05000278/LER-2011-001, Regarding Containment Isolation Valve Inability to Close for a Design Basis Event Due to Degraded Lubricant
| ML11343A682 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 12/09/2011 |
| From: | Armstrong J Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 11-001-00 | |
| Download: ML11343A682 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2782011001R00 - NRC Website | |
text
Exelknt Exelon Nuclear www.exeloncorp.com Nuclear Peach Bottom Atomic Power Station 1848 Lay Rd.
Delta, PA 17314 10CFR 50.73 December 9, 2011 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station (PBAPS) Unit 3 Renewed Facility Operating License No. DPR-56 NRC Docket No. 50-278
Subject:
Errata for Licensee Event Report (LER) 3-11-001 The subject LER was submitted on 11/9/11 and contained an error on NRC Form 366, item 6. The LER number should have been 11-001 -00 instead of 11-003-00. All other references to the LER number on the cover page and other pages of the LER were correct. Enclosed is an update of the subject LER with a corrected NRC Form 366, item
- 6. We regret any inconvenience that this error may have caused.
If you have any questions or require additional information, please do not hesitate to contact us.
Sincerely, James M. Armstrong Regulatory Assurance Manager Peach Bottom Atomic Power Station GLS/djf/IR 1266600/1266604/1295818 Attachment cc:
US NRC, Administrator, Region I US NRC, Senior Resident Inspector R. R. Janati, Commonwealth of Pennsylvania S. Grey, State of Maryland P. Steinhauer, PSE&G, Financial Controls and Co-owner Affairs INPO Records Center CCN: 11-106
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may sfor each block) not conduct or sponsor, and a person is not required to respond to, the digits/characters finformation collection.
- 3. PAGE Peach Bottom Atomic Power Station (PBAPS) Unit 3 05000278 1 OF 4
- 4. TITLE Containment Isolation Valve Inability to Close for a Design Basis Event due to Degraded Lubricant
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER MONTH DAY Y
YEAR SEQUENTIAL REV MONTH DAY YEAR 05000
,MNH DY YA YER NUMBER NO.____________________
1 FACILITY NAME DOCKET NUMBER 09 21 2011 11 001 00 11 09 2011 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[1 20.2201(b)
El 20.2203(a)(3)(i)
[I 50.73(a)(2)(i)(C)
[I 50.73(a)(2)(vii) 5 [1 20.2201(d)
El 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
[I 20.2203(a)(1)
El 20.2203(a)(4) 0l 50.73(a)(2)(ii)(B)
[I 50.73(a)(2)(viii)(B)
[I 20.2203(a)(2)(i)
Cl 50.36(c)(1)(i)(A)
[3 50.73(a)(2)(iii) 0l 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
[I 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
[I 50.73(a)(2)(v)(A)
El 73.71(a)(4) 0%
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5)
[I 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
[I 50.73(a)(2)(v)(C)
El OTHER [E 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in Analysis of the Event, continued During power operations, the RWCU Outboard Isolation Valve (MO-3-12-018) is a normally open motor-operated valve located in the supply line to the RWCU pumps from the reactor coolant system. The valve has no safety function in the open position. It remains open during power operations primarily to provide a flow path for purification of reactor water.
RWCU supports maintaining reactor water quality within limits by circulating reactor coolant through a filter-demineralizer system and returning it to the reactor coolant system. The MO-3-12-018 does provide an active safety function in the closed direction.
It is an outboard primary containment isolation valve for containment penetration N-14. The valve receives an auto-closure signal for Primary Containment Isolation System signals including a rupture in non-safety related RWCU piping and preventing the removal or dilution of sodium pentaborate solution by the RWCU system when the Standby Liquid Control system is in operation.
The data obtained during the performance testing indicated that the as-found thrust of the valve at the point of torque switch actuation was less than the required thrust value. This condition may have resulted in the valve prematurely stopping motion in the closed direction under design basis demand conditions (e.g., high energy line break just downstream of the MO-3-12-018 valve).
Engineering has determined that for normal plant operations and for design events where there is not a high differential pressure across the MO-3-12-018 valve, the MO-3-12-018 valve would have closed as designed. However, the MO-3-12-018 may not have fully closed for the design event involving a high energy line break just downstream of the MO-3-12-018 and the assumption of a single failure of the RWCU Inboard Isolation Valve (MO-3-12-015). Based on conservative assumptions during the high energy line break event, it is estimated that the valve would have traveled approximately 89% closed.
The redundant RWCU Inboard Isolation Valve (MO-3-12-015) was maintained operable during this event.
Therefore, the isolation capability of this containment penetration was maintained.
There was no occurrence of high energy line breaks. Had a worst case design basis event occurred (RWCU high energy line break coupled with a single failure involving the inability to close the RWCU Inboard Isolation Valve (MO-3-12-015)), the resultant discharge of coolant would be into the Secondary Containment. The Secondary Containment and the Emergency Core Cooling systems (including the Automatic Depressurization System) would have been available to mitigate the event.
Cause of the Event
The cause of the MO-3-12-018 degradation is due to grease hardening in the stem nut area of the motor-operator. It was identified that the grease on the stem thread area was dry, with no functioning lubricant on the stem threads. The stem nut is the device in the motor operator that interfaces with the threaded valve stem. The motor operator turns the stem nut resulting in movement of the valve stem.
The Limitorque Corporation supplied the motor-operator (Model SMB-1-40). The grease was manufactured by Exxon (Nebula EP-1). The replacement grease is 'MOV Long Life.'
Corrective Actions
The MO-3-12-018 valve was repaired by 9/23/11. The grease was replaced with a new type of grease (MOV Long Life).
An extent-of-condition evaluation for other susceptible MOVs on both Units 2 and 3 was performed. This has resulted in a decrease in the MOV preventive maintenance time interval for MO-3-12-018 and other valves. Susceptible valves with Nebula EP-1 grease were evaluated to ensure appropriate timing exists for the change to MOV Long Life grease.
Additionally, the grease for other Unit 2 and Unit 3 MOVs will be changed to the MOV Long Life type of grease, in accordance with the upgrades to the MOV lubrication program that were already being implemented at the time of discovery.
Appropriate upgrades to the MOV lubrication program had already been made and were being implemented at the time of discovery.
Previous Similar Occurrences There was one previous LER identified involving an inoperable MOV at Peach Bottom due to a lubrication deficiency. LER 3-09-03 reported a condition where the 3D Residual Heat Removal Suction Valve (MO-3-10-013D) was determined to be inoperable due to hardened grease. The actions performed as a result of the event reported in LER 3-09-03 included extent-of-condition reviews concerning the possibility of hardened grease for other MOVs. This previous review performed in 2009 did not prioritize the MO-3-12-018 MOV for expedited grease replacement based on the lower expected susceptibility that was previously determined for the MO-3-12-018.