Answer to Question #667 Submitted to "Ask the Experts"

Q

If an employee who is not required to be monitored under CFR 20.1502 has a skin contamination event in which I calculate a skin dose (of 1, 10, 100 mrem, etc.), when am I required to record the exposure? Is it 10% of the allowable limit? Also, if I have an employee who is monitored under 20.1502, and a skin contamination occurs giving a "small" dose, when am I required to add this to their Form 5? Because they are monitored, must I record any dose, no matter how small?

A

The 10% criterion for monitoring occupationally exposed individuals is not intended to be a de minimis dose level, or a level below which doses are of no regulatory concern. It is only intended to provide relief for the common situation in which a significant fraction of the licensee's workers, or most of them, were being monitored but did not receive any measurable doses or received very low doses that were typically just above the detection limits. Licensees in such cases may stop monitoring these workers and therefore realize significant savings in effort and resources. However, if workers are monitored, their doses must be recorded on their Form 5, regardless of how far the dose is below the 10% criterion. It should also be noted that the 10% monitoring criterion is prospective; that is, it is intended to be applied at the beginning of the monitoring year, and workers are either monitored or not monitored based on such a prospective assessment. However, if conditions change and it becomes apparent that some workers who had not been included in the monitored population should in fact have been included, then these workers must be reclassified and included in the monitored population of workers. Similarly, should an event occur that requires an assessment of a worker's dose, such as an intake of radioactive material, then the assessed dose should be recorded on a Form 5, even if it is below the 10% monitoring criterion, because now the worker is being monitored. This would be the case in the event of a skin contamination mentioned in the question.

There is a minor discontinuity in the scheme described above, because workers who are not monitored may receive doses close to the 10% criterion, whereas those who are monitored may have recorded doses that are significantly below that level. Nevertheless, this is not viewed as a serious drawback of the system in view of the potentially significant monitoring relief it is capable of providing without at the same time resorting to the concept of a dose that is below regulatory concern.

Sami Sherbini NRC