Spent fuel reprocessing technology began in the 1960s. Its purpose is to recover unburned and newly produced uranium and plutonium from the irradiated fuel in the reactor through physical and chemical methods, and to remove fission products. The uranium and plutonium obtained through reprocessing can be returned to the reactor for reuse, thus realizing the nuclear fuel cycle. At present, countries engaged in commercial post-processing in the world include France, the United Kingdom, Russia, Japan and India, among which the commercial post-processing level of France and the United Kingdom is in the leading position in the world. The annual processing capacity of the Hague plant in France reaches 1700t/a, and the annual processing capacity of the Thorp reprocessing plant in the UK reaches 900t/a.
 
With the development and expansion of the commercial scale of spent fuel reprocessing, the requirements for the performance, safety and reliability of valves are getting higher and higher in the construction of reprocessing plants in China. A large number of pipelines are involved in the spent fuel reprocessing process system, and tens of thousands of valves are required in these pipelines to ensure the normal operation of the entire process system. In this article, through the detailed classification of the reprocessing valves, the selection of the spent fuel reprocessing valves is carried out under the conditions of full consideration of the safety, reliability, functionality, operability and economy of the spent fuel reprocessing process. In the design of the valve, the radiation resistance, corrosion resistance, strength and rigidity, sealing and service life of the valve are fully considered. In the spent fuel reprocessing process pipeline, special selection and design of valves are carried out according to specific environments due to the large amount of radioactive and corrosive media in the application scene and structure research of process valves.
 
Classifications of spent fuel reprocessing process valves
Valves can be classified according to actuators and use.
 
Classifications by the driving mode
Automatic valves
Automatic valves do not require external force to drive, relying on the energy of the medium to drive valves, such as check valves, safety valves, pressure reducing valves, and steam traps.
 
Active valves
Active valves are valves operated or driven by power, which are mostly manual, electric and pneumatic in the post-processing process system.
 
Ground-piercing valves
The valve body penetrates the ground shielding layer, and the valve body is located on the side with higher radioactivity (below the shielding layer), which is used for valves of medium and high radioactive pipelines. The ground-piercing valve uses the actuator to drive the valve stem extension rod to operate. Most of them are manual or pneumatic bellows globe valves.
 
Remote transmission valves
The valve and the actuator are connected through the remote transmission mechanism, the remote transmission mechanism penetrates the shielding layer (the wall), and the valve is located on the side with higher radioactivity, and is used for the valve of medium and high radioactive pipelines. Remote valves are operated by universal joints and transmission shafts, mostly manual or electric ball valves, butterfly valves, and bellows globe valves. If the torque is great, a reduction device such as a gearbox can be provided.
 
Classifications by uses
Valves for opening and closing
Valves for opening and closing are used to cut off or connect pipeline media, such as globe valves, ball valves, and butterfly valves.
 
Regulating valves
Regulating valves are used to regulate and control the flow or pressure of the medium in the pipeline, such as throttle valves, regulating valves, and pressure reducing valves.
 
Distribution valves
The distribution valve is a valve used to change the flow direction of the medium in the pipeline, such as three-way ball valves and steam traps.
 
Safety valves
A safety valve is a valve that provides overpressure protection for equipment to prevent the pressure of the medium in equipment such as pressure vessels from exceeding the specified value.
 
Check valves
The check valve is a valve used to prevent the medium from flowing back into the pipeline.