Question 90: Can a licensee require its workers to
routinely take potassium iodide (KI) when handling large
quantities of radioiodine and take credit for the reduction
in occupational dose that results from the use of the KI?
Answer: No. Requiring the use of KI for this purpose is
neither a "process or engineering control...to control the
concentration of [radioiodine] in air" 10 CFR 20.1701).
Furthermore, because KI blocks uptakes (not intakes), the
use of KI for thyroidal blocking cannot be considered to be
among the "other controls" required by 10 CFR 20.1702 for
limiting intakes. The following cautionary note in NRC
Information Notice 88-15 (4/18/88) continues to be
applicable under the Revised Part 20:
"It is important to stress that the use of potassium iodide
is not a substitute for preventive measures; e.g., proper
handling techniques, control measures, and emergency
procedures that protect the individual from exposure to
radioactive material."
A licensee should optimize design and engineering controls,
as well as operating procedures, as a means of ensuring
that doses from airborne radioiodine are ALARA. However,
in situations where KI has been administered following a
suspected intake, the licensee may take credit for the
protection if bioassays support the effectiveness of the KI
in blocking the thyroid.
Finally, although licensees are not authorized to require
their employees to routinely take KI when working with
radioiodine, nothing in NRC regulations prohibits an
individual from taking KI on a purely voluntary basis;
however, the NRC does not recommend the voluntary use of KI
in this manner. (Reference 10 CFR 20.1701)