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).