Abstract
A neutronics benchmark experiment on a pure Copper block (dimensions 60 × 70 × 70 cm3 ) aimed at testing and validating the recent nuclear data libraries for fusion applications was performed in the frame of the European Fusion Program at the 14 MeV ENEA Frascati Neutron Generator (FNG). Reaction rates, neutron flux spectra and doses were measured using different experimental techniques (e.g. activation foils techniques, NE213 scintillator and thermoluminescent detectors). This paper first summarizes the analyses of the experiment carried-out using the MCNP5 Monte Carlo code and the European JEFF-3.2 library. Large discrepancies between calculation (C) and experiment (E) were found for the reaction rates both in the high and low neutron energy range. The analysis was complemented by sensitivity/uncertainty analyses (S/U) using the deterministic and Monte Carlo SUSD3D and MCSEN codes, respectively. The S/U analyses enabled to identify the cross sections and energy ranges which are mostly affecting the calculated responses. The largest discrepancy among the C/E values was observed for the thermal (capture) reactions indicating severe deficiencies in the 63,65 Cu capture and elastic cross sections at lower rather than at high energy. Deterministic and MC codes produced similar results. The 14 MeV copper experiment and its analysis thus calls for a revision of the JEFF-3.2 copper cross section and covariance data evaluation. A new analysis of the experiment was performed with the MCNP5 code using the revised JEFF-3.3-T2 library released by NEA and a new, not yet distributed, revised JEFF-3.2 Cu evaluation produced by KIT. A noticeable improvement of the C/E results was obtained with both new libraries.
Highlights
Benchmarking of cross section data against integral experiments is considered since the early days of neutronics studies a fundamental step which provides feedback to the evaluators for improving both the nuclear data and the nuclear models used to produce them.In the field of fusion neutronics, benchmark experiments were carried out in the USA (e.g. [1,2,3] ) already in the 80’s
The objective of the sensitivity/uncertainty post-analyses was to determine the impact of the cross section uncertainties in the accuracy of the reaction rates (RR) results and this was accomplished by using the SUSD3D code
The results presented in this paper clearly indicate that the new copper cross section evaluation in the JEFF3.3T2 and in the not yet released JEFF-3.2 revision by
Summary
Benchmarking of cross section data against integral experiments is considered since the early days of neutronics studies a fundamental step which provides feedback to the evaluators for improving both the nuclear data and the nuclear models used to produce them. The data analysis was complemented by sensitivity/uncertainty (S/U) analyses using deterministic and Monte Carlo based approaches as available with the SUSD3D and MCSEN codes, respectively [10,11,12]. This analysis allowed to identify the main contributions to the observed discrepancies between experiment and calculation and it is addressed in Sect. In accordance to the finding of the new FNS and the FNG experiments, revised copper cross section evaluations were produced by the NEA Data Bank, Paris, and KIT. The results presented in this paper include the re-analysis performed using the not yet released version of the copper cross sections developed by KIT and included in JEFF-3.3T3
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