Occupational dose limits

The NRC requires that the occupational intake of americium isotopes not exceed certain specified Annual Limits on Intake (ALIs) for the inhalation and oral routes of exposure. For241 Am and 243Am, the oral ingestion ALI is 0.8 JLlCi and the inhalation ALI is 0.006 pCi, both of which are based on the deterministic dose limit to the bone surface (NRC 2000). 

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. 

Occupational dose limits for adults Annual limit Total weekly limit... 

USNRC. 1995a. United States Nuclear Regulatory Commission. Occupational dose limits. Code of Federal Regulations. 10 CFR 20, Subpart C. 

A prospective upper bound on the individual dose which is used in the optimisation of protection and safety for sources. For occupational exposures, dose constraint is a source-related value of individual dose used to limit the range of options considered in the process of optimisation. For public exposure, the dose constraint is an upper bound on the annual doses that members of the public should receive from the planned operation of any controlled source. The exposure, to which the dose constraint applied is the annual dose to any critical group, summed over all exposure pathways, arising from the predicted operation of the controlled source. The constraint for each source should ensure that the sum of doses to the critical group from all controlled sources remains within the dose limit. For medical exposure the dose constraint levels should be interpreted as guidance levels, except when used in optimising the protection of persons exposed for medical research purposes or of persons, other than workers, who assist in the care, support or comfort of exposed patients. 

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. 

Human biological exposure indices are guidance levels of determinants for assessing worker dose from occupational exposures. They differ from other occupational exposure limits (OELs) for chemicals, which typically are measured in air, in that their determinants are measured in biological materials from the workers. BEIs consider the dose that has entered a worker s body by all routes. Thus, these measurements can provide more complete estimates of exposure, especially for chemicals that may be absorbed by routes other than inhalation and when inhalation rates are altered because, for example, of increased work rates. 

The annual occupational dose limit to an adult radiation worker is the more limiting of (1) total effective dose of 5 rem (0.05 Sv) or (2) the sum of deep-dose equivalent and the committed dose equivalent to any individual organ or tissue, other than the lens of the eye, being equal to 50 rem (0.5 Sv). 

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). 

Personnel monitoring is required when an occupational worker is likely to receive an excess of 10% of the annual dose limit from radiation sources and for individuals entering high or very high radiation areas. Monitoring is accomplished by using film badges or thermoluminiscent dosimeters (TLD). 

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

DOE Occupational dose limits for general employees Total effective dose equivalent 5 rems (0.05 Sv) DOE 2001d 10CFR835.202... 

Occupational dose limits for minors (total effective dose equivalent in a year) 0.1 rem (0.001 Sv) DOE 2001 e 10CFR835.207... 

Occupational dose limits for minors 10% of the annual dose limits specified for adult workers in 10CFR20.1201 NRC 20010 10CFR20.1207... 

Occupational exposures Effective dose limits Annual 50 mSv... 

DOE. 2001d. Occupational dose limits for general employees. U.S. Department of Energy. Code of... 

DOE. 200 le. Occupational dose limits for minors. U.S. Department of Energy. Code of Federal Regulations. 10 CFR 835.207. Http //frwebgate.access.gpo.gov/cgi-bin/..PART=835 SECTION=207 YEAR=2001 TYPE=TEXT. May 11, 2001. 

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. 

The dose limits are the levels not to be exceeded, but they should not be considered as a goal. The revised standard requires the licensee to use, to the extent practicable, procedures and engineering controls based upon sound radiation protection principles to achieve occupational doses and doses to members of the public that are ALARA. 

The DAC and ALI values are given in Table 1, Appendix B, of Part 20 and can be used in the determination of an individual s internal dose and to demonstrate compliance with required occupational dose limits. Table 2, Appendix B lists the maximum permissible concentrations in effluents and Table 3 lists the maximum concentrations permitted for release into sewers. 

The aimual occupational dose limits for minors are 10% of the limits for adult workers as listed in 10 CFR 20.1201. 

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