THE (ALPHA,N) PRODUCTION-RATE OF PLUTONIUM ALPHA-PARTICLES ON VERMICULITE

The (alpha,n) production rate for plutonium alpha particles on vermicu lite relative to that on PuO2 is estimated within the framework of a h omogeneous medium model using thick target elemental values evaluated at 5.5 MeV. The composition of the vermiculite is highly variable and the predicted relative (alpha,n) rate varies over a range of approxima tely 7-25, but this is in broad agreement with an empirical observatio n on a particular sample of (13.2+/-0.7). These results demonstrate th at plutonium standards for the calibration of non-destructive assay ne utron monitors prepared by the absorption of plutonium nitrate solutio n onto a vermiculite carrier cannot be considered to be true analogues of plutonium nitrate wastes. Additional information is presented allo wing the extension of these results to a variety of other media contai ning elements of low atomic number with a significant (alpha,n) produc tion rate. Copyright (C) Elsevier Science Ltd.