How can nuclear wastewater be treated safely



How scary is nuclear contaminated wastewater?

To answer the question of whether nuclear waste water can be dumped into the sea, we must first tell where it came from.

In 2011, Japan suffered from the "3·11" earthquake, the two units of the Fukushima nuclear power plant were submerged in the towering waves rolled up by the tsunami, and then because of a series of wrong operations by the Tokyo Electric Power Company, the temperature in the machine room continued to rise, the reactor exploded and the reactor core melted, the situation was once very critical. To avoid further damage, TEPCO has been pumping seawater into the reactors' containment vessels to reduce the amount of heat they generate. When this seawater flows through the damaged core, it comes into direct contact with nuclear materials, picking up various radionuclides and becoming nuclear waste water. Add to this the amount of rainwater, groundwater and other natural water bodies that have seeped in over the years, and the total amount of nuclear wastewater becomes quite staggering.

The composition of these nuclear wastewater is very complex, containing at least strontium 90, cesium 134, cobalt 60, iodine 129 and tritium and other radionuclides, and the radiation intensity is far beyond the safety standard. However, the approach taken by the Japanese side is to remove most of the strontium, cesium, cobalt and other nuclides through the multi-nuclide processing system (ALPS), using filtration, adsorption, reverse osmosis and other means to reduce their radiation intensity.

However, tritium - that is, hydrogen nuclide containing 3 neutrons (3H, often abbreviated as T), is an isotope of hydrogen, it and oxygen after the formation of superheavy water (T2O), chemical and physical properties are highly similar to ordinary water, with the above means almost impossible to remove. According to the Tokyo Electric Power Company, after treatment, the activity of tritium (which can be approximately understood as the concentration) is still as high as 730,000 Bq/L, which is more than 7,000 times the amount of tritium allowed in drinking water (the European Union standard is 100 Bq/L), even if compared with Japan's own emission standards, it is 486 times higher than the standard.

At the same time, tritium has strong radioactivity, once it enters the human body through the diet, it will cause internal radiation damage to the human organs and seriously damage human health. To make matters worse, tritium has a half-life of about 12.4 years - that is, if a person has tritium in their body and they are lucky enough to live another 12 years, half of the tritium in their body has not decayed out. The radiation is still eating away at his body, and his quality of life will continue to be severely affected.

Second, how to treat nuclear wastewater?

So, with the development of science and technology today, how to deal with these nuclear wastewater?

Chemical reactions confirm that we can never change one atom into another, so radionuclides cannot be destroyed by chemical reactions. Using nuclear physics methods, such as bombarding nuclei with high-speed particles, can indeed change them into another kind of atom, thus reducing radioactivity, but the cost of doing so is prohibitively high: Bombarding a microgram-sized target consumes as much electricity as the inhabitants of a small town consume in a month, and it would take a fraction of the energy of the sun to target a million tons of nuclear wastewater. In other words, it is impossible to use this method on such a large scale, and if you want to fundamentally eliminate the impact of radionuclides in nuclear wastewater, the current human science and technology cannot achieve it.

Since "elimination" can not be, it is only to find a way to "quarantine". The half-life of tritium is about 12.4 years, that is to say, if it is placed for 20 or 30 years, it can basically complete the decay, and the harm to the environment is greatly reduced. Therefore, the proper and long-term preservation of these nuclear waste water is a smart approach. However, to achieve this isolation method, there are certain technical challenges.

First, storing nuclear wastewater requires very large containers, which occupy land for a long time. What's more, the protective power of the container is limited after all, if you encounter earthquakes, hurricanes and other disasters, resulting in the rupture of the container, a large amount of nuclear waste water leakage, and will cause secondary pollution.

A more secure way is to solidify these radionuclides, for example, mix them with cement and stones, make concrete, and then pour them into cement boards and cement blocks, wrap them with waterproof materials and bury them deep in the soil, so that the nuclides can be firmly blocked in them, and will not pollute groundwater. Even in the event of an earthquake, the most is to crack and break the cement components, causing very limited pollution to the surrounding environment. In 1986, when the Chernobyl nuclear power plant suffered a nuclear accident of the same magnitude as Fukushima, the Soviet Union completely covered the reactor with a huge cement envelope, trapping the radioactive dust inside and no new spread has been detected.

However, this method also has one of the biggest disadvantages: expensive. To make more than one million tons of nuclear wastewater into cement components, the amount of cement, stones and steel bars required is difficult to count, and in the process of mixing and pouring cement, tritium radioactivity still exists, which puts forward extremely high requirements for the protective measures of the staff.

Third, don't make environmental problems worse

Solidifying the nuclides is a more effective way to treat nuclear waste, but TEPCO has chosen the cheapest option: diluting the waste water and dumping it directly into the sea.

However, before this, humans have never really treated this high concentration of nuclear wastewater, and it is impossible to predict how fast it will spread once it is discharged into the sea, and what harm it will bring to the Marine ecosystem and neighboring countries.

The ocean is an extremely complex and sensitive ecosystem, especially the plankton at the bottom of the food chain, after being affected by nuclides, it is highly likely to be transmitted to the next level of organisms, and then from the next level of organisms to the top of the biological chain, and eventually destroy the entire earth ecology.

Today, our earth is still facing many environmental problems, and the discharge of nuclear wastewater into the sea will undoubtedly make the already severe environmental problems worse. According to the logic of "user pays, polluter treats", whoever creates pollution has the obligation to clean up the pollution, and must not interfere with the legitimate rights and interests of others. Even if the cost of treatment is huge, the proper treatment of this nuclear waste water is also the obligation of Tokyo Electric Power Company and Fukushima nuclear power plant.