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)