U.S. Nuclear Regulatory Commission
Question 75: Representatives of the nuclear power industry
have expressed a concern regarding 10 CFR 20.1502, which
requires licensees to monitor individual internal or
external doses for each individual likely to exceed 10% of
the applicable annual limit. Licensees are required to
maintain records of individuals for whom monitoring was
required under §20.1502 [§20.2106 (a)]. The handling of
internal doses at less than 10% of the limit is of
particular interest. Since a licensee cannot predict
future exposures at other licensee facilities during the
remainder of the year, a question arises regarding summing
of doses at these small fractions of the limit if a worker
transfers to another licensees during the year. The
following procedures have been suggested regarding
reporting of internal doses at nuclear power plants that
are less than 10% of the limit.
1. At nuclear power plants, an entrance bioassay is
typically performed for all incoming radiation workers.
Upon departure from the facility, an exit bioassay is
typically performed. If no net internal contamination is
detectable in the exit bioassay, no internal dose
assessment is required. If internal contamination is
detected, an assessment will undoubtedly be made. Any
positive result above the LLD is available for reporting.
2. Respiratory protection programs are required, under
§20.1703, to monitor workers to assess intake. Air
sampling results and bioassay measurements are acceptable
methods to perform this monitoring, with the results used
to perform an intake assessment.
3. Therefore, if a worker is monitored for potential
internal exposure, data regarding the results of such
monitoring will be available and must be recorded. Since
these records are available, positive results, above LLD,
should be reported to subsequent licensees, even if there
is no reason to expect the worker will exceed 10% of the
annual internal committed effective dose equivalent limit.
Does the NRC have any objections to this procedure?
Answer: No. This procedure for nuclear power plants goes
beyond the requirements of the revised Part 20 for
monitoring, recording, and reporting internal doses to
workers. See the answer to Question 114. (For example,
routine entrance and exit bioassays for all workers are not
required by Part 20). However, the procedure is not
inconsistent with the Part 20 requirements. (References:
10 CFR 20.1502, 10 CFR 20.2106)