Study on corrosion products removal in PWR primary circuit

In recently constructed domestic PWRs, a fine mesh prefilter with nominal porosity of 0.8 microns, is installed upstream of the CVCS mixed-bed demineralizer to remove particulate corrosion products (CPs). However, Sendai unit No.1 and No.2, which are 3-loop PWRs with generation capacity of 890 MWe and commenced commercial operation in 1984 and 1985 respectively, are not provided with the prefilter because the concept of positive removal of CPs was not clear in design stage to both of the units. The removal of particulate CPs by the prefilter prevents the resin contamination of the demineralizer, and is effective for radiation source reduction. Therefore, study was carried out to obtain information about CPs removal efficiency by the filters with various porosity, nature and behavior of CPs in the primary coolant at Sendai unit No.1, and discussed concerning the improvement of operation procedure and the service life extension of the demineralizer, and also evaluated the effect of installing the prefilter on radiation source reduction. (authors). 4 figs., 1 tab., 3 refs