Validation and verification of the ICRP biokinetic model of 32P: The criticality accident in Tokai-mura, Japan

Regrettably, a criticality accident occurred at a uranium conversion facility in Tokai-mura, Ibaraki, Japan, on 30 September, 1999. Radioactivities of 32P in urine, blood and bone samples of the victims who were severely exposed to neutrons were measured. 32P was induced in their whole bodies at the moment of the first nuclear release by the reaction 31P(n,gamma)32P and 32S(n,p)32P. A realistic biokinetic model was assumed as the exchange of 32P between the extracellular fluid compartment and soft tissue compartment occurs only through the intracellular compartment, and the model was used for preliminary calculations. Some acute excretion of 32P, caused by decomposition or elution of tissues which occurred at the time of the accident, may have happened in the victims' bodies in the first few days. The working hypotheses in the present work should initiate renewed discussion of 32P biokinetics.