Cooper Junk SRVs: 63% Failed Technical Specification Safety Testing

***Update 1/19

Spoke to Cooper's "new" senior resident inspector and the seasoned resident on the phone this afternoon for about 20 minutes. I swear the women are taking over the world(good). She said she is evaluating the LER update as we speak...LER 2015-001-01. Basically the below was my talking points. I gave her this blog's address.... 

I asked how close Cooper is to their MAPI...the SRV piping stresses when outside Tech Specs.

Looking forward to the new inspection report.

***updated 1/17

"Or the fix could be as simple as cycling each SRV open and close once every month to disrupt the oxidize bonding"

The NRC are supposed to be sticklers for details and telling the truth...

Right, Hope Creek this testing period had a 71% failure rate and Cooper has a 63% failure rate...kind of in the ball park, you think each? 

The drastic increase in failures compared to the last four outages should should raise the hairs on the back of your head. Any ethical engineering report like this should openly question this drastic increase and vow to immediately fix it. Why didn't they mention this in the report...what else is Cooper habitually not confronting and fixing at the plant? How come in Mrs Bower's letter to me on Hope Creeks SRV problems he didn't discuss the increase in setpoint accuracy problems? I just saying he is not discussing the painful truth... It is like he is a advertising executive and not a federal regulator. How many SRVs would have failed testing if the limits were +/- 1% or didn't have a stellite coating the on seat and valve? The +/- 3% and Stellite coating is accommodating these defectively designed valves. It is just giving a illusion they fix the problem.  It is destructive "Normalization of Deviance" on steroids. It is a common organizational mental illness.  

On the second SRV going INOP Cooper needs to be shutdown in 24 hours. 

You get it, a ethical organization(s) would never preform an experiment on nuclear power plant safety equipment. They would put the stellite coated internals and valve on a test stand and exactly model the environment and length of duty as in the nuclear plant. They would put the valve in a much more harsh environment than the plant, so the problems would be exaggerated. Then they would test the valves just like they do when it comes out of the nuclear plant. They'd never put that stellite into a nuclear plant without being 1000% sure how the stellite would perform. It would fix the lift setpoint accuracy problems. I am telling you something stinks rotten here.      

LER 2015-001-01: 5 failed TS safety testing 

LER 2011-005-00: 1 failed TS safety testing  

LER 2010-001-00: 2 failed TS safety testing 

LER 2008-002-00: 1 failed TS safety testing  

LER 2008-002-00: 1 failed TS safety testing

Licensee Event Report No. 2015-001-01

***Read what this below sentence in the LER. This is Coopers title of the document. The NRC wants me to make believe these below 16 words don't matter.  Ask Cooper what they are required to do in this case if they find this specific "condition prohibited by technical specification while at power". They are required to emediately shutdown. This is all "Catch 22" crazy circular logic. Right, "a loss of safety function.

Right, it like your brake peddle goes almost down to the floor. It wasn't like that a day ago. Once you put your foot on the peddle it emediately began braking is what it was a day ago. You test your braking power by slamming on the brakes. The car quickly stops like it should. Come on, but are you safe by ignoring this new problem. Normal people's alarm horns would loudly be going on their heads. They would quickly take the car to a mechanic and drive much more slowly while getting it to them.      

Valve Test Failures Result in a Condition Prohibited by Technical Specifications and a Loss of Safety Function

PLANT STATUS

Cooper Nuclear Station (CNS) was in Mode 1, Power Operation, at 100 percent power, when the event was discovered; i.e., January 26, 2015.

BACKGROUND

The pressure relief system includes three American Society of Mechanical Engineers code safety valves (SV) [EllS: SB] and eight safety relief valves (SRV) [EllS: RV], all of which are located on the main steam lines [EIlS: SB] within the drywell [EllS: NH], between the reactor vessel [EllS: RPV] and the first main steam isolation valve [EllS: ISV]. The SVs provide protection against over pressurization of the nuclear system and discharge directly into the interior space of the drywell. The SRVs discharge to the suppression pool and provide three main functions: overpressure relief operation to limit the pressure rise and prevent safety valve opening, overpressure safety operation to prevent nuclear system over pressurization, and depressurization operation (opened automatically or manually) as part of the emergency core cooling system [EllS: B J, BM, BO].

Technical Specification (TS) Limiting Condition for Operation 3.4.3 requires the safety function of seven SRVs and three SVs to be operable. The nominal set pressure and tolerances for these valves are established in CNS TS Surveillance Requirements (SR) 3.4.3.1.

The SRVs installed at CNS are Target Rock Model 7567F, two-stage, pilot-actuated valves with pilot assemblies comprised of Stellite 21 pilot discs and Stellite 6B pilot body seats. The pilot assemblies had been in continuous service since installation in Refueling Outage (RE) 27.

Corrosion bonding occurs when the protective oxide layers of the seat and disc break down and allow a crevice corrosion process to develop between the seat and disc. The seat is machined and then lapped with the disc to create a tight fit with one another. During the material removal process (machining) on both the seat and disc, the protective oxide layer that provides corrosion protection is removed. Because the SRV pilot valves are then assembled, the oxide layer is not given sufficient time to reestablish itself naturally, and no external process, such as pickling, is done to ensure that the oxide layer is reestablished to its full extent without any breaks or discontinuities. When the SRV pilot valves are assembled, the seat and disc are jammed together and air cannot reach the surfaces, therefore the full benefits of the oxide layer of the anti-corrosion material is diminished.

EVENT DESCRIPTION

On January 26 and February 11, 2015, three complete SRVs and five SRV pilot assemblies, removed during RE28 in the Fall of 2014, were as-found tested at National Technical Systems Laboratories, formerly Wyle Laboratories.

The pressure setpoint for SRV pilot assembly serial number 385 is 1090 psig. The TS SR 3.4.3.1 as-found limit of acceptance is 1090 +/- 3%. The first actual lift pressure of this SRV pilot assembly was recorded as 1124 psig, 3.119% above the pressure setpoint. For informational purposes, the technicians performed a second and third lift. The results were 1087 psig and 1087 psig, both within 3% of the pressure setpoint.

The pressure setpoint for SRV pilot assembly serial number 386 is 1100 psig. The TS SR 3.4.3.1 as-found limit of acceptance is 1100 +/- 3%. The first actual lift pressure of SRV number 386 was 1192 psig, 8.36% above the pressure setpoint. A second and third lift was performed and the results were 1108 psig and 1112 psig, both within 3% of the pressure setpoint.

The pressure setpoint for SRV pilot assembly serial number 1242 is 1090 psig. The TS SR 3.4.3.1 as found limit of acceptance is 1090 +/- 3%. The first actual lift pressure of this SRV pilot assembly was recorded as 1267.7 psig, 16.24% above the pressure setpoint. The results of a second and third lift were 1091 psig and 1090 psig, both meeting the pressure setpoint.

After this failure, testing was halted in order to verify testing accuracy. Testing was found to be the same as used in years past, and testing resumed on February 10 and February 11 for the remaining five SRVs.

The TS SR 3.4.3.1 as-found limit of acceptance for SRV pilot assembly serial number 1243 is 1100 psig +/- 3%. The first actual lift pressure of this SRV pilot assembly was recorded as 1139 psig, 3.545% above the pressure point. For informational purposes, a second and third lift was performed. The results were 1112psig and 1105 psig, both meeting the pressure setpoint.

SRV pilot assembly serial number 1241 was tested. The TS SR 3.4.3.1 as-found limit of acceptance is 1090 psig +/- 3%. The first actual lift pressure of this SRV pilot assembly was recorded as 1138 psig, 4.404% above the pressure point. A second and third lift was performed. The results were 1106 and 1092 psig, both meeting the pressure setpoint.

BASIS FOR REPORT

CNS is reporting this event as an operation or condition prohibited by plant TS per 10 CFR

50.73(a)(2)(i)(B), and also as a condition that could have prevented the fulfillment of the safety function of structures or systems as defined under 10 CFR 50.73(a)(2)(v).

An existing engineering analysis demonstrated that the reactor vessel would not be challenged during an overpressure event. In addition, a new analysis determined that the existing Minimum Critical Power Ratio (MCPR) operating limit would have protected the MCPR safety limit in the event of an anticipated operational occurrence. As such, this event will not be counted as a Safety System Functional Failure for the Nuclear Regulatory Commission performance indicator since no loss of safety function occurred.

SAFETY SIGNIFICANCE

Although the TS related to the set point lift pressures of the SRV pilot valve assemblies were exceeded, an analysis of this event indicates that the design basis pressures to ensure safety of the reactor vessel and its pressure related appurtenances would not be challenged. Public safety was not at risk. Safety to plant personnel and plant equipment were not at risk.

CAUSE

The direct cause of five of eight SRV pilot valves failing their lift tests is corrosion bonding.

CORRECTIVE ACTIONS

The following corrective actions have been entered into CNS' corrective action program:

1. CNS shall inspect the SRVs during disassembly to ensure there are no indications of binding, vibration, or other mechanical problems that might cause effects similar to that of corrosion bonding.

2. Laboratory work, under the direction of CNS, shall be undertaken to confirm or deny corrosion bonding of the disc and seats as needed. A comparison with previous laboratory findings about SRV pilot valves will be performed to determine, if possible, the role time in-service played in the failures.

3. Based on the results of the inspection and laboratory work, specific findings and corrective action recommendations in the form of a revised root cause investigation report will be completed.

4. If no evidence to refute corrosion bonding is identified, ensure after machining and lapping processes have been completed, that the oxide, passive layer on the seat and disc are fully restored by pickling or an equivalent process.

5. Presuming that no technical reason is discovered to prevent the following, submit to the Nuclear Regulatory Commission a Technical Specification change that requests setpoint changes as noted in EE 10-053; NEDC-33 543P, Revision 0, Class Ill, DRF 0000-0103-4647, dated February 2010; GE-H NEDC-3362OP, Revision 0, May 2011; and GE-H, report 002N5242-R0, entitled, Cooper Cycle 28 SRV Set Point Study.

PREVIOUS EVENTS

Licensee Event Report (LER) 2011-005-00 - On June 22, 2011, one of eight Target Rock SRV pilot valve assemblies failed to lift within TS lift setpoint requirements. Wyle Laboratories performed this testing. The pressure setpoint of the failed pilot assembly was 1090 +/- 32.7 psig; it lifted at 1199 psig. Two subsequent informational lifts were performed for the SRV pilot assembly and were within the TS pressure setpoint tolerances. The mechanistic cause was the same as reported in previous LERs, pilot disc-to-seat corrosion bonding.

LER 2010-001-00 - On January 12, 2010, two of eight Target Rock SRV pilot valve assemblies failed to lift within TS lift setpoint requirements. Wyle Laboratories performed this testing. The pressure setpoint for the first pilot assembly is 1100 +1- 33.0 psig; the SRV pilot assembly lifted at 1166 psig. The pressure setpoint for the second pilot assembly is 1090 +1- 32.7 psig; it lifted at 1139 psig. Two subsequent informational lifts were performed for both SRV pilot assemblies and were within the TS pressure setpoint tolerances. The mechanistic cause was the same as reported in previous LERs, pilot disc-to-seat corrosion bounding.

LER 2008-002-00 - On July 7 through July 9, 2008, the results of Target Rock SRV test data performed at Wyle Laboratories identified that one of eight SRV pilot assemblies failed as-found pressure setpoint testing. The SRV pilot assembly lifted at 1165 psig, outside its TS setpoint tolerance of 1100 +/- 33.0 psig. The mechanistic cause was pilot disc-to-seat corrosion bounding between the Stellite 21 pilot disc and Stellite 6B pilot body seat to cause the SRV pilot assembly to lift outside its TS setpoint tolerance.

LER 2007-002-00 - On February 28 through March 2, 2007, the results of Target Rock SRV tests performed at Wyle Laboratories identified that one of eight SRV pilot valve assemblies failed to lift within its TS lift setpoint of 1090 +/- 32.7 psig. The failure was a result of sufficient corrosion bonding between the SRV pilot valve assembly Stellite 21 disc and the pilot valve Stellite 6B body seat to cause the SRV pilot valve to lift outside its TS setpoint tolerance.