Update May 20
***Update: Had a talk to the NRC project manager Mr Hall. He essentially agreed to everything I said about this valves...Meant this: "The pre-mature abutment gap closure is most likely due to loose manufacturing tolerances leading to SRV setpoint drift. The phrase "most likely" is killing me. We are operating these plants in a casino. There is certainly collusion going on between the vendor and licensee...certainly the NRC is in the game too.This abutment gape thing has been going on in other plants and it is a rather new phenomena. It started in Pilgrim.They can't knowingly put counterfeit and fraudulent parts in a safety system and startup the plant.They are certainly putting these new and refurbished valves in the plants at the edge of stability. A little wear then shows up and they don't pass their test. The design is and has always been unstable.As time goes on, as the industry continues to decline, they won't have the resources to keep these valves at the edge of stability. As the valve's support systems and Target Rock continues to decay...And they are barely used and tested. I don't think any one knows the true operability and reliability = of these valves...their true condition and how they might malfunction. The testing and infrequent usage is cover-upping the true and real reliability of these valves. You put a stress of them, surprises are going to show up.
New LER: On June 30 2017, with Unit 2 at 100 percent rated thermal power {RTP), "as-found" testing of the 3-stage main steam safety relief valves (SRVs) (EBS Code RV) showed that two of the eleven main steam SRVs that were tested had experienced a drift in pressure lilt setpoint during the previous operating cyde such that the anowable technical specification (TS) surveillance requirement (SR) 3.4.3.1 limit of 1150 +/-34.5 psig had been exceeded. Below is a table illustrating the Unit 2 SRVs that failed as found testing results alter being removed tom service during the Spring 2017 refueling outage.
MPL 2821-F013C 2821-F013E
Event cause Analysis
Drift -39 psig -49 psig
The SRV pilots were disassembled and inspected while investigating the reason for the drift It was found that the abutment gap closed prematurely during testing using a linear variable differential transformer (l von to measure pilot stroke distance. The pre-mature abutment gap closure is most likely due to loose manufacturing tolerances leading to SRV setpoint drift
Hatch Plant 1 and 2Reason for Request Section ISTC-5240, "Safety and Relief Valve," directs that safety and relief valves meet the inservice testing requirements set forth in Appendix I of the ASME OM Code. Appendix I, Section l-1320(a) of the ASME OM Code states that Class 1 pressure relief valves shall be tested at least once every 5 years, starting with initial power generation. This section also states a minimum of 20% of the pressure relief valves shall be tested within any 24-month period, and that the test interval for any individual valve shall not exceed 5 years. The required tests ensure that the SRV main bodies will open at the pressures assumed in the safety analysis. Due to the current 24-month operating cycle for each HNP unit, SNC is required to remove and test approximately half of the 11 SRV main bodies every refueling outage to ensure that SRV main bodies are tested in accordance with the ASME OM Code requirements. This ensure compliance with the ASME OM Code for testing all Class pressure relief valve within a 5-year interval. With the current 5-year interval, Hatch is required to remove and test all11 SRV main bodies over two refueling cycles (i.e. 4 years). Approval to extended the test interval to 6 years with a 6-month allowable grace period would reduce the number of SRV main bodies removed during an individual refueling outage such that the full scope of 11 SRV main bodies are tested over 3 refueling cycles (i.e. 6 years). Without Code relief, the incremental outage work due to the inclusion of the additional two SRV main bodies per outage would be contrary to the principal of maintaining radiation dose As Low As Reasonably Achievable (ALARA). The removal and replacement of the additional SRV main bodies per outage results in an additional personnel radiation exposure of approximately 2.4 Rem every 6 years per unit.
LER 1-2014-003, identified multiple SRV setpoint drifts for 5 of the 11 two-stage SRVs installed on Unit 1. The two-stage SRVs with platinum-coated pilot discs were removed from Unit 1 during the 2014 refueling outage and replaced with 3-stage SRVs that have a modified pilot. The modified pilots will help reduce spurious openings and leak-by due to system vibration.LER 1-2012-004, identified multiple SRV setpoint drift for 8 of the 11 SRVs. Corrective actions included replacement of the 2-stage SRVs with 2-stage SRVs whose pilot discs had undergone a platinum surface treatment which was considered at that time to be the long term fix for this corrosion bonding issue.LER 2-2011-002, identified multiple SRV setpoint drift for 8 of the 11 SRVs. Corrective actions included replacement of the 2-stage SRVs with 3-stage SRVs during the Unit 2 Spring 2011 refueling outage which was considered at that time to be the long term fix for this corrosion bonding issue. Subsequent to that outage the 3-stage SRVs exhibited signs of unacceptable leakage which resulted in two separate outages that involved changing out four SRVs during the first outage and the remaining seven SRVs during the subsequent outage in May 2012. The 3-stage SRVs were replaced with 2-stage SRVs containing pilot discs that had undergone the platinum surface treatment.LER 1-2010-001, identified multiple SRV setpoint drift for 5 of the 11 SRVs. Corrective actions included refurbishment of the pilot valves and included the replacement of the pilot discs with discs made from Satellite 21 material. Additionally, the insulation surrounding each SRV was upgraded to improve resistance toPrevious Similar Events:LER 2-2008-004; identified multiple SRV setpoint drift for three of the four tested SRV's. Corrective actions for that LER, replacement of discs were implemented but discs made of stellite 21 for the Unit 2 SRV's were not available for all of the replaced discs and thus could not have prevented the current event.LER 1-2008-002; identified multiple SRV setpoint drift for three of the eleven SRV's. Corrective actions for that LER, replacement of discs with stellite 21 discs, were not yet implemented for the Unit 1 SRV's and thus could not have prevented the current event.LER 2-2007-006; identified multiple SRV setpoint drift for five of the eleven SRV's. Corrective actions for this LER, replacement of discs with stellite 21 discs, were not yet implemented for the Unit 2 SRV's and thus could not have prevented the current event.LER 1-2006-003; which identified an error in reporting multiple SRV setpoint drift, also described results from the previous three outages where multiple SRV setpoint drift had occurred. Corrective actions for this LER focused on ensuring the proper reporting of SRV se!point drift was performed.
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