Abstract
There were two similar series of burst waiting time experiments carried out on Godiva-II and Caliban respectively and analyzed for neutron initiation study, unfortunately both the strength of spontaneous fission neutron source given in the published papers are not consistent with the spontaneous fission data of U-235 and U-238. In this paper, the discrepancies of spontaneous fission data of U-235 and U-238 from different references are reviewed and clarified and the correct strength of spontaneous fission neutron source for Godiva-II and Caliban are calculated respectively, then the multiplication equivalence method of arbitrary source is introduced and the equivalent fundamental-mode(EFM) co-efficiencies of spontaneous fission neutron source for Godiva-II and Caliban are calculated with MC software, lastly the strength of neutron source for these two HEU metal burst reactor in EFM are deduced. The EFM neutron strength of this two burst reactors are much less than proposed values used for burst waiting investigation in published papers respectively, and with the new data, the inconsistency of burst waiting time to the published results is presented and discussed.
Highlights
Godiva-II and Caliban are the same type of highly enriched uranium (HEU) metal, fast neutron burst reactors, and both can be operated to produce a burst in a slightly super prompt-critical
The data were used as a sample analyzed for the investigation of neutron initiation, but the experimental results had not matched the analytical results with the Hansen initiation model[3]
With the simulation method proposed by Xiao[4], the burst waiting time experiment simulation program are developed, and tested using the same parameter of Godiva-II and Caliban presented in the papers above via comparing the simulation results with the reference
Summary
Godiva-II and Caliban are the same type of HEU metal, fast neutron burst reactors, and both can be operated to produce a burst in a slightly super prompt-critical. Later in 2014 Nicolas Authier analyzed the Caliban’s waiting time results with the same simulation method, and drew the same conclusion that the simulation matches the experiment well[5] For this type of experiments, the neutron source includes two kinds of origins, one is the spontaneous fission neutron (intrinsic source) from U-235 and U-238, the other is from the delayed neutrons precursors which are born and accumulated before the burst initiation takes place. This makes this type of experiment hard to be used for initiation study, Liu[6,7] established a novel experimental method for validating the neutron initiation. Both the strength of spontaneous fission neutron source used for Godiva-II and Caliban waiting time experiment simulation in the published papers are not consistent with the spontaneous fission data of U-235 and U-238. Firstly the basic information of Godiva-II and Caliban reactor and the discrepancies of spontaneous fission data of U-235 and U-238 from different references are reviewed, the EFM coefficiencies for spontaneous fission neutron source and EFM neutron strength of these two reactors are calculated; lastly with the new neutron strength data, the waiting time experiment simulation was carried out and the inconsistency of burst waiting time between this results to the published results is presented and discussed
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