Oyster Creek: Yellow Safety Relief Valve Problems.

This is probably the model for end-of-life plants in the future. The plant is operating with obscenely obsolete equipment and in its closing years it is just not worth wasting money on a dying plant.

You catch here with these severe safety relief valve (electromatic relief valve) problems it seems to only occur in plants who are severely troubled and many other component have been implicated in degradations.  

What I never got, it was a initial design defect...why did it only show up at end of life?

OFFICE OF ENFORCEMENT NOTIFICATION OF SIGNIFICANT ENFORCEMENT ACTION Subject: ISSUANCE OF FINAL SIGNIFICANCE DETERMINATION AND NOTICE OF VIOLATION

This is to inform the Commission that two separate Notices of Violation (NOV), one associated with a Yellow Significance Determination Process (SDP) finding and one associated with a White SDP finding, will be issued on or about April 27, 2015, to Exelon Generation Company, LLC (Exelon) as a result of separate inspections at its Oyster Creek Nuclear Power Station. The Yellow finding represents an issue of substantial safety significance. The White finding represents an issue of low to moderate safety significance. These findings will result in additional NRC inspection and potentially other NRC action.

The Yellow finding involved the failure by Exelon to establish adequate measures for the selection and review for suitability of application of materials, parts, equipment, and processes that are essential to the safety-related functions of the electromatic relief valves (EMRVs). Specifically, since original installation of the EMRVs in 1969, until the valves were redesigned and reinstalled during the 2014 refueling outage, the EMRV actuators were inadequate because when they were placed in an environment where the actuator was subject to vibration associated with plant operation, the mechanical tolerance between posts and guides created a condition where the springs could wedge between the guides and the posts, jamming the actuator plunger assembly. In addition, given the original design of the valve, the maintenance refurbishing processes were not adequate to maintain the required internal tolerances to prevent excessive fretting and wear of the internal components. As a result, the staff determined that two EMRVs were inoperable for greater than the allowed Technical Specification outage time of 24 hours.

The White finding involved the failure by Exelon to review the suitability of a new emergency diesel generator (EDG) belt maintenance process that was essential to a safety-related function of the EDGs and to verify the acceptance criteria of that process. Specifically, from May 13, 2005, to September 9, 2014, Exelon changed the method for tensioning the cooling fan belt on the EDG from measuring belt deflection to measuring belt frequency and did not verify the adequacy of the acceptance criteria stated for the new method. As a result, the specified belt frequency imposed a stress above the fatigue endurance limit of the shaft material, making the EDG cooling fan shaft susceptible to fatigue and failure which occurred on July 28, 2014. As a result, the staff determined that EDG No. 2 was inoperable for greater than the allowed Technical Specification outage time of 7 days...