Junk Plant Hatch and NRC: Ping Ponging between the 2 and 3 Stage SRVs

You know what see here, the object failure of the NRC and Hatch engineering problem analysis and anticipating component degradation since 2010. Their engineering sucks. Don't forget the southern company is hugely influential  It really scares me the experimentation going on here. The inability of the NRC to control SRV durability and reliability. I am sure this is not limited to the SRV valves.

This LER comes from the outage comes before this May's 2016 most recent outage. So the 2 stage is leak prone and has issues of not passing the lift point accuracy test.

Safety Relief Valves As Found Settings Resulted In Not Meeting Tech Spec Surveillance Criteria

Licensee Event Report 2014-003-00

On May 7, 2014, at approximately 0837, Unit 1 was at 99.9 percent rated thermal power (RTP) when the "as-found" testing results of the 2-stage main steam safety relief valves (SRVs) were received which indicated that five of eleven SRVs had experienced setpoint drift during the previous operating cycle which resulted in their failing to meet the Technical Specification (TS) opening setpoints of 1150 psig +1- 3 percent as required by TS surveillance requirement 3.4.3.1.

That is about a 50% test failure rate. Check out these guys with lift setpoint drift test failures of about 50% since 2010 and multiple shutdowns over the leaking 3 stage. The basic 2 stage and 3 stage valve designs are defective. For some reason, they can't dump these target rock valves and jump into a better and newer design.

In 2014 the cause of the setpoint drift is corrosion induced bonding.   

The root cause of the SRV setpoint drift is attributed to corrosion-induced bonding between the pilot disc and seating surfaces. This conclusion is based on previous root cause analyses and the repetitive nature of this condition at Hatch and within the BWR industry. The 2-stage SRVs with platinum coated pilot seats were removed from Unit 1 during the 2014 refueling outage and replaced with 3-stage SRVs with a modified pilot. 3-stage SRVs typically do not exhibit set point drift, additionally the modified pilot reduces instances of vibration induced spurious openings and leak-by.

A 3-stage SRV with a similar modified pilot was installed on Unit 2 during the 2013 outage. Current plans are to replace the remaining ten valves at Unit 2 with the same modified pilot valves during the next outage in 2015.

PREVIOUS SIMILAR EVENTS:

LEA 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.

LEA 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 SAVs containing pilot discs that had undergone the platinum surface treatment.

LEA 1-201 0·001, 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 Stellite 21 material. Additionally, the insulation surrounding each SRV was upgraded to improve resistance to corrosion induced bonding. These were the same actions that were taken following similar failures reported in LEA 2-2009- 001, since improved results had been seen to some degree in the industry for at least one operating cycle when these actions were implemented.