:ot to Be Taken from This Room

Several methods for determining by persons accidentally exposed the dose received to a criticality ekc&sion have been in;est;gated. The dosimet~ methods included use of film badges, thermoluminescent dosimeters, threshold detector units, Hurst proportional neutron counters, 10-in.-sphere neutron detectors, the multisphere technique, bloodsodium activation, and Geiger counter readings at the abdomen. Five critical assemblies with leakage spectra varying from a fast neutron spectrum to a highly moderated spectrum were studied. The effects of distance from the assembly, room scatter, shielding, and assembly height above the floor were investigated. The results indicate that considerable information must be available before an accurate assessment of a Person’s dose can be made. If no information about the accident is available, dosimetry using a ratio of the hair and blood-sodium activation will give the where massive dose to within *2O to 3@4 except uranium or iron shielding occurs. The neutron activation of sodium in the body has been used to assist in determining the neutron dose received by the individual 1-8 in criticality accidents. A sample of the person’s blood may be counted or, if the dose received was low, he may be placed in a whole-body counter to determine his blood7,8 sodium activation. Variations in the factor used to convert blood-sodium activation to dose have been noted for different critical systems. 6 These variations are caused by the capture cross section of the body which is approxi9-11 mately uniform for all neutron energies, while the contribution of each neutron to the dose is a strong function of the neutron 12 energy. Consequently, after being exposed to a critical system whose leakage-neutron spectrum has a large component of thermal