Year
1999
Abstract
Two methods for measuring the plutonium mass in waste container are presented in this paper. They have been developed, optimized and validated for two shift register passive neutron coincidence counting system with high (30%) and low efficiencies (7%). The first method is based on the model developed by Hage and Cifarelli for a known efficiency county system. This Three-Parameter analysis of the neutron signal correlation has been successfully used with the high efficiency counting system. The second method which is called \"a two parameter method\", has been applied for the low efficiency counting device. this method assumes a known efficiency of the cell and a known (a, n) ratio that characterized the plutonium chemical form. Both methods are presented as well as the results obtained with plutonium metal or plutonium oxide ranging from a few milligrams up to 12 kg. For instance, These methods gave respectively a deviation lower than 1% (for a 150 g plutonium metal sample) compared to the declared values. These results come from the use of these systems in the field since 1995 by French domestic safeguards inspectorate for the control of nuclear material.