Criticality Analysis of Fuel Salt Composition and Enrichment Level in a 50 MWth Chloride-Based Molten Salt Fast Reactor

Öz

Achieving high fuel utilization efficiency in Molten Salt Fast Reactors relies on the determination of an appropriate molten fuel salt composition. In this context, this study investigates the neutronic performance of a chloride-based NaCl–UCl₃ molten fuel salt for a 50 MWth cylindrical Molten Salt Fast Reactor (MSFR), which is a Generation IV nuclear energy system. Through analyses conducted using the MCNP6.3.1 Monte Carlo code and the ENDF/B-VIII.1 continuous-energy data library, the effects of varying heavy metal (UCl₃) molar ratios and initial ²³⁵U enrichment levels ranging from 19.75% to 35% on core criticality (keff) were examined. The findings indicate that UCl₃ molar ratios between 30% and 40% fail to satisfy the targeted criticality condition (keff > 1), whereas increasing the heavy metal fraction to 45% and above allows the reactor to reach the criticality limit.

Anahtar Kelimeler

• Molten Salt Fast Reactor (MSFR)
• core criticality (keff)
• chloride-based molten salt

Etik Beyan

The authors of this article declare that the materials and methods they use in their work do not require ethical committee approval and/or legal-specific permission.

Teşekkür

This study was supported by the Scientific and Technological Research Council of Türkiye (TUBITAK) under the Grant Number 125M611. The authors thank TUBITAK for their support.

50 MWth Klorür Esaslı Ergimiş Tuz Hızlı Reaktöründe Yakıt Tuzu Bileşimi ve Zenginleştirme Oranının Kritiklik Analizi

Öz

Ergimiş Tuz Hızlı Reaktörlerinde yüksek yakıt kullanım verimliliğinin sağlanması, uygun ergimiş yakıt tuzu bileşiminin belirlenmesine bağlıdır. Bu kapsamda, bu çalışmada 4. Nesil nükleer enerji sistemlerinden biri olan 50 MWth gücündeki silindirik bir Ergimiş Tuz Hızlı Reaktörü (ETHR) için klorür esaslı NaCl–UCl₃ ergimiş yakıt tuzunun nötronik performansı incelenmiştir. MCNP6.3.1 Monte Carlo kodu ve ENDF/B-VIII.1 sürekli enerji veri kütüphanesi kullanılarak gerçekleştirilen analizlerde, farklı ağır metal (UCl₃) molar oranları ile %19,75–35 arasında değişen başlangıç ²³⁵U zenginleştirme seviyelerinin kor kritikliği (keff) üzerindeki etkileri araştırılmıştır. Bulgular, %30–40 aralığındaki UCl₃ molar oranlarının hedeflenen kritiklik koşulunu (keff > 1) sağlayamadığını, buna karşılık ağır metal oranının %45 ve üzerine çıkarılmasıyla reaktörün kritiklik sınırına ulaştığını göstermiştir.

Anahtar Kelimeler

• Ergimiş Tuz Hızlı Reaktörleri (ETHR)
• kor kritikliği (keff)
• klor bazlı ergimiş tuz

Etik Beyan

Bu makalenin yazarları çalışmalarında kullandıkları materyal ve yöntemlerin etik kurul izni ve/veya yasal-özel bir izin gerektirmediğini beyan ederler

Teşekkür

Bu çalışma, Türkiye Bilim ve Teknolojik Araştırma Konseyi (TÜBİTAK) tarafından 125M611 numaralı proje ile desteklenmiştir. Projeye verdiği destekten ötürü TÜBİTAK'a teşekkürlerimizi sunarız.

Kaynakça

1. [1] Nguyen T. D., van Rooijen W. F. G. Design of reactor physics experiments in support of chloride-fueled Molten Salt Reactor research & development. Ann. Nucl. Energy, 181, (2023). doi: 10.1016/j.anucene.2022.109479.
2. [2] Mausolff Z., DeHart M., Goluoglu S. Design and assessment of a molten chloride fast reactor. Nuclear Engineering and Design, 379, (2021). doi: 10.1016/j.nucengdes.2021.111181.
3. [3] Kloosterman J. L. Molten Salt Reactors and Thorium Energy, edited by Dolan T. J. Ann. Nucl. Energy, 117, (2018) 1–2. doi: 10.1016/J.ANUCENE.2018.02.017.
4. [4] Status of Molten Salt Reactor Technology, Vienna, 2023.
5. [5] Alexander L. G. vd. Experimental Molten-Salt Fueled 30 Mw Power Reactor, Tennesse, 1960.
6. [6] Sooby E. S., Nelson A. T., White J. T., McIntyre P. M. Measurements of the liquidus surface and solidus transitions of the NaCl-UCl3 and NaCl-UCl3-CeCl3 phase diagrams. Journal of Nuclear Materials, 466, (2015) 280–285. doi: 10.1016/j.jnucmat.2015.07.050.
7. [7] Sridar S. vd. Thermodynamic modeling of the KCl-LiCl-NaCl-UCl3 system for molten salt electrolysis and reprocessing of spent nuclear fuel. CALPHAD, 88: 2025, (2025). https://doi.org/10.1016/j.calphad.2025.102801.
8. [8] Klueh R. L. vd. Ferritic/martensitic steels - Overview of recent results. Journal of Nuclear Materials, 307–311: 1 SUPPL., (2002) 455–465. doi: 10.1016/S0022-3115(02)01082-6.

9. [9] Azhazha V. M. vd. Alloys For Molten-Salt Reactors, Kharkov, Ukraine, 2005.
10. [10] Ambrosek J. Molten Chloride Salts for Heat Transfer in Nuclear Systems, University of Wisconsin-Madison, Madison, USA, 2011. doi: 10.13140/RG.2.2.32098.09924.
11. [11] Gentile R., Hawkins L., Woods M., Gakhar R., Murray D., He L. Corrosion Response of Ni-19Cr-5Fe in Molten NaCl-MgCl2 Salt. JOM, 78, (2025) 11. doi: 10.1007/s11837-025-08019-1.
12. [12] Noori-kalkhoran O., Jain L., Powell L., Jones A., Aflyatunova D., Merk B. On the Employment of a Chloride or Floride Salt Fuel System in Advanced Molten Salt Reactors, Part 2; Core Inventory, Fuel Burnup, and Salt Clean-Up System. Energies (Basel)., 17: 6, (2024). doi: 10.3390/en17061475.
13. [13] Taube M. Fast Reactors Using Molten Chloride Salts as Fuel: Final Report (1972-1977), Würenlingen, Swiss, 1978.
14. [14] Holcomb D. E., Flanagan G. F., Patton B. W., Gehin J. C., Howard R. L., Harrison T. J. Fast Spectrum Molten Salt Reactor Options, 2011.
15. [15] Scott I. R. A pratical molten salt fission reactor UK Patent Application, GB 2508537 A, 2014.
16. [16] Wang X. vd. The Neutron Physical Feasibility Of A Small Modular Dual Fluid Reactor. The Proceedings of the International Conference on Nuclear Engineering (ICONE) 2019.27, Tsukuba, Ibaraki (Japan), 2019. doi: 10.1299/jsmeicone.2019.27.1229.
17. [17] Pheil E. Elysium Industries Molten Chloride Salt Fast Reactor, Thorium Energy Alliance, Harvard, USA, 2019.
18. [18] Brovchenko M. vd. Neutronic benchmark of the molten salt fast reactor in the frame of the EVOL and MARS collaborative projects. EPJ - Nuclear Sciences & Technologies, 5, (2019) 2. doi: 10.1051/EPJN/2018052.
19. [19] Merk B., Detkina A., Atkinson S., Litskevich D., Cartland-Glover G. Evaluation of the breeding performance of a NaCl-UCl-Based reactor system. Energies (Basel)., 12: 20, (2019). doi: 10.3390/en12203853.
20. [20] Gregg L. Design of a Molten Chloride Fast Spectrum Reactor, 2018.
21. [21] Dwijayanto R. A. P., Harto A. W. Neutronic Analysis of LEU-started Molten Chloride Fast Reactor without Fuel Reprocessing. Computational And Experimental Research In Materials And Renewable Energy, 4: 1, (2021) 8. doi: 10.19184/cerimre.v4i1.24962.
22. [22] Bushnag M., Oh T., Kim Y. A Neutronic Study on Safety Characteristics of Fast Spectrum Stable Salt Reactor (SSR). Transactions of the Korean Nuclear Society Virtual Autumn Meeting, Daejeon, South Korea, 2021.
23. [23] Southern Company T. L. B. E. A. L. Technology Inclusive Content of Application Project For Non-Light Water Reactors TerraPower Molten Chloride Reactor Experiment TICAP Tabletop Exercise Report Document Number, 2021.
24. [24] Mochizuki H. Neutronics and thermal-hydraulics coupling analyses on transient and accident behaviors of molten chloride salt fast reactor. J. Nucl. Sci. Technol., 60: 6, (2023) 642–668. doi: 10.1080/00223131.2022.2131647.
25. [25] Nasr M. A., Zolfaghari A., Akbari R., Cammi A., Amirkhosravi S. Neutronic and fuel cycle performance analysis of fluoride and chloride fuels in Molten Salt Fast Reactor (MSFR). Nuclear Engineering and Design, 413, (2023). doi: 10.1016/j.nucengdes.2023.112506.
26. [26] Hartanto D., Chandler D., Hogue K., Westphal G. Analyzing Safeguards-Relevant Parameters of a Fast-Spectrum Molten Chloride Salt Reactor, 2023.
27. [27] Peng Y., Zhu G., Wang H., Yao A., Song Y., Niu M. Design space analysis for a NaCl-UCl3 based breed and burn reactor system. Ann. Nucl. Energy, 214, (2025). doi: 10.1016/j.anucene.2025.111225.
28. [28] Choi S. vd. Nuclide inventory analysis and fission product monitoring for nuclear safeguards in molten chloride fast reactors. Nuclear Engineering and Technology, 57: 11, (2025). doi: 10.1016/j.net.2025.103793.
29. [29] Tano M. E. vd. Coupled neutronics, thermochemistry, corrosion modeling and sensitivity analyses for isotopic evolution in molten salt reactors. Progress in Nuclear Energy, 178, (2025). doi: 10.1016/j.pnucene.2024.105503.
30. [30] Dwijayanto A. P., Nishihara K., Okamura T., Nakase M. Preliminary design and front-end fuel cycle assessment of 200 MWt marine molten chloride fast reactor. Ann. Nucl. Energy, 229, (2026) 112124. doi: 10.1016/j.anucene.2026.112124.
31. [31] Noori-kalkhoran O., Litskevich D., Detkina A., Jain L., Cartland-Glover G., Merk B. On the Employment of a Chloride or Fluoride Salt Fuel System in Advanced Molten Salt Reactors, Part 1: Thermophysical Properties and Core Criticality. Energies (Basel)., 15: 23, (2022). doi: 10.3390/EN15238865.
32. [32] EVOL Project Consortium (CNRS). EVOL (Project n°249696) Final Report, 2015.
33. [33] Dwivedi D. K., Srivastava A. K., Gupta A., Kannan U. Neutronics study of chloride fuel salts for experimental design of small Molten Salt Reactor. Nuclear and Particle Physics Proceedings, 339–340, (2023) 129–132. doi: 10.1016/J.NUCLPHYSBPS.2023.08.009.
34. [34] ANSYS, Inc. ANSYS DesignModeler, 2025 (R2) Canonsburg, PA, ABD, 2025.
35. [35] Kulesza J. A. vd. MCNP® Code Version 6.3.1 Theory & User Manual.
36. [36] Rising M. vd. MCNP® Code Version 6.3.1 Release Notes.
37. [37] Dassault Systèmes SolidWorks Corp. SOLIDWORKS, 2025. Waltham, MA, ABD, 2025.
38. [38] Şahin H. M., Akbayır Ö, Tunç G., Atalay U. Neutronic evaluation of a thermo-hydraulically optimized 50 MWth molten salt fast reactor. Ann. Nucl. Energy, 238, (2026). doi: 10.1016/j.anucene.2026.112540.
39. [39] Akbayır Ö, Şahin H. M. Thermal-hydraulic analysis of a 50 MWth Molten Salt Fast Reactor to optimise pump configuration and core geometry. Progress in Nuclear Energy, 195, (2026). doi: 10.1016/j.pnucene.2026.106303.
40. [40] Gibson N. A., Saller T., Haeck W., Kleedtke N. A., Neudecker D. Release of Lib81: ENDF/B-VIII.1-Based ACE Data Files for Neutron Transport Memorandum XCP-5 Materials and Physical Data, 2025.
41. [41] Şahin S., Şahin H. M., Tunç G., Şahiner H. Design studies for A 50 MWth molten salt fast reactor. Progress in Nuclear Energy, 166, (2023) 104964. doi:10.1016/j.pnucene.2023.104964
42. [42] DeHart, M. vd. (2023). A Review of Candidates for a Validation Data Set for High-Assay Low-Enrichment Uranium Fuels. Journal of Nuclear Engineering. https://doi.org/10.3390/jne4030038
43. [43] Kemp R.S. vd. The weapons potential of high-assay low-enriched uranium. Science 384, 1071-1073 (2024). doi:10.1126/science.ado8693