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, 1,130 tons of spent nuclear fuel is stored in the cooling pool in Hamaoka and 770 tons and 1,140 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 (620 Gal – 1200 Gal), since the nuclear power plants in Japan are just copies of the ones in USA where the earthquake is not a major risk factor. The anticipated earthquake of M8.4 has 200 times more energy than that of M6.5. (2933 Gal in Tohoku earthquake (2011), 2828 Gal in Noto Ishikawa earthquake (2024)) In the Nankai Trough Earthquake the seismic source zone might be directly underneath the land and we need to prepare the extremly fierce quakes. 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 reactor, the fuel and the sodium have not been radioactively contaminated. The decommission process of Monju is a much easier task compared to that of RAPSODIE and SUPERPHÉNIX, but in the plan of JAEA it is going to take 30 years until 2047. (IAEA [7]) Plutonium is an extremely harmful substance for living creatures. 500 gram of plutonium can kill two billion people. There are about 8.6 tons of plutonium stored in Japan (400 kg in Monju), which must be kept safely isolated from the biosphere. 

Figure 3 is the combination of Figure 1 and Figure 2. In Ikata nuclear power plant located on the top of the Median Tectonic Line, the No 3 reactor is still running using the MOX fuel and 770 tons of the spent fuel is stored in the cooling pool. In Hamaoka nuclear power plant built on the top of the three tectonic plates boundaries, 1,130 tons of the spent fuel is stored in the cooling pool. 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.