Cesium content significantly increased. TEPCO announced the first round of data on the discharge of nuclear polluted water into the sea.

On September 12th, local time, according to the information released by Tokyo Electric Power Company in official website, as of 12: 15 noon on the 11th, the first round of discharge of nuclear polluted water from Fukushima Daiichi Nuclear Power Plant ended, with the cumulative discharge of 7788 cubic meters in the first round.

Tokyo Electric Power Company said that after relevant confirmation and equipment inspection, the second discharge will start as early as the second half of this month, and it is estimated that about 7,800 tons of nuclear polluted water will be discharged into the ocean.

According to official data, at present, more than 1.3 million tons of nuclear contaminated water containing radioactive substances have been accumulated at the Fukushima Daiichi nuclear power plant, and it is still increasing at the rate of 100 tons per day. It is estimated that in the future, Japan’s nuclear polluted water will be discharged into the sea for at least 30 years.

Affected by the earthquake and tsunami in 2011, the cores of Units 1-3 of the Fukushima Daiichi Nuclear Power Plant in Japan melted down. This is one of the most serious nuclear accidents in the world so far. After the accident, Tokyo Electric Power Company continued to inject water into the containment of Units 1 to 3 to cool the reactor core and recover sewage.

There are three main sources of radioactive wastewater from Fukushima nuclear power plant in Japan: the original coolant of the reactor, the newly injected water for continuous cooling of the reactor core after the accident, and a large amount of groundwater and rainwater that infiltrated into the reactor.

One year after the Fukushima nuclear accident, in March, 2012, Tokyo Electric Power Company first measured the composition and concentration of radioactive substances contained in nuclear polluted water. The results at that time showed that there were as many as 64 kinds of radioactive elements with excessive concentrations.

Of these 64 radioactive elements, 21 have a half-life of more than 10 years, and some nuclides have a half-life of more than a thousand years.Carbon -14 and iodine -129 are the most harmful to human beings and marine life. The half-life of carbon -14 is about 5370 years, and the half-life of iodine -129 is even longer, about 15.7 million years (important data are shown in bold).Carbon -14 will accumulate in marine organisms, that is, fish, and the abundance or concentration of carbon -14 accumulation may be 50 times that of tritium.

On September 1st, Tokyo Electric Power Company of Japan announced that after the Fukushima nuclear polluted water was discharged into the sea, the Japanese side detected radioactive tritium for the first time in seawater sampled near the discharge port on August 31st. However, TEPCO claimed in the notification that the concentration of tritium was "completely safe".

The concentration of radioactive tritium in the seawater sampled this time is 10 Bekkerel per liter. According to the report, the staff set up 10 sampling points in Fiona Fang, 3km away from the Fukushima Daiichi nuclear power plant. The seawater from which tritium was detected this time was taken from the sampling point closest to the discharge port. The concentration of tritium in the seawater sampled at this sampling point on 24th was 2.6 Bekkerel, and the conventional analysis at that time did not reach the detection limit.

As for the sharp rise of tritium concentration in just a few days, TEPCO admitted that this was caused by the discharge of nuclear polluted water into the sea, but they insisted that this concentration was "completely safe".

In addition, Tide News reporters combed the monitoring data released by official website of TEPCO, and found that the content of cesium -137 detected in the water intake of units 1~4 was significantly higher than before.

Cesium -137 is usually one of the products of nuclear energy reaction, nuclear explosion or nuclear accident, which is harmful to human body because it emits beta particles and gamma rays. These rays can interact with human tissues and cause cell damage.

Chen Xin, a researcher at the South China Sea Institute of Oceanography, Chinese Academy of Sciences, once pointed out in an interview that from the perspective of diffusion path, Japanese nuclear pollution will affect the South China Sea, the East China Sea, the Bohai Sea and the Yellow Sea in China. The North Pacific is one of the seriously polluted areas. In fact,The world can’t escape the influence of Japan’s nuclear polluted water.

During the diffusion of radioactive elements in Japan’s nuclear polluted water, radioactive nuclear elements will not only stay on the ocean surface. "It can be said that the ocean is polluted in three dimensions." Chen Xin said that the ocean is a layered system because of the different temperatures and salinities in the upper and lower layers. For example, pouring a little oil into a glass of water is equivalent to forming a two-layer system, and it is difficult for oil to enter the lower layer. But in the ocean, through the "ocean transport belt" and the vertical water exchange process, the oil originally located in the upper layer can also enter the deep layer.

As early as 2021, the team of Academician Zhang Jianmin and Associate Professor Hu Zhenzhong from the Institute of Ocean Engineering of Shenzhen International Graduate School in Tsinghua University established the diffusion model of radioactive substances at the ocean scale from macro and micro perspectives respectively, and realized the long-term simulation of the Fukushima nuclear wastewater discharge plan.

The macro-simulation results show that the nuclear waste water will reach the coastal waters of China 240 days after discharge, and will reach the coast of North America and cover almost the whole North Pacific after 1200 days. Subsequently, the pollutants spread rapidly along the American coast to the South Pacific under the action of equatorial currents, and on the other hand, they transferred to the Indian Ocean through the northern Australian waters.

It is worth noting that although the pollutant discharge location is near Fukushima, with the passage of time, the high concentration area of pollutants will extend eastward along the 35°N line, and spread from the sea near East Asia to the sea near North America. On the 2400th day, the southeast coast of China was mainly light pink with low concentration, while the west coast of North America was basically covered with red with high concentration.

"The impact of nuclear polluted water entering the sea is not only reflected in the ocean current system, but also in the biological system. Through the cumulative effect of the food chain, radioactive substances will eventually enter the human body through seafood such as fish and shrimp." Chen Xin said.