KBS-3 Spent Fuel Container Corrosion And The Critical Safety Analysis Of Container After Groundwater Immersion

The KBS-3 canister for geological repository of spent nuclear fuel in Sweden consists of a ductile cast iron insert and a copper shielding. The groundwater surrounding of geological repository will be radiated by strong irradiation radiation decomposition of spent fuel in container, so as to enhance the water oxidation and accelerate the corrosion of the container material. After the corrosion damage, long-life nuclide spontaneous fission neutron will be moderated when groundwater inflow the spent fuel container, which will increase the microscopic reaction cross section of neutrons and fissile material, and lead to critical safety accidents of container.First, this thesis calculates the spent fuel container of PWR surface dose rate distribution. Subsequently, groundwater irradiation experiment has been carried out to study the corrosion rate of spent fuel container structure materials after water radiolysis. Finally, it researches the effect of criticality safety of different amount of groundwater in the spent fuel container of PWR after container damaged. Through analysis, we can come to conclusion as follows:1. Around the spent fuel container of PWR, there is a very strong dose distribution. The simulation of the photon dose rate two meters away from the container wall can reach 15.9 mSv/h, and it can reach 142.8 mSv/h two meters away from the container surface, which exceed the national standard of the transportation rules(10 mSv/h). Therefore, effective isolation measures are needed in the process of transportation and storage.2. With the increase of irradiation dose, when the pH of water samples falls slowly from 7.82 to 7.47, the oxidation reduction potential slowly increases from +24 mv to +29 mv. The oxidation performance of water will increase after the irradiation.3. The groundwater will affect spent fuel container simulation material corrosion rate after irradiation. And the concentration of copper ion in the solution has increased from 0.1822mg/L to 0.3949mg/L, the concentration of total iron ion increased from 0.857mg/L to 1.4246mg/L. So it can provide a certain basis for our country to choose the material of containers.4. In terms of the spent fuel container of PWR on the condition of the immersed water accident, in a very long period of time, the maximum effective multiplication factor of that is 0.796, less than the critical minimum allowance(0.95), which meets the criticality safety standards.