Improvement of Precoat Type Condensate Filter Performance

The precoat type condensate filter system, equipping most BWR plants in Japan, is sought to be improved in terms of filtering performance-i.e. to lower the concentration of crud in filtered condensate water and to extend the filter run length. Laboratory experiments were performed on various measures for improving the filter performance, among which those found to be promising were : (a) Use of more suitable precoat material (cation resin of suitably low cross-linkage and mixture with fibrous cation exchange resin), (b) Adoption of improved precoating procedure (body feed coating-i.e. feeding precoat material continuously during filter operation), (c) Improvement of flow pattern through filtering vessel (insertion of draft tube), and (d) Modification of filter system operating mode (swelling operation-i.e. interruptions in individual filter use in-between backwash operations). Trial application on actual plants of some of the above measures has demonstrated that the envisaged improvement of filter system performance can duly be expected to be realized.