The analysis of thermal state of storage container for spent nuclear fuel under accident conditions is main part of the complex safety analysis of the dry spent nuclear fuel storage facility on all stages of its lifecycle. As literatures review shown, the thermal analysis of some accidents was not carried out. In the work by solving of the conjugate heat transfer problems the thermal processes in ventilating storage containers for spent nuclear fuel under some design basis accidents were analyzed. The maximum temperatures at different variants of the container's falls, storage cask displacement and at extremely high and low ambient temperatures were calculated. The most dangerous accidents from the thermal point of view are accidents with container's falls. In this case, the maximum temperatures of fuel can be higher than allowable by safety criteria temperatures. Consequences of the accidents with container's falls should be removed in the first instance; heat removing by natural convection should be restored or additional cooling should be organized. As results shown, none of considered accidents could be detected by container surface temperature measurement because container is not warmed-up fully. Accidents can be detected by visual monitoring (at container's falls) or by measurement of the ventilating air temperature (at the storage cask displacement). The studies were carried out for containers, which are operated on the unique in Ukraine the Dry Spent Nuclear Fuel Storage Facility on the Zaporizhska NPP.
Keywords: spent nuclear fuel, thermal processes, mathematical modelling.
1. Еxperimental studies on safety of dry cask storage technology of spent fuel allowable temperature of cladding and integrity of cask under accidents / T. Saegusa, M. Mayuzumi, C. Ito, K. Shirai // Journal of Nuclear Science and Technology. – 1996. – Vol. 33, Iss. 3. – P. 250 – 258.
2. Chahi H. Thermal-hydraulic investigations to the flow of model gases at a PWR fuel assembly dummy and overflow of air above the top of the dummy / H. Chahi, W. Kästner, S. Alt // International Conference on Nuclear Engineering, Proceedings, ICONE-2016. Vol. 3, 2016, Charlotte, United States.
3. Experimental investigation of heat removal performance of a concrete storage cask / Y. Zhang, Y. Ouyang, Y. Zhou, J. Liu // Annals of Nuclear Energy. – 2 September 2014. – Vol. 85. – P. 679 – 686.
4. Modeling of heatmasstransfer in "wet" and "dry" storages for spent nuclear fuel / E. D. Fedorovich, Y. E. Karyakin, V. E. Mikhailov, V. O. Astafieva, A. A. Pletnev // 14th International Heat Transfer Conference, IHTC 14. Vol. 7, 2010, P. 303 – 310.
5. CFD analyses of the TN-24P PWR spent fuel storage cask / R. A. Brewster, E. Baglietto, E. Volpenhein, C. S. Bajwa // ASME-2012 Pressure Vessels and Piping Conference, PVP 2012; Toronto, ON; Canada. Vol. 3, 2012, P. 17 – 25.
6. Lo Frano R. Thermal analysis of a spent fuel cask in different transport conditions / R. Lo Frano, G. Pugliese, G. Forasassi // Energy. – April 2011. – Vol. 36, Iss. 4. – P. 2285 – 2293.
7. Pugliese G. Spent fuel transport cask thermal evaluation under normal and accident conditions / G. Pugliese, R. L. Frano, G. Forasassi // Nuclear Engineering and Design. – 2010. – Vol. 240, Iss. 6. – P. 1699 – 1706.
8. Accident safety evaluation method for spent fuel dry storage facilities / Y. Zhang, Y. Ouyang, Y. Zhou, J. Liu // International Conference on Nuclear Engineering, Proceedings, ICONE-2017. Vol. 7, 2017.
9. Testing of Metal Cask and Concrete Cask / K. Shirai, M. Wataru, H. Takeda, J. Tani, T. Arai, T. Saegusa (2015) // Proceedings of an International Conference Management of Spent Fuel from Nuclear Power Reactors. International Atomic Energy Agency (IAEA): IAEA.
10. Safety Analysis report for Dry Spent Nuclear Fuel Storage Facility of Zaporizhska NPP. Version 3.01.1 / SE «Zaporizhska NPP». - Inv. No. 1526(3). – Energodar, 2008. – 624 p. (Rus)
11. Spent Nuclear Fuel Dry Storage Safety / V. G. Rudychev, S. V. Alyokhina, V. N. Goloschapov et al. ; Edited by acad. NAS of Ukraine Yu. М. Matsevity and corr. member of NAS of Ukraine I. I. Zalubovsky. – Kharkiv, 2013. – 200 p. (Rus)
12. Alyokhina S. Solar Radiation Influence on the Spent Nuclear Fuel Dry Storage Container / S. Alyokhina, S. Kapuza, A. Kostikov // Problems of Atomic Science and Technology (PAST). – 2018. – Vol. 2(114). – P. – 57 – 62.
13. Launder B. E. The Numerical Computation of Turbulent Flow / B. E. Launder, D. B. Spalding // Comp. Meth. Appl. Eng. – 1974. – № 3. – P. 269 – 289.
14. Thermal hydraulic analysis compared with tests of full-scale concrete casks / M. Wataru, H. Takeda, K. Shirai, T. Saegusa // Nuclear Engineering and Design. – 2008. – № 238. – Р. 1213 – 1219.
15. Alyokhina S. Equivalent thermal conductivity of the storage basket with spent nuclear fuel of VVER-1000 reactors / S. Alyokhina, A. Kostikov // Kerntechnik. – 2014. – Vol. 79, No. 6. – P. 484 – 487, DOI: 10.3139/124.110443.
16. Simulation of thermal state of containers with spent nuclear fuel: multistage approach / S. Alyokhina, V. Goloshchapov, A. Kostikov, Yu. Matsevity // International Journal of Energy Research. – 2015. – Vol. 39, Iss. 14, Nov. – P. 1917 – 1924, DOI: 10.1002/er.3387.
17. Alyokhina S. Unsteady heat exchange at the dry spent nuclear fuel storage / S. Alyokhina, A. Kostikov // Nuclear Engineering and Technology. – 2017. – Vol. 49, Iss. 7, Oct. – P. 1457 – 1462, DOI: 10.1016/j.net.2017.07.029.