Year
1997
Abstract
Neutron Multiplicity Counting (Neutron Triple Correlation Analysis) is increasingly employed in the measurement of plutonium containing waste. The technique brings the potential for both improved measurement accuracy and the ability to gain sample matrix information as part of the waste assay measurement. Neutron coincidence counting or neutron pair correlation using shift register electronics, allows one to determine the Totals and the Reals count rate from plutonium. In contrast, neutron multiplicity counting allows the determination of three parameters including the correlated triples rate. The technique employs the point source interpretation model which allows one to determine three of the four unknown assay parameters by measuring the Totals count rate, the Reals count rate (correlated pairs) and the correlated Triples rate. Thus, where one of the unknown assay parameters can be established or is known, then absolute measurements of waste are possible. The present paper describes the collaborative development of a multiplicity drum monitor for the measurement of plutonium containing waste in 200 litre drums. The device can be used with coincidence electronics although it is designed specifically for neutron multiplicity counting using the ANTECH neutron Time Correlation Analyser. Data is presented in this paper from measurements on the prototype drum monitor developed at the Joint Research Centre and on a recent production instrument. The measurements include both Pu and Cf252 samples as well as Plutonium measurements for an empty and a concrete drum containing a Pu sample.