Year
2005
Abstract
“Known multiplication” method is the one of neutron method for Pu mass determination in samples. It is also included in basic software for neutron analysis such as INCC, NCC, NDA2000, NAS etc. Nevertheless, application of method was very confined, whereas primary (standard) methods were “known alpha” and “multiplicity”. However, there are cases when standard methods come into collision with insuperable difficulties. It is a matter mainly about control of so-called impure plutonium compound, which can contain unknown amount of low-Z impurities. At that the value of neutron yield due to (a,n) reaction becomes unknown and “known alpha” method become invalid. At same time implementation of “multiplicity” method required suitable neutron counters with high efficiency and shift registers for multiplicity counting, which were not delivered to Russian nuclear facilities. Uselessness of application of standard neutron methods for plutonium mass control was display for most of samples during neutron measurements of samples with plutonium dioxide at RT-1 plant in Mayak facility. Detailed chemical analysis of samples shows presence of considerable and not well defined amount of low-Z impurities, which makes impossible of “known alpha” method application for proper analysis. In this paper authors consider the advantages of “known multiplication” method application for plutonium mass assay in plutonium dioxide samples at RT-1 plant. Also they compare the results of analysis for all four methods “calibration curve”, “known alpha”, “multiplicity” and “known multiplication”, consider reasons of difficulties of analysis by these methods and possibility of “known multiplication” method using for confirmatory measurements of various plutonium materials at Russian nuclear facilities.