Request for 35 Cl(n,p) reaction cross-section measurements and re-evaluations from the standpoint of molten chloride salt fast reactor design

Abstract

ABSTRACTA molten chloride salt fast reactor with inherent safety features is being studied in order to utilize spent fuel discharged from light-water reactors effectively and to reduce environmental burdens. A hard neutron spectrum is required to achieve the transmutation of TRU efficiently, which can be realized by using a molten chloride salt. However, it was found that the criticality analysis shows a large difference of 2%Δk among the effective multiplication factors (keff) obtained using several evaluated nuclear data libraries. A sensitivity analysis was performed to investigate the cause of the difference in keff and it was clarified that the difference of 2%Δk/k reactivity was due to the difference in cross sections of the 35Cl(n,p)35S reaction. Such a large difference in keff makes a reliable core design difficult and strongly affects important core characteristics such as the TRU transmutation rate, conversion ratio, and so on. Therefore, this paper has been prepared to make a strong request for measurements and re-evaluations of the (n,p) cross section of 35Cl.KEYWORDS: Molten salt reactorchloridefast reactortransmutationTRU35Cl(np) reactionDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also. AcknowledgmentsWe would like to thank Assistant Prof. Chikako Ishizuka at the Tokyo Institute of Technology for her helpful discussions, encouragement and also for computer maintenance to proceed calculations.Fig. 1 Conceptual design for 700-MWt reactor core with four heat exchangers (unit in meters).Display full sizeFig. 2 Bird’s-eye view of the reactor with four loops and a stainless steel reflector.Display full sizeFig. 3 Calculation model of the MCSFR.Display full sizeFig. 4 Average neutron spectrum in the core of the MCSFR.Display full sizeFig. 5 Sensitivities of keff to the reaction cross sections of 35Cl calculated using Serpent 2Display full sizeand ENDF/B-VIII.0.(n,p), (n,α), and (n,γ) cross sections(n,n) and (n,n’) cross sectionsFig. 6 Relative cross-section differences of 35Cl between ENDF/B-VIII.0 and JENDL-5.Display full sizeThe reference of the relative difference is ENDF/B-VIII.0.(n,p), (n,α), and (n,γ) cross sections(n,n) and (n,n’) cross sectionsFig. 7 Contribution of the relative difference in the (n,p) cross sections for 35Cl between ENDF/B-VIII.0 and JENDL-5 to reactivity.Display full sizeThe reference of the relative difference is ENDF/B-VIII.0.Fig. 8 Comparison of nuclear data libraries for the 35Cl (n,p) 35S reaction cross sections with the experimental values. There are three experimental values around 14 MeV: one of Schantl at 14.7 MeV (1970) [Citation21] and the other two of Nagel at 14.6 MeV (1966) [Citation22].Display full sizeFig. 9 Comparison of the 35Cl (n,p) 35S reaction cross sections of JENDL-4.0, JENDL-5, and ENDF/B-VIII.0 with the new experimental data.Display full sizeTable 4 Comparison of effective multiplication factors calculated using the differentnuclear data libraries.TableDownload CSVDisplay Table