Junk Plant Hatch Junk FirstTime Used 3-Stage SRVs

EDWIN I. HATCH NUCLEAR PLANT - NRC INTEGRATED INSPECTION REPORT 05000321/2016002 AND 05000366/2016002; AND EXERCISE OF ENFORCEMENT DISCRETION

This guys have been jumping back and forth between the two stage and three stage Safety Relief Valves like Mexican jumping beans. I believe this is the newest operational period with all three stage SRV. With the 2 stage it was corrosion bonding causing the setpoint drift, now with the 3 stage it is:  "The licensee determined that the abutment gap closed pre-maturely most likely due to manufacturing tolerances". I think all this is unreliable small parts mechanical tolerances and metallurgy tolerances. Basically the design is too delicate, you look at it the wrong way the set pressure drifts out of specs. I don't think the technicians are skilled or trained adequately to service the SRVS.

The three stage was put into the plant to fix the setpoint drift, now they got this new magical "abutment gap" setpoint drift problem in the 3 stage   problem they couldn't see in design testing.  They always find some explanation for the drift problem without fixing it right the last time.

(CLOSED) LER 05000321/2016-004-00 Safety Relief Valves As Found Setting Resulted in Not Meeting Technical Specifications

a. Inspection Scope
The inspectors reviewed this LER for potential performance deficiencies and/or violations of regulatory requirements. Additionally, discussions were held with licensee
staff members to understand the details surrounding this issue. This condition was documented in the licensee’s corrective action program as CR 10204045. 

b. Findings
Description: During the February 2016 Unit 1 refueling outage, all eleven 3-stage safety

Inspecting and testing all eleven 3 stage in a outage is a sign of weakness. They don't have complete confidence in the design. Some plants won't trust the 3 stage design based on the Pilgrim problem.  

relief valves (SRVs) were removed and replaced. The SRVs were Target Rock model 0867F, a 3-stage valve design which was in its first use. This design was adopted as a
corrective action to address corrosion bonding experienced by 2-stage SRV model 7687F valves which were previously in use at Hatch. "As-found" test results indicated two of the eleven SRVs had experienced a setpoint drift during the previous operating cycle which resulted in their failure to meet the Technical Specification (TS) opening setpoint pressure as required by TS Surveillance Requirement (SR) 3.4.3.1. The SRV pilot valves were disassembled and inspected while investigating the reason for the drift.
For the 3-stage design, the pilot disc seating stresses should increase proportionally as reactor pressure increases to where a mechanical gap within the valve stem
mechanism, referred to as the “abutment gap,” is closed. Additional pressure increases will cause the valve stem mechanism to reduce the disc seat pressure until the valve eventually opens. The licensee determined that the abutment gap closed pre-maturely most likely due to manufacturing tolerances. The cause of the setpoint drift could not be attributed to any known preventive maintenance requirement or operating experience because of the limited operating history of this specific valve model. Additionally, there
were no symptoms available to operators or maintenance personnel to indicate the potential for the set point drift prior to post-service testing. 

Enforcement: Hatch Unit 1 TS limiting condition for operation 3.4.3, “Safety/Relief Valves,” required 10 of 11 SRVs be operable in MODES 1, 2 and 3. With two or more
SRVs inoperable, the required TS action must be taken by the applicable completion time. Contrary to the above, Unit 1 operated from the initiation of the degraded condition
until February 8, 2016, with two SRVs inoperable. The inspectors concluded that the violation would normally be characterized as a Severity Level IV violation because it was of very low safety significance (Green). However, the NRC is exercising enforcement discretion (EA-16-158) in accordance with Section 2.2.4.d of the Enforcement Policy because the violation was not associated with a licensee performance deficiency. This issue was documented in the licensee’s corrective action program as CR10204045.