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Information × Registration Number 0218U001472, 0116U000828 , R & D reports Title Changing the characteristics of the external radiation from the dry storage of spent nuclear fuel at Ukrainian NPPs popup.stage_title Head Igor Girka, Registration Date 19-04-2018 Organization Kharkov National University named after V.N. Karazin popup.description2 The aim of this work is to develop techniques for determining contribution of certain nuclides contained in spent nuclear fuel (SNF) to dose rate of the containers external radiation at their long-term storage, as well as methods of control for the destruction of fuel rod shells with respect to variation of the radiation characteristics and of the air temperature. The object of the research and development is the radiation fields produced by neutrons and gamma-quanta emitted by SNF when stored in ventilated storage containers (VSC) in the open air. The method of research and development consists in studying the processes and mechanisms of emission and propagation of gamma and neutron radiation with changes in their spectral composition in time taken into account when they are transported in heterogeneous shielding constructions. For the ventilated storage containers (VSC) of the dry storage facility for spent nuclear fuel (DSSNF) at Zaporizhzhya nuclear power plant (NPP), the techniques using Monte Carlo methods were modified, the yield functions and angular distributions of ?-rays generated by primary photons in the energy range of SNF spectrum in the radial and axial directions were calculated. Application of the calculated data on the yield functions and angular distributions of ?-rays allows determining the dose rates at various distances and at different time of fuel storage for potential variants of containers loading (for different burnup and cooling time of SNF). It is shown, that the dose rate outside the container at SNF storage time up to 10 years is determined by the radiation of 106Ru, 144Ce, 134Cs and 154Eu. At longer terms of SNF storage, the dose rate is determined by the radiation of 154Eu, 90Sr and 137Cs; at SNF storage time of about 35 years the main contribution to DR? is made by 154Eu, and after that period - by 137Cs. The contribution of radionuclides to heat release at dry storage of SNF of WWER-1000 was studied. It is shown that in the range of the storage time up to 50 years the main contribution to the heat release is made by ?- and ?- emitters (fission products). The contribution of ?-radiation is determined by 90Sr (90Y) and 137Cs (137mBa). Heat release induced by ?-radiation at short cooling periods (up to ~20 years) is determined by three radionuclides: 137mBa, 134Cs and 154Eu, and at longer periods - by 137mBa. At SNF storage time over 50 years, the main contribution is made by ?-emitters (actinides) 238Pu, 239Pu, 241Am. A technique for determining the thermal state of spent nuclear fuel in storage containers has been developed. It is shown that when the fuel rod shells are destroyed and the SNF mixture and SFA (spent fuel assembly) material are spilled, the temperature of the storage basket increases, and the heat release from the basket is more intensive. As a result, the temperature in the ventilation outlets of the container (in which the temperature sensors are installed) remains almost unchanged. Such a nature of the thermal processes in the event of an accident with the collapse of the fuel rods doesn't allow its identification by measuring the temperature of the air escaping the container. The variants of the fuel rod shells destruction have been considered. Monte Carlo methods show that when a mixture of SNF and SFA material is spilled down the storage basket, the dose rate on the weather cover and in the inlet ventilation duct of the container changes abruptly. The contribution of neutron and gamma radiation to DR has been determined. Since the temperature in the outlet ventilation openings of the container (where the temperature sensors are installed) is almost unchanged due to the destruction of the fuel rod shells, then the measurement of the dose rate on the weather cover and in the inlet ventilation ducts is the only current method for indicating to the fuel rod shells destruction at SNF dry storage. The absence of the dose rate abrupt change subject to the storage term would allow to confirm safety of SNF dry storage at Zaporizhzhya NPP. Product Description popup.authors C. Альохіна І. Гірка В. Пишкін В. Рудичев Г. Ветрова Г. Махненко Е. Рудичев popup.nrat_date 2020-04-02 Close