Question 375: In supporting a conclusion that individual
monitoring of internal occupational dose is not required
[10 CFR 20.1502 (b)] and, therefore, that summing of
internal and external dose is not required [10 CFR 20.1202
(a)], what is considered to be acceptable for bioassay
frequency, DAC-hour administrative limit, and whole-body
counting minimum testing level?
Answer: Under 10 CFR 20.1502 (b), there is no required
frequency for bioassay, DAC-hour administrative limit, or
minimum testing level for whole-body counting either for
individuals for whom monitoring is required or to support a
conclusion that individual monitoring is not required.
However, the answer to Question 54 provided a number of
examples of measures that could be used at nuclear power
plants to verify that the expected degree of respiratory
protection will be achieved so that the concentrations of
radionuclides in air after credit is taken for respiratory
protection may be used in making the prospective assessment
that individual monitoring for internal dose is not
required. These measures "include, (but are not limited
to) measurements of nasal smears from workers who have used
respirators and whole body counting, relatively soon after
a job, of one or more workers among a group of workers who
wore respiratory protective equipment while working on the
job and periodic whole-body counting (e.g., annually) of
all workers who wear respiratory protective equipment."
It should be recognized that in addition to the bioassay
requirements of 10 CFR 20.1502 (b), there is the bioassay
requirement of 10 CFR 20.1703 (a) (3) (ii), which is
related to the use of individual respiratory protection
equipment. If whole body counting is to be used to verify
the effectiveness of the respiratory protection program, it
must be able to demonstrate that estimates of intake based
on exposure calculations (i.e., on air concentrations and
on taking credit for protection factors) are consistent
with estimates of intake based on bioassay. The licensee
should take into account the fact that demonstrating
effectiveness of the respiratory protection program may
have to be based on exposures over durations much shorter
than a year, particularly for materials that are expected
to be cleared rapidly from the body. Some general guidance
on air sampling is provided in Regulatory Guide 8.25, Rev.
1, (which states that this guide does not apply to reactor
facilities), and general guidance on bioassay will be
provided in Regulatory Guide 8.9, Rev. 1. (References: 10
CFR 20.1502, 10 CFR 20.1202, 10 CFR 20.1703, Regulatory
Guide 8.9)