Year
1995
Abstract
The potential for improved measurement accuracy and the ability to gain sample matrix information as part of a waste assay are but two of the advantages of multiplicity measurements of waste. Neutron Multiplicity Counting (or Neutron Time Correlation Analysis) using the point source interpretation model 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 current collaborative development of a multiplicity drum monitor for the measurement of plutonium contained in 200 litre waste drums is described in the present paper. Although the device may be employed with conventional shift register based coincidence electronics for pair correlation analysis, it has been designed specifically for neutron multiplicity counting using the Time Correlation Analyzer (TCA) for triple correlation analysis. Data is presented for measurements on a prototype drum monitor developed at the Joint Research Centre. The recent evolution of the design, both in order to optimize measurement performance and to satisfy specific customer requirements, is described in this paper.