Challenges to Overcome Towards the HEU to LEU Fuel Conversion of Research and Test Reactors
The conversion of research and test reactors from the use of Highly Enriched Uranium (HEU) to the use of Low Enriched Uranium (LEU) fuel (235U/U < 20wt%) is a Global Threat Reduction Initiative (GTRI) program that is a continuation of the Reduced Enrichment for Research and Test Reactor (RERTR) program begun in 1978 under the technical leadership of Argonne. Argonne remains a leader of the global effort. As of today, more than 85 reactors have been converted or shutdown prior to conversion but the most challenging reactors remain to be converted.
Conversion analyses begin by intensive benchmarking of models by comparison to measurements of the existing HEU cores and against other codes. After satisfactory benchmarking, feasibility analyses to design a new LEU fuel element are performed. In order to succeed, the core performance and safety margins must be preserved despite the greatly increased uranium loading. Designing an LEU reactor for manufacturing and utilization costs, while at the same time requiring minimum modifications of the facilities are also core principles of conversions.
While these “conversion principles” are common among conversions in the program, the fact that the remaining reactors to be converted have unique and exotic designs makes each conversion distinctly complex.
This seminar will present some examples of technical challenges and proposed solutions to overcome them:
- Monte-Carlo analyses for detailed benchmarking, depletion, and performance calculations applied to compact, exotic geometries.
- Integrated modeling of neutronic and thermal-hydraulics to prepare sound safety bases.
- Fuel performance modeling during irradiation by coupling CFD calculations and fuel behavior model.