Alpha spectrometric determinations of plutonium isotopic composition and concentration--application to nuclear safeguards

In the processing of irradiated nuclear fuel, assurance that plutonium is not being diverted is based, in part, on analytical data showing that the isotopic composition (identity) across the system is invariant and the material balance is exact. It appears that our alpha spectrometric (AS) methods could provide the quality of data required for this. Mounts are prepared by extracting the plutonium into hexone followed by evaporation on a glass planchet in an area of about 1 cm2. The methods were evaluated using pressurized-water reactor plutonium, material in which the 238/239/240 activity ratios re about 1/1/1. About 1x10-7 g was mounted (6x102 Bq), the geometry was 5%, the counting time was 24 hr, the number of 238, 239 and 240 counts were each about 1x106. Peak resolution was limited to that of our detector, 12 keV; the ratios of peak channel count rates to background count rates of other isotopes were 3,000 for 239/238 and 240/238, 15 for 240/239 and 4 for 239/240. The relative errors in key identify and concentration measurements were 0.2%. Mass spectrometric (MS) methods are presently used to monitor plutonium in nuclear fuel processing plants