Plutonium Dispositioning in CANDU

Abstract

Recently, the U.S. Department of Energy (DOE) sponsored Atomic Energy of Canada Limited (AECL),to evaluate salient technical, strategic, schedule, and cost related parameters of using CANDU reactors for dispositioning of weapons grade plutonium in the form of Mixed OXide (MOX) fuel. A study team consisting of key staff from the CANDU reactor designers and researchers (AECL), operators (Ontario Hydro) and fuel suppliers analyzed all significant factors involved in such application, with the objective of identifying an arrangement permitting burning of MOX in CANDU at the earliest date.One of Ontario Hydro's multi-unit stations, Bruce A nuclear generating station (4x769 MW(e)), was chosen as the reference for the study. The assessment showed that no significant modifications of reactor or process systems are necessary to operate with a full MOX core. Plant modifications would be limited to fuel handling and modifications necessary to accommodate enhanced security and safeguards requirements. No major safety limitations were identified. An important task of the study was to define the optimum design parameters of MOX fuel to achieve the target disposition rates -- two tonnes of plutonium per year in the reference case, and four tonnes per year for an alternative case -- without altering the design base of operating and safety parameters of the reactor system, and without requiring excessive fuel supply. The reference MOX fuel design employed the standard 37-element CANDU geometry bundle. This fuel would operate within the same burnup and power rating envelope as standard CANDU natural-uranium fuel, and its nuclear parameters would allow the reactor to operate within its existing licensing envelope. The 43-element CANFLEX fuel bundle was chosen for the alternative case. This fuel bundle, which is currently being qualified for commercial use, has two sizes of elements, and operates at a lower linear power rating, thus permitting higher plutonium concentrations and higher burnups. Use of this design would reduce the quantity of MOX fuel bundles required by almost half, a significant economic advantage. Two Bruce A reactors would be used for the reference case of dispositioning of two tonnes of plutonium per year, and four for the alternative case of dispositioning of four tonnes per year.