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Cover StoryHowever, to be on the safe side,Davis-Besse decided to install a FLÜSsystem – a Framatome ANP continualhumidity monitoring system. A finalverification will not be made at Davis-Besse until after the plant is broughtto normal operating temperaturesand pressures for about a week. Thenthey will be reduced and the bottomof the vessel reinspected.Of the 69 PWRs with lower vesselpenetrations, 22 have performedvisual inspections over the past severalyears. Many would not be consideredbare metal visual inspections by theNRC today. In discussing the bottomportion of the RV vessel, the NRC’sSheron noted,” The safety concerns aregreater with the lower reactor vesselpenetrations... these penetrations aremuch more difficult to access thanthe upper portion of the vessel. If thelower portion of the vessel is insulatedand there is a leak… could we detectit? Do we need to enhance ourdetection methods?”The South TexasProject ExperienceDuring a regular refueling andmaintenance outage, a visual inspectionby the South Texas Project (STP)revealed a small amount of a powderysubstance around two penetrations inthe lower reactor pressure vessel (RPV).Framatome ANP was contractedto perform a first-of-a-kind inspectionin the US market of STP’s Unit 1RPV BMI nozzles. This was theworld’s first indication of leakagearound the BMI.The ProblemThe results of testing showed that thesubstance was boric acid, indicatingthat the source was reactor coolantfluid. After confirming the discovery,STP shared the information withthe NRC as well as EPRI and othernuclear power operators. STP decidedSTP’s penetration #46 showing its 3 mg of deposits.to perform exhaustive inspectionson all 58 BMI penetration tubesand their welds.Knowing the importance of thispotential leakage, the company wantedsomeone to perform the inspectionswho had similar experience, eventhough this was the first time that thistype of inspection had been performedin the US, and someone who couldmeet their schedule.PreparationFramatome ANP was awarded acontract to perform the inspectionand any necessary repairs. Part ofthe reason for the award was that thecompany, working with its Frenchnon-destructive examination (NDE)subsidiary, Intercontrôle, hadperformed more than 80 RV closurehead inspections since the early 1990s.More than 1,200 nozzles wereinspected through 2002 as well as18 BMI inspections in Europe. STPwas impressed with the capabilitydemonstrations which they requestedas well as the number of extensive,innovative inspection and repair toolsand techniques that Framatome ANPhad developed in performing the RVhead inspections and repair.A team of 25 experts and techniciansfrom the US and France worked12 Advanced Nuclear Power N O 9 November 2003