Evaluation of Neutron Cross Sections for Hafnium in the Resolved Resonance Range

The international High Priority Request list notes: “In the nuclear industry hafnium is used as neutron absorbing material to regulate the fission process. Interpretation of critical experiments with UOx fuel conducted by CEA in the AZUR zero-power reactors has shown systematic underestimation of the reactivity worth that may be attributed to an overestimated natural hafnium capture cross section in the epi-thermal energy range” To service the request for improved resonance data a PhD project has:a) Improved REFIT R-matrix evaluation code. b) Obtained hafnium oxide samples enriched in Hf176, 177, 178, 179 isotopes. c) Gained support from NUDAME and EUFRAT projects. d) Prepared enriched and natural Hf samples. e) Performed capture and transmission Time of Flight measurements at the GELINA linear accelerator. f) Analysed the capture counts to generate yields using AGS and AGL codes. g) Used REFIT to perform least squares analysis of GELINA measurements. (Included previous ORNL, Harwell and RPI transmissions and capture yields.) h) Submitted results to EXFOR. i) Included resolved resonance parameters in JEFF evaluations taking the resolved range to over 1 keV. j) Tested evaluations with suitable benchmarks. k) Passed resolved resonance data to CEA Cadarache for unresolved analysis. Resultant Hf evaluations will be included in JEFF3.2.