Estimation of personal neutron dose in nuclear accidents

In the case of a nuclear accident, it is important to quickly know personal exposure doses. In spite of the recent advances in physical dosimetry, the detection of neutron exposure dose is not always possible, because of the absence of an adequate system of physical dosimetry. The object of this study is to obtain information concerning personal neutron exposure doses on human hair, nails, and blood, with the view to determining a convenient method of detecting unexpected exposure. The most easily detectable nuclides in the hair were ²⁴Na, ⁵⁶Mn, ⁶⁴Cu and ³²P. In case of serum, ²⁴Na was the element easily detected, while ²⁴Na, ⁵⁶Mn, ⁶⁴Cu and ³²P were also found in the nails. The production of ³²P is the result of ³²S (n, p) ³²P reaction with fast neutrons, while the other nuclides have been mainly produced with thermal neutrons. The effect of competing reactions was found to be negligibly small. In order to know the content of each element in the human hair, nails and blood, neutron activation analyses of ²⁴Na, ⁵⁶Mn, ⁶⁴Cu, ³⁸Cl and ³²P were carried out. The detectable limits for 1 g of hair were 5 rem for thermal neutron exposure and 60 rem for fast neutron exposure. The result of this study shows that the hair is a useful detector for estimating the fast and thermal neutron exposure doses in the case of nuclear accident. (author)