Intercomparison of whole-body counters by using a subject who had incorporated 137Cs into the body

During the years 1996-2000, eight whole-body counting facilities (WBC) from Finland, Germany, Japan and Russia took part in an intercomparison using a resident of the Russian town of Novozybkov who had been seriously contaminated as a result of the Chernobyl accident. The subject R (adult male, height 172 cm average body mass 64 kg; and 137Cs body burden within the range of 1-15 kBq) was investigated in the participating institutions during his business trips. The experimentally obtained data for his 137Cs body burden were compared with the predicted values, which had been deduced from the measurements of subject R using the reference WBC (St Petersburg Institute of Radiation Hygiene) and from his effective half-time of 137Cs in the body (68 days). The obtained results did not deviate more than 20% from reference activities. Four facilities were able to quantity the 40K in the subject's body. The differences between reported values of potassium did not exceed 10%. For subject R, the average annual effective dose from radiocaesium was 0.25 mSv and it was 0.18 mSv from 40K in the years 1996/97. The reliability of using a subject with naturally incorporated artificial radionuclides ('walking standard') instead of an anthropomorphous phantom for calibration and intercomparison of whole-body counters in a large-scale nuclear accident is discussed.