Junk Plant Hatch Plant Junk SRVs

05000321/366

This is the 3 stage model that got Pilgrim plant into so much trouble last year. This model is supposed to be immune to setpoint drift. This is why they recently jumped out of the 2 stage SRVs.

I think Target Rock thinks why even bother playing with these little nuke boys. Or the valves are to old to repaired and tested by them. So the local two bit "NWS Technologies" now does the testing and repair on the obsolete SRVS.  

Across the board, Hatch has been having a lot of problems with maintaining the reliability of the 2 stage or the three stage SRVs for many years. They wasted a lot of money on their SRVS.

I believe the dimensions and the material quality of the components are in play. We generially don't know the true material quality of the component, there is just is no facts to predict how these components will fail.       

Edwin I. Hatch Nuclear Plant Unit 1

LER 2016-004-001
Safety Relief Valves As Found Settings Resulted in Not Meeting Tech Spec
Surveillance Criteria

On March 30 2016, with Unit 1 at 100 percent rated thermal power (RTP) , "as-found" testing of the 3-stage main steam safety relief valves (SRVs) (EllS Code RV) showed that two of the eleven main steam SRVs that were tested had experienced a drift in pressure lift setpoint during the previous operating cycle such that the allowable technical specification (TS) surveillance requirement (SR) 3.4.3.1 limit of 1150 +1- 34.5 ( +1- 3%) psig had been exceeded. Below is a table illustrating the Unit 1 SRVs that failed as found testing results after being removed from service during the Spring

2016 refueling outage.
MPL
1821-F013D
1B21-F013E 

Usually it's seat/valve bonding. This gap thing problem is new. In the Pilgrim 3 stage issue, they seemed to blame it on inappropriate test stand testing. I always thought the components in the valves are of a poor quality. There is generially poor service from Target Rock. I don't trust these guys and I don't trust the NRC's diagnoses with why the failing and why target rock is getting to unreliable.  

The SRV pilots were disassembled and inspected while investigating the reason for the drift. SNC has determined that the abutment gap closed pre-maturely. The pre-mature abutment gap closure is most likely due to loose manufacturing tolerances leading to SRV setpoint drift. They assume they know what caused this.

I am pretty sure if they were up at power with two SRVs inop, then they would be immediately be required to shutdown the plant.  

The two SRVs which failed to meet their Tech Spec required actuation pressure setpoint lifted early (3.2% low and 3.8% low). None of the eleven SRVs tested this cycle had as-found test results out of range high. Therefore, since the two identified SRVs lifted earlier than expected, the ASME Code Limit of 1375 psig peak vessel pressure would be maintained under normal and accident conditions. The opening of one or more SRVs at lower pressures would result in a less severe transient with reduced peak vessel pressure. Also, the slightly lower actuating pressure does not pose a significant LOCA initiator threat because the reactor steam dome would not experience > 11 00 psig during normal operation.

It is utterly disgraceful they can't detect these problems before installation in the plant.

The vendor specifications will be revised to tighten as-left tolerances of abutment and pre-load gap, increase the minimum set for abutment pressure at the high end of specification, and tighten diametrical and face run-out tolerances for bellows assembly on pre-load spacer mounting end.