Early faecal excretion of inhaled plutonium

Special individual monitoring has been performed for suspected cases of inhalation of plutonium at the Tokai Works of the Japan Nuclear Cycle Development Institute (JNC). Some experimental data obtained from this special individual monitoring during the past 20 years are presented and discussed in this paper. Our experience suggests the following conclusions. The daily plutonium excretion rate, normalised to the total excretion for the first 5 days after inhalation, was approximately in agreement with the latest ICRP 78 dosimetric model. Maximum faccal excretion is observed on the second day after inhalation of plutonium compounds. On the other hand, the activity ratio for total alpha activity observed in early faeces to that detected in nasal swabs showed a wide distribution range, and it was proven that variations in this ratio followed a log-normal distribution. The logarithmic mean probability is about 2.1 for PuO2 and about 15.7 for Pu(NO3)4. In practice, a conservative dose assessment from nasal swabs can be performed on the basis of these experimental ratios.