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spectrum from a 232U sample containing 250 ppm of 232U is totally dominated by the 232U
decay gamma rays, thus eliminating the possibility of direct gamma-ray assay. Passive
techniques employing calorimetry are also complicated since 232U decay particles can contribute
significantly to the heat generation in a fuel sample. It has been calculated,3,6
that for a fresh sample of 233U containing 400 ppm 232U, nearly 50% of the thermal heat
generation can be attributed to 232U decay, which increases to 75% after only one year.
It is, therefore, apparent that fissile content assay for denatured uranium fuels will
require more sophisticated active NDA techniques which must overcome the obstacles of
material dilution and 232U-a~tivity contamination.
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Fig. 3.3-2. Gama-Ray S ectrum from a 233U Sample Containing 250 ppm 232U. All
major peaks are attributed to ! 2U decay products. Gamma-ray energies indicated in MeV.
(From ref. 3.)