Regulations, radiation dose limits

NRC. 1997. Radiation dose limits for individual members of the public. U.S. Nuclear Regulatory Commission. Code of Federal Regulations. 10 CFR 20, Subpart D. 

As stated earlier, the purpose of health physics is to control the radiation dose to people, including workers, both the power plant operators and subcontractors, and also members of the public. The governing regulations are Title 10 Part 20 of the Code of Federal Regulations, or 10 CFR 20. In 10 CFR 20, the U.S. Nuclear Regulatory Commission (USNRC) has set radiation dose limits for various categories of individuals. These categories are as follows ... 

In the United States, the current federal radiation protection guidance (EPA, 1987) and associated implementing regulations (NRC, 1991 DOE, 1993) include dose limits expressed as effective dose equivalent (Hf). The current National Council on Radiation Protection and Measurements (NCRP) radiation protection recommendations (NCRP, 1993) include dose limits expressed as effective dose (E). To monitor compliance with such dose limits correctly and fairly, practical monitoring data must be related to or E. 

This Report is one of the series developed under the auspices of Scientific Committee 46, a scientific program area committee of the National Council on Radiation Protection and Measurements (NCRP) concerned with operational radiation safety. The Report provides practical recommendations on the use of personal monitors to estimate effective dose equivalent (Hg) and effective dose (E) for occupationally-exposed individuals. The Report is limited to external exposures to low-LET radiation. Recent additions to the radiation protection literature have made the recommendations possible. In order to avoid delay in utilizing the recommendations in the United States, the quantity as well as E, has been included until such time as the federal radiation protection guidance and associated implementing regulations are revised to express dose limits in E as recommended by the NCRP. 

NRC regulations described above represent a case-by-case approach to establishing exemption levels for radioactive material. Although the various exemption levels are expected to correspond to low doses from use and disposal of materials compared, for example, with dose limits in radiation protection standards for the public... 

Current federal and state regulations limit radiation workers doses to a total effective dose equivalent (TEDE) of 5 rem/year and a committed dose equivalent to any organ, other than the lens of the eye, of 50 rem/year (EPA 1988c USNRC 1995a). These limits apply to the sum of external and internal doses. The limits are upper limits, and an important philosophy in radiahon protection is to keep radiation doses as low as reasonably achievable (ALARA). 

Authorized limits are limits specified by the regulating authority for a specific practice or source. In setting limits the authority must consider the requirements of radiation protection and individual dose limitation. The authorized limits will not exceed the upper bound. For practical reasons limits for releases of radioactive effluents to the environment are expressed as limits of releases over a specified period. 

Many of the recommendations of the ICRP and other radiation protection groups regarding radiation exposure have been incorporated into regulatory requirements by various countries. For the U.S. Department of Energy facilities, radiation exposure limits are found in Title 10, Part 835 of the Code of Federal Regulations (10CFR835). Table 3.1 provides a summary of the dose limits for occupational external exposures. 

Although regulations allow an annual maximum permissible dose to radiation workers, one should make considerable efforts to adopt strict protective measures in working with radiations so as to reduce the radiation dose as low as reasonably achievable (ALARA). Under this concept, techniques, equipment, and procedures are critically evaluated and adopted to minimize the radiation dose to the worker. The NRC has set two goals for a radiation worker to achieve 10% of the occupational dose per quarter (Action level I) and 30% of the occupational dose per quarter (Action level II). If these limits are exceeded, corrective action must be taken or higher limits must be justified for a particular situation. The principles of radiation protection described later should be followed strictly to achieve ALARA compliance. 

In the field of radiation safety, the basic document by which the health and inspection protection bodies are guided is Radiation safety standards (RSS-76). These standards were worked out on the basis of recommendations of the International Commission on Radiological Protection (ICRP) and establish the system of dose-limits and principles of their application. The health regulations for design and operation of nuclear power plants, issued in 1978, further develop and specify the basic RSS-76 document to include siting, monitoring, and inspection problems. 

While such doses would no longer be acceptable, the adequacy of the current radiation level limits, in terms of radiological safety, has been confirmed by a number of surveys where radiation exposure of transport workers has been determined [29-32] and by an assessment performed by the IAEA in 1985 [33]. However, it is recognized that the permitted radiation levels around packages and conveyances do not alone ensure acceptably low doses, and the Regulations also require the establishment of radiation protection programmes (para. 301) and the periodic assessment of radiation doses to persons due to the transport of radioactive material (para. 304). 

The approach to the MBRU-12 safety design is based on the concept of retaining radionuclides in the fuel during normal operation and in emergency modes, so that radiation impact on personnel and in the NPP area is within the allowable limits, hi this, the dose limits for the MBRU-12 design are set well below the current regulations. 

Ionising radiation occurs naturally as well as from man-made processes and about 87% of all radiation exposure is from natural sources. The Ionising Radiations Regulations 1999 specify a range of dose limits, some of which are given in Table 17.8. 

The main aim of the Regulations and the supporting ACoP is to establish a framework for ensuring that exposure to ionising radiation arising from work activities, whether from man-made or natural radiation and from external radiation (e.g. X-ray set) or Internal radiation (e.g. inhalation of a radioactive substance), is kept as low as reasonably practicable and does not exceed dose limits specified for Individuals. IRR99 also ... 

Nuclear Regulatory Conmission Standards for Protection Against Radiation (10 CFR 20) 1 These regulations apply to activities licensed by the Nuclear Regulatory Commission and specify radiation dose standards for individuals in restricted and unrestricted areas. (See Table 2 for emission concentration limits.) Relevant and appropriate standards for the emission of specific radionuclides. Managing remediation activities in a manner to ensure emission standards are not exceeded. Monitoring remediation activities in a manner to verify emission standards are not exceeded. 1 2 3 4 o i 1— 0 5. VO SC X9 vO (P O - ... 

The Nil SAPs (Reference 12.3) assign levels and objectives for radiation doses to individuals and groups these are the basic safety levels (BSLs) and the basic safety objectives (BSOs), respectively. These encompass the legal limits defined in the Ionising Radiation Regulations. Between the BSL and the BSO, designers and operators, need to justify that the dose is ALARP. The ALARP principle will be applied below the BSO. 

All requirements of the regulations concerning nuclear, radiological and technical safety are met. The annual radiation dose to an individual of the local population at a distance of 3 km during normal operation of the plant away will not exceed 0.004 mSv, which is much lower than the limit set in Russia and is quite n igible compared with the natural radiation background (less than 0.2%). The assessed value of the frequency of severe core-disruptive accidents for BN-800 is less than lxE-6 per reactor-year. The probability of a radioactivity release corresponding to the limit for severe accidents is not more than l.E-8 per reactor-year. 

---