A worker inhales 1000 Bq of a Pu-239 aerosol and is asked to immediately start to collect urine for a 24 hour sample. How much Pu-239 is expected to be excreted during the first 24 hours? What activity is expected in a 24 hour sample taken on day 10?

Pu-239 may occur in the form of type M or type S aerosols. If the absorption type is not known, it is recommended to assume type M. This should be done also in this exercise. If the particle size is not known, the value of 5 µm AMAD should be used for dose assessment.

For calculation of the expected excretion rate on the first day after inhalation of 1000 Bq Pu-239 you have to multiply the respective urine excretion function 2,32E-04 Bq/d per Bq by 1000 Bq, this resulting in 2,32E-01 Bq/d = 232 mBq/d. For day 10 the expected excretion rate would be 1,54E-02 Bq/d = 15,4 mBq/d. These excretion rates would be far above the lower limit of detection (1 mBq/d for alpha-spectrometry following radiochemical separation of Plutonium) and thus easily be detected.

It should be noted that Pu-239 may occur also in the form of type S aerosols. If so, the expected excretion rates would be only 2,35 E-03 Bq/d at day 1 and 2,24E-04 Bq/d at day 10. So in case of type S aerosols the inhalation of 1000 Bq Pu-239 would be detected on day 1 but not on day 10.

Prof. Dr.-Ing. Hans Richard Doerfel

IDEA System GmbH, Am Burgweg 4, D-76227 Karlsruhe, Germany.

E-Mail: info@idea-system.com