3. Nuclear power plants

There are 16 major power plants, two reprocessing plants (Rokkasho, Tokai), and one fast breeder reactor (Monju) in Japan. (Figure 2)(Nuclear power of Japan [5]) As of January in 2025, 13 reactors in the 7 power plants are operating, Onagawa (unit 2), Genkai(unit 3, unit 4), Ikata(unit 3), Sendai(unit 1, unit 2), Takahama(unit 1, unit 2, unit 3, unit 4), Oi(unit 3, unit 4), Mihama(unit 3).

Each nuclear reactor produces about 100 tons of spent nuclear fuel each year. The radioactivity of the spent nuclear fuel is billion-times more intense than the natural uranium. About 19,000 tons of spent nuclear fuel are stored in Japan. For instance, 1100 tons of spent nuclear fuel is stored in the cooling pool in Hamaoka and 600 tons and 900 tons are kept in Ikata and in Sendai respectively. The cooling pools exist in the same space where we live our daily lives and the loss of electricity causes the meltdown of the nuclear fuel within three days.

The earthquake‐resistant limits of the nuclear power plants are about M6.5. The anticipated earthquake of M8.4 has 200 times more energy than that of M6.5. Immediately after the huge earthquake, the colossal tsunami would come along and completely destroy the plants. In Wakasa bay there are four power plants (Takahama, Oi, Mihama, Tsuruga) and one fast breeder reactor (Monju) sitting densely along the coastal line. If we lost control of one reactor, we would lose control of all reactors because we have to evacuate from the region anyway.

In reprocessing plants, the spent nuclear fuel is melted in the high temperature to retrieve uranium and plutonium. The remaining substance is called high-level radioactive waste. Vitrified waste is obtained by melting the high-level radioactive waste with glass and solidifying it in the steel vessel. JAEA (Japan Atomic Energy Agency) keeps 6,500 high-level radioactive solid waste (in the 200-liter vessel), 404 cubic meters of high-level radioactive liquid waste and 247 vitrified waste (in the 120-liter vessel) in Tokai. JNFL (Japan Nuclear Fuel Limited) has 1367 vitrified waste (in the 150-liter vessel) in Rokkasho.(JAEA [6]) Most of vitrified waste (1310 vitrified waste) were made in France. JAEA had planned to vitrify the high-level radioactive liquid waste until 2028, but after the series of accidents they postponed the schedule until 2038.

Fast breeder reactor uses plutonium 239 instead of uranium 235 as the fuel and generates more plutonium 239 at the end of the process. The reactor uses the liquid sodium as the coolant and it is extremely difficult to safely operate with this explosive substance. In 2016, the Japanese government confirmed the closure of the fast breeder reactor Monju. Monju has never run. Fortunately the fuel and the sodium has not been radioactively contaminated. There are no dangers in Monju, if we can safely keep the plutonium isolated from the environment. Unfortunately JAEA who has no skills to run the breeder reactor and to produce the vitrified waste is operating the breeder reactor and the reprocessing plant. The decommission of Monju is an easy task compared to that of RAPSODIE and SUPERPHÉNIX .([7]) However, in their plan it is going to take 30 years until 2047. 

Figure 3 is the combination of Figure 1 and Figure 2.
The Nankai Trough Earthquake would kill 320,000 people and have 200 times larger energy than the earthquake‐resistant limits of the nuclear plants. It is difficult to imagine that those active nuclear plants and the spent nuclear fuel in the cooling pools can survive the earthquakes. From the experience of Fukushima 2011 we know that no one can save the nuclear disaster. No one even knows what would happen if the spent nuclear fuel melted down in the cooling pools. No research has not been conducted based on such a condition. However, the radioactive cloud is going to be generated continuously and cover the whole globe. All of us are going to lose safe food and safe water forever.