In nuclear power plants, due to the large amount of waste water and high concentration of radioactive substances, a special radioactive sewage treatment system is built, and the common processes are evaporation and filtration. As mentioned earlier, most radioactive elements in wastewater are not volatile. Using this feature, scientists heat the wastewater to evaporate it, and then concentrate the radioactive materials that cannot evaporate. This method has two advantages. First, there is a lot of useless waste heat during the operation of nuclear power plants, and heating wastewater will not consume more energy. Secondly, the evaporation method basically does not need to use other substances, and it will not produce other forms of pollutants because of the transfer of pollutants like other methods. Another method is filtration, similar to the water purifier used in our daily life. A resin specially used to adsorb radioactive substances is put in the pipeline where the wastewater flows, so that the water flows away and the radioactive substances remain in the resin. After a period of time, the resin is "saturated" and can be replaced with new resin. Resin filled with radioactive substances can be reduced in volume by compression and then sealed with cement. If the radioactivity in the resin is not high, it can also be sealed in an iron drum.