Monte Carlo Modelling of the Guinevere Detector and Fuel Assembly System for Nuclear Safeguards

A European based Guinevere (Generator of Uninterrupted Intense NEutrons at the lead VEnus REactor) project conducted within FP5 ¿IP-Eurotrans¿, addresses issues concerned with the development of Advanced Driven Systems for the purpose of partitioning and transmutation for nuclear waste volume and radio toxicity reduction and aims to obtain a validated methodology for on-line reactivity monitoring. A substantial part of this project consists in the modification of the VENUS water moderated criticality facility of the SCK/CEN (in Mol Belgium) into a fast lead core reactor facility which will be coupled to a purposely Modified 14 MEV neutron generator (GENEPI-C). The proposed new fuel assemblies, 88 of them each containing 9 Uranium fuel rods interspaced with lead blocks, are constructed with lead blocks and uranium fuel for the core and lead blocks for the reflectors. Within the Euratom treaty, this new fuel assemblies need to be safeguarded and verified. For this purpose, the European Commission Inspectors (DG-TREN) intend to use an Active Well Coincidence Counter (AWCC) which can not unfortunately be calibrated and used for verification in the classical sense due to the fact that there are no reference materials representing the new fuel magazines. The solution adopted is a Monte Carlo based calibration and verification procedure which has now been fully investigated and found very sound when applied to many NDA neutron counting systems [1]. The AWCC has been fully modelled using the Monte Carlo code, MCNP-PTA, which simulate both the neutron transport and the coincidence electronics. The AWCC model has been extensively validated following measurements carried out in the JRC-Ispra Performance Laboratories (PERLA) using our MTR materials. Measurements agreed within 1-3 % with our calculations. Furthermore the new Genuivere fuel magazines have fully modelled using MCNP, based on detailed engineering drawings kindly provided to us by the site operators (SCK/CEN). This paper describes the Monte Carlo simulation methodology and models applied and gives the results of our measurements and calculations.JRC.G.8-Nuclear securit