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ORIGINAL RESEARCH article

Front. Phys.

Sec. Nuclear Physics​

Comparative Analysis of Top Beryllium Shim Worth in NIRR-1 HEU and LEU Cores Using WIMS-ANL and REBUS-ANL

Provisionally accepted
DENNIS BALAMIDENNIS BALAMI1*John SimonJohn Simon2Asuku AbdulsamadAsuku Abdulsamad3Yakubu Ibrahim VivaYakubu Ibrahim Viva3Rabiu NasiruRabiu Nasiru4
  • 1University of Maiduguri, Maiduguri, Nigeria
  • 2National Open University of Nigeria Faculty of Science, Abuja, Nigeria
  • 3Ahmedu Bello University Centre for Energy Research and Training, Zaria, Nigeria
  • 4Ahmadu Bello University, Zaria, Nigeria

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This study aims to estimate and compare the worth of beryllium shim plates in the Nigerian Research Reactor-1 (NIRR-1) following its conversion from High Enriched Uranium (HEU) to Low Enriched Uranium (LEU) fuel. The study utilized the WIMS-ANL and REBUS-ANL codes to compute the reactor core reactivity and the worth of beryllium shims. The total worth of the beryllium shims was estimated to be 14.16 π‘šπ‘˜ or 1416 π‘π‘π‘š (through 1 π‘šπ‘˜= 100 π‘π‘π‘š) and 13.28 π‘šπ‘˜ or 1328 π‘π‘π‘š for the HEU and LEU core respectively. The results revealed a difference in the total shim worth in the two reactor cores with a saturation in reactivity worth observed at a shim thickness of approximately 10 βˆ’12 π‘π‘š as expected. The comparison with measured differential worth of beryllium shims showed 26% deviation of the calculated value from the measured one, thus indicating the level of accuracy of the REBUS-ANL code. These research findings highlight the importance of MNSR's conversion from HEU to LEU and indicates that in addition to minimization of proliferation concerns, the conversion process does not significantly impact on the top beryllium shim worth which is used to extend the operational cycle of the reactor.

Keywords: beryllium shim plates, NIRR-1, Reactivity worth, REBUS-ANL code, WIMS-ANL code

Received: 11 Aug 2025; Accepted: 09 Jan 2026.

Copyright: Β© 2026 BALAMI, Simon, Abdulsamad, Ibrahim Viva and Nasiru. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: DENNIS BALAMI

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

Supplementary Material