A TRIAL PRODUCTION OF PLUTONIUM CONTAMINATED WOUND COUNTERS.

Abstract A rapid increase of the amount of plutonium to be handled in our Institute has accelerated the need for preparation of wound counters capable of detecting at least a fraction of MPBB (40 nCi) in a plutonium contaminated wound. Two kinds of wound counters, a xenon gas-filled proportional counter and a cesium iodide crystal scintillation counter, were constructed and their characteristics were examined. The minimum detectable amount for the former was 5.5 nCi and that for the latter was 0.83 nCi when the plutonium was imbedded 6 mm under tissue and the window of the detector was positioned at 3 mm above the skin surface. In order to determine the location of plutonium, a 0.1-mm-thick lead plate and a lead-impregnated flexible material were prepared. The method of determination of the effective depth of contaminants is discussed below mainly for the cases of pure plutonium and plutonium with an unknown content of americium in the wound. Furthermore, we have shown that the depth distribution of the contaminants can be obtained in fairly good agreement with the actual distribution by the method of expansion of source distribution using the orthonormal function series method. This method will be valid provided the contaminant lies continuously in the wound.