Reactivity Worth Measurement of Major Fission Products in MINERVE LWR Lattice Experiment

The CERES collaborative program between the French Atomic Energy Commission (CEA) and the United Kingdom Atomic Energy Agency (UKAEA) was performed in the MINERVE and DIMPLE reactors at Cadarache and Winfrith, respectively. CERES Phase II was devoted to the validation of fission product (FP) poisoning through the reactivity worth measurements of FP samples. This paper describes the oscillation experiment at the center of the MINERVE pressurized water reactor–type test lattice. This experiment is strongly representative of the FP poisoning in light water reactor spent fuels because the separated FP isotope is introduced into real UO₂ pellets where ²³⁸U/ⁱFP resonance overlap occurs. In order to preserve the experimental results within the International Reactor Physics Experiment Evaluation international database, slight corrections to define a two-dimensional benchmark are presented. The evaluation of experimental uncertainties is detailed. Therefore, the accurate APOLLO2.8 analysis of this benchmark is described, using recent JEFF-3.1.1 and ENDF/B-VII.0 nuclear data files. JEFF-3.1.1 FP worth is particularly satisfactory, except for ¹⁵³Eu, which is underestimated by 8.1% + 2.6%. The CERES integral measurement data also suggest improvements to ⁹⁹Tc and ¹⁴⁵Nd evaluations in the ENDF/B-VII.0 library.