Health Physics Questions and Answers - Question 43
Question 43: The licensee initially was required to monitor internal dose. The results indicate that monitoring is not required, i.e., levels are positive but less than 10% of the allowable limits. Can the measured internal dose values be ignored? If yes, will the licensee be in noncompliance if it sums internal and external doses?
Answer: The licensee was required to monitor internal dose [because the licensee had made a prospective determination that the individual (s) was (were) "likely to receive" an intake in excess of 10% of the limits]. The internal dose values cannot be ignored regardless of the fact that they are less than 10% of the limits. If the licensee was not required to monitor internal dose because the licensee had made a prospective determination that the doses likely would be less than 10% of the limits but elected to monitor internal dose anyway, the licensee could choose to "ignore" the measured values that are less than 10% or to add those values to the external doses to obtain the sum of the internal and external doses. Nothing in Part 20 prohibits the licensee from monitoring or summing internal doses at less than 10% of the limits; therefore, a licensee can never be in noncompliance for summing the internal and external doses.
(Reference: 10 CFR 20.1502)