Neutron Generation Time in Highly-Enriched Uranium Core at Kyoto University Critical Assembly. (1st December 2020)

• Record Type: Journal Article
• Authors: Pyeon, Cheol Ho; Yamanaka, Masao; Endo, Tomohiro; Chiba, Go; Van Rooijen, Willem F. G; Watanabe, Kenichi
• Is Part Of: Nuclear science and engineering. Volume 194:Number 12(2020)
• Page Start: 1116
• Page End: 1127
• Publication Date: 2020-12-01
• Subjects: Neutron generation time -- highly enriched uranium core -- Kyoto University Critical Assembly -- near critical -- thermal neutron spectrum; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; Nuclear energy; Nuclear engineering; Periodicals; 539.705
• DOI: 10.1080/00295639.2020.1774230
• Languages: English
• ISSNs: 0029-5639

Abstract

Abstract: At the Kyoto University Critical Assembly experiments on kinetics parameters are carried out at near-critical configurations, supercritical and subcritical states, in the thermal neutron spectrum made with a highly enriched uranium fuel. The main calculated kinetics parameters, the effective delayed neutron fraction (βeff ) and the neutron generation time (Ʌ), are used effectively for the estimation of experimental parameters, and the accuracy of experiments on prompt neutron decay constant (α) and subcriticality (ρ$ ) in dollar units is attained by the numerical results of βeff and Ʌ. Furthermore, the value of βeff /Ʌ is experimentally deduced with the use of the experimental results of α and ρ$, ranging between 250 and −80 pcm. Thus, the experimentally deduced values of βeff /Ʌ that reveal good accuracy through a comparison with those by the MCNP6.1 calculations with JENDL-4.0 are then taken as an index of Ʌ by introducing an acceptable assumption of βeff at near-critical configurations. From the results of experimental and numerical analyses, the experimental value of βeff /Ʌ is important for the validation of Ʌ since kinetics parameters are successfully obtained from the clean cores of near-critical configurations in the thermal neutron spectrum.