Health Physics Questions and Answers - Question 404
Question 404: NRC Form 5 (Item No. 10) provides for reporting of individual radionuclides involved in an intake. How does the NRC plan on using this data (i.e., what is the NRC's purpose in collecting this data)?
Answer: NRC Form 5 (Item 10) provides for recording / reporting of individual radionuclides involved in an intake because 10 CFR 20.2106, records of individual monitoring results, requires that the records include, when applicable, the estimated intake or body burden of radionuclides. There are several reasons for inclusion of intake information on Form 5. One reason is that if the internal dose models and weighting factors are changed at some future date, the NRC can recalculate the reported doses using the new models and weighting factors. Another reason, of benefit to licensees, is to make it possible for a licensee to determine the CDE to the maximally exposed organ for an individual who has organ doses reported from previous employers. For example, consider an individual, who, during a year, was employed by licensee A and received a CDE of 20 rem to the lung, then was employed by licensee B and received a CDE of 20 rem to the bone, and finally was employed by licensee C and received a CDE of 20 rem to the thyroid. NRC Form 5 does not provide a space for recording which organ is the maximally exposed organ (unless the "Comments" space is used for this purpose). In the absence of information on which organ was maximally exposed and on the intakes of individual radionuclides, the total CDE to the maximally exposed organ in this example would be considered to be the total of these three 20-rem doses (to different organs), or a total of 60 rem, which would appear to be a potential violation of the organ dose limit. With the individual radionuclide intake information, the CDE to the maximally exposed organ could be recalculated and very likely would be below the limit. The NRC will also use the intake data from some of the earlier reports to the NRC under revised Part 20 to recalculate the doses to ensure that the reported doses are reasonably consistent (within a factor of 2 or so). Finally, the recordkeeping and reporting requirements of revised Part 20 are consistent with implementing an NRC staff recommendation to establish a registry of radiation workers and their radiation doses. Such a registry will be of value for a number of reasons, one of which is to facilitate epidemiological studies of potential radiation-induced health effects. The inclusion of the radionuclide intake data in the dose records provides a better basis for these studies than records of dose alone.
(References: 10 CFR 20.2106, 10 CFR 20.2206, Regulatory Guide 8.7)