Removal of a Tubesheet Sample From a Retired Point Beach Unit 1 Steam Generator

摘要

The project described in the following report was undertaken by NUS Operating Services Corporation (NUSOSC) to remove a tubesheet sample from a steam generator that was retired from service due to corrosion damage to tubes particularly in the tubesheet. The field work was performed at the Wisconsin Electric Power Company's (WEPCO) Point Beach Nuclear Plant where two Westinghouse steam gener¬ators from the Unit 1 pressurized water reactor system are stored in an on-site storage building. The sample removed is for subsequent detailed analyses of causes of the corrosion in the crevice area between the Inconel tubes and the tubesheet.nThree concepts to remove the sample were investigated by NUSOSC:drilling, plasma arc cutting, and electric discharge machining (EDM). The electric dis¬charge machining technique was finally chosen to remove the sample. Although the report discusses all three concepts investigated, the primary emphasis is on the work activities undertaken by NUSOSC which resulted in the successful removal of a steam generator sample by EDM. A great deal of insight was gained regarding the problems involved in the removal of the sample in a high radiation environment using EDM.