United States Nuclear Regulatory Commission - Protecting People and the Environment

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).

Page Last Reviewed/Updated Thursday, March 29, 2012