Nuclear power plant auxiliary system analysis

Vacuum technology used in nuclear power plant auxiliary systems is mainly vacuum purification, vacuum degassing and vacuum distillation.

Coolant quality control system: Water flows as pressure stack coolant in the high temperature, high pressure and strong radiation field of the main circuit. A series of reactions will occur and the material will be corroded. Therefore, water quality control is an extremely important process in nuclear power plant operation.

Strictly control oxygen, chlorine, fluorine, and pH as well as solids and radioactive intensity. The primary loop coolant in modern large-scale pressure reactor nuclear power plants is provided with a circulation purification system, which continuously draws a stream of water from the main circuit and then returns it to the main circuit after purification.

Since entering the 1970s, many pressure reactors in other countries have been cleaned by vacuum and purified by ion exchangers. Vacuum purification can easily remove free oxygen, hydrogen, chlorine and other gases, which is much better than the pure ion exchanger. The primary circuit water is at a high temperature and must be cooled to allow ion exchange purification, while vacuum purification is arranged during the cooling process.

(1) Three waste treatment systems

The waste water, waste gas, and waste solids of a nuclear power plant contain radioactivity. The three-waste treatment is an important part of the normal operation of a nuclear power plant.

It is not yet a problem that has been completely resolved. In recent years, the vacuum process has been commonly used in the three-phase treatment of nuclear power plants.

(2) Two-way coolant degassing

Gases such as Kr, Xe, and H2 in the two-way coolant are difficult to chemically remove. Under extreme conditions, the radioactive concentration of fissile gas in the coolant can reach 10 -1Ci/L. If the purpose of coolant purification is emission or reuse, at least the fission gas concentration should be reduced by 4 - 5 orders of magnitude or more. The requirements are quite high. Foreign studies have shown that vacuum degassing can reach this level.

Currently used degassing methods are thermal method, inert gas blowing method and vacuum method. In contrast, vacuum degassing has greater advantages than the other two methods.

It does not require a heat source and can be carried out at room temperature. At room temperature, the upper part of the liquid is evacuated to allow the water to boil, thus achieving the purpose of degassing. In recent years, the vacuum degassing method has developed rapidly and there are already dedicated vacuum pumps.

(3) Waste water treatment

Nuclear fuel fission and coolant activation inevitably produce helium. Wastewater treatment with rubidium is cumbersome. At present, there is no alternative to dilute the discharge of waste water containing rubidium. Since the late 1960s, foreign countries have begun to separate waste water and waste gas.

In the study of æ°š, but so far, there is no way to put it into practice. From an economic point of view, the more promising is vacuum distillation, which is the distillation separation of hydrophobic and light water under vacuum conditions. This approach is very simple to operate.

(4) Boiling water treatment

The boiling water reactor is where water is directly converted into steam in the reactor. It is radioactive, so that the turbine and its accessories are all radioactive, and the discharged steam and waste water are also radioactive, and its intensity is equivalent to the pressure of the first-circuit water. In recent years, these problems have been better solved

In conclusion, the boiling water reactor has become a reactor type with more pressure outside the reactor. A successful method for the treatment of waste water from boiling water reactors

It is an activated carbon adsorption method using a vacuum process.

(5) Exhaust gas treatment

The emission gases contained in the process exhaust of the pressure reactor are mainly isotopes of helium and neon. In recent years, the vacuum method has been widely used to remove helium. 85. The main Wangyi process for the vacuum removal of helium 85 used in the Sanonovule pressure reactor in the US is to first reduce the pressure of the stored exhaust gas from 7×105 Pa to 7×104 Pa. After filtration and preheating, oxygen is removed in the catalytic composite gas. After cooling, the water and water separators, the dryer, and the filter were successively removed to completely remove the water and C02, and the gas was then cooled to -190°C and sent to a carbon bed for operation. Then gradually warmed to 50 °C, while evacuation, the adsorption gas desorption down, pressed into the cylinder. The vacuum removal process for the helium 85 is simple and has been successfully used in the Winkker and Elle plants.