Abstract

Available nuclear data for molybdenum included in the nuclear data libraries are not of sufficient quality for reactor physics or criticality safety issues and indeed information about uncertainties and covariance is either missing or leaves much to be desired. Therefore, IRSN and JAEA performed experimental measurements on molybdenum at the J-PARC (Japan Proton Accelerator Research Complex) facility in Japan. The aim was to measure capture cross section and transmission of natural molybdenum at the ANNRI (Accurate Neutron-Nucleus Reaction measurement Instrument) in the MLF (Material Life and science Facility) of J-PARC. The measurements were performed on metallic natural molybdenum samples with various thicknesses. A NaI detector, placed at a flight-path length of about 28 m, was used for capture measurements and a Li-glass detector (flight-path length of about 28.7 m) for transmission measurements. Following the data reduction process, the measured data are being analyzed and evaluated to produce more accurate cross sections and associated uncertainties.

Highlights

  • A precise knowledge of neutron cross sections is of a great importance to accurately calculate reaction rates and detailed neutron flux distributions in many nuclear applications

  • Molybdenum capture cross sections and transmission measurements were performed on five metallic natural molybdenum samples of various thicknesses

  • New differential experiments were performed at J-PARC facility on natural molybdenum samples of various thicknesses in the frame of a JAEA-IRSN collaboration

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Summary

INTRODUCTION

A precise knowledge of neutron cross sections is of a great importance to accurately calculate reaction rates and detailed neutron flux distributions in many nuclear applications. Reducing uncertainties in the neutron cross section data can result in an enhanced safety of present and future nuclear systems. Molybdenum isotopes are mainly encountered in irradiated fuel as fission products or in molybdenum alloys in research or naval reactors. Accurate nuclear data of molybdenum isotopes in a wide energy range are of great importance. Molybdenum isotopes are among the greatest contributors to the global nuclear data uncertainty on calculated keff in UPu-MoZr deposits configurations. The available nuclear data for molybdenum included in the nuclear data libraries are not of sufficient quality for reactor physics or criticality safety issues and information about uncertainties and. The aim was to measure the capture cross section and transmission of natural molybdenum

MEASUREMENTS AT THE J-PARC FACILITY
J-PARC facility
Transmission measurements
MEASUREMENTS ANALYSIS AND EVALUATION
SAMMY fit of the experimental data
Comparison of thermal cross section values
FUTURE WORK AND PERSPECTIVES
CONCLUSIONS

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