U.S. Nuclear Regulatory Commission
Question 179: If a licensee implements the revised Part 20 in July, 1993, is the licensee required to go back and evaluate internal dose for the purpose of determining total effective dose equivalent for the year?
Answer: No. The footnote to 10 CFR 20.2104 (d), as amended in 57 FR 57877, 12/8/92, states, "Licensees are not required to partition historical dose between the external dose equivalent (s) and the internal committed dose equivalent (s)." As long as all of the licensee's worker's doses are below the old limits and/or the workers will not participate in planned special exposures, the licensee need not reevaluate prior doses before implementing the revised Part 20. However, the licensee must subtract the dose already received during the year from the new annual dose limits to find the limits for the remainder of the year, as explained in Question 1, Set 1.
(Reference: 20.1202, 10 CFR 20.2104)