New filters for radioactive liquid waste in LWR power plants

Two types of radioactive materials in liquid waste are produced by light water reactors (LWRs): radioactive suspended particles (crud) and radioactive ions, which are easily removed with filters and ion exchange resins, respectively. Initially, precoated or cartridge-type filters were used to remove crud from liquid waste. However, these filters possess disadvantages, such as generating large amounts of spent materials as secondary waste, a low separation efficiency, and the potential for radiation exposure to plant personnel. As a result, highly efficient, nonprecoated-type filters have been developed to replace the precoated type. JGC has further advanced this development with the super-fine (SF) filter that has been and is being applied at many Japanese LWR nuclear power plants. The SF filter consists of porous hollow fibers with pore sizes of < 0.1 μm. Therefore, crud, whose diameter is usually > 0.1 μm, can be completely removed from liquid waste by using the SF filter. The SF filter, which is made of modified polyvinyl alcohol, is backwashable and combustible. Results of experimental research and in-plant tests are provided