05000483/LER-2013-005, Regarding Lnoperability of ESW Cross Connect Valve

Regarding Lnoperability of ESW Cross Connect Valve

ML13155A236
Person / Time
Site:	Callaway
Issue date:	06/03/2013
From:	Cox B Ameren Missouri, Union Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC-06001 LER 13-005-00
Download: ML13155A236 (9)

LER-2013-005, Regarding Lnoperability of ESW Cross Connect Valve

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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)(v), Loss of Safety Function 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)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)
4832013005R00 - NRC Website

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WAmeren MISSOURI Callaway Plant June 3, 2013 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 ULNRC-0600 1 10 CFR 50.73(a)(2)(i)(B) 10 CFR 50.73(a)(2)(v)(A) 10 CFR 50.73(a)(2)(v)(B) 10 CFR 50.73(a)(2)(v)(D)

Ladies and Gentlemen:

DOCKET NUMBER 50-483 CALLA WAY PLANT UNIT 1 UNION ELECTRIC CO.

FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2013-005-00 IN OPERABILITY OF ESSENTIAL SERVICE WATER (ESW)

CROSS CONNECT VALVE The enclosed licensee event report (LER) is submitted in accordance with 10CFR50.73(a)(2)(i)(B) to report a condition prohibited by Technical Specification 3.7.9 due to the inoperability of an Essential Service Water (ESW) to Service Water (SW) cross connect valve, and pursuant to 10CFR50.73(a)(2)(v)(A), 10CFR50.73(a)(2)(v)(B), and 10CFR50.73(a)(2)(v)(D) due to concurrent unavailability of the backup A/C power source for the in-series cross-connect valve resulting in Ultimate Heat Sink (UHS) inoperability.

This letter does not contain new commitments.

Enclosure: LER 2013-005-00 tt~~

Barry L. Cox Sr. Director, Nuclear Operations PO Box 620 Fulton, MO 65251 AmerenMissouri.com

ULNRC-0600 1 June 3, 2013 Page 2 cc:

Mr. Arthur T. Howell 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. Fred Lyon Project Manager, Callaway Plant Office ofNuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 0-8B 1 Washington, DC 20555-2738

ULNRC-0600 1 June 3, 2013 Page 3 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 4150 International Plaza Suite 820 Fort Worth, TX 76109 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)

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 B. L. Cox S. A. Maglio R. Holmes-Bobo Corporate Oversight NSRB Secretary T. B. Elwood Performance Improvement Coordinator Resident Inspectors (NRC)

STARS Regulatory Affairs Mr. John O'Neill (Pillsbury Winthrop Shaw Pittman LLP)

Missouri Public Service Commission Records Center (INPO)

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)

, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.

,3. PAGE Callaway Plant Unit 1 05000483 1 OF 6

4. TITLE lnoperability of ESW Cross Connect Valve

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED YEAR ISEQUENTIALJ REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.

MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 04 04 2013 2013 - 005 -

00 06 03 2013

9. OPERATING MODE

11. THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)

D 20.2201 (b)

D 20.2203(a)(3)(i)

D 50.73(a)(2}(i)(C)

D 50.73(a)(2)(vii) 1 D 20.2201 (d)

D 20.2203(a)(3)(ii)

D 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 20.2203(a)(1)

D 20.2203(a)(4)

D 50.73(a)(2}(ii)(B)

D 50.73(a)(2)(viii)(B)

D 20.2203(a)(2)(i)

D 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)

D 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) 1:81 50. 73(a)(2}(v)(A)

D 73.71 (a)(4)

D 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii) 1:81 50. 73(a)(2)(v)(B)

D 73.71(a)(5) 84%

D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

D 50.73(a)(2)(v}(C) 0 OTHER D 20.2203(a)(2)(vi) 1:81 50. 73(a)(2)(i)(B) 1:81 50.73(a)(2)(v)(D)

Specify in Abstract below or in Inoperability of a cross-connect valve can affect either ESW or UHS operability, or both, depending on which valve is inoperable. Operations procedure ODP-ZZ-00002, "Equipment Status Control,"

provides guidance for ensuring Technical Specification (TS) compliance when a cross-connect valve is declared inoperable. With the EFHV0024 valve inoperable, entry into Condition B ofTS 3.7.9, "Ultimate Heat Sink (UHS)," is required. Required Actions B.1 and B.2 for Condition B require the plant to be shut down to Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />, respectively. Condition B (and its associated Required Actions) may be exited, however, if the EFHV0026 valve is closed and deactivated, thereby removing EFHV0024 from the ESW system flow paths required by SR 3.7.8.1 and SR 3.7.8.2. Closing and deactivating EFHV0026 ensures isolation of the associated ESW train (from the SW system) by a passive barrier. This preserves UHS function(s) by precluding the potential for UHS inventory to be pumped into the SW system via the affected ESW train.

2.

INITIAL PLANT CONDITIONS

On 4/7/2013, the plant was in MODE 1 at 84-percent rated thermal power (due to the commencement of coastdown for the Refuel-19 outage). Apart from the ESW train that was identified to be inoperable per the event description below, no other significant equipment was concurrently inoperable.

3.

EVENT DESCRIPTION

On 4/4/2013, during the performance of an Inservice Leakage Test (ISLT) on valve EFHV0024 (SERV WTR TO ESW TRN B UPSTRM HV), leakage in excess of 10 gpm was identified. In an effort to better quantify the leakage rate, on 4/5/2013, flow was measured through a %-inch diameter vent line located between the two in-series isolation valves. The measurement indicated a flow rate (leakage) of approximately 25 gpm. On 4/6/2013, during troubleshooting to determine the source of the identified leakage, a leak rate of 30 gpm was identified. This leakage was evaluated to determine the input on UHS operability, and was found to be acceptable. During further troubleshooting on 4/7/2013, the socket head cap screws that clamp the coupling halves to the actuator and valve stems were found to be loose, allowing the coupling to slide down onto the valve stem, completely decoupling the valve from the actuator. Thus, the valve was in fact in the open position and not capable of being closed by the valve actuator.

After receipt of this information in the control room, EFHV0024 was declared inoperable on 4/7/2013 at 20:46. This required declaring the UHS inoperable (and entering Required Actions B.1 and B.2 ofTS 3.7.9) until power was removed from closed valve EFHV0026 by opening its feeder breaker on 4/7/2013 at 22:41. Repair of the EFHV0024 valve was completed on 4/8/2013 at 0445.

4.

ASSESSMENT OF SAFETY CONSEQUENCES

A sufficient volume of water is required to be maintained in the UHS so that it is able to service safety-related loads for a 30-day mission time following a Design Basis Accident (DBA) or transient.

As previously noted, the UHS (via the ESW system) provides a heat sink for the removal of process, operating, and residual (decay) heat from safety-related components during a DBA or transient.

During the time that the EFHV0024 valve was inoperable, the in-series EFHV0026 valve remained available to isolate the affected ESW train from the SW system under all conditions, including a loss ofoffsite power (LOOP) (except when the valve's backup safety-related A/C power source was unavailable).

It should also be noted that non safety-related EA V0185 (SERV WTR TO ESW TRN B CHK VL V)

[EllS component V], which is in series with EFHV0024 and EFHV0026, would serve to preclude or minimize a flow path ofESW into the SW piping. This valve is contained in seismically analyzed piping, and can be considered a reliable additional means of isolation.

This event was evaluated with the Callaway Probabilistic Risk Assessment (PRA) model. The evaluation determined the conditional core damage probability (CCDP) of this event was less than 1E-6; therefore, this event was of very low risk significance. Use of the PRA model to evaluate the event provides for a comprehensive, quantitative assessment of the potential safety consequences and implications of the event, including consideration of alternative conditions beyond those analyzed in the FSAR.

5.

REPORTING REQUIREMENTS

This LER is submitted pursuant to 10CFR50.73(a)(2)(i)(B) to report a condition prohibited by the Technical Specifications. This event is also required to be reported pursuant to 10CFR50.73(a)(2)(v)(A) as an event or condition that could have prevented fulfillment ofthe safety function of structures or systems that are needed to shut down the reactor and maintain it in a safe shutdown condition, and 10CFR50.73(a)(2)(v)(B) as an event or condition that could have prevented fulfillment ofthe safety function of structures or systems that are needed to remove residual heat, and 10CFR50.73(a)(2)(v)(D) as an event or condition that could have prevented fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.

Upon identification of the decoupled actuator condition for the EFHV0024 valve, and as previously noted, the UHS was declared inoperable at on 4/7/2013 at 20:46, and Required Action B.1 and B.2 of TS 3.7.9 were entered. Power was removed from closed valve EFHV0026 by opening its feeder breaker on 4/7/2013 at 22:41, thereby restoring operability to the UHS after a period of one hour and 55 minutes. Repair ofEFHV0024 was completed on 4/8/2013 at 0445, allowing return of the valve to operable status after a period of 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> and 59 minutes.

Prior to discovery of the decoupled actuator condition on 4/7/2013, MOV diagnostic testing was performed on EFHV0024 and completed on 4/2/2013. Review of the as-left test results, in conjunction with subsequent testing performed on 5116/2013, however, did not conclusively support past operability ofEFHV0024. The last time when the EFHV0024 valve was clearly confirmed to be operable was on 4/2/2012 when a leak check performed on EFHV0024 and EFHV0026 found zero leakage.

Technical Specification Violation Based on the above, if it is assumed that the EFHV0024 valve was inoperable (but unknown to be inoperable) from 4/2/2012 to 4/7/2013 and that the EFHV0026 valve was not closed and deactivated during that timeframe, then it must be concluded that the UHS was inoperable during that same timeframe (per the guidance of ODP-ZZ-00002). On this basis, the period oftime that the UHS was inoperable exceeded the time limits ofTS 3.7.9. The condition thus constituted an operation or operation prohibited by the Technical Specifications.

Condition that Could Prevent Fulfillment of a Safety Function With respect to the Technical Specification requirements, operability of the UHS is preserved when the capability to isolate the ESW system from the SW system can still be ensured with an assumed single active failure (under DBA conditions, including a concurrent loss of offsite power). For the condition addressed by this LER, this requirement would be met when the passive barrier created by the closed and deactivated EFHV0026 valve exists. However, with respect to reporting a condition that could prevent fulfillment of a safety function on demand (i.e., during a DBA and concurrent loss of offsite power), the additional single active failure is not required to be assumed. Thus, in this case, with the EFHV0024 valve inoperable, the potential for preventing fulfillment of the UHS safety function(s) existed whenever the EFHV0026 valve was in a condition such that it could not close under loss-of-offsite power conditions (i.e., when the valve did not have its backup safety-related A/C power source available with the valve open).

During the period from 4/2/2012 to 4/8/2013, there were eight instances when EFHV0026 was unable to be supplied by its safety-related backup A/C power source. At the below listed times, either the 'B' EDG or the EFHV0026 supply breaker was out of service with EFHV0026 in the open position. During these times, it is concluded that a condition existed such that fulfillment of the UHS safety function could have been prevented.

4/10/2012@ 0700 to 4/11/2012@ 1401 (31 hrs) 6/5/2012@ 1155 to 6/5/2012@ 1922 (7.5 hrs) 6114/2012@ 1608 to 6/14/2012@ 1704 (0.9 hrs) 10/23/2012@ 0706 to 10/24/2012@ 1310 (30 hrs) 11/20/2012@ 0104 to 11/20/2012@ 0106 (0.1 hrs) 11/20/2012@ 0108 to 11/20/2012@ 0111 (0.1 hrs) 2/14/2013@ 0721 to 2/16/2013@ 1307 (53.8 hrs) 4/2/2013@ 0404 to 4/8/2013@ 1506 (155 hrs)

Based on all of the above, the condition is reportable as a condition or operation prohibited by Technical Specifications, as well as a condition that could have prevented fulfillment of a safety function(s).

6.

CAUSE OF THE EVENT

The most probable cause of the decoupled actuator condition is that bolts fastening the coupling block to the valve stem gradually loosened from environmental effects such as vibration and heating I cooling cycles over time.

Review of work history for EFHV0024 found no record of work on the coupling block or its bolting after the valve was replaced on 5/4/1995

7.

CORRECTIVE ACTIONS

A check of the valve shaft coupling torque is being added to the MOV PM for the affected valves.

This PM is to have an appropriately assigned frequency (to be determined by Engineering).

8.

PREVIOUS SIMILAR EVENTS

An extent of condition review performed for this event found one additional similar valve, EFHV0023 (SERV WTR TO ESW TRN A UPSTRM HV), had reduced engagement in the coupling block area. After discovery of this condition on EFHV0023, a stroke test was performed, which demonstrated operability. This was entered into Callaway's corrective action program, and the condition was promptly repaired.

Prior to this, the coupling on EFHV0037 (ESW TRN A TO UHS HV) came loose in 1990 and the coupling on EFHV0026 (SERV WTR TO ESW TRN B DNSTRM HV) came loose in 1993.

Corrective actions included specifying vendor specified torque values for the coupling in the applicable Maintenance procedure. When changing EFHV0024 from a Jamesbury valve to an Anchor Darling valve in 1995, a specific torque value was not included in the work instructions or the MOV procedure.