The long-lived radionuclides radiotoxicity ranking the nuclear fuel cycle of the Belarusian NPP

Using a methodical approach to the potential biological hazard (radiotoxicity) assessment of radionuclides, computational studies and a comparative analysis of the contributions to the total radiotoxicity of long-lived fission products and actinides accumulated in the nuclear fuel cycle of the Belarusian NPP were carried out. In order to estimate correctly the 237Np isotope mass at the long-term stage of SNF management, the mathematical model of the nuclear fuel cycle of the Belarusian NPP of the code CUB was modified to take into account the transmutation chain of 241Pu, 241Am and 237Np isotopes. The initial concentrations for the main radiation-hazardous radionuclides at the time of fuel unloading from the VVER1200 reactor core are presented in the database “Radiation Characteristics of Spent Nuclear Fuel of the Belarusian NPP” developed by the authors. The database development is carried out in accordance with the recommendations of the RB-093-20 “Radiation and thermophysical characteristics of spent nuclear fuel of pressurized water power reactors and high-power channel reactors”. The main characteristics used in the nuclear fuel cycle simulation in the CUB code, such as the total mass of spent nuclear fuel (2492 tons), the number of spent fuel assemblies (5294) and the average burnup, are taken in accordance with the Spent Fuel Management Strategy of the Belarusian NPP data. It is shown that at the stage up to 100 years, the main contributors to the total radiotoxicity are the isotopes of 238Pu, 239Pu, 240Pu, 243Am, 241Pu, 241Am, 237Np, where contributions of three last of them are 0.07, 49.0 and 0.007%, respectively. But 5000 years later, the contribution of 241Am will be 0.24%, and the isotope 237Np – up to 0.1% of the total actinides radiotoxicity. The results obtained can be used to substantiate for the recovery degree requirements of 237Np, 241Pu, 241Am during the SNF of the Belarusian NPP reprocessing.

1. Korchova J. A., Harbachova N. V., Kuzmina N. D., Kulich N. V. Assessment of activity resources by nomenclature of main radiation-hazardous radionuclides during the long-term management of spent nuclear fuel of the Belarusian NPP. Vestsi Natsyyanal’nai akademii navuk Belarusi. Seryya fizika-technichnych navuk = Proceedings of the National Academy of Sciences of Belarus. Physical-technical series, 2020, vol. 65, no. 2, pp. 243–251 (in Russian). https://doi.org/10.29235/15618358-2020-65-2-243-251

2. Korchova J. A., Harbachova N. V., Kuzmina N. D., Kulich N. V., Petrovskiy A. M. Computational Studies of the Radiotoxicity of Irradiated WWER-1200 Fuel and Its Loss of Activity during the Long-Term Treatment of Spent Nuclear Fuel from the Belarusian NPP. Bulletin of the Russian Academy of Sciences: Physics, 2020, vol. 84, no. 10, pp. 1300–1303. https:// doi.org/10.3103/S1062873820100159

3. Korchova J. A., Harbachova N. V., Kuzmina N. D., Kulich N. V., Yatsko S. N. Analysis of ponential hazard of the spent nuclear fuel at the intermediate and long-term stages of the nuclear fuel. Nonlinear Dynamics and Applications: Proceeding of the 28th Anniversary Seminar NPCS-2021, May 18–21, 2021, Minsk Belarus. Minsk, 2021, vol. 27, pp. 217–227.

4. Lopatkin A. V., Platonov I. V., Popov V. E. Conditions for Reaching Radiation Equivalence of Native Raw Materials and Long-Lived Radioactive Waste in Nuclear Energy in Russia. Atomic Energy, 2020, vol. 129, iss. 4, pp. 188–193. https://doi.org/10.1007/s10512-021-00732-9

5. A Basic Toxicity classification of radionuclides. Technical reports series no. 15. Vienna, IAEA, 1963. 45 p.

6. Gorbacheva N. V., Beresneva N. V., Kulich N. V., Skurat V. V. Verification and use of a set of mathematical programs for assessing radioactivity reserves to ensure the safety of nuclear installations at the NP site. Obespechenie bezopasnosti AES s VVER: materialy 6-i Mezhdunarodnoi nauchno-tekhnicheskoi konferentsii [Ensuring the Safety of Nuclear Power Plants with WWER: Reports of the 6th International Scientific and Technical Conference]. Podol’sk, 2009. Available at: https://gosatomnadzor.mchs.gov.by/upload/iblock/a76/npa-yrb-1.pdf (in Russian).