U.S. Nuclear Regulatory Commission
Question 434: How are occupational dose limits applied in
regard to the revised Part 20 definition of "year"? The
purpose of this question is to obtain additional
clarification of the intent and application of the "year"
as it is defined in the revised Part 20 and discussed
previously in Question 40. Apparently, licensees may
establish a year that is other than January 1 through
December 31 (e.g., Question 40 addresses a year that is
from January 31 of one year through January 30 of the
following year). In responding to the question, consider
the following example. A worker receives dose sequentially
at facilities of two different licensees, the first
licensee using a year of January 1 - December 31, and the
second licensee using a year of January 31 - January 30.
The worker receives 4 rems total effective dose equivalent
(TEDE) at the facility of the first licensee during the
period January 1 - January 30, and then transfers to the
second licensee's facility, arriving for work on February
1. For work performed at the second licensee's facility,
is the individual's remaining available TEDE 1 rem or 5
Answer: Five rems. For a particular licensee, the
relevant time period for determining compliance with an
annual dose limit is the year beginning and ending on the
dates specified by that licensee, providing that the time
period chosen by the licensee is consistent with the
definition of "year" in 10 CFR 20.1003. In the example
provided, the worker started work at the facility of the
second licensee at the beginning of that licensee's "year"
and, therefore, the worker had no prior occupational dose
during that licensee's "year." (Reference: 10 CFR 20.1003).