NEUTRON FIELD MOCK-UP DEVELOPMENT FOR THE FLUORIDE SALT REACTORS NEUTRONIC RESEARCH

Evžen Losa,Vojtěch Rypar,Tomáš Czakoj,Jan Šimon,Nicola Burianová,Vlastimil Juříček,Michal Košťál,M Margulis,P Blaise

doi:10.1051/epjconf/202124708013

Abstract

Experimental work at the LR-0 reactor was carried out to determine the possibility of the mock-up neutron field creation for the fluoride salt-based reactors. Previous calculations and experiments have shown that the fast part of the molten salt reactor (MSR) spectrum is shaped by fluorine and even the Teflon material is suitable for neutronics in that energy range. Properly selected spectrum indices can describe the neutron field of the MSR in fast thermal and intermediate parts of the spectrum. Current research has focused on a deeper study of the possibility of using the filtered thermal and intermediate neutron spectrum of the experimental light water reactor for the physics of fluoride salt-based reactor. LiF-BeF2 (FLIBE) capsule and teflon cylinders are used as a spectrum filters in the LR-0 reactor. Measured results show acceptable C/E-1 agreement in the reaction rates and satisfactory agreement for usage of the FLIBE filtered neutron spectrum determined by the 181Ta(n, γ) monitor as a mock-up in thermal to intermediate energy in the fluoride high-temperature reactor (FHR). Concerning MSR, intermediate spectrum can be reproduced to some extent but not as good as in the case of FHR.

Highlights

For reactor technology development, the good knowledge of neutronics plays a crucial role as the parameters of neutrons e.g. spectrum and flux can influence the criticality, safety parameters, or material aging
It was concluded that the calculated spectral indices are sufficiently sensitive to changes in the fast neutron tails of different advanced reactor concepts; at the same time, the neutron spectrum of the molten salt reactor (MSR) showed very good agreement with the filtered spectrum of the light water research reactor by the filter containing LiF-BeF2 (FLIBE) salt
The comparison of the expected neutron spectra obtained from calculation models is shown in Fig. 4, where the case “Empty channel” means the central channel without neutron filter, “Teflon” and “FLIBE” are referencing the filters “MSR” is a generic model of the single fluid molten salt reactor and “fluoride high-temperature reactor (FHR)” is the spectrum in the coolant of the small reactor with the plank microparticle fuel [12]

Summary

Introduction

The good knowledge of neutronics plays a crucial role as the parameters of neutrons e.g. spectrum and flux can influence the criticality, safety parameters (feedbacks), or material aging. It has been found that the fast part of the MSR spectrum can be simulated in the LWR by other compounds than FLIBE, containing substantial amounts of bound fluorine, for example with Teflon [2] We demonstrate how sensitive the different materials are in the observed part of the neutron spectrum, and based on the reaction evolution, proper monitors can be selected for the experiments described in the following paragraphs

Methods

Results

Conclusion