Dose limits, radiation

1 Radiation Dose Limits. For routine exposure of individual members of the public to all man-made sources of radiation combined (i.e., excluding exposures due to natural background, indoor radon, and deliberate medical practices), NCRP currently recommends that the annual effective dose should not exceed 1 mSv for continuous or frequent exposure or 5 mSv for infrequent exposure. The quantity effective dose is a weighted sum of equivalent doses to specified organs and tissues (ICRP, 1991), which is intended to be proportional to the probability of a stochastic response for any uniform or nonuniform irradiations of the body (see Section 3.2.2.3.3). 

The recommended dose limits for the public define limits on the probability of stochastic responses that are regarded as necessary for protection of public health. Doses above the limits are regarded as intolerable and normally must be reduced regardless of cost or other circumstances, except in the case of accidents or emergencies (see Section 3.3.1). For continuous exposure over a 70 y lifetime, and assuming a nominal probability coefficient for fatal cancers (i.e., the probability of a fatal cancer per unit effective dose) of 5 X 10 2 Sv 1 (ICRP, 1991 NCRP, 1993a), the dose limit for continuous exposure corresponds to an estimated lifetime fatal cancer risk of about 4 X 10 3. However, meeting the dose limits is not sufficient to ensure that routine exposures of the public to man-made sources would be acceptable. 

NCRP (1993a) also has emphasized the importance of source constraints in radiation protection of the public. NCRP has reaffirmed a previous recommendation (NCRP, 1984b 1987a) that whenever the potential exists for routine exposure of an individual member of the public to exceed 25 percent of the limit on annual effective dose as a result of irradiation attributable to a single site, the site operator should ensure that the annual effective dose to the maximally exposed individual from all man-made sources combined does not exceed 1 mSv on a continuous basis. Alternatively, if such an assessment is not conducted, no single source or set of sources under one control should result in an individual receiving an annual effective dose of more than 0.25 mSv. 

The recommended limit on annual effective dose of 0.25 mSv per source corresponds to an estimated lifetime fatal cancer risk of about 

1 X 10 3. Annual effective doses in the range of 0.25 to 1 mSv from all man-made sources combined are acceptable if they are ALARA. However, doses toward the upper end of this range are regarded as only barely tolerable (ICRP, 1991), and doses below this range are expected to be justifiable and achievable in most cases, based on site-specific application of the ALARA principle. Therefore, lifetime risks from routine exposure to all man-made sources combined usually should not exceed about 1 X 10 3. 

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Radiation dose limits at a disposal site boundary are specified by the NRC as 25 x 10 Sv/yr (25 mrem/yr), a small fraction of the average radiation exposure of a person in the United States of 360 x 10 /Sv/yr (360 mrem/yr). Protection against nuclear radiation is fully described elsewhere... 

Is the employer using means other than employee rotation to eomply with permissible exposure limits (PELs) or ionizing radiation dose limits, exeept where no other feasible way exists [OSHA Referenee. 120(g)(l)(iii)]... 

Review of NCRP Radiation Dose Limit for Embryo and Fetus... 

Owen, R. L., Rudino-Pmera, E. and Carman, E. F. (2006). Experimental determination of the radiation dose limit for cryocooled protein crystals. PNAS 103, 4912-4917. 

Critical Issues in Setting Radiation Dose Limits, Proceed-... 

James F. Crow (1981) [Available also in Critical Issues in Setting Radiation Dose Limits, see above]... 

For the purpose of developing a risk-based hazardous waste classification system, prevention of deterministic responses should be of concern only for hazardous chemicals, but not for radionuclides. Deterministic responses from exposure to radionuclides can be ignored because radiation dose limits for the public intended to limit the occurrence of stochastic responses are sufficiently low that the doses in any organ or tissue would be well below the thresholds for deterministic responses (see Section 3.2.2.1). 

Dose burdens on personnel as a result of gamma radiation during SNF unloading from Victor II Submarine will not exceed 2-3 mSv. It is 10-15% from accepted radiation dose limit for category A persons. 

The annual radiation dose limit to (a) the declared pregnant woman during the gestation period is (b) to the minor and (c)... 

Standards for protection against radiation—dose limits for individual members of the public Total effective dose equivalent to individual 0.1 rem/year NRC 2001q 10CFR20.1301... 

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. 

Most studies have dealt exclusively with vitreous silica, which compacts by only a few hundred ppm at doses as great as 10 rad. Some commercial borosilicate glasses compact up to 40 times as much as vitreous silica for comparable radiation doses. Limited data for alkaline earth aluminosilicate glasses suggests that they expand slightly under these same conditions. 

The basic purposes of safety analysis are to assist in the design of safety-related systems, and then to confirm that the radiation dose limits are met. As such, safety analysis requires predictions of the consequences of hypothetical accidents. 

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 ... 

The external and internal doses are then summed to evaluate compliance with the radiation dose limits. Table 25.1 lists these limits. For the general public, there is an additional dose limit for unrestricted areas that requires that the dose received in any 1 h must be <0.002 rem. This limit is not a dose "rate" but a limit. The 0.002 rem could be reached in 1 min, a "rate" of 0.120 rem/h, but if no other dose is received in the remainder of the hour, then the limit has not been exceeded. This requirement is worded... 

Annual Radiation Dose Limits for Various Populations According to Different Agencies... 

Regulatory dose limits are set by international, federal, and state agencies for the general public and occupational exposure to limit cancer risk (Table 4.7). Other radiation dose limits are applied to potential specific biological effects with workers skin and lens of the eye that will not be elaborated here. 

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