Structurally, nuclear power plants around the world have both strong and fragile sides. Generally, the sidewalls of the facility are relatively strong, while the top wall is weak.

Japan's Nuclear Regulation Authority conducts a safety review of air terrorism countermeasures. Even if the nuclear reactor system and the spent fuel storage pool are partially destroyed and water leaks, the content of the plan is to install a second control room, a water source and a cooling system in a new underground facility. It is assessed that the accident can be prevented by injecting water into the facility.
However, the evaluation method, while seemingly correct, remains seriously flawed. Specifically, in the case of a nuclear reactor system, there are few fatal problems, but in the case of a spent fuel storage pool, the upper wall of the PWR and BWR facility is very thin, so the facility will be destroyed, resulting in water leakage, moreover, a large number of spent fuel assemblies are destroyed, releasing a large amount of radioactive material into the environment.
The safety review of the Nuclear Regulation Authority assumes a collision from the horizontal direction of the aircraft, but does not assume a collision from diagonally above(upper wall). Therefore, it is not a countermeasure against aircraft terrorism.