Selection and Design of Valves for Spent Fuel Reprocessing

3.1 Selecting valves
For the selection of spent fuel reprocessing valves, it is necessary to ensure their safety, reliability, functionality, operability and economy. First, clarify the requirements for the safety of the valve according to the requirements of the process system, such as safety level, anti-seismic category and quality assurance level. Second, clarify the material, use and type of the valve according to the valve's nominal parameters, medium characteristics and environmental characteristics, such as nominal pressure, nominal diameters, medium temperature, pressure, flow characteristics, environment and medium radiation dose and acid-base corrosion. Combined with the processing system, installation, operation, maintenance and other factors to select the appropriate valve structure and drive mode, and determine the ends between the valve and the pipeline.
 
3.2 Classifications of valves
Valves belong to chemical equipment, which are divided into safety valves (RS-1 and RS-2) and non-safety valves (NR(S), NR), and the quantity ratio in the project is about 1:3. RS-1 valve refers to a valve that contains a large amount of radioactive material and its failure will lead to an accident; RS-2 valve refers to a valve that contains a small number of radioactive materials and its failure will cause an accident condition; the NR (S) valve is a non-safety valve with special requirements, which are important safety-related valves, but their failure will not cause the radiation dose of relevant personnel to exceed the specified limit.
 
Valves with chemical and chemical safety grades are all classified into valves of anti-seismic category 1, and anti-seismic category 1 valves are divided into anti-seismic category 1I valves and anti-seismic category 1A valves according to different functions. Category 1I valves can guarantee structural integrity under the limit safe seismic vibration (SL2) load, and no restriction on deformation is put forward; category 1A is suitable for active valve devices, in addition to requiring structural integrity, earthquake protection is also required. Being operable is required during and after earthquakes. The NA mark has no seismic requirements.
 
The quality assurance level is divided into quality assurance QA1 level, quality assurance QA2 level, quality assurance QA3 level and non-nuclear quality assurance QAN level, among which RS-1 valves with non-standard production and harsh working environment correspond to QA1 level, and other RS-1 valves and non-standardized RS-2 valves produced in harsh working environment correspond to the QA2 level; the remaining RS-2 valves and NR(S) valves correspond to the QA3 level, and the NR valves correspond to the QAN level.
 
At present, there is no clear specification level for the process valves of spent fuel reprocessing projects in China, and they can only be designed and manufactured concerning energy industry standards and corresponding national standards.