05000483/LER-2011-005, Regarding Manual Isolation Valve Unable to Meet Closure Requirements
| ML113550112 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 12/20/2011 |
| From: | Diya F Ameren Missouri |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ULNRC-05833 LER 11-005-00 | |
| Download: ML113550112 (7) | |
| 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 |
| 4832011005R00 - NRC Website | |
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WAmeren MISSOURI December 20, 2011 ULNRC-05833 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Ladies and Gentlemen:
10 CFR 50.73 DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.
FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2011-005-00 Fadi M. Diya Vice President Nuclear Operations Ameren Missouri Callaway Plant T 573.676.6411 F 573.676.4056 MANUAL ISOLATION VALVE UNABLE TO MEET CLOSURE REQUIREMENTS The enclosed licensee event report is submitted in accordance with 10 CFR 50. 73(a)(2)(i)(B). This report describes an event in which an atmospheric steam dump manual isolation valve was discovered to be unable to meet the closure requirements as described by the Final Safety Analysis Report.
This letter does not contain new commitments.
ACS/nls Enclosure: LER 2011-005-00 Sincerely, Fadi M. Diya Vice President Nuclear Operations Junction CC & Hwy 0 PO Box 620, MC CA-460 Fulton, MD 65251 AmerenMissouri.com
ULNRC-05833 December 20, 2011 Page2 cc:
Mr. Elmo E. Collins, Jr.
Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Mohan C. Thadani (2 copies)
Senior Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-8B 1 Washington, DC 20555-2738
ULNRC-05833 December 20, 2011 Page 3 Index and send hardcopy to QA File A160.0761 Hardcopy:
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LEREvents@inpo.org (must send the WORD version of the LER to this address)
Electronic distribution for the following can be made via LER ULNRC Distribution:
A C. Heflin F.M.Diya C. 0. Reasoner III L. H. Graessle D. W. Neterer S. A Maglio R. Holmes-Bobo K. W. Kuechenmeister D. T. Wingbermuehle J. D. Schnack C. B. Serfas R. M. Nelson NSRB Secretary T. B. Elwood A C. Schnitz D. E. Dumbacher (NRC)
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Mr. John O'Neill (Pillsbury Winthrop Shaw Pittman LLP)
Missouri Public Service Commission Records Center (INPO)
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- 13. PAGE Callaway Plant Unit 1 05000483 1 OF 4
- 4. TITLE Manual Isolation Valve Unable to Meet Closure Requirements
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 10 24 2011 2011 - 005 -
00 12 20 2011
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
D 20.2201(b)
D 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C)
D 50.73(a)(2)(vii)
NO MODE D 2o.2201(d)
D 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2203(a)(1)
D 20.2203(a)(4) 0 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(2)(i) 0 50.36(c)(1 )(i)(A)
D 50.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL D 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(A)
D 73.71 (a)(4)
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(B)
D 73.71 (a)(5) 0%
D 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(C) 0 OTHER D 20.2203(a)(2)(vi) 1251 50.73(a)(2)(i)(B)
D 50.73(a)(2)(v)(D)
Specify in Abstract below or in isolation valves to remove existing hardened grease and add fresh grease. These valves were then satisfactorily stroke time tested to ensure that they could be closed in a time that supports the credited response to a postulated SGTR.
4. ASSESSMENT OF SAFETY CONSEQUENCES
The degraded condition of ABV0040 did not result in a significant adverse impact on nuclear safety.
- 3. PAGE OF 4
The analysis of a postulated SGTR as described in the Callaway Plant Final Safety Analysis Report (FSAR) includes consideration of a stuck open ASD associated with the faulted steam generator, coincident with a loss of offsite power. A release to the environment is postulated to occur for a 20-minute duration via the stuck-open ASD. In response to the condition identified for ABV0040, a sensitivity evaluation was performed in which a 60-minute release duration was assumed in order to bound the as-found stroke times observed for ABV0040.
RCS radioiodine levels used for initial conditions in the sensitivity evaluation were set to levels that bounded the most limiting steady-state concentrations measured in the past 3 years. The results of sensitivity evaluation demonstrated that SGTR consequences would have remained significantly below the consequences reported in the FSAR.
5. REPORTING REQUIREMENTS
As described below, the degraded condition of ABV0040 documented in this LER meets the criteria for reportability under 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specification (TS) 3. 7.4.
Technical Specification 3.7.4 requires four atmospheric steam dump lines to be Operable. Each atmospheric steam dump line is defined in the TS 3.7.4 Bases as consisting of the ASD and the associated manual isolation valve. Thus, successful demonstration of Operability of the atmospheric steam dump line in accordance with TS 3.7.4 includes Operability of both the ASD and the associated manual isolation valve. Because the ability of ABV0040 to isolate its atmospheric steam dump line within the required time cannot be demonstrated in this event, Operability of the associated atmospheric steam dump line cannot be supported.
In this condition, TS 3. 7.4 Required Action A.1 requires the inoperable atmospheric steam dump line to be restored within 7 days. If this Completion Time is not met, Mode 3 entry is required within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> per TS 3.7.4 Required Action E.1. Although the exact time that ABV0040 became unable to be closed within the required time is not known, it is reasonable to assume that the period of inoperability of the atmospheric steam dump line exceeded the Completion Times specified in TS 3. 7.4.
As stated in Section 4, a SGTR with failed-open ASD scenario was modeled using bounding values of RCS activity levels and a manual isolation valve operation time of 60 minutes. This analysis shows that the radioactive release that could have resulted from such an event would have remained well within the limiting values described in the accident analysis of this event, despite the degraded condition of ABV0040. Thus, this condition is not considered to be an unanalyzed condition that significantly degraded plant safety.
6. CAUSE OF THE EVENT
The failure of ABV0040 to close within the time requirements of the SGTR analysis was due to hardened grease in the valve actuator. The formal evaluation of this event identified two causes that resulted in the presence of this hardened grease:
First, no Preventative Maintenance task existed to replace the grease in the valve actuator. Grease had been added to the ASD manual isolation valve ABV0040 in 2007, but the existing grease was not removed before the fresh grease was added.
The site failed to develop a maintenance/testing program for the ASD isolation valves to ensure that they could be stroked closed to meet the time requirement in the Safety Analysis. The cause evaluation identified opportunities in which ASD manual isolation valve actuator lubrication requirements could have been addressed prior to this event Two such opportunities are described in Section 8 of this LER.
7. CORRECTIVE ACTIONS
Corrective actions developed to address the causes listed in Section 6 of this LER include the implementation of Preventative Maintenance to replace the grease in the ASD manual isolation valve actuators and a procedure change to ensure periodic verification that the ASD manual isolation valves can be closed in a time that supports the SGTR event response. Additional training on the safety function of the ASD manual isolation valves will also be evaluated in accordance with the Callaway Plant Training Program.
The existing grease was removed from the actuators of all four ASD manual isolation valves prior to the addition of fresh grease. These manual isolation valves were tested satisfactorily and returned to service.
8. PREVIOUS SIMILAR EVENTS
In May 2007, Operations generated a Corrective Action Document that stated that operators experienced difficulty while operating ABV0040 and questioned the ability of the valve to close within the time specified in the SGTR analysis. In this event, closure of ABV0040 required 6 minutes, 30 seconds. Similar to the October 2011 events, the other three ASD manual isolation valves were significantly easier to operate, as the next highest stroke time was 1 minute, 56 seconds. Grease was added to the ABV0040 actuator, and the valve's stroke time was reduced to 4 minutes, 41 seconds. No additional actions were taken.
In March 2010, Callaway Plant personnel received relevant external Operating Experience (OE) that documented a failure to properly lubricate a manual isolation valve credited for accident mitigation. The Callaway Plant evaluation of this OE determined that six valves, including the four ASD manual isolation valves, could be similarly affected by the lack of regular Preventative Maintenance. Jobs were written to replace the grease in each ASD manual isolation valve. The as-found condition of the valves will determine the frequency at which Preventative Maintenance will be performed.
- 9. OTHER INFORMATION Identification information for manual isolation valve ABV0040 is as follows:
Manufacturer: Anchor/Darling Valve Co.
Model: E-6208-6 The Energy Industry Identification System (EllS) identifiers for the components and systems mentioned in this report are as follows:
System: AB, Reactor Coolant System Component:
SG, Steam Generator System: BP, Residual Heat Removal System System: SB, Main Steam System Components: ISV, Isolation Valve; RV, Relief Valve