THERMODYNAMIC MODELING OF THE EQUILIBRIUM COMPOSITION OF THE REACTION PRODUCTS IN THE DEWATERING PROCESS OF THE CHANNEL OF URANIUM-GRAPHITE REACTOR

The paper discusses the phenomena and processes occurring in the industrial, power and research uraniumgraphite nuclear reactors at heat removal trouble, clad damage and technological channel dewatering. The authors describe the accidental situations leading to build-up of the fragments of irradiated nuclear fuel in graphite stack of the Magnox, HTR, AGR reactors and B and N reactors in Hanford. The processes occurring at serious fuel element bridging which consisting of metal uranium are best documented. Moreover, the paper analyzes the possible chemical compounds of metal uranium with fuel element case, technological channel material, steam gas mixture, water and graphite stack. The authors adduce data on qualitative composition of compounds that could contain accidental release of nuclear fuel in the graphite stack. Such data were obtained by thermodynamic method based on the principle of the entropy maximum. It was shown that at reaching the melting temperature of metal uranium various solid and gaseous chemical compounds such as oxides, hydrates, carbides and others could form, but their concentration and amount depend on temperature inside of the graphite stack. The paper also shows the mathematical model of dewatering and steam lock of technological channel of the B and N type reactors. Aforementioned model follows the non-stationary heat transfer equation with Dirichlet and Neumann boundary conditions. Solution algorithm of this equation is realized in Ansys Fluent and Matlab. It was clearly shown that UO2 is the main product that build-up in the graphite stack at the heat removal trouble, clad damage and technological channel dewatering. Furthermore, it is possible to form the gaseous products such as CO, CH4 and H2, and it is unlikely to form the compound of metal uranium and hydrogen (tritium). The results could be used in choosing the way of treatment of irradiated graphite in particular at the disassembling graphite stack.

1. Izmestiev A., Pavliuk A., Kotlyarevsky S. Application of void-free filling technology for additional safety barriers creation during uranium-graphite reactors decommissioning. Advanced Materials Research, 2015;1084:613–619 (in Eng.).

2. Pavliuk A.O., Kotlyarevskiy S.G., Bespala E.V. et al. Experimental simulation of the radionuclide behavior in the process of creating additional safety barriers in solid radioactive waste repositories containing irradiated graphite. IOP Conf. Series: Materials Science and Engineering, 2016;142:1–7 (in Eng.).

3. Jackson S.F., Monk S.D., Riaz Z. An investigation towards real time dose rate monitoring, and fuel rod detection in a First Generation Magnox Storage Pond. Applied Radiation and Isotopes, 2014;94:254–259 (in Eng.).

4. Dawson J.W. Gas-cooled nuclear reactor designs, operation and fuel cycle. London: Woodhead Publishing Limited, 2002 (in Eng.).

5. Bushuev A.V., Kozhin A.F. Petrova E.V., Zubarev V.N., Aleeva T.B., Girke N.A. Radioactive reactor graphite (Radioaktivnyi reaktornyi grafit). Moscow: NIYaU MIFI, 2015 (in Russ.).

6. Reed B.C. The history and science of the Manhattan Project. Alma: Springer-Verlag Berlin Heidelberg, 2014.

7. Toffer H. Evolution of the Hanford graphite reactor technology. 50 Years with Nuclear Fission, 1989;237–243 (in Eng.).

8. Onishi Y. Fukushima and Chernobyl nuclear accidents’ environmental assessments and U.S. Hanford Site’s waste management. Procedia IUTAM, 2014;372–381 (in Eng.).

9. Burn D. Nuclear power and the energy crisis. London: The macmillan press LTD, 1978 (in Eng.).

10. Nuclear energetics metallurgy and influence of irradiation on materials (Metallurgiya yadernoi energetiki i deistvie oblucheniya na materialy), Proceedings, Мoscow, Gosudarstvennoe nauchno-tekhnicheskoe izdatel'stvo literatury po chernoi i tsvetnoi metallurgii, 1956 (in Russ.).

11. Emel'yanov V.S., Evstyukhin A.M. Metalurgy of nuclear fuel material (Metallurgiya yadernogo goryuchego). College textbook (Vol. 2). Мoscow, Atomizdat, 1968 (in Russ.).

12. Turaev N.S., Zherin I.I. Chemistry and technology of uranium (Khimiya i tekhnologiya urana). Мoscow, Published house “Ruda i Metally”, 2006 (in Russ.).

13. Trusov B.G. Program system TERRA for simulation of phase and chemical equilibriums in plasmachemical systems (Programmnaya sistema TERRA dlya modelirovaniya fazovykh i khimicheskikh ravnovesii v plazmokhimicheskikh sistemakh). III Mezhdunar. simp. po teor. i prikl. Plazmokhimii, 2002;1:217–220 (in Russ.).

14. Belov G.V., Trusov B.G. Thermodynamic simulation of chemically reactive systems (Termodinamicheskoe modelirovanie khimicheski reagiruyushchikh sistem). Мoscow, MGTU imeni N.E. Baumana, 2013 (in Russ.).

15. Pupyshev A.A. Thermodynamic simulation of thermochemical processes (Termodinamicheskoe modelirovanie termokhimicheskikh protsessov). Ekaterinburg, UGTU-UPI, 2007 (in Russ.).

16. Gurvich L.V., Veits I.V., Medvedev V.A. Thermodynamic properties of individual materials (Termodinamicheskie svoistva individual'nykh veshchestv), Reference book. Мoscow: Nauka, 1978–1982 (in Russ.).

17. Barnaby F. Plutonium and Security. New York: St. Martin’s press, 1992 (in Eng.).

18. IAEA. Characterization, Treatment and Conditioning of radioactive graphite from decommissioning of nuclear reactors. IAEA-TECDOC-1521. September, 2006 (in Eng.).

19. Paasch R.A. A compilation of Carbon-14 Data. UNC Nuclear Industries, 1985 (in Eng.).

20. Ojovan M.I., Lee W.E., Sobolev I.A., et al. Thermochemical processing using powder metal fuels of radioactive and hazardous waste. Journal of Process. Mechanical Engineering, 2004;218:1–9 (in Eng.).

21. Vulpius D., Baginski K., Fischer C., Thomauske B. Location and chemical bond of radionuclides in neutron-irradiated nuclear graphite. Journal of Nuclear Materials. 2013;438: 163–177 (in Eng.).

22. Takahashi R., Toyahara M., Maruki S. Investigation of morphology and impurity of nuclear grade graphite, and leaching mechanism of Carbon-14. IAEA Technical Committee Meeting on Nuclear Graphite Waste Management, 1999:176–190 (in Eng.).

23. Kashcheev V.A., Ustinov A.O., Yakunin S.A., Zagumennov V.S., Pavlyuk A.O., Kotlyarevskii S.G., Bespala E.V. Technology and device for burning irradiated reactor graphite (Tekhnologiya i ustanovka dlya szhiganiya obluchennogo reaktornogo grafita). Atomic Energy, 2017;122(4):210–213 (in Russ.).

24. Bespala E., Novoselov I., Ushakov I. Heat transfer during evaporation of cesium from graphite surface in an argon environment. MATEC Web of Conferences, 2016;72:1–5 (in Eng.).

25. Bushuev A.V., Verzilov Yu.M., Zubarev V.N., et al. Fission products and actinides in spent graphite stacks of reactors of Siberian Group of Chemical (Produkty deleniya i aktinoidy v otrabotavshem grafite kladok reaktorov Sibirskogo khimicheskogo kombinata). Atomic Energy, 2000;89(2):139–146 (in Russ.).

26. Bondar’kov M.D., Bondar’kov D.M., Maksimenko A.M., Zheltonozhskii V.A., Zheltonozhskaya M.V., Petrov V.V., Savin A.I. Activity study of graphite from the chenobyl NPP Reactor. Bulletin of the Russian Academy of Science: Physics, 2000;73(2):261–265 (in Eng.).

27. Bulanenko V.I., Frolov V.V., Nikolaev A.G. Radiation characteristics of graphite removed from operation in uranium-graphite reactors. Atomic Energy, 1996;81(4):743–745 (in Eng.).

28. Bespala E.V., Myshkin V.F., Pavlyuk A.O., Novoselov I.Yu. Thermal and mass transfer at vaporizing cesium from graphite surface in argon environment (Teplomassoperenos pri isparenii tseziya s poverkhnosti grafita v argonovoi srede). Atomic Energy, 2017;122(6):325–329 (in Russ.).

29. Berlizov A.N., Malyuk I.A., Sajeniouk A.D., Tryshyn V.V., Petrov V.V., Savin A.I., Abousahl S., Rasmussen G., Sadikov I.I., Tashimova F.A. Transuranium elements and fission products in technological channels of unit No. 2 of Chernobyl Nuclear Power Plant. Journal of Radioanalytical and Nuclear Chemistry, 2008;277(1):49–57 (in Eng.).

30. Bushuev A.V., Verzilov Yu. M., Zubarev V.N., Proshin I.M., Petrova E.V., Aleeva T.B., Dmitriev A.M., Zakharova E.V., Ushakov S.I., Baranov I.I., Kabanov Yu. I., Kolobova E.I., Nikolaev A.G. 60Co content in the spent graphite masonry of commercial reactors at the Siberian Chemical Combine. Atomic energy, 1999;86(3):183–188 (in Eng.).

31. Barbin N.M., Terent'ev D.I., Alekseev S.G. Modeling mode of behavior of uranium, plutonium, europium and americium at radioactive graphite burning (Modelirovanie povedeniya urana, plutoniya, evropiya I ameritsiya pri gorenii radioaktivnogo grafita). Sovremennaya nauka, 2012;2(10):134–137 (in Russ.).