Fission neutron source in Rome

Calculation of radiation exposure for VVER reactor vessel is a key task for the following determination of their burn-up life. This problem is especially topical for VVER-440 reactors of the first generation which now require substantiation report of safe operation over-designed service life. The estimation of radiation exposure of the reactor vessel involves the calculation of fast neutron fluence (E≥0.5 MeV) on welded joints and basis metal of the reactor vessel. The result of neutron fluence calculation and the associated estimation error are affected by the precision of fission neutron source definition in the reactor core. This study examines two approaches to defining fission neutron source in the fuel assembly: specifically, assembly-wise distribution, as well as rod-wise distribution approaches.The main objective of this work is to characterize the difference in calculation results of neutron fluence (E≥0.5MeV) on the VVER-440 reactor vessel at rod-wise and assembly-wise definition of the fission neutron source inperipheral fuel assemblies, and to estimate the accuracy of fluence calculation for each source definition method, bycomparing them with some experimental data. The present study examines the results of two different experiments carried out on the block of No.1 of Kola Nuclear Power Plant (V-230): each involving activity measurement for templates cut out on the internal reactor vessel surface and activity measurement of neutron-activation detectors of Niobium on the external reactor vessel surface.

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REVIEW ON THE NEUTRON SOURCE STRENGTH OF HEU METAL BURST REACTOR

EPJ Web of Conferences ◽

10.1051/epjconf/202124707004 ◽

2021 ◽

Vol 247 ◽

pp. 07004

Author(s):

Xiaobo Liu

Keyword(s):

Neutron Source ◽

Waiting Time ◽

Fundamental Mode ◽

Spontaneous Fission ◽

Fission Neutron ◽

Source Strength ◽

Similar Series

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.

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