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--> 3 Standard Practices in Civilian Radiation Protection To determine whether the NATO guidance embodied in the ACE Directive adequately follows generally accepted practices of radiation protection, we must first review standard practice. At the foundation of any system is an underlying philosophy, however implicit it may be. The international basis of radiation protection practice has been developed explicitly by the International Commission on Radiological Protection (ICRP). This has been considered and adapted for use in the United States by the National Council on Radiation Protection and Measurements (NCRP). Based on their own needs and the recommendations of these bodies, various U.S. federal agencies, such as the Nuclear Regulatory Commission and the Environmental Protection Agency, develop specific implementing regulations. In this section we summarize the current radiation protection philosophy in the United States. We will then use this as a yardstick against which to compare the ACE Directive. Control Philosophy The philosophy of radiation protection has to include social as well as scientific judgments in order to provide an appropriate standard of protection without unduly limiting practices. The overall aim of radiation protection, regardless of the specifics of the situation leading to exposure, is to prevent the occurrence of acute effects (e.g., cataracts in the eyes, radiation bums, and acute radiation sickness) and ensure that all reasonable steps are taken to reduce the potential long-term effects, such as cancer (ICRP, 1991a), to a level that is acceptable to
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--> society. The methods applied to achieve that aim will vary, depending upon the radiation exposure scenario. The two types that we will address are practices (routine and potential), and interventions. The first of these, the practice, is an intentional activity in which the practitioner is routinely at risk of exposure. Workers who are exposed to radiation during the course of their duties include, for example, x-ray technicians in hospitals, nuclear power plant workers, and researchers who use radioactive materials. The practices in which they engage include taking x rays of patients, running a nuclear reactor, or making measurements using radioactive sources. These occupationally exposed individuals are trained to appreciate the hazards of radiation, acknowledge those risks as a condition of employment, and follow safety precautions in order to minimize their exposure. Any practice may have exposures that do not routinely occur (such as accidents). If these have not yet happened, they are called potential exposures. Both the probability of such events happening and the magnitude of expected radiation doses can be calculated in planning responses. These also should be considered in the introduction and management of new practices. If an accident actually happens, interventions are taken to reduce exposure. An intervention is an action that one takes to reduce a radiation exposure (often to other individuals or groups) from specific radiation sources by (ICRP, 1993): reducing or removing the existing sources, improving the reliability of the existing sources, modifying pathways,7 or reducing the number of exposed individuals. An example of an intervention would be the response of the firefighters who fought to control the fire in the Chernobyl nuclear reactor accident. Often an intervention is associated with an emergency action. To distinguish practice from intervention, it is helpful to consider that prior to the accident, the Chernobyl workers were engaged in a practice—production of electric power for the Ukraine. The workers in the plant were operating under a radiation protection program required for a practice, which included management's option of discontinuing or changing the practice to eliminate or reduce radiation exposure. The firefighters who responded after the accident were operating under different rules and exposure criteria—those intended for an intervention situation. 7 Pathways are the routes by which radiation gets to the exposed individual (e.g., contaminated foodstuffs or radionuclides carried by the wind).
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--> In both practices and interventions, one applies three basic principles: justification, optimization/ALARA,8 and limits or reference levels. Radiation exposure is generally considered as something to be avoided, at least unless there is a good reason that justifies it. As mentioned in the introduction, effects of radiation at low doses (less than 50 mSv) have not been observed in humans. However, because of the uncertainty surrounding low-dose effects, most radiation protection philosophy presumes that even small radiation doses may produce some deleterious effects. For that reason, the first principle of radiation protection is justification: All practices that involve exposure should produce a benefit that outweighs the potential harm from radiation (ICRP, 1991a). As an example of justification, consider the use of medical x rays. Technicians may receive small doses of radiation and potentially some harm, but the greater good provided to patients by the diagnostic x ray is enormous, hence the practice is justified. Justification is essential in developing radiation protection for practices and interventions and also will be applied in planning for potential exposures. Once an activity involving exposure has been justified, one must then Minimize the exposure that will result from that action. Optimization is the word used by ICRP to describe that minimization process. An activity is optimized when the resulting dose is reduced to a level that is ''as low as is reasonably achievable (ALARA), economic and social factors having been taken into account'' (ICRP, 1991a). Finally, even when a practice is justified and has been optimized, there are limits above which people should not routinely be exposed. Dose limits, when observed, prevent individuals from acquiring doses that are clearly unacceptable. This could happen in a poorly controlled occupational situation involving radiation. Dose limits apply only to practices. For interventions—where the primary goal is to accomplish the emergency action—dose limits are not used. Neither are dose limits applicable in planning for potential exposures. When the potential is realized—such as in an accident—the response is often an intervention rather than a practice. In the case of a postaccident intervention, application of an occupational dose limit could prevent emergency workers from performing critical actions necessary to limit great harm to a large population. Dose limits do not apply to (or include) natural 8 ALARA is an acronym that conveys the principle that "In relation to any particular source within a practice, the magnitude of individual doses, the number of people exposed, and the likelihood of incurring [radiation] exposures where these are not certain to be received should all be kept as low as reasonably achievable, economic and social factors being taken into account" (ICRP, 1991a, para 112(b)).
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--> background radiation. Nor do they apply to patients undergoing medical procedures that involve radiation exposure. Thus far, we have discussed radiation protection principles without regard to the population that is being protected. Although the principles apply to anyone, the implementation depends on the circumstances under which one is exposed. Workers who are exposed to radiation as a consequence of their employment choose to accept that exposure and the practice of protection as conditions of employment. Members of the general public may also be exposed to radiation sources (e.g., while waiting in a radiology clinic or a cancer therapy department). Unlike occupational workers, however, the general public does not receive direct compensation in return for their exposure, nor do they formally accept the risk of exposure. Because of that, limits for exposures are lower for these groups. Occupational doses are currently limited (CFR, 1991) to 50 mSv per year, whereas exposures to the general public are limited to one fiftieth of that—1 mSv per year (approximately the same as the annual background dose from sources excluding radon) (NCRP, 1987). While both these limits apply to both males and females, more stringent limits (5 mSv, which is 10 times lower than the usual worker limit) apply to a fetus during gestation.9 By contrast, dose limit guidance for an adult acting to save valuable property during an emergency is set much higher (100 mSv, EPA, 1991). Dose limits can easily be misinterpreted. They are not intended as demarcations of safety—keeping doses below the limits does not guarantee the absence of increased cancer risk. Dose limits represent, for a defined set of practices, a level of dose above which the consequences for the individual would be widely regarded as unacceptable (ICRP, 1991a). In the current system of radiation protection in the U.S. (CFR, 1991), a continuous annual dose to a worker above the annual limit (50 mSv) is considered unacceptable. Intervening to limit damage after a nuclear accident (urgent action) presents its own set of problems (ICRP, 1991b). People who are in the immediate vicinity may be exposed to radiation levels that can only be estimated after the incident. Those who respond to the situation (firefighters and other emergency workers) may be exposed to doses in excess of the annual U.S. occupational limit of 50 mSv in trying to protect valuable equipment, save lives, or prevent radiation exposure of large populations. In this scenario, the principles of justification and optimization continue to apply. However, since worker exposures may be unpredictable, unknown, and difficult to control in the earliest stages of an accident, dose limits are inappropriate. Nevertheless, ICRP recommends that, where possible, the effective dose to individuals be kept below 1,000 mSv to limit deterministic effects. Where possible, except to save a life, dose to the skin should be limited to 5,000 mSv. Also, intervention levels for sheltering and evacuation, 9 This exposure limit applies only to the fetus of pregnant women who have acknowledged (declared) their pregnancy to their employer. See reference CFR, 1991.
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--> contamination levels for foodstuffs, and procedures for thyroid protection have been recommended by the ICRP (1991b) and the EPA (1991). After the urgent action phase of an accident, additional personnel may assist with evacuation of the local population, provide emergency medical care, or provide security around the accident site. During that phase, justification and at least crude optimization are applied (ICRP, 1991b). The ICRP also recommends that doses be kept within occupational limits, if possible. Finally, once the accident is under control, a recovery period begins, during which the hazard at the site is brought under permanent control. Since this may take an extended period of time, during which the urgency of the situation is diminished, conventional occupational radiation protection controls are appropriate. In summary, radiation protection is based on justification, optimization, and, in the case of routine practices, dose limits. However, it would be terribly inefficient to go through the justification and optimization processes every time a recurring situation arose. For many recurring situations, it may be possible to go through these processes once and define what actions should be taken in response to a set of similar circumstances when a particular level of exposure or dose is exceeded. The resulting reference levels (ICRP, 1991a) take into account justification, optimization, and dose limits in directing radiation protection policy changes, administrative responses, or other actions. Reference levels are fundamentally different from dose limits. Whereas dose limits specify (usually with regulatory authority) a dose level that should not be exceeded during routine operations, reference levels give guidance that certain decisions should be made or certain actions should be taken if or when the level is exceeded. A variety of organizations have recommended dose limits and reference levels (Table 3-1). These are applicable to a number of different populations in a variety of exposure scenarios. The table is by no means an inclusive list but provides comparisons that put radiation exposure into perspective. In addition to the underlying philosophy, radiation protection programs include provisions for actions such as monitoring compliance, recordkeeping, training, health surveillance, and defining the responsibilities of management and governmental authorities.
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--> Table 3-1. Examples of Typical Radiation Doses and Dose Limits or Reference Levels (mSv) Description of level Effective Dose (mSv) Reference Annual background dose to a person living in the United States, excluding radon 1 NCRP, 1987 Typical effective dose from a CT scan 1 NCRP, 1987 Annual limit on exposure of members of the general public 1 ICRP, 1991a One-year continuous exposure at the edge of the "Radiological Hazard Area" as defined by ACE Directive 80-63 20 NATO, 1996 Annual dose limit for radiation workers (averaged over a 5-year period) 20 ICRP, 1991a Lifetime increase in background dose from living in Denver vs. national average 20 IOM, 1995 Limit for emergency services, except lifesaving, protection of valuable property, or protection of large populations 50 EPA, 1991 Annual dose limit for radiation workers 50 CFR,1991 Total background radiation, excluding radon, over a 70-year lifespan 70 NCRP, 1987 Limit for protecting valuable property 100 EPA, 1991 Total background radiation, including radon, over a 70-year lifespan 210 NCRP, 1987 Limit for saving a life 250 EPA, 1991 Limit for volunteers saving a life >250 EPA, 1991 Threshold for deterministic effectsa (e.g., bone marrow depression) 500 ICRP, 1984 Career dose limit for radiation workers 1,000 ICRP, 1991a Astronaut career cumulative dose (female, career beginning at age 25) 1,000 NCRP, 1989 Astronaut career cumulative dose (male, career beginning at age 25) 1,500 NCRP, 1989 NATO Emergency Risk for disaster situations 1,500 HQDA, 1994 Lethal dose (50% mortality in 60 days without treatment) 3,000 Schull, 1995 a That is, not cancer or hereditary effects.
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--> Notification, Training, and Informed Understanding Training is an essential part of all radiation protection programs (NCRP, 1983). It is the mechanism by which those at risk are notified of the likelihood of exposure to radiation and the accompanying risk of adverse effects. Training provides the knowledge by which those at risk can minimize their dose and, therefore, the potential adverse effects on their health. A clear understanding of the risk from radiation in comparison to other competing hazards allows one to weigh various risks to make better informed decisions. A cavalier attitude toward radiation can lead to actions that yield unnecessarily high exposures. Likewise, excessive fear of radiation can produce decisions that trigger more severe risks and consequences than the radiation itself would have occasioned. The degree of training required for an individual depends upon the likelihood and extent of the radiation hazard to which that person may be exposed. For example, annual instruction in radiation safety may be considered sufficient for radiological technicians in a clinical environment as part of a program to keep their doses as low as reasonably achievable. By contrast, workers at a nuclear power plant receive detailed training on radiation exposure reduction techniques every time they conduct special operations in a high radiation area. Recordkeeping Recordkeeping is another essential element of a radiation protection program (ICRP, 1991a). Maintaining records (NCRP, 1992) on exposure serves to: aid in protection of individuals; evaluate the effectiveness of radiation protection programs; provide for accuracy, reliability, confidentiality, and retrievability of data; provide evidence of regulatory compliance; provide data for epidemiologic studies; and provide information for making or contesting claims for radiation-induced injury. Among the records commonly kept on radiation exposures are the following: Program documents record any authorizations and accreditations that allow or regulate the exposure of individuals to radiation (e.g., radioactive material licenses from the USNRC or DoD authorizations to possess radioactive commodities). They also include all documentation necessary to define the radiation protection program that safeguards the health and well-being of workers. Among these records one would find records of training programs, dosimetry procedures, environmental monitoring plans, documentation of efforts to keep exposures ALARA, and so on. Individual records document relevant data on each individual exposed to radiation as part of occupational duties. These include items such as exposure
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--> categories for individuals (e.g., managers who get minimal radiation doses vs. technicians who get larger doses). Also of interest are individual dose records (internal and external), training records, and details of any overexposures, as well as age, gender, and other identification data that allow individuals to be followed in epidemiologic studies. Records should follow the individual as he or she changes employer or work situation. It also is useful to record individual work history and conditions; that allows calculation of accumulated internal dose after an exposure occurs. Workplace records document activities and conditions in the environs of the individual exposures. These records include data on radiation levels in various areas, descriptions of restricted areas, descriptions of activities that require personnel exposures (work permits), records of movements of radioactive materials, data on protective equipment availability and condition, and documentation of accidents and incidents. Environmental records document radiologically significant characteristics of the environment to include results of measurements of radionuclide content of the air, ground, and water. These records can be valuable in reconstructing doses to personnel who may have been exposed during a release of radioactivity. Instrumentation records are maintained to document the availability, calibration, maintenance, and capability of radiation detection and measurement devices. These are used for quality control purposes to ensure the accuracy of radiological measurements.
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