Year
2006
Abstract
The Pu isotopic abundances are frequently determined from gamma spectra taken by HRGS and analysed by codes like MGA and FRAM. The limitation of this method is the evaluation of 242Pu. Actually, this isotope emits a few weak gamma lines that do not become visible in the gamma spectra and therefore can not be used by these codes. The problem is partially solved through the application of isotope correlations estimating the relative abundance of 242Pu from relations to ratios of other plutonium isotopes measurable by HRGS. In the mid of the nineties a new type of isotope correlation had been proposed for LWR plutonium. We have adopted this type of correlation for the routine analysis of safeguards samples in the Euratom On-Site Laboratories (OSL's) at Sellafield and La Hague, and in the Institute for Transuranium Elements (ITU). From isotopic measurement data accumulated during the first 4-5 years of operation of the OSL's we have now determined adjusted coefficients for the correlation for the 4 major types of fuels occurring in the OSL's, i.e., PWR, BWR, AGR and Magnox fuels. Sets of coefficients approximating best the correlation were determined from the available measurement data. Performance data for the 242Pu estimate are presented and discussed.