Patent Number: 
Section: claims

1. A cooling air amount adjustment device of a concrete cask, configured to: naturally convect external air as cooling air from an air inlet port provided at a lower portion of a concrete container to an air outlet port provided at an upper portion thereof; and store and simultaneously cool a canister sealing spent nuclear fuel, the device comprisingat least one air outlet port opening level adjustment mechanism or at least one air inlet port opening level adjustment mechanism, which is configured to automatically perform:adjustment to reduce a flow rate of the cooling air when a temperature of the cooling air at the air outlet port is lower than an adjustment reference temperature, andadjustment to increase the flow rate of the cooling air so as to restore the flow rate of the cooling air when the temperature of the cooling air at the air outlet port is higher than the adjustment reference temperature,wherein the at least one air outlet port opening level adjustment mechanism or the at least one air inlet port opening level adjustment mechanism comprises:a rotary shaft connected to the air inlet port or to the air outlet port; anda bimetal portion forming a spiral fixed to the rotary shaft, wherein the spiral is configured to unwind in response to a change in temperature causing the rotary shaft to rotate to reduce the flow rate of the cooling air. 2. The cooling air amount adjustment device of a concrete cask according to claim 1, wherein the air outlet port opening level adjustment mechanism includes a member or a portion provided at the air outlet port and having a shape or a phase autonomously changed at the adjustment reference temperature as a boundary. 3. The cooling air amount adjustment device of a concrete cask according to claim 1, wherein the air inlet port opening level adjustment mechanism includes a member or a portion provided at the air outlet port and having a shape or a phase autonomously changed at the adjustment reference temperature as a boundary. 4. The cooling air amount adjustment device of a concrete cask according to claim 1, wherein the air outlet port opening level adjustment mechanism includes a temperature-sensitive member configured to change a shape and adjust an opening level of the air outlet port at the adjustment reference temperature as a boundary. 5. The cooling air amount adjustment device of a concrete cask according to claim 1, comprising the at least one air outlet port opening level adjustment mechanism, wherein the spiral unwinds to cause the rotary shaft to rotate so as to adjust the opening level of the air outlet port at the adjustment reference temperature. 6. The cooling air amount adjustment device of a concrete cask according to claim 1, wherein the air outlet port opening level adjustment mechanism includes:a power source;an air outlet port opening level adjustment unit;a temperature sensor configured to measure a temperature of the cooling air at the air outlet port; anda control unit configured to actuate the air outlet port opening level adjustment unit so as to reduce the opening level of the air outlet port when the temperature measured by the temperature sensor is lower than the adjustment reference temperature and furthermore so as to restore the opening level of the air outlet port when the temperature measured by the temperature sensor is higher than the adjustment reference temperature. 7. The cooling air amount adjustment device of a concrete cask according to claim 6, wherein an apparatus configured to generate power by a temperature difference between the cooling air heated by heat generation from the canister and external air is provided instead of the power source or together with the power source. 8. A concrete cask comprising the cooling air adjustment device of a concrete cask according to claim 1. 9. The cooling air amount adjustment device of a concrete cask according to claim 1, wherein the air outlet port opening level adjustment mechanism comprises an air outlet port opening level adjustment member and a temperature-sensitive actuator configured to actuate the air outlet port opening level adjustment member so as to adjust the opening level of the air outlet port, andwherein the temperature-sensitive actuator comprises a spring formed from a shape memory alloy configured to deform to adjust a position of the air outlet port opening level adjustment member. 10. The cooling air amount adjustment device of a concrete cask according to claim 1, wherein the air outlet port opening level adjustment mechanism comprises an air outlet port opening level adjustment member and a temperature-sensitive actuator configured to actuate the air outlet port opening level adjustment member so as to adjust the opening level of the air outlet port, andwherein the temperature-sensitive actuator comprises a material configured to change phase in response to changes in temperature to adjust a position of the air outlet port opening level adjustment member. 11. The cooling air amount adjustment device of a concrete cask according to claim 10, wherein the material configured to change phase comprises ethanol.