Radiation doses limits for

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. 

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). 

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. 

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. 

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 ... 

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

The optimal dose of radiation therapy for patients with limited stage disease is unknown. Full dose radiation therapy is critical to achieve the therapeutic gain of local tumor control. Effective chemotherapy may allow a decrease in the radiation dose needed for local control (26). In the presence of chemotherapy, the radiation dose theoretically can be reduced 20% to control the tumor. Thus the dose for complete response, approx 70 Gy, can be decreased to 55 Gy (26). Local recurrence is still around 40-50% (27). Retrospective trials revealed that doses less than 40 Gy were not adequate for local control (28). 

NCRP Statement on Dose Limit for Neutrons (National Council on Radiation Protection and Measurements, Washington, 1980) Control of Air Emissions of Radionuclides (National Council on Radiation Protection and Measurements, Bethesda, Maryland, 1984)... 

Based on these differences, the use of RfDs for hazardous chemicals that induce deterministic effects to define acceptable exposures of the public often may be considerably more conservative (provide a substantially larger margin of safety) than the dose limits for radiation induced deterministic effects. The likely degree of conservatism embodied in RfDs has important implications for establishing limits on allowable exposures to substances causing deterministic effects for the purpose of developing a risk-based waste classification system. Dose limits for deterministic effects for radiation should not be important in classifying waste (see Section 3.2.2.1). 

NCRP has recommended that annual effective doses to individuals from any practice or source of 10 p.Sv or less are negligible (see Section 4.1.2.5.3). This dose is one percent of the dose limit for continuous exposure to all man-made sources combined discussed in the previous section, and it also is about one percent of the dose from natural background radiation, excluding radon (NCRP, 1987b). The recommended negligible individual dose corresponds to an estimated lifetime fatal cancer risk of about 4 X 10 5. 

Establishing an acceptable risk or dose. There also are a number of precedents for establishing an acceptable (barely tolerable) risk or dose of substances that cause stochastic responses for the purpose of classifying waste as low-hazard or high-hazard. For radionuclides, the annual dose limit for the public of 1 mSv currently recommended by ICRP (1991) and NCRP (1993a) and contained in current radiation protection standards (DOE, 1990 NRC, 1991) could be applied to hypothetical inadvertent intruders at licensed near-surface disposal facilities for low-hazard waste. This dose corresponds to an estimated lifetime fatal cancer risk of about 4 X 10 3. Alternatively, the limits on concentrations of radionuclides in radioactive waste that is generally acceptable for near-surface disposal,... 

The present distinction between radioactive waste that arises from operations of the nuclear fuel cycle and NARM waste provides an unnecessary impediment to development of a classification system that applies to all radioactive wastes. This distinction is not based on considerations of protection of public health but is based only on the source of the waste. NCRP notes that EPA s proposed guidance on radiation protection of the public (EPA, 1994d) encourages elimination of this legal distinction, because the guidance specifies that dose limits for all sources of radiation exposure combined and authorized limits for individual sources or practices should be applied to essentially all controllable sources, excluding indoor radon, not just to sources associated with the nuclear fuel cycle. 

Some general annual dose limits for exposure to radiation are as follows ... 

Alternatively, a threshold of concern could be assumed for the risk of serious effects, such as cancer and hereditary disease or serious impairment of the intellectual ability (loss of more than 10 IQ points). One option might be that lifetime exposure entails a lifetime risk of 10 in one million of suffering such a serious effect. This is the level of cancer risk associated with the WHO guidelines for drinking water for the sake of comparison, it is about 400 times stricter than the risk for cancer and hereditary disease associated with radiation exposures at the dose limit for the public (ICRP 2008). 

Calculation results of radiation factors analysis show that maximum annual effective radiation dose for population in case of the design-basis accident during Victor II dismantling will not exceed 0.1 mSv. It is considerably less than dose limit for population under normal operational conditions given in Radiation Safety Standards (NRB -99). 

A limit is a value that must not be exceeded and the primary dose limits for individuals are set by the ICRP. These limits are related to individuals irrespective of the source. If an individual is likely to be exposed to other sources of radiation, source related limits must be set by a regulatory authority. These limits must be lower than the dose limit and are called the source upper bound. 

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. 

In this special case, additional approval is needed from the national authorities overseeing radiation safety. For example, in the United Kingdom this is the Administration of Radioactive Substances Advisory Committee (ARSAC). Application to ARSAC only requires a summary of the study protocol, but a careful scientific justification of the amount of radiation employed and the number of subjects exposed. The EU Directive 97/43/EurATOM sets dose limits for healthy subjects and patients. 

The annual occupational effective dose limit for the minor (<18 years working with radiation) is 0.5 rem (5mSv). The occupational dose limit to the embryo/fetus during the entire gestation period of a declared pregnant radiation worker is 0.5 rem (5 mSv) with a monthly limit of 0.05 rem (0.5 mSv). 

The occupational dose limits for radiation workers are effective dose dose to the lens of the eye and dose to extremities... 

Neuroradiologists are familiar with factors that affect patient dose such as pitch, milliamperes (mA), kilovoltage peak (kVp), and collimation, but there are additional ways to further reduce radiation exposure. The combination of low kilovolt peak (80 kVp) with low milliamperes-seconds (no more than 200 mAs) has already been noted and is an accepted strategy for dose reduction [36, 87, 88]. (Tube current is directly proportional to dose, but at a cost of increased noise, which is increased by 1/VmA). In our institution, we recently lowered the mAs of our CTP protocol from 200 to 150 mA resulting in 25% dose reduction, previously estimated at 0.47 Gy (the FDA suggests 0.5 Gy as the upper dose limit for a CTP study). Table 5.4 summarizes the radiation parameters of the sample CTP protocol of Tables 5.2 and 5.3. 

Notes mSv, millisievert as can be seen from the table, the dose limits for the public are much lower than for people who can be exposed to radiation as part of their occupation. Averaged over a defined 5-year period. 

EPA. 1977. Proposed guidance on dose limits for persons exposed to transuranium elements in the general environment. EPA 520/4-77-016. Office of Radiation Programs, Washington, DC. 

The International Commission on Radiological Protection (ICRP) recommends specific limits of dose, applicable to stated time intervals (a quarter, a year, and so forth) as guidance for protection of radiation workers these are called maximum permissible doses and are applicable to individuals exposed continuously or intermittently from time to time as their work requires (40). To assist the planning of nuclear designs and operations so as to minimize, appropriately, the low level exposure of members of the public which may ordinarily result from normal operations, dose limits for individual members of the public are recommended by ICRP which are one-tenth or less of the maximum permissible doses for radiation workers. Though these maximum permissible doses and dose limits have little to do directly with the control of major radiation emergencies (i.e., reactor accidents) they are quoted in brief in Table VII. 

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. 

Occupationally exposed individuals are commonly known as "rad workers" and the training courses one takes to become a rad worker are usually referred to as "rad worker I" and "rad worker II" depending on the level of training provided. To be considered an occupationally exposed individual, a worker s job duties must involve exposure to radiation or a radioactive material. They must also be trained as required by 10 CFR 19.12 on how to properly handle radioactive material or work in areas where radiation exposure is possible and the proper precautions and procedures to follow. Because risks are involved, it is necessary that those exposed be knowledgeable about those risks and, more importantly, know how to minimize them to perform their jobs in a safe and effective maimer. Dose limits for occupational workers apply for all occupational dose received in a given year, even if it was from multiple employers. 

---