Junk Plant Ginna MSSV: Disfgracefull Standard With "The Most Probable Cause"

LER 2017-001, During Surveillance Testing, Lift Pressure Setpoints on Three Main Steam Safety Valves Found Outside Technical Specifications Limits Due to Stiction.

On April 23, 2017, with the plant in Mode I, during in-place testing of main steam safety valve (MSSV) 3509, the as-found lift pressure did not meet the acceptance criteria of+ I%/ -3% of setpoint (1140 psig), required by Technical Specifications (TS) surveillance SR 3.7.1.1. This was the second unsatisfactory MSSV as-found lift pressure, as MSSV 3508 had failed to meet the same as-found acceptance criteria during earlier in-place sequential testing (on April 21, 2017). Later, on May 5, 2017, a third MSSV (3512) tested at a vendor's facility failed to meet the same as-found acceptance criteria. (All three of the MSSVs have the same manufacturer and model number.) The most probable cause of exceeding the MSSV upper acceptance limit is the programmatic issue of the narrowness of the as-found acceptance band. A contributing cause was minor stiction on the disc. The as-found settings of all three MSSVs remained within analytical bounds; therefore, operation of the facility in this condition had no impact on the health and safety of the public.

Sounds like a new emergent failure with the new valves. You catch it, nobody yet knows what caused the mircro fouling. 

The most probable cause of the MSSVs' as-found lift pressures being outside +1 % / -3% of setpoint is the programmatic issue of the narrowness of the as-found acceptance band. A contributing cause was minor stiction in the disc. Note that all the Ginna MSSVs were upgraded in 2009/2012 to lnconel 618 flexi-discs and 316SS nozzles, so corrosion of these sub-components (a contributor to some MSSV failures) is insignificant.

• Evaluate changing the test frequency from 5 years to 3 years. This will prevent the formation of micro-fouling and reduce the likelihood of stiction.