10 CFR 50, Appendix B, Criterion III, Design Control, requires, in part, that design control measures shall provide for verifying or checking the adequacy of designs such as by the performance of design reviews, by the use of alternate or simplified calculational methods, or by the performance of a suitable testing program. Contrary to this, the licensee identified in CR398124 that they failed to verify the adequacy of design changes that implemented a new drainage path through the primary shield wall. The design changes were inadequate because the impact to the
sump from Microtherm insulation known to be installed on the reactor vessel head had not been evaluated or tested. The licensee removed all Microtherm from the Unit 1 reactor head and plans on removing all Microtherm from the Unit 2 reactor head during the outage in Spring 2011. The violation was determined to be of very low safety significance because the licensee was able to show that the debris loading was bounded by testing
