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Preliminary Design of Thermal Test Equipment of Dry Canister for Equivalent Fuel Assembly
The temperature of the spent fuel cladding is the basis for the evaluation of integrity. It is almost impossible to directly measure the temperature of spent nuclear fuel. Because spent nuclear fuel is dangerous. We are preparing a test to measure the cladding temperature with an equivalent fuel assembly by simulating the characteristics of spent nuclear fuel. PLUS7 was selected as the test target in consideration of the amount of generation, thermal water retention, residual moisture content, and manufacturability of domestic spent nuclear fuel. The nuclear fuel assembly is planned to be manufactured in two main ways. Except for the cladding tube that simulates decay heat, the structure will be manufactured by KEPCO Nuclear Fuel, and fuel rods and canisters will be manufactured by SUKEGAWA Electric in Japan. The same nuclear fuel assemblies as commercial skeleton will be applied. The temperature of the fuel cladding will be measured by attaching a thermocouple directly to the surface of the cladding tube. The canister is composed of a basket, a basket supporter, a heater and drain tube, a lead, and an observation window. The working fluid is water and helium, and the maximum pressure inside the canister is 1.1 MPa and the minimum pressure is 0.05 kPa. The maximum temperature of the surface of the cladding was designed to be 500°C, and the maximum temperature of the sealing to keep airtightness was designed to be 250°C. To satisfy this condition, we plan to evaluate the leak rate below 10−5 std.cm3·s−1, which is equivalent to helium tightness. The maximum heat of decay per fuel rod is 13 W, and one assembly is up to 3 kW. Production of the test equipment is expected to be completed in the first half of next year, and testing is scheduled to begin in the second half of next year. The test will evaluate all environments that the spent nuclear fuel may experience, such as dry normal conditions, abnormal conditions, wet conditions, and dry conditions. All data will be used for interpretation verification purposes.
