Negligible Individual Dose

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. 

3 Application of NCRP Recommendations to Waste Classification. NCRP s recommendations on dose limits and a negligible dose for individual members of the public, and their associated cancer risks, could be used in developing a risk-based waste classification system. Specifically, the dose limits applicable to all man-made sources of exposure combined could be used in establishing concentration limits of radionuclides or hazardous chemicals in dedicated hazardous waste disposal facilities based on assumed scenarios for exposure of the public. Similarly, the negligible individual dose could be used in establishing concentration limits of radionuclides in disposal facilities for nonhazardous waste. These applications are discussed in Sections 6.2 and 6.3 where NCRP s recommendations on risk-based waste classification are presented. 

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NCRP has developed a recommendation on a negligible individual dose that could be used to establish exemption levels for radioactive waste for such purposes as disposal and recycle/reuse, but this recommendation has not been adopted by regulatory authorities. Indeed, NRC is prohibited by law from implementing a proposed generic policy on exemption of radioactive materials that was consistent with the NCRP recommendation. 

An important function of NCRP is to develop basic recommendations on radiation protection NCRP s current recommendations are contained in Report No. 116 (NCRP, 1993a). With regard to radiation protection of the public, two recommendations are potentially relevant to the development of a risk-based waste classification system. These recommendations involve limits on radiation dose and a negligible individual dose. 

The National Coimcil for Radiation Protection (NCRP) has identified a negligible individual risk level (NIRL) as a level of annual excess risk of health effects attributable to irradiation below which further effort to reduce radiation to the individual is unwarranted. The NCRP emphasized that this level should not be confused with an acceptable risk level, a level of significance or a standard. The NCRP recommended a level around half the natural background radiation level the final recommended NIRL level is 1 mrem this level is now called negligible individual dose (NID) level (Harley, 2001, 2008). 

Effective dose was a parameter used to assess biological risk related to radiation exposure, from dual-energy X-ray absorptiometry (DXA). Children are a worst case estimate because they absorb higher doses than adults. With the exception of the hip scans in 1- and 5-year-old children, the effective doses were below the negligible individual dose limit of 1 mrem per year (Thomas et al, 2005). 

The NCRP recommends an annual effective dose for continuous members of the public in some circumstances of 1 mSV (100 mrem). This value is in addition to natural background level of irradiation approximately twice that (2mSv 200 mrem). In this context, the NIRL was taken to be 1/100 of this level, or 0.01 mSv/year (1 mrem/year). This level of exposure was low enough to have a risk of <1 cancer/1,000,000 and the risk for lung cancer <1/10,000,000. The notation is negligible individual dose (NID) (Harley 2001, 2008). 

Based on the negligible annual dose to individuals of 10 pSv and assumed scenarios for unrestricted disposal of waste, IAEA has developed recommendations on exemption levels for radionuclides in solid waste (IAEA, 1995) the recommended exempt concentrations have values in the range of about 0.1 to 104 Bq g 1 depending on the radionuclide. IAEA also has issued recommendations on total activities and activity concentrations of radionuclides that could be exempted from any requirements for notification, registration, or licensing of sources or practices, based on the same exemption principles and assumed scenarios for exposure of the public (IAEA, 1996). The recommended exemption levels for naturally occurring radionuclides are limited to their incorporation in consumer products, use as a radioactive source, or use for their elemental properties. 

Negligible Individual Risk Level (Negligible Dose)... 

EPS, extra pyramidal side effects. Relative side-effect risk , negligible +, low ++, moderate +++, moderately high ++++, high. °Side effects shown are relative risk based on doses within the recommended therapeutic range, individual patient risk varies depending on patient-specific factors. 

The basic waste classification system includes a general class of exempt waste, which is defined in terms of a dose to an individual member of the public, resulting from waste disposal, that is regarded as negligible. 

The approach to risk management for radionuclides, when they are regulated under AEA, incorporates a limit on acceptable dose (and therefore risk) and a requirement that doses be reduced below the limit as low as reasonably achievable (ALARA), economic and social factors being taken into account this approach conforms to NCRP s recommendations on radiation protection. In this approach, risks to individuals are divided into three categories of significance, which are commonly termed unacceptable, acceptable, and negligible. ... 

Exempt waste would be defined as waste that contains such low concentrations of radionuclides that it could be exempted from regulatory control as radioactive material because the radiological hazards associated with disposal of the waste would be negligible. The basis for defining exempt radioactive waste recommended by IAEA is a limit on annual dose to individuals from waste disposal of 10 xSv (see Section 4.1.3.2). 

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