Comparison of fast neutron spectra in graphite and FLINA salt inserted in well-defined core assembled in LR-0 reactor

Abstract

The present paper aims to compare the calculated and measured spectra after insertion of candidate materials for the MSR/FHR reactor system concept into the LR-0 reactor. The calculation is realized with MCNP6 code using ENDF/B VII.0, JEFF 3.1, JENDL 3.3, JENDL 4, ROSFOND and CENDL 3.1 nuclear data libraries. Additionally, comparisons between the slowing down power of each media were performed. The slowing down properties are important parameters affecting the thickness of moderator media in a reactor.

Special Issue: Research Center Řež: Nuclear-Engineering Activities in 2020

“…Some variations of the spectra occur in the region below 0.2 eV, with deviations less than 2 %; however in several groups in the resonance region around 300 eV, these deviations can reach up to 10 % (refer to Figure 3). Indeed, for reactions with a threshold above 0.1 MeV, where the spectrum was well-validated (Kostal et al, 2015, Kostal et al, 2017a, the computationally evaluated spectral shift effect does not exceed calculational uncertainties, typically on the order of 0.1%. This leads to the conclusion that the evaluations of spectrum averaged cross sections of threshold reactions in various arrangements can be combined, only in the case of capture reactions they must be corrected for the spectral shift effect.…”

“…The actual neutron flux in the reference volume is then obtained simply by calculating neutron flux multiplied by the scaling factor. This approach is possible as the neutron field used in the defined position of the monitors is the benchmark reference neutron field (Kostal et al, 2020), where the mathematical models used for the flux calculations were validated within study of the criticality (Kostal et al, 2016a), flux distribution (Kostal et al, 2018b), fission source distribution (Kostal et al, 2016b, and neutron spectrum (Kostal et al, 2015).…”

Measurement of the23Na(n,2n) cross section in235U and252Cf fission neutron spectra

“…1). It is a well-defined core with an already characterized reactivity [6], fission rates distribution [7] and also neutron spectra [8] (see Fig. 2).…”

“…Two kinds of activation material were employed: gold (1% Au in Al) and nickel (100% Ni). The following activation reactions were used: 197 Au (n,γ ) 198 Au and 58 Ni (n,p) 58 Co. From comparison with measured values, the scaling factor K was determined [8]. Its physical meaning is the core neutron emission rate.…”