Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Modeling Isotope Kinetics in a Circulating Fuel System: a Case Study of the MBIR Reactor Loop

12/14/2022 2022 - #04 Fuel cycle and nuclear waste management

Kuzenkova D.S. Blandinsky V.Yu.

DOI: https://doi.org/10.26583/npe.2022.4.05

UDC: 621.039.5

The paper presents the results of modeling changes in the isotopic composition of the liquid-salt fuel circulating in the experimental channel of the MBIR reactor facility. The authors tested the ISTAR software environment adapted for solving burnup equations in problems with variable power levels. The loop channel parameters, including two heat exchanger options, were estimated to obtain the appropriate salt transit time through the loop channel zones.

Two problems of modeling a circulating fuel system (loop) are considered, namely: (1) modeling the equilibrium salt isotope composition in such a system; and (2) developing a technique for modeling nonstationary isotope kinetics in the MBIR reactor loop.

Non-stationary isotope kinetics can be modeled as sequential burnup of nuclides in the neutron field and decay during movement in the external circuit.

The authors also developed an algorithm for modeling changes in the isotopic composition of fuel salt during its circulation, taking into account the sequential transfer of a given salt volume from the burnup zone to the zone outside the reactor core. Based on this algorithm, a software package was created using the Python 3.9 programming language and ISTAR modules. In addition, a description of the calculation methodology was given and some calculation results obtained using the software were presented.

In the process of working with the program, it was found that, for the given times of the fuel being in each of the zones (2 and 200 seconds, respectively), modeling the change in the isotopic composition during the fuel campaign (500 days) will require the calculation of more than 500 thousand steps. In order to save time, it is necessary to find out whether it will be possible to reduce the number of calls to the neutronic calculation program due to a slight change in the isotopic composition of the fuel in the loop per one burnup step. Work is currently underway to optimize this process.


  1. Blinkin V.L., Novikov V.M. Molten Salt Nuclear Reactors. Moscow. Atomizdat Publ., 1978, 112 p. (in Russian).
  2. Novikov V.M., Slesarev I.S., Alekseev P.N., Ignatiev V.V., Subbotin S.А. Nuclear Reactors of Increased Safety (Analysis of Conceptual Designs). Moscow. Energoatomizdat Publ., 1993, 348 p. (in Russian).
  3. Ignatiev V.V., Kormilitsyn M.V., Kormilitsyna L.A., Semchenkov Y.M., Fedorov Y.S., Feinberg O.S., Kryukov O.V., Khaperskaya A.V. Molten-Salt Reactor for Nuclear Fuel Cycle Closure on All Actinides. Atomic Energy. 2019, v. 125, pp. 279-283; DOI: https://doi.org/10.1007/s10512-019-00481-w .
  4. Dragunov Yu.G., Tretiyakov I.T., Lopatkin A.V., Romanova N.V., Lukasevich I.B. MBIR Multipurpose Fast Reactor – Innovative Tool for the Development of Nuclear Power Technologies. Atomic Energy. 2012, v. 113, no. 1, pp. 24-28; DOI: https://doi.org/10.1007/s10512-012-9590-x .
  5. Blandinskiy V.Y., Kuzenkova D.S. Computational Validation of Experiments with Molten-Salt Thorium-Uranium Fuel Compositions in MBIR Test Loop. Atomic Energy. 2020, v. 128, no. 5, pp. 271-276; DOI: https://doi.org/10.1007/s10512-020-00687-3 .
  6. Capelli E. Thermodynamic investigation of the LiF-ThF4 system. The Journal of Chemical Thermodynamics. 2013, v. 58, pp. 110-116; DOI: https://doi.org/10.1016/j.jct.2012.10.013 .
  7. Benesh O., Konings R.J.M. Thermodynamic Properties and Phase Diagrams of Fluoride Salts for Nuclear Applications. Journal of Fluorine Chemistry. 2009, v. 130, no. 1, pp. 22– 29; DOI: https://doi.org/10.1016/j.jfluchem.2008.07.014 .
  8. Usynin G.B., Karabasov A.S., Chirkov V.A. Optimization Models of Fast Reactors. Moscow. Atomizdat Publ., 1981. 232 p. (in Russian).
  9. MCNP – A General Monte Carlo N-Particle Transport Code. Version 5 / X-5 Monte Carlo Team. LA-UR-03-1987, LLC, 2008. Available at: https://mcnp.lanl.gov/pdf_files/la-ur-03-1987.pdf (accessed Sep. 19, 2022).
  10. Dudnikov A.A. Program for Modeling Isotope Kinetics in Multicomponent Structure of Nuclear Industry «ISTAR». Patent RF, No. 2020619218, 2020. Available at: https://www.elibrary.ru/item.asp?id=43889370 (accessed Sep. 19, 2022) (in Russian).
  11. Alekseevsky L.D. Search for a possible structure of a stationary system for future nuclear power engineering with a closed nuclear fuel cycle based on the study of nuclide balances. VANT. Ser. Fizika Yadernykh Reaktorov. 2008, iss. 2, pp.21-26 (in Russian).
  12. Blandinskiy V.Yu., Dudnikov A.A. Calculations of Spent Fuel Isotopic Composition for Fuel Rod from VVER-440 Fuel Assembly Benchmark Using Several Evaluated Nuclear Data Libraries. Kerntechnik. 2018, v. 83, no. 4, pp. 325-330; DOI: https://doi.org/10.3139/124.110917 .
  13. Kuzenkova D.S., Blandinskiy V.Yu. Program for Calculating Isotope Kinetics in Circulating Fuel Systems Based on the ISTAR PS. Patent RF, No. 2022614236, 2022. Available at: https://www.elibrary.ru/item.asp?id=48139601 (accessed Sep. 19, 2022) (in Russian).

MBIR molten-salt reactors molten-salt loop ISTAR software modeling neutronic characteristics

Link for citing the article: Kuzenkova D.S., Blandinsky V.Yu. Modeling Isotope Kinetics in a Circulating Fuel System: a Case Study of the MBIR Reactor Loop. Izvestiya vuzov. Yadernaya Energetika. 2022, no. 4, pp. 58-66; DOI: https://doi.org/10.26583/npe.2022.4.05 (in Russian).