Burn up calculations and validation by gamma scanning of a TRIGA HEU fuel

Abstract

The TRIGA Mark II research reactor operated by Atominstitut is one of the few TRIGA reactors which still utilizes several High Enrich Uranium (HEU) Zirconium-Hydride (U-ZrH) fuel elements. Its current core is a completely mixed core with three different types of fuel elements including one HEU type with 70% enrichment and a stainless steel cladding. The present paper calculates the burn up of the FLIP (Fuel Lifetime Improvement Program) fuel using the burn up code ORIGEN2 and validates the theoretical results by high resolution gamma spectrometry using a unique fuel scanning device (FSD) developed at the Atominstitut especially for TRIGA fuel. For this purpose a FLIP fuel element was removed from the reactor core and stored in the reactor tank for an optimal cooling period. The fuel element was then transferred into the fuel scanning device to determine the Cesium-137 isotope distribution along the axis of the fuel element. The comparison between theoretical predictions and experimental results is the highlight of the present paper.