Measurement of various monitors reaction rate in a special core at LR-0 reactor

Abstract

Validation of the selected materials cross sections is an important task for their use as flux monitors within experimental measurements. As the reaction rate is a function of neutron spectrum and material cross section, the neutron spectrum must be well defined for the correct cross section validation. This criterion is met in the special core of the LR-0 reactor, where the reaction rates of 181Ta(n,γ), 54Fe(n,p), 54Fe(n,α) and 89Y(n,2n) reactions were measured. The 197Au(n,γ) and 58Ni(n,p) reactions were used as flux monitors during measurements. Results of calculation show that in case of 181Ta(n,γ) reaction, the values reported in JEFF-3.2 provide a good agreement, while ENDF/B-VII.1 is underpredicting the experiment. In case of 54Fe(n,p) reaction, JEFF-3.2 is in satisfactory agreement, while ENDF/B-VII.1 overpredicts the result by about 10%. The 54Fe(n,α) shows significant discrepancies, JEFF-3.2 under predicts by about 20%, while ENDF/B-VII.1 overpredicts result by 40%. The high threshold 89Y(n,2n) reaction is interesting from the point of view of spectral averaged cross section. It is worth noting that the resulted spectral averaged cross section, being 0.169 with 1σ uncertainty of 0.007 mb, is in very good agreement with previous result, being 0.172 ± 0.006 mb.