Total Neutron-Counting Plutonium Inventory Measurement Systems (PIMS) and their Potential Application to Near Real Time Materials Accountancy (NRTMA)

A radiometric method of determining the inventory of an operating plutonium plant is described. An array of total neutron counters distributed across the plant is used to estimate hold-up at each plant item. Corrections for the sensitivity of detectors to plutonium in adjacent plant items are achieved through a matrix approach. This paper describes our experience in design, calibration and operation of a Plutonium Inventory Measurement System (PIMS) on an oxalate precipitation plutonium finishing line. Data from a recent trial ofNear- Real-Time Materials Accounting (NRTMA) using the PIMS are presented and used to illustrate its present performance and problem areas. The reader is asked to consider what role PIMS might have in future accountancy systems.