proper records must be maintained of all exercises and evacuation drills.

Emergency Medical Services

Casualties in a fire or explosion must receive immediate medical aid or be moved speedily to a hospital after being given first aid.

It is essential that management provide one or more first-aid post(s) and, where necessary because of the size and hazardous nature of the industry, one or more mobile paramedical appliances. All first-aid posts and paramedical appliances must be staffed at all times by fully trained paramedics.

Depending upon the size of the industry and the number of workers, one or more ambulance(s) must also be provided and staffed on the premises for removal of casualties to hospitals. In addition, arrangement must be  made to ensure that additional ambulance facilities are available at short notice when needed.

Where the size of the industry or workplace so demands, a full-time medical officer should also be made available at all times for any emergency situation.

Prior arrangements must be made with a designated hospital or hospitals at which priority is given to casualties who are removed after a fire or explosion. Such hospitals must be listed in the emergency plan along with their telephone numbers, and the emergency plan must have suitable provisions to ensure that a responsible person shall alert them to receive casualties as soon as an emergency arises.

Facility Restoration

It is important that all fire protection and emergency facilities are restored to a “ready” mode soon after the emergency is over. For this purpose, responsibility must be assigned to a person or section of the industry, and this must be included in the emergency plan. A system of checks to ensure that this is being done must also be introduced.

Public Fire Department Relations

It is not practicable for any management to foresee and provide for all possible contingencies. It is also not economically feasible to do so. In spite of adopting the most up-to-date method of fire risk management, there are always occasions when the fire protection facilities provided on the premises fall short of actual needs. For such occasions, it is desirable to preplan a mutual assistance programme with the public fire department. Good liaison with that department is necessary so that the management knows what assistance that unit can provide during an emergency on its premises. Also, the public fire department must become familiar with the risk and what it could expect during an emergency. Frequent interaction with the public fire department is necessary for this purpose.

Handling of Hazardous Materials

Hazards of the materials used in industry may not be known to fire-fighters during a spill situation, and accidental discharge and improper use or storage of hazardous materials can lead to dangerous situations that can seriously imperil their health or lead to a serious fire or explosion. It is not possible to remember the hazards of all materials. Means of ready identification of hazards have, therefore, been developed whereby the various substances are identified by distinct labels or markings.

Hazardous materials identification

Each country follows its own rules concerning the labelling of hazardous materials for the purpose of storage, handling and transportation, and various departments may be involved. While compliance with local regulations is essential, it is desirable that an internationally recognized system of identification of hazardous materials be evolved for universal application. In the United States, the NFPA has developed a system for this purpose. In this system, distinct labels are conspicuously attached or affixed to containers of hazardous materials. These labels indicate the nature and degree of hazards in respect of health, flammability and the reactive nature of the material. In addition, special possible hazards to fire-fighters can also be indicated on these labels. For an explanation of the degree of hazard, refer to NFPA 704, Standard System for the Identification of the Fire Hazards of Materials (1990a). In this system, the hazards are categorized as health hazards, flammability hazards, and reactivity (instability) hazards.

Health hazards

These include all possibilities of a material causing personal injury from contact with or absorption into the human body. A health hazard may arise out of the inherent properties of the material or from the toxic products of combustion or decomposition of the material. The degree of hazard is assigned on the basis of the greater hazard that may result under fire or other emergency conditions. It indicates to fire-fighters whether they can work safely only with special protective clothing or with suitable respiratory protective equipment or with ordinary clothing.

Degree of health hazard is measured on a scale of 4 to 0, with 4 indicating the most severe hazard and 0 indicating low hazard or no hazard.

Flammability hazards

These indicate the susceptibility of the material to burning. It is recognized that materials behave differently in respect of this property under varying circumstances (e.g., materials that may burn under one set of conditions may not burn if the conditions are altered). The form and inherent properties of the materials influence the degree of hazard, which is assigned on the same basis as for the health hazard.

Reactivity (instability) hazards

Materials capable of releasing energy by itself, (i.e., by self-reaction or polymerization) and substances that can undergo violent eruption or explosive reactions on coming in contact with water, other extinguishing agents or certain other materials are said to possess a reactivity hazard.

The violence of reaction may increase when heat or pressure is applied or when the substance comes in contact with certain other materials to form a fuel-oxidizer combination, or when it comes in contact with incompatible substances, sensitizing contaminants or catalysts.

The degree of reactivity hazard is determined and expressed in terms of the ease, rate and quantity of energy release. Additional information, such as radioactivity hazard or prohibition of water or other extinguishing medium for fire-fighting, can also be given on the same level.

The label warning of a hazardous material is a diagonally placed square with four smaller squares (see figure 1).

Figure 1. The NFPA 704 diamond.

The top square indicates the health hazard, the one on the left indicates the flammability hazard, the one on the right indicates the reactivity hazard, and the bottom square indicates other special hazards, such as radioactivity or unusual reactivity with water.

To supplement the above mentioned arrangement, a colour code may also be used. The colour is used as background or the numeral indicating the hazard may be in coded colour. The codes are health hazard (blue), flammability hazard (red), reactivity hazard (yellow) and special hazard (white background).

Managing hazardous materials response

Depending on the nature of the hazardous material in the industry, it is necessary to provide protective equipment and special fire-extinguishing agents, including the protective equipment required to dispense the special extinguishing agents.

All workers must be trained in the precautions they must take and the procedures they must adopt to deal with each incident in the handling of the various types of hazardous materials. They must also know the meaning of the various identification signs.

All fire-fighters and other workers must be trained in the correct use of any protective clothing, protective respiratory equipment and special fire-fighting techniques. All concerned personnel must be kept alert and prepared to tackle any situation through frequent drills and exercises, of which proper records should be kept.

To deal with serious medical hazards and the effects of these hazards on fire-fighters, a competent medical officer should be available to take immediate precautions when any individual is exposed to unavoidable dangerous contamination. All affected persons must receive immediate medical attention.

Proper arrangements must also be made to set up a decontamination centre on the premises when necessary, and correct decontamination procedures must be laid down and followed.

Waste control

Considerable waste is generated by industry or because of accidents during handling, transportation and storage of goods. Such waste may be flammable, toxic, corrosive, pyrophoric, chemically reactive or radioactive, depending upon the industry in which it is generated or the nature of goods involved. In most cases unless proper care is taken in safe disposal of such waste, it may endanger animal and human life, pollute the environment or cause fire and explosions that may endanger property. A thorough knowledge of the physical and chemical properties of the waste materials and of the merits or limitations of the various methods of their disposal is, therefore, necessary to ensure economy and safety.

Properties of industrial waste are briefly summarized below:

1. Most industrial waste is hazardous and can have unexpected significance during and after disposal. The nature and behavioural characteristics of all waste must therefore be carefully examined for their short- and long-term impact and the method of disposal determined accordingly.
2. Mixing of two seemingly innocuous discarded substances may create an unexpected hazard because of their chemical or physical interaction.
3. Where flammable liquids are involved, their hazards can be assessed by taking into consideration their respective flash points, ignition temperature, flammability limits and the ignition energy required to initiate combustion. In the case of solids, particle size is an additional factor that must be considered.
4. Most flammable vapours are heavier than air. Such vapours and heavier-than-air flammable gases that may be accidentally released during collection or disposal or during handling and transportation can travel considerable distances with the wind or towards a lower gradient. On coming in contact with a source of ignition, they flash back to source. Major spills of flammable liquids are particularly hazardous in this respect and may require evacuation to save lives.
5. Pyrophoric materials, such as aluminium alkyls, ignite spontaneously when exposed to air. Special care must therefore be taken in handling, transportation, storage and disposal of such materials, preferably carried out under a nitrogen atmosphere.
6. Certain materials, such as potassium, sodium and aluminium alkyls, react violently with water or moisture and burn fiercely. Bronze powder generates considerable heat in the presence of moisture.
7. The presence of potent oxidants with organic materials can cause rapid combustion or even an explosion. Rags and other materials soaked with vegetable oils or terpenes present a risk of spontaneous combustion due to the oxidation of oils and subsequent build-up of heat to the ignition temperature.
8. Several substances are corrosive and may cause severe damage or burns to skin or other living tissues, or may corrode construction materials, especially metals, thereby weakening the structure in which such materials may have been used.
9. Some substances are toxic and can poison humans or animals by contact with skin, inhalation or contamination of food or water. Their ability to do so may be short lived or may extend over a long period. Such substances, if disposed of by dumping or burning, can contaminate water sources or come into contact with animals or workers.
10. Toxic substances that are spilled during industrial processing, transportation (including accidents), handling or storage, and toxic gases that are released into the atmosphere can affect emergency personnel and others, including the public. The hazard is all the more severe if the spilled substance(s) is vaporized at ambient temperature, because the vapours can be carried over long distances due to wind drift or run-off.
11. Certain substances may emit a strong, pungent or unpleasant odour, either by themselves or when they are burnt in the open. In either case, such substances are a public nuisance, even though they may not be toxic, and they must be disposed of by proper incineration, unless it is possible to collect and recycle them. Just as odorous substances are not necessarily toxic, odourless substances and some substances with a pleasant odour may produce harmful physiological effects.
12. Certain substances, such as explosives, fireworks, organic peroxides and some other chemicals, are sensitive to heat or shock and may explode with devastating effect if not handled carefully or mixed with other substances. Such substances must, therefore, be carefully segregated and destroyed under proper supervision.
13. Waste materials that are contaminated with radioactivity can be as hazardous as the radioactive materials themselves. Their disposal requires specialized knowledge. Proper guidance for disposal of such waste may be obtained from a country’s nuclear energy organization.

Some of the methods that may be employed to dispose of industrial and emergency waste are biodegradation, burial, incineration, landfill, mulching, open burning, pyrolysis and disposal through a contractor. These are briefly explained below.

Biodegradation

Many chemicals are completely destroyed within six to 24 months when they are mixed with the top 15 cm of soil. This phenomenon is known as biodegradation and is due to the action of soil bacteria. Not all substances, however, behave in this way.

Burial

Waste, particularly chemical waste, is often disposed of by burial. This is a dangerous practice in so far as active chemicals are concerned, because, in time, the buried substance may get exposed or leached by rain into water resources. The exposed substance or the contaminated material can have adverse physiological effects when it comes in contact with water that is drunk by humans or animals. Cases are on record in which water was contaminated 40 years after burial of certain harmful chemicals.

Incineration

This is one of the safest and most satisfactory methods of waste disposal if the waste is burned in a properly designed incinerator under controlled conditions. Care must be taken, however, to ensure that the substances contained in the waste are amenable to safe incineration without posing any operating problem or special hazard. Almost all industrial incinerators require the installation of air pollution control equipment, which must be carefully selected and installed after taking into consideration the composition of the stock effluent given out by the incinerator during the burning of industrial waste.

Care must be taken in the operation of the incinerator to ensure that its operative temperature does not rise excessively either because a large amount of volatiles is fed or because of the nature of the waste burned. Structural failure can occur because of excessive temperature, or, over time, because of corrosion. The scrubber must also be periodically inspected for signs of corrosion which can occur because of contact with acids, and the scrubber system must be maintained regularly to ensure proper functioning.

Landfill

Low-lying land or a depression in land is often used as a dump for waste materials until it becomes level with the surrounding land. The waste is then levelled, covered with earth and rolled hard. The land is then used for buildings or other purposes.

For satisfactory landfill operation, the site must be selected with due regard to the proximity of pipelines, sewer lines, power lines, oil and gas wells, mines and other hazards. The waste must then be mixed with earth and evenly spread out in the depression or a wide trench. Each layer must be mechanically compacted before the next layer is added.

A 50 cm layer of earth is typically laid over the waste and compacted, leaving sufficient vents in the soil for the escape of gas that is produced by biological activity in the waste. Attention must also be paid to proper drainage of the landfill area.

Depending on the various constituents of waste material, it may at times ignite within the landfill. Each such area must, therefore, be properly fenced off and continued surveillance maintained until the chances of ignition appear to be remote. Arrangements must also be made for extinguishing any fire that may break out in the waste within the landfill.

Mulching

Some trials have been made for reusing polymers as mulch (loose material for protecting the roots of plants) by chopping the waste into small shreds or granules. When so used, it degrades very slowly. Its effect on the soil is, therefore, purely physical. This method has, however, not been used widely.

Open burning

Open burning of waste causes pollution of the atmosphere and is hazardous in as much as there is a chance of the fire getting out of control and spreading to the surrounding property or areas. Also, there is a chance of explosion from containers, and there is a possibility of harmful physiological effects of radioactive materials that may be contained in the waste. This method of disposal has been banned in some countries. It is not a desirable method and should be discouraged.

Pyrolysis

Recovery of certain compounds, by distillation of the products given out during pyrolysis (decomposition by heating) of polymers and organic substances, is possible, but not yet widely adopted.

Disposal through contractors

This is probably the most convenient method. It is important that only reliable contractors who are knowledgeable and experienced in the disposal of industrial waste and hazardous materials are selected for the job. Hazardous materials must be carefully segregated and disposed of separately.

Specific classes of materials

Specific examples of the types of hazardous materials that are often found in today’s industry include: (1) combustible and reactive metals, such as magnesium, potassium, lithium, sodium, titanium and zirconium; (2) combustible refuse; (3) drying oils; (4) flammable liquids and waste solvents; (5) oxidizing materials (liquids and solids); and (6) radioactive materials. These materials require special handling and precautions that must be carefully studied. For more details on identification of hazardous materials and hazards of industrial materials, the following publications may be consulted: Fire Protection Handbook (Cote 1991) and Sax’s Dangerous Properties of Industrial Materials (Lewis 1979).

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Life Safety and Property Protection

As the primary importance of any fire protection measure is to provide an acceptable degree of life safety to inhabitants of a structure, in most countries legal requirements applying to fire protection are based on life safety concerns. Property protection features are intended to limit physical damage. In many cases these objectives are complementary. Where concern exists with the loss of property, its function or contents, an owner may choose to implement measures beyond the required minimum necessary to address life safety concerns.

Fire Detection and Alarm Systems

A fire detection and alarm system provides a means to detect fire automatically and to warn building occupants of the threat of fire. It is the audible or visual alarm provided by a fire detection system that is the signal to begin the evacuation of the occupants from the premises. This is especially important in large or multi-storey buildings where occupants would be unaware that a fire was underway within the structure and where it would be unlikely or impractical for warning to be provided by another inhabitant.

Basic elements of a fire detection and alarm system

A fire detection and alarm system may include all or some of the following:

1. a system control unit
2. a primary or main electrical power supply
3. a secondary (stand-by) power supply, usually supplied from batteries or an emergency generator
4. alarm-initiating devices such as automatic fire detectors, manual pull stations and/or sprinkler system flow devices, connected to “initiating circuits” of the system control unit
5. alarm-indicating devices, such as bells or lights, connected to “indicating circuits” of the system control unit
6. ancillary controls such as ventilation shut-down functions, connected to output circuits of the system control unit
7. remote alarm indication to an external response location, such as the fire department
8. control circuits to activate a fire protection system or smoke control system.

Smoke Control Systems

To reduce the threat of smoke from entering exit paths during evacuation from a structure, smoke control systems can be used. Generally, mechanical ventilation systems are employed to supply fresh air to the exit path. This method is most often used to pressurize stairways or atrium buildings. This is a feature intended to enhance life safety.

Portable Fire Extinguishers and Hose Reels

Portable fire extinguishers and water hose reels are often provided for use by building occupants to fight small fires (see figure 1). Building occupants should not be encouraged to use a portable fire extinguisher or hose reel unless they have been trained in their use. In all cases, operators should be very cautious to avoid placing themselves in a position where safe egress is blocked. For any fire, no matter how small, the first action should always be to notify other building occupants of the threat of fire and summon assistance from the professional fire service.

Figure 1. Portable fire extinguishers.

Water Sprinkler Systems

Water sprinkler systems consist of a water supply, distribution valves and piping connected to automatic sprinkler heads (see figure 2). While current sprinkler systems are primarily intended to control the spread of fire, many systems have accomplished complete extinguishment.

Figure 2. A typical sprinkler installation showing all common water supplies, outdoor hydrants and underground piping.

A common misconception is that all automatic sprinkler heads open in the event of a fire. In fact, each sprinkler head is designed to open only when sufficient heat is present to indicate a fire. Water then flows only from the sprinkler head(s) that have opened as the result of fire in their immediate vicinity. This design feature provides efficient use of water for fire-fighting and limits water damage.

Water supply

Water for an automatic sprinkler system must be available in sufficient quantity and at sufficient volume and pressure at all times to ensure reliable operation in the event of fire. Where a municipal water supply cannot meet this requirement, a reservoir or pump arrangement must be provided to provide a secure water supply.

Control valves

Control valves should be maintained in the open position at all times. Often, supervision of the control valves can be accomplished by the automatic fire alarm system by provision of valve tamper switches that will initiate a trouble or supervisory signal at the fire alarm control panel to indicate a closed valve. If this type of monitoring cannot be provided, the valves should be locked in the open position.

Piping

Water flows through a piping network, ordinarily suspended from the ceiling, with the sprinkler heads suspended at intervals along the pipes. Piping used in sprinkler systems should be of a type that can withstand a working pressure of not less than 1,200 kPa. For exposed piping systems, fittings should be of the screwed, flanged, mechanical joint or brazed type.

Sprinkler heads

A sprinkler head consists of an orifice, normally held closed by a temperature-sensitive releasing element, and a spray deflector. The water discharge pattern and spacing requirements for individual sprinkler heads are used by sprinkler designers to ensure complete coverage of the protected risk.

Special Extinguishing Systems

Special extinguishing systems are used in cases where water sprinklers would not provide adequate protection or where the risk of damage from water would be unacceptable. In many cases where water damage is of concern, special extinguishing systems may be used in conjunction with water sprinkler systems, with the special extinguishing system designed to react at an early stage of fire development.

Water and water-additive special extinguishing systems

Water spray systems

Water spray systems increase the effectiveness of water by producing smaller water droplets, and thus a greater surface area of water is exposed to the fire, with a relative increase in heat absorption capability. This type of system is often chosen as a means of keeping large pressure vessels, such as butane spheres, cool when there is a risk of an exposure fire originating in an adjacent area. The system is similar to a sprinkler system; however, all heads are open, and a separate detection system or manual action is used to open control valves. This allows water to flow through the piping network to all spray devices that serve as outlets from the piping system.

Foam systems

In a foam system, a liquid concentrate is injected into the water supply before the control valve. Foam concentrate and air are mixed, either through the mechanical action of discharge or by aspirating air into the discharge device. The air entrained in the foam solution creates an expanded foam. As expanded foam is less dense than most hydrocarbons, the expanded foam forms a blanket on top of the flammable liquid. This foam blanket reduces fuel vapour propagation. Water, which represents as much as 97% of the foam solution, provides a cooling effect to further reduce vapour propagation and to cool hot objects that could serve as a source of re-ignition.

Gaseous extinguishing systems

Carbon dioxide systems

Carbon dioxide systems consist of a supply of carbon dioxide, stored as liquified compressed gas in pressure vessels (see figures 3 and 4). The carbon dioxide is held in the pressure vessel by means of an automatic valve that is opened upon fire by means of a separate detection system or by manual operation. Once released, the carbon dioxide is delivered to the fire by means of a piping and discharge nozzle arrangement. Carbon dioxide extinguishes fire by displacing the oxygen available to the fire. Carbon dioxide systems can be designed for use in open areas such as printing presses or enclosed volumes such as ship machinery spaces. Carbon dioxide, at fire-extinguishing concentrations, is toxic to people, and special measures must be employed to ensure that persons in the protected area are evacuated before discharge occurs. Pre-discharge alarms and other safety measures must be carefully incorporated into the design of the system to ensure adequate safety for people working in the protected area. Carbon dioxide is considered to be a clean extinguishant because it does not cause collateral damage and is electrically non-conductive.

Figure 3. Diagram of a high-pressure carbon dioxide system for total flooding.

Figure 4. A total flooding system installed in a room with a raised floor.

Inert gas systems

Inert gas systems generally use a mixture of nitrogen and argon as an extinguishing medium. In some cases, a small percentage of carbon dioxide is also provided in the gas mixture. The inert gas mixtures extinguish fires by reducing oxygen concentration within a protected volume. They are suitable for use in enclosed spaces only. The unique feature offered by inert gas mixtures is that they reduce the oxygen to a low enough concentration to extinguish many types of fires; however, oxygen levels are not sufficiently lowered to pose an immediate threat to occupants of the protected space. The inert gases are compressed and stored in pressure vessels. System operation is similar to a carbon dioxide system. As the inert gases cannot be liquefied by compression, the number of storage vessels required for protection of a given enclosed protected volume is greater than that for carbon dioxide.

Halon systems

Halons 1301, 1211 and 2402 have been identified as ozone-depleting substances. Production of these extinguishing agents ceased in 1994, as required by the Montreal Protocol, an international agreement to protect the earth’s ozone layer. Halon 1301 was most often used in fixed fire protection systems. Halon 1301 was stored as liquefied, compressed gas in pressure vessels in a similar arrangement to that used for carbon dioxide. The advantage offered by halon 1301 was that storage pressures were lower and that very low concentrations provided effective extinguishing capability. Halon 1301 systems were used successfully for totally enclosed hazards where the extinguishing concentration achieved could be maintained for a sufficient time for extinguishment to occur. For most risks, concentrations used did not pose an immediate threat to occupants. Halon 1301 is still used for several important applications where acceptable alternatives have yet to be developed. Examples include use on-board commercial and military aircraft and for some special cases where inerting concentrations are required to prevent explosions in areas where occupants could be present. The halon in existing halon systems that are no longer required should be made available for use by others with critical applications. This will militate against the need to produce more of these environmentally sensitive extinguishers and help protect the ozone layer.

Halocarbon systems

Halocarbon agents were developed as the result of the environmental concerns associated with halons. These agents differ widely in toxicity, environmental impact, storage weight and volume requirements, cost and availability of approved system hardware. They all can be stored as liquefied compressed gases in pressure vessels. System configuration is similar to a carbon dioxide system.

Design, Installation and Maintenance of Active Fire Protection Systems

Only those skilled in this work are competent to design, install and maintain this equipment. It may be necessary for many of those charged with purchasing, installing, inspecting, testing, approving and maintaining this equipment to consult with an experienced and competent fire protection specialist to discharge their duties effectively.

Further Information

This section of the Encyclopaedia presents a very brief and limited overview of the available choice of active fire protection systems. Readers may often obtain more information by contacting a national fire protection association, their insurer or the fire prevention department of their local fire service.

Back

This article describes several significant radiation accidents, their causes and the responses to them. A review of the events leading up to, during and following these accidents can provide planners with information to preclude future occurrences of such accidents and to enhance an appropriate, rapid response in the event a similar accident occurs again.

Acute Radiation Death Resulting from an Accidental Nuclear Critical Excursion on 30 December 1958

This report is noteworthy because it involved the largest accidental dose of radiation received by humans (to date) and because of the extremely professional and thorough work-up of the case. This represents one of the best, if not the best, documented acute radiation syndrome descriptions that exists (JOM 1961).

At 4:35 p.m. on 30 December 1958, an accidental critical excursion resulting in fatal radiation injury to an employee (K) took place in the plutonium recovery plant at the Los Alamos National Laboratory (New Mexico, United States).

The time of the accident is important because six other workers had been in the same room with K thirty minutes earlier. The date of the accident is important because the normal flow of fissionable material into the system was interrupted for year-end physical inventory. This interruption caused a routine procedure to become non-routine and led to an accidental “criticality” of the plutonium-rich solids that were accidentally introduced into the system.

Summary of estimates of K’s radiation exposure

The best estimate of K’s average total-body exposure was between 39 and 49 Gy, of which about 9 Gy was due to fission neutrons. A considerably greater portion of the dose was delivered to the upper half of the body than to the lower half. Table 1 shows an estimate of K’s radiation exposure.

Table 1. Estimates of K’s radiation exposure

Clinical course of patient

In retrospect, the clinical course of patient K can be divided into four distinct periods. These periods differed in duration, symptoms and response to supportive therapy.

The first period, lasting from 20 to 30 minutes, was characterized by his immediate physical collapse and mental incapacitation. His condition progressed to semi-consciousness and severe prostration.

The second period lasted about 1.5 hours and began with his arrival by stretcher at the emergency room of the hospital and ended with his transfer from the emergency room to the ward for further supportive therapy. This interval was characterized by such severe cardiovascular shock that death seemed imminent during the whole time. He seemed to be suffering severe abdominal pain.

The third period was about 28 hours long and was characterized by enough subjective improvement to encourage continued attempts to alleviate his anoxia, hypotension and circulatory failure.

The fourth period began with the unheralded onset of rapidly increasing irritability and antagonism, bordering on mania, followed by coma and death in approximately 2 hours. The entire clinical course lasted 35 hours from the time of radiation exposure to death.

The most dramatic clinicopathological changes were observed in the haemopoietic and urinary systems. Lymphocytes were not found in the circulating blood after the eighth hour, and there was virtually complete urinary shutdown despite administration of large amount of fluids.

K’s rectal temperature varied between 39.4 and 39.7°C for the first 6 hours and then fell precipitously to normal, where it remained for the duration of his life. This high initial temperature and its maintenance for 6 hours were considered in keeping with his suspected massive dose of radiation. His prognosis was grave.

Of all the various determinations made during the course of the illness, changes in white cell count were found to be the simplest and best prognostic indicator of severe irradiation. The virtual disappearance of lymphocytes from the peripheral circulation within 6 hours of exposure was considered a grave sign.

Sixteen different therapeutic agents were employed in the symptomatic treatment of K over about a 30-hour period. In spite of this and continued oxygen administration, his heart tones became very distant, slow and irregular about 32 hours after irradiation. His heart then became progressively weaker and suddenly stopped 34 hours 45 minutes after irradiation.

Windscale Reactor No. 1 Accident of 9-12 October 1957

Windscale reactor No. 1 was an air-cooled, graphite-moderated natural uranium-fuelled plutonium production reactor. The core was partially ruined by fire on 15 October 1957. This fire resulted in a release of approximately 0.74 PBq (10⁺¹⁵ Bq) of iodine-131 (¹³¹I) to the downwind environment.

According to a US Atomic Energy Commission accident information report about the Windscale incident, the accident was caused by operator judgement errors concerning thermocouple data and was made worse by faulty handling of the reactor that permitted the graphite temperature to rise too rapidly. Also contributory was the fact that fuel temperature thermocouples were located in the hottest part of the reactor (that is, where the highest dose rates occurred) during normal operations rather than in parts of the reactor which were hottest during an abnormal release. A second equipment deficiency was the reactor power meter, which was calibrated for normal operations and read low during the annealing. As a result of the second heating cycle, the graphite temperature rose on 9 October, especially in the lower front part of the reactor where some cladding had failed because of the earlier rapid temperature rise. Although there were a number of small iodine releases on 9 October, the releases were not recognized until 10 October when the stack activity meter showed a significant increase (which was not regarded as highly significant). Finally, on the afternoon of 10 October, other monitoring (Calder site) indicated the release of radioactivity. Efforts to cool the reactor by forcing air through it not only failed but actually increased the magnitude of the radioactivity released.

The estimated releases from the Windscale accident were 0.74 PBq of ¹³¹I, 0.22 PBq of caesium-137 (¹³⁷Cs), 3.0 TBq (10¹²Bq) of strontium-89 (⁸⁹Sr), and 0.33 TBq of strontium-90
(⁹⁰Sr). The highest offsite gamma absorbed dose rate was about 35 μGy/h due to airborne activity. Air activity readings around the Windscale and Calder plants often were 5 to 10 times the maximum permissible levels, with occasional peaks of 150 times permissible levels. A milk ban extended over a radius of approximately 420 km.

During operations to bring the reactor under control, 14 workers received dose equivalents greater than 30 mSv per calendar quarter, with the maximum dose equivalent at 46 mSv per calendar quarter.

Lessons learned

There were many lessons learned concerning natural uranium reactor design and operation. The inadequacies concerning reactor instrumentation and reactor operator training also bring up points analogous to the Three Mile Island accident (see below).

No guidelines existed for short-term permissible exposure to radioiodine in food. The British Medical Research Council performed a prompt and thorough investigation and analysis. Much ingenuity was used in promptly deriving maximum permissible concentrations for ¹³¹I in food. The study Emergency Reference Levels that resulted from this accident serves as a basis for emergency planning guides now used worldwide (Bryant 1969).

A useful correlation was derived for predicting significant radioiodine contamination in milk. It was found that gamma radiation levels in pastures which exceeded 0.3 μGy/h yielded milk which exceeded 3.7 MBq/m³.

Absorbed dose from inhalation of external exposure to radioiodines is negligible compared to that from drinking milk or eating dairy products. In an emergency, rapid gamma spectroscopy is preferable to slower laboratory procedures.

Fifteen two-person teams performed radiation surveys and obtained samples. Twenty persons were used for sample coordination and data reporting. About 150 radiochemists were involved in sampling analysis.

Glass wool stack filters are not satisfactory under accident conditions.

Gulf Oil Accelerator Accident of 4 October 1967

Gulf Oil Company technicians were using a 3 MeV Van de Graaff accelerator for the activation of soil samples on 4 October 1967. The combination of an interlock failure on the power key of the accelerator console and the taping of several of the interlocks on the safety tunnel door and the target room inside door produced serious accidental exposures to three individuals. One individual received approximately 1 Gy whole-body dose equivalent, the second received close to 3 Gy whole-body dose equivalent and the third received approximately 6 Gy whole-body dose equivalent, in addition to approximately 60 Gy to the hands and 30 Gy to the feet.

One of the accident victims reported to the medical department, complaining of nausea, vomiting and generalized muscular aches. His symptoms initially were misdiagnosed as flu symptoms. When the second patient came in with approximately the same symptoms, it was decided that they may possibly have received significant radiation exposures. Film badges verified this. Dr. Niel Wald, University of Pittsburgh Radiological Health Division, supervised the dosimetry tests and also acted as coordinating physician in the work-up and treatment of the patients.

Dr. Wald very quickly had absolute filter units flown in to the western Pennsylvania hospital in Pittsburgh where the three patients had been admitted. He set up these absolute filter/laminar flow filters to clean the patients’ environment of all biological contaminants. These “reverse isolation” units were used on the 1 Gy exposure patient for about 16 days, and on the 3 and 6 Gy exposure patients for about a month and half.

Dr. E. Donnal Thomas from the University of Washington arrived to perform a bone marrow transplant on the 6 Gy patient on the eighth day after exposure. The patient’s twin brother served as the bone marrow donor. Although this heroic medical treatment saved the 6 Gy patient’s life, nothing could be done to save his arms and legs, each of which received tens-of-gray absorbed dose.

Lessons learned

If the simple operating procedure of always using a survey meter when entering the exposure room had been followed, this tragic accident would have been avoided.

At least two interlocks had been taped closed for long periods of time prior to this accident. Defeating of protective interlocks is intolerable.

Regular maintenance checks should have been made on the key-operated power interlocks for the accelerator.

Timely medical attention saved the life of the person with the highest exposure. The heroic procedure of a complete bone marrow transplant together with the use of reverse isolation and quality medical care were all major factors in saving this person’s life.

Reverse isolation filters can be obtained in a matter of hours to be set up in any hospital to care for highly exposed patients.

In retrospect, medical authorities involved with these patients would have recommended amputation earlier and at a definitive level within two or three months after the exposure. Earlier amputation decreases the likelihood of infection, gives a shorter period of severe pain, reduces pain medication required for the patient, possibly reduces the patient’s hospital stay, and possibly contributes to earlier rehabilitation. Earlier amputation should, of course, be done while correlating dosimetry information with clinical observations.

The SL–1 Prototype Reactor Accident (Idaho, USA, 3 January 1961)

This is the first (and to date the only) fatal accident in the history of US reactor operations. The SL-1 is a prototype of a small Army Package Power Reactor (APPR) designed for air transportation to remote areas for production of electrical power. This reactor was used for fuel testing, and for reactor crew training. It was operated in the remote desert location of the National Reactor Testing Station in Idaho Falls, Idaho, by Combustion Engineering for the US Army. The SL-1 was not a commercial power reactor (AEC 1961; American Nuclear Society 1961).

At the time of the accident, the SL-1 was loaded with 40 fuel elements and 5 control rod blades. It could produce a power level of 3 MW (thermal) and was a boiling water–cooled and –moderated reactor.

The accident resulted in the deaths of three military personnel. The accident was caused by the withdrawal of a single control rod for a distance of more than 1 m. This caused the reactor to go into prompt criticality. The reason why a skilled, licensed reactor operator with much refuelling operation experience withdrew the control rod past its normal stop point is unknown.

One of the three accident victims was still alive when initial response personnel first reached the scene of the accident. High activity fission products covered his body and were embedded in his skin. Portions of the victim’s skin registered in excess of 4.4 Gy/h at 15 cm and hampered rescue and medical treatment.

Lessons learned

No reactor designed since the SL-1 accident can be brought to “prompt-critical” state with a single control rod.

All reactors must have portable survey meters onsite that have ranges greater than 20 mGy/h. Survey meters of 10 Gy/h maximum range are recommended.

Note: The Three Mile Island accident showed that 100 Gy/h is the required range for both gamma and beta measurements.

Treatment facilities are required where a highly contaminated patient can receive definitive medical treatment with reasonable safeguards for attendant personnel. Since most of these facilities will be in clinics with other ongoing missions, control of airborne and waterborne radioactive contaminants may require special provisions.

X-ray Machines, Industrial and Analytical

Accidental exposures from x-ray systems are numerous and often involve extremely high exposures to small portions of the body. It is not unusual for x-ray diffraction systems to produce absorbed dose rates of 5 Gy/s at 10 cm from the tube focus. At shorter distances, 100 Gy/s rates have often been measured. The beam is usually narrow, but even a few seconds’ exposure can result in severe local injury (Lubenau et al. 1967; Lindell 1968; Haynie and Olsher 1981; ANSI 1977).

Because these systems are often used in “non-routine” circumstances, they lend themselves to the production of accidental exposures. X-ray systems commonly used in normal operations appear to be reasonably safe. Equipment failure has not caused severe exposures.

Lessons learned from accidental x-ray exposures

Most accidental exposures occurred during non-routine uses when equipment was partially disassembled or shield covers had been removed.

In most serious exposures, adequate instruction for the staff and maintenance personnel had been lacking.

If simple and fail-safe methods had been used to ensure that x-ray tubes were turned off during repairs and maintenance, many accidental exposures would have been avoided.

Finger or wrist personnel dosimeters should be used for operators and maintenance personnel working with these machines.

If interlocks had been required, many accidental exposures would have been avoided.

Operator error was a contributing cause in most of the accidents. Lack of adequate enclosures or poor shielding design often worsened the situation.

Industrial radiography accidents

From the 1950s through the 1970s, the highest radiation accident rate for a single activity has consistently been for industrial radiographic operations (IAEA 1969, 1977). National regulatory bodies continue to struggle to reduce the rate by a combination of improved regulations, strict training requirements and ever tougher inspection and enforcement policies (USCFR 1990). These regulatory efforts have generally succeeded, but many accidents associated with industrial radiography still occur. Legislation allowing huge monetary fines may be the most effective tool in keeping radiation safety focused in the minds of industrial radiography management (and also, therefore, in workers’ minds).

Causes of industrial radiography accidents

Worker training. Industrial radiography probably has lower education and training requirements than any other type of radiation employment. Therefore, existing training requirements must be strictly enforced.

Worker production incentive. For years, major emphasis for industrial radiographers was placed on the amount of successful radiographs produced per day. This practice can lead to unsafe acts as well as to occasional non-use of personnel dosimetry so that exceeding dose equivalent limits would not be detected.

Lack of proper surveys. Thorough surveying of source pigs (storage containers) (figure 1) after every exposure is most important. Not performing these surveys is the single most probable cause of unnecessary exposures, many of which are unrecorded, since industrial radiographers rarely use hand or finger dosimeters (figure 1).

Figure 1. Industrial radiography camera

Equipment problems. Because of heavy use of industrial radiographic cameras, source winding mechanisms can loosen and cause the source to not completely retract into its safe storage position (point A in figure 1). There are also many instances of closet-source interlock failures that cause accidental exposures of personnel.

Design of Emergency Plans

Many excellent guidelines, both general and specific, exist for the design of emergency plans. Some references are particularly helpful. These are given in the suggested readings at the end of this chapter.

Initial drafting of emergency plan and procedures

First, one must assess the entire radioactive material inventory for the subject facility. Then credible accidents must be analysed so that one can determine the probable maximum source release terms. Next, the plan and its procedures must enable the facility operators to:

1. recognize an accident situation
2. classify the accident according to severity
3. take steps to mitigate the accident
4. make timely notifications
5. call for help efficiently and quickly
6. quantify releases
7. keep track of exposures both on- and offsite, as well as keep emergency exposures ALARA
8. recover the facility as quickly as practical
9. keep accurate and detailed records.

Types of accidents associated with nuclear reactors

A list, from most likely to least likely, of types of accidents associated with nuclear reactors follows. (The non-nuclear reactor, general-industrial type accident is by far the most likely.)

1. Low level unexpected release of radioactive material with little or no external radiation exposure to personnel. Usually occurs during major overhauls or in shipment of spent resin or spent fuel. Coolant system leakage and coolant-sample sink spills are often causes of spread of radioactive contamination.
2. Unexpected external exposure of personnel. This usually occurs during major overhauls or routine maintenance.
3. A combination of contamination spread, contamination of personnel, and low-level personnel external radiation exposure is the next most likely accident. These accidents occur under the same conditions as 1 and 2 above.
4. Gross surface contamination due to a major reactor coolant system leak or a leak of spent fuel coolant.
5. Chips or large particles of activated CRUD (see definition below) in or on skin, ears or eyes.
6. High-level radiation exposure of plant personnel. This is usually caused by carelessness.
7. Release of small but greater than permissible quantities of radioactive wastes to outside the plant boundary. This is usually associated with human failures.
8. Meltdown of reactor. Gross contamination offsite plus high personnel exposure would probably occur.
9. Reactor excursion (SL–1 type of accident).

Radionuclides expected from water-cooled reactor accidents:

• activated corrosion and erosion products (commonly known as CRUD) in the coolant; for example, cobalt-60 or -58 (⁶⁰Co, ⁵⁸Co), iron-59 (⁵⁹Fe), manganese-58 (⁵⁸Mn) and tantalum-183 (¹⁸³Ta)
• low level fission products usually present in the coolant; for example, iodine-131 (¹³¹I) and caesium-137 (¹³⁷Cs)
• in boiling water reactors, 1 and 2 above plus continuous off-gassing of low levels of tritium 
• (³H) and noble radioactive gases such as xenon-133 and -135 (¹³³Xe, ¹³⁵Xe), argon-41 (⁴¹Ar), and krypton-85 (⁸⁵Kr)
• tritium (³H) manufactured inside the core at the rate of 1.3 × 10^–4 atoms of ³H per fission (only a fraction of this leaves the fuel).

Figure 2. Example of a nuclear power plant emergency plan, table of contents

Typical Nuclear Power Plant Emergency Plan, Table of Contents

Figure 2 is an example of a table of contents for a nuclear power plant emergency plan. Such a plan should include each chapter shown and be tailored to meet local requirements. A list of typical power reactor implementation procedures is given in figure 3.

Figure 3. Typical power reactor implementation procedures

Radiological Environmental Monitoring during Accidents

This task is often called EREMP (Emergency Radiological Environmental Monitoring Programme) at large facilities.

One of the most important lessons learned for the US Nuclear Regulatory Commission and other government agencies from the Three Mile Island accident was that one cannot successfully implement EREMP in one or two days without extensive prior planning. Although the US government spent many millions of dollars monitoring the environment around the Three Mile Island nuclear station during the accident, less then 5^% of the total releases were measured. This was due to poor and inadequate prior planning.

Designing Emergency Radiological Environmental Monitoring Programmes

Experience has shown that the only successful EREMP is one that is designed into the routine radiological environmental monitoring programme. During the early days of the Three Mile Island accident, it was learned that an effective EREMP cannot be established successfully in a day or two, no matter how much manpower and money are applied to the programme.

Sampling locations

All routine radiological environmental monitoring programme locations will be used during long-term accident monitoring. In addition, a number of new locations must be set up so that motorized survey teams have pre-determined locations in each portion of each 22½° sector (see figure 3). Generally, sampling locations will be in areas with roads. However, exceptions must be made for normally inaccessible but potentially occupied sites such as camp grounds and hiking trails within about 16 km downwind of the accident.

Figure 3. Sector and zone designations for radiological sampling and monitoring points  within emergency planning zones

Figure 3 shows the sector and zone designation for radiation and environmental monitoring points. One may designate 22½° sectors by cardinal directions (for example, N, NNE, and NE) or by simple letters (for example, A through R). However, use of letters is not recommended because they are easily confused with directional notation. For example, it is less confusing to use the directional W for west rather than the letter N.

Each designated sample location should be visited during a practice drill so that people responsible for monitoring and sampling will be familiar with the location of each point and will be aware of radio “dead spaces,” poor roads, problems with finding the locations in the dark and so on. Since no drill will cover all the pre-designated locations within the 16 km emergency protection zone, drills must be designed so that all sample points will be visited eventually. It is often worthwhile to predetermine the ability of survey team vehicles to communicate with each pre-designated point. The actual locations of the sample points are chosen utilizing the same criteria as in the REMP (NRC 1980); for example, line of site, minimum exclusion area, closest individual, closest community, closest school, hospital, nursing home, milch animal herd, garden, farm and so                                                                                                                     on.

Radiological monitoring survey team

During an accident involving significant releases of radioactive materials, radiological monitoring teams should be continuously monitoring in the field. They also should continuously monitor onsite if conditions allow. Normally, these teams will monitor for ambient gamma and beta radiation and sample air for the presence of radioactive particulates and halogens.

These teams must be well trained in all monitoring procedures, including monitoring their own exposures, and be able to accurately relay these data to the base station. Details such as survey-meter type, serial number, and open-or closed-window status must be carefully reported on well-designed log sheets.

At the beginning of an emergency, an emergency monitoring team may have to monitor for 12 hours without a break. After the initial period, however, field time for the survey team should be decreased to eight hours with at least one 30 minute break.

Since continuous surveillance may be needed, procedures must be in place to supply the survey teams with food and drink, replacement instruments and batteries, and for back-and-forth transfer of air filters.

Even though survey teams will probably be working 12 hours per shift, three shifts a day are needed to provide continuous surveillance. During the Three Mile Island accident, a minimum of five monitoring teams was deployed at any one time for the first two weeks. The logistics for supporting such an effort must be carefully planned in advance.

Radiological environmental sampling team

The types of environmental samples taken during an accident depend on the type of releases (airborne versus water), direction of the wind and time of year. Soil and drinking water samples must be taken even in winter. Although radio-halogen releases may not be detected, milk samples should be taken because of the large bioaccumulation factor.

Many food and environmental samples must be taken to reassure the public even though technical reasons may not justify the effort. In addition, these data may be invaluable during any subsequent legal proceedings.

Pre-planned log sheets using carefully thought out offsite data procedures are essential for environmental samples. All persons taking environmental samples should have demonstrated a clear understanding of procedures and have documented field training.

If possible, offsite environmental sample data collection should be done by an independent offsite group. It is also preferable that routine environmental samples be taken by the same offsite group, so that the valuable onsite group may be used for other data collection during an accident.

It is notable that during the Three Mile Island accident every single environmental sample that should have been taken was collected, and not one environmental sample was lost. This occurred even though the sampling rate increased by a factor of more than ten over pre-accident sampling rates.

Emergency monitoring equipment

The inventory of emergency monitoring equipment should be at least double that needed at any given time. Lockers should be placed around nuclear complexes in various places so that no one accident will deny access to all of these lockers. To ensure readiness, equipment should be inventoried and its calibration checked at least twice a year and after each drill. Vans and trucks at large nuclear facilities should be completely outfitted for both on and offsite emergency surveillance.

Onsite counting laboratories may be unusable during an emergency. Therefore, prior arrangements must be made for an alternate or a mobile counting laboratory. This is now a requirement for US nuclear power plants (USNRC 1983).

The type and sophistication of environmental monitoring equipment should meet the requirements of attending the nuclear facility’s worst credible accident. Following is a list of typical environmental monitoring equipment required for nuclear power plants:

1. Air sampling equipment should include units which are battery operated for short-term sampling and AC operable with strip chart recorders and alarm capabilities for longer-term surveillance.
2. Liquid sampling equipment should contain continuous samplers. The samplers must be operable in the local environment, no matter how harsh it is.
3. Portable gamma survey meters for implant work should have a maximum range of 100 Gy/h, and separate survey equipment should be able to measure beta radiation up to 100 Gy/h.
4. Onsite, personnel dosimetry must include beta measurement capability, as well as finger thermoluminescent dosimeters (TLDs) (figure 4). Other extremity dosimetry also may be needed. Extra sets of control dosimeters are always needed in emergencies. A portable TLD reader may be needed to link with the station computer via telephone modem in emergency locations. In-house survey teams, such as rescue and repair teams, should have low- and high-range pocket dosimeters as well as pre-set alarm dosimeters. Careful thought must be given to pre-established dose levels for teams that may be in high radiation areas.
5. Supplies of protective clothing should be supplied in emergency locations and in emergency vehicles. Extra back-up protective clothing should be available in case of accidents lasting for an extended period of time.
6. Respiratory protection equipment should be in all emergency lockers and vehicles. Up-to-date lists of respiratory trained personnel should be kept in each of the major emergency equipment storage areas.
7. Mobile vehicles equipped with radios are essential for emergency radiation monitoring survey teams. The location and availability of back-up vehicles must be known.
8. Environmental survey team equipment should be stored in a convenient place, preferably offsite, so that it is always available.
9. Emergency kits should be placed in the Technical Support Center and the Emergency Offsite Facility so that replacement survey teams need not go onsite in order to receive equipment and be deployed.
10. For a severe accident involving the release of radioactive materials into the air, preparations must be in place for the use of helicopters and single-engine airplanes for airborne surveillance.

Figure 4. An industrial radiographer wearing a TLD badge and a ring thermoluminescent dosimeter (optional in the US)

Data analysis

Environmental data analysis during a serious accident should be shifted as soon as possible to an offsite location such as the Emergency Offsite Facility.

Pre-set guidelines about when environmental sample data are to be reported to management must be established. The method and frequency for transfer of environmental sample data to governmental agencies should be agreed upon early in the accident.

Health Physics and Radiochemistry Lessons Learned from the Three Mile Island Accident

Outside consultants were needed to perform the following activities because plant health physicists were fully occupied by other duties during the early hours of the 28 March 1979 Three Mile Island accident:

• radioactive effluent release assessment (gaseous and liquid), including sample collection, coordination of laboratories for sample counting, quality control of laboratories, data collection, data analysis, report generation, distribution of data to government agencies and power plant owner
• dose assessment, including suspected and actual overexposure investigations, skin contamination and internal deposition investigations, significant exposure mock-ups, and dose calculations
• radiological environmental monitoring programme, including complete coordination of sample taking, data analysis, report generation and distribution, action-point notifications, expansion of programme for the accident situation and then contraction of the programme for up to one year after the accident
• special beta dosimetry studies, including studies of the state of the art in beta personnel monitoring, modelling of the beta dose to skin from radioactive contaminants, inter-comparisons of all commercially available beta-gamma TLD personnel dosimetry systems.

The above list includes examples of activities that the typical utility health physics staff cannot adequately accomplish during a serious accident. The Three Mile Island health physics staff was very experienced, knowledgeable and competent. They worked 15 to 20 hours per day for the first two weeks of the accident without a break. Yet, additional requirements caused by the accident were so numerous that they were unable to perform many important routine tasks that ordinarily would be performed easily.

Lessons learned from the Three Mile Island accident include:

Auxiliary building entry during accident

1. All entries must be on a new radiation work permit reviewed by the senior health physicist onsite and signed by the unit superintendent or designated alternate.
2. The appropriate control room should have absolute control over all Auxiliary and Fuel Handling Building entries. No entries must be allowed unless a health physicist is at the control point during the entry.
3. No entries without a properly operating survey meter of appropriate range should be allowed. A spot check of meter response should be performed immediately prior to entry.
4. Exposure history for all persons prior to their entry into a high radiation area must be obtained.
5. Allowable exposures during entry, no matter how important the task should be designated.

Primary coolant sampling during accident

1. All samples to be taken on a new radiation work permit should be reviewed by the senior health physicist onsite and signed by the unit superintendent or alternate.
2. No coolant samples should be taken unless an extremity dosimeter is worn.
3. No coolant samples should be taken without the availability of shielded gloves and tongs at least 60 cm long in case a sample is more radioactive than expected.
4. No coolant samples should be taken without a leaded-glass personnel shield in place in case a sample is more radioactive than expected.
5. Sample-taking should be discontinued if the exposure to an extremity or to the whole-body is likely to exceed pre-set levels stated on the radiation work permit.
6. Significant exposures should be distributed among a number of workers if possible.
7. All cases of skin contamination in excess of action levels within 24 hours should be reviewed.

Make-up valve room entry

1. Beta and gamma area surveys using remote detectors with appropriate maximum range must be performed.
2. Initial entry in an area with an absorbed dose rate of more than 20 mGy/h must have prior review to verify that exposure to radiation will be kept as low as reasonably achievable.
3. When water leaks are suspected, possible floor contamination should be detected.
4. A consistent programme for type and placement of personnel dosimetry must be put into operation.
5. With persons entering an area with an absorbed dose rate of more than 20 mGy/h, TLDs must be assessed immediately after exit.
6. It should be verified that all radiation work permit requirements are being carried out prior to entry into an area with an absorbed dose rate of more than 20 mGy/h.
7. Controlled-time entries into hazardous areas must be timed by a health physicist.

Protective actions and offsite environmental surveillance from the local government’s perspective

1. Before beginning a sampling protocol, criteria for stopping it should be established.
2. Outside interference should not be allowed.
3. Several confidential telephone lines should be in place. The numbers should be changed after each crisis.
4. The capabilities of aerial measuring systems are better than most people think they are.
5. A tape recorder should be in hand and data recorded regularly.
6. While the acute episode is in progress, the reading of newspapers, watching television and listening to the radio should be abandoned as these activities only add to existing tensions.
7. Food delivery and other comforts such as sleeping facilities should be planned for as it may be impossible to go home for a while.
8. Alternate analytic capabilities should be planned for. Even a small accident can alter laboratory background radiation levels significantly.
9. It should be noted that more energy will be expended in heading off unsound decisions than in dealing with real problems.
10. It should be understood that emergencies cannot be managed from remote locations.
11. It should be noted that protective action recommendations are not amenable to committee vote.
12. All non-essential calls should be put on hold, time-wasters are to be hung up on.

The Goiânia Radiological Accident of 1985

A 51 TBq ¹³⁷Cs teletherapy unit was stolen from an abandoned clinic in Goiânia, Brazil, on or around 13 September 1985. Two people looking for scrap metal took home the source assembly of the teletherapy unit and attempted to disassemble the parts. The absorbed dose rate from the source assembly was about 46 Gy/h at 1 m. They did not understand the meaning of the three-bladed radiation symbol on the source capsule.

The source capsule ruptured during disassembly. Highly soluble caesium-137 chloride (¹³⁷CsCl) powder was disbursed throughout a part of this city of 1,000,000 people and caused one of the most serious sealed source accidents in history.

After the disassembly, remnants of the source assembly were sold to a junk dealer. He discovered that the ¹³⁷CsCl powder glowed in the dark with a blue colour (presumably, this was Cerenkov radiation). He thought that the powder could be a gemstone or even supernatural. Many friends and relatives came to see the “wonderful” glow. Portions of the source were given to a number of families. This process continued for about five days. By this time a number of people had developed gastro-intestinal syndrome symptoms from radiation exposure.

Patients who went to the hospital with severe gastro-intestinal disorders were misdiagnosed as having allergic reactions to something they ate. A patient who had severe skin effects from handling the source was suspected of having some tropical skin disease and was sent to the Tropical Disease Hospital.

This tragic sequence of events continued undetected by knowledgeable personnel for about two weeks. Many people rubbed the ¹³⁷CsCl powder on their skins so that they could glow blue. The sequence might have continued much longer except that one of the irradiated persons finally connected the illnesses with the source capsule. She took the remnants of the ¹³⁷CsCl source on a bus to the Public Health Department in Goiânia where she left it. A visiting medical physicist surveyed the source the next day. He took actions on his own initiative to evacuate two junkyard areas and to inform authorities. The speed and overall size of response of the Brazilian government, once it became aware of the accident, were impressive.

About 249 people were contaminated. Fifty-four were hospitalized. Four people died, one of whom was a six-year-old girl who received an internal dose of about 4 Gy from ingesting about 1 GBq (10⁹ Bq) of ¹³⁷Cs.

Response to the accident

The objectives of the initial response phase were to:

• identify the main sites of contamination
• evacuate residences where levels of radioactivity exceeded the intervention levels adopted
• establish health physics controls around these areas, preventing access where necessary
• identify persons who had incurred significant doses or were contaminated.

The medical team initially:

• upon its arrival in Goiânia, took histories and triaged according to acute radiation syndrome symptoms
• sent all acute radiation patients to Goiânia Hospital (which was set up in advance for contamination and exposure control)
• transferred by air the next day the six most critical patients to the tertiary care center at a naval hospital in Rio de Janeiro (later eight more patients were transferred to this hospital)
• made arrangements for cytogenetic radiation dosimetry
• based medical management on each patient on that patient’s clinical course
• gave informal instruction to clinical laboratory staff to diminish their fears (the Goiânia medical community was reluctant to help).

Health physicists:

• assisted physicians in radiation dosimetry, bioassay and skin decontamination
• coordinated and interpreted analysis of 4,000 urine and faecal samples in a four-month period
• whole-body counted 600 individuals
• coordinated radio-contamination monitoring of 112,000 individuals (249 were contaminated)
• performed aerial survey of entire city and suburbs utilizing hastily assembled NaI detectors
• performed auto-mounted NaI detector surveys of over 2,000 km of roads
• set up action levels for decontamination of people, buildings, autos, soil and so on
• coordinated 550 workers employed in decontamination efforts
• coordinated demolition of seven houses and decontamination of 85 houses
• coordinated hauling of 275 truckloads of contaminated waste
• coordinated decontamination of 50 vehicles
• coordinated packaging of 3,500 cubic metres of contaminated waste
• utilized 55 survey meters, 23 contamination monitors and 450 self-reading dosimeters.

Results

Acute radiation syndrome patients

Four patients died as a result of absorbed doses ranging from 4 to 6 Gy. Two patients exhibited severe bone marrow depression, but lived in spite of absorbed doses of 6.2 and 7.1 Gy (cytogenetic estimate). Four patients survived with estimated absorbed doses from 2.5 to 4 Gy.

Radiation-induced skin injury

Nineteen of twenty hospitalized patients had radiation-induced skin injuries, which started with swelling and blistering. These lesions later ruptured and secreted fluid. Ten of the nineteen skin injuries developed deep lesions about four to five weeks after irradiation. These deep lesions were indicative of significant gamma exposure of deeper tissues.

All skin lesions were contaminated with ¹³⁷Cs, with absorbed dose rates up to 15 mGy/h.

The six-year-old girl who ingested 1 TBq of ¹³⁷Cs (and who died one month later) had generalized skin contamination that averaged 3 mGy/h.

One patient required an amputation about a month after exposure. Blood-pool imaging was useful in determining the demarcation between injured and normal arterioles.

Internal contamination result

Statistical tests showed no significant differences between body burdens determined by whole body counting as opposed to those determined by urinary excretion data.

Models that related bioassay data with intakes and body burden were validated. These models were also applicable for different age groups.

Prussian Blue was useful in promoting the elimination of ¹³⁷CsCl from the body (if dosage was greater than 3 Gy/d).

Seventeen patients received diuretics for the elimination of ¹³⁷CsCl body burdens. These diuretics were ineffective in de-corporating ¹³⁷Cs and their use was stopped.

Skin decontamination

Skin decontamination using soap and water, acetic acid, and titanium dioxide (TiO₂) was performed on all patients. This decontamination was only partly successful. It was surmised that sweating resulted in recontaminating the skin from the ¹³⁷Cs body burden.

Contaminated skin lesions are very difficult to decontaminate. Sloughing of necrotic skin significantly reduced contamination levels.

Follow-up study on cytogenetic analysis dose assessment

Frequency of aberrations in lymphocytes at different times after the accident followed three main patterns:

In two cases the frequencies of incidence of aberrations remained constant up to one month after the accident and declined to about 30^% of the initial frequency three months later.

In two cases a gradual decrease of about 20^% every three months was found.

In two of the cases of highest internal contamination there were increases in the frequency of incidence of aberrations (by about 50^% and 100^%) over a three-month period.

Follow-up studies on ¹³⁷Cs body burdens

• Patients’ actual committed doses followed by bioassay.
• Effects of Prussian Blue administration followed.
• In vivo measurements for 20 people made on blood samples, wounds and organs to look for non-homogenous distribution of ¹³⁷Cs and its retention in body tissues.
• A woman and her newborn baby studied to look for retention and transfer by nursing.

Action levels for intervention

House evacuation was recommended for absorbed dose rates greater than 10 μGy/h at 1 m height inside the house.

Remedial decontamination of property, clothing, soil and food was based on a person not exceeding 5 mGy in a year. Applying this criterion for different pathways resulted in decontaminating the inside of a house if the absorbed dose could exceed 1 mGy in a year and decontaminating soil if the absorbed dose rate could exceed 4 mGy in a year (3 mGy from external radiation and 1 mGy from internal radiation).

The Chernobyl Nuclear Power Reactor Unit 4 Accident of 1986

General description of the accident

The world’s worst nuclear power reactor accident occurred on 26 April 1986 during a very low-powered electrical engineering test. In order to perform this test, a number of safety systems were switched off or blocked.

This unit was a model RBMK-1000, the type of reactor that produced about 65^% of all nuclear power generated in the USSR. It was a graphite-moderated, boiling-water reactor that generated 1,000 MW of electricity (MWe). The RBMK-1000 does not have a pressure-tested containment building and is not commonly built in most countries.

The reactor went prompt critical and produced a series of steam explosions. The explosions blew off the entire top of the reactor, destroyed the thin structure covering the reactor, and started a series of fires on the thick asphalt roofs of units 3 and 4. Radioactive releases lasted for ten days, and 31 people died. The USSR delegation to the International Atomic Energy Agency studied the accident. They stated that the Chernobyl Unit 4 RBMK experiments that caused the accident had not received required approval and that the written rules on reactor safety measures were inadequate. The delegation further stated, “The staff involved were not adequately prepared for the tests and were not aware of the possible dangers.” This series of tests created the conditions for the emergency situation and led to a reactor accident which most believed could never occur.

Release of Chernobyl Unit 4 accident fission products

Total activity released

Roughly 1,900 PBq of fission products and fuel (which together were labelled corium by the Three Mile Island Accident Recovery Team) were released over the ten days that it took to put out all the fires and seal off Unit 4 with a neutron absorbing shielding material. Unit 4 is now a permanently sealed steel and concrete sarcophagus that properly contains the residual corium in and around the remains of the destroyed reactor core.

Twenty-five per cent of the 1,900 PBq was released on the first day of the accident. The rest was released during the next nine days.

The most radiologically significant releases were 270 PBq of ¹³¹I, 8.1 PBq of ⁹⁰Sr and 37 PBq of ¹³⁷Cs. This can be compared with the Three Mile Island accident, which released 7.4 TBq of ¹³¹I and no measurable ⁹⁰Sr or ¹³⁷Cs.

Environmental dispersion of radioactive materials

The first releases went in a generally northern direction, but subsequent releases went toward the westerly and southwesterly directions. The first plume arrived in Sweden and Finland on 27 April. Nuclear power plant radiological environmental monitoring programmes immediately discovered the release and alerted the world about the accident. Part of this first plume drifted into Poland and East Germany. Subsequent plumes swept into eastern and central Europe on 29 and 30 April. After this, the United Kingdom saw Chernobyl releases on 2 May, followed by Japan and China on 4 May, India on 5 May and Canada and the US on 5 and 6 May. The southern hemisphere did not report detecting this plume.

The deposition of the plume was governed mostly by precipitation. The fallout pattern of the major radionuclides (¹³¹I, ¹³⁷Cs, ¹³⁴Cs, and ⁹⁰Sr) was highly variable, even within the USSR. The major risk came from external irradiation from surface deposition, as well as from ingestion of contaminated food.

Radiological consequences of the Chernobyl Unit 4 accident

General acute health consequences

Two persons died immediately, one during the building collapse and one 5.5 hours later from thermal burns. An additional 28 of the reactor’s staff and fire-fighting crew died from radiation injuries. Radiation doses to the offsite population were below levels that can cause immediate radiation effects.

The Chernobyl accident almost doubled the worldwide total of deaths due to radiation accidents through 1986 (from 32 to 61). (It is interesting to note that the three dead from the SL-1 reactor accident in the US are listed as due to a steam explosion and that the first two to die at Chernobyl are also not listed as radiation accident deaths.)

Factors which influenced onsite health consequences of the accident

Personnel dosimetry for the onsite persons at highest risk was not available. The absence of nausea or vomiting for the first six hours after exposure reliably indicated those patients who had received less than potentially fatal absorbed doses. This also was a good indication of patients who did not require immediate medical attention because of radiation exposure. This information together with blood data (decrease in lymphocyte count) was more useful than personnel dosimetry data.

Fire-fighters’ heavy protective garments (a porous canvas) allowed high specific activity fission products to contact bare skin. These beta doses caused severe skin burns and were a significant factor in many of the deaths. Fifty-six workers received severe skin burns. The burns were extremely difficult to treat and were a serious complicating element. They made it impossible to decontaminate the patients prior to transport to hospitals.

There were no clinically significant internal radioactive material body burdens at this time. Only two people had high (but not clinically significant) body burdens.

Of the about 1,000 people screened, 115 were hospitalized due to acute radiation syndrome. Eight medical attendants working onsite incurred the acute radiation syndrome.

As expected, there was no evidence of neutron exposure. (The test looks for sodium-24 (²⁴Na) in blood.)

Factors which influenced offsite health consequences of the accident

Public protective actions can be divided into four distinct periods.

1. The first 24 h: The downwind public remained indoors with doors and windows shut. Distribution of potassium iodide (KI) began in order to block thyroid uptake of ¹³¹I.
2. One to seven days: Pripyat was evacuated after safe evacuation routes were established. Decontamination stations were established. The Kiev region was evacuated. The total number of people evacuated was more than 88,000.
3. One to six weeks: The total number of evacuated people rose to 115,000. All these were medically examined and resettled. Potassium iodide was administered to 5.4 million Russians, including 1.7 million children. Thyroid doses were reduced by about 80 to 90^%. Tens of thousands of cattle were removed from contaminated areas. Local milk and foodstuffs were banned over a large area (as dictated by derived intervention levels).
4. After 6 weeks: The 30 km radius circle of evacuation was divided into three sub-zones: (a) a zone of 4 to 5 km where no public re-entry is expected in the foreseeable future, (b) a 5 to 10 km zone where limited public re-entry will be allowed after a specific time and (c) a 10 to 30 km zone where the public will eventually be allowed to return.

A great effort has been expended in decontaminating offsite areas.

The total radiological dose to the USSR population was reported by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) to be 226,000 person-Sv (72,000 person-Sv committed during the first year). The worldwide estimated collective dose equivalent is on the order of 600,000 person-Sv. Time and further study will refine this estimate (UNSCEAR 1988).

International Organizations

International Atomic Energy Agency

P.O. Box 100

A-1400 Vienna

AUSTRIA

International Commission on Radiation Units and Measurements

7910 Woodmont Avenue

Bethesda, Maryland 20814

U.S.A.

International Commission on Radiological Protection

P.O. Box No. 35

Didcot, Oxfordshire

OX11 0RJ

U.K.

International Radiation Protection Association

Eindhoven University of Technology

P.O. Box 662

5600 AR Eindhoven

NETHERLANDS

United Nations Committee on the Effects of Atomic Radiation

BERNAM ASSOCIATES

4611-F Assembly Drive

Lanham, Maryland 20706-4391

U.S.A.

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