Technical findings report for Generic Issue 135: Steam Generator and Steam Line Overfill Issues

A detailed review of the tasks and available literature pertaining to Generic Issue 135 (GI 135), Steam Generator and Steam Line Overfill Issues, has been conducted and is documented in this technical findings report. The purpose of the review was to evaluate the current status of the issues and to determine whether sufficient information exists for resolution, or whether additional work is required for the 14 remaining subissues derived from GI 67 associated with the four tasks of GI 135. The review indicates that because sufficient information exists for eight of the subissues they should no longer be pursued as part of GI 135. Six of these eight subissues have been determined to be resolved, and the other two subissues, 67.3.1 and 67.9.0, are addressed in TMI Action Plan I.C.1 as well as in Unresolved Safety Issues A-47 and A-45 respectively. Two subissues (eddy current testing and supplemental tube inspection) are being handled as part of the effort to develop revisions of Regulatory Guides 1.83 and 1.121 and through existing surveillance procedures. Two other subissues (sleeving and denting) have been concluded to be of little safety significance and have been designated as regulatory impact issues. The remaining two subissues, concerning reassessment of radiological consequences (67.5.1) and reevaluation of the steam generator tube rupture design basis event (67.5.2), are also being pursued as separate generic issues and should no longer be considered under GI 135. In addition, a data search and evaluation were conducted on the frequency and effects of steam generator overfill events (67.3.1). Potential mitigating actions were considered. It was concluded that the public health and safety risks associated with these events are relatively minor and do not justify additional mitigating actions or regulations. 70 refs., 5 tabs