Fission Track Assay for Fissile Nuclides in Tissue.

Abstract : Fundamental techniques for a Fission Track Assay for Fissile Nuclides in Tissue have been developed. Accomplishments can be summarized as follows: Pu and U have been chemically separated from each other and from bulk contaminants frequently encountered in ashed tissue specimens. The preparation of sample-detector assemblies has been standardized and conditions for neutron irradiation, subsequent track etching and quantification have been established. Program controlled procedures have been developed to eliminate erroneous interpretations of fission track images and to guarantee the statistical validity of the track quantitation. The background due to external contamination with uranium has been reduced to acceptable levels. A survey of Pu-distributions in livers, kidneys, spleens, and lungs and skeletons of experimental animals has been performed. Reproducibility and accuracy of the assay have been tested on small beef liver samples tagged with 1.0 and 0.1 fCi 239Pu and on dry, 239Pu-containing liver powder obtained from the National Bureau of Standards. The Pu distribution and average concentration of six livers of humans from Southern Utah and Northern Utah have been determined and the results were compared witrh those obtained from the same organs by alpha-spectrometric methods. Presently, the lower limit of the 239Pu quantitation using a reported thermal neutron fluence of 5 x 10 to the 17th power n/sqcm is approximately 1 fg or less than 10 to the -16th power Ci. Thus, Pu resulting from 1/10,000 of the maximum permissible whole body burden of .00000004 Ci could be quantitated in a 100 mg bone specimen, assuming a uniform skeletal deposit of 239Pu.