05000395/LER-2016-001-01, Transmittal of Low Refrigerant Renders A-Chiller Non-Functional and A-Charging Pump Inoperable

Transmittal of Low Refrigerant Renders A-Chiller Non-Functional and A-Charging Pump Inoperable

ML16302A075
Person / Time
Site:	Summer
Issue date:	10/25/2016
From:	Lippard G South Carolina Electric & Gas Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 16-001-01
Download: ML16302A075 (5)

LER-2016-001, Transmittal of Low Refrigerant Renders A-Chiller Non-Functional and A-Charging Pump Inoperable

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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)(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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
3952016001R01 - NRC Website

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A SCANA COMPANY Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Sir I Madam:

George A. Lippard Vice President, Nuclear Operations 803.345.4810 October 25, 2016

Subject:

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS), UNIT 1 DOCKET NO. 50-395 OPERATING LICENSE NO. NPF-12 LICENSEE EVENT REPORT (LER 2016-001-01)

LOW REFRIGERANT RENDERS A-CHILLER NON-FUNCTIONAL AND A-CHARGING PUMP INOPERABLE Attached is the revised Licensee Event Report (LER) 2016-001-01, for the Virgil C.

Summer Nuclear Station (VCSNS) Unit 1. This report describes an additional cause that rendered the A-Train chiller non-functional that impacted the A-Train charging pump operability. This revised report is submitted in accordance with 10 CFR 50.73(a)(2)(i)(B).

Should you have any questions, please call Mr. Bruce*"fhompson at (803) 931-5042.

WHK/GAL/wm Attachment

. c:

K. B. Marsh S. A. Byrne J.B. Archie N.S.Carns J. H. Hamilton S. M. Shealy W. M. Cherry C. Haney S. A. Williams NRG Resident Inspector QA Manager -; L. W. Harris Very truly yours, Paulette Ledbetter J.C. Mellette ICES Coordinator K. M. Sutton INPO Records Center Marsh USA, Inc.

Maintenance Rule Engineer NSRC RTS (CR-15-04395, CR-16-00992)

File (818.07)

PRSF (RC-16-0132).

V. C. Summer Nuclear Station

• P. 0. Box 88

• Jenkinsville, SC* 29065

• F (803) 941-9776

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2018 (06-2016)

Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.

..... ~.

Reported lessons learned are incorporated into the licensing process and fed back to industry.

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\\

LICENSEE EVENT REPORT (LER)

Send comments regarding burden estimate to the FOIA, Privacy and lnfonmation Collections

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Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail (See Page 2 for required number of digits/characters for each block) to lnfocollects.Resource@nrc.gov, and. to the Desk Officer, Office of lnfonmation and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a (See NUREG-1022, R.3 for instruction and guidance for completing this form means used to impose an information collection does not display a currently valid OMB control httg://www nrc,gQv[reading-rmldoc-co)lection~f[]U[eg:;i/staff/srJ 022/r~f) number, the NRG may not conduct or sponsor, and a person is not required to respond to, the infonmation collection.

3. PAGE VC SUMMER - UNIT 1 05000 395 1 OF 4

4. TITLE LOW REFRIGERANT RENDERS A-CHILLER NON-FUNCTIONAL AND A CHARGING PUMP INOPERABLE

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED I

SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NO.

05000 FACILITY NAME DOCKET NUMBER 07 22 2016 2016 -

002 -

01 10 25 2016 05000

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)

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

D 50.73(a)(2)(viii)(A) 1 D 20.2201(d)

D 20.2203(a)(3)(iiJ D

50.73(a)(2)(ii)(B)

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

D 20.2203(a)(1 >

D 20.2203(a)(4)

D so.73(a)(2)(iii)

D 50.73(a)(2)(ix)(A)

D 20.2203(a)(2)(i)

D 50.36(c)(1)(i)(A)

D 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

10. POWER LEVEL D 20.2203(a)(2J(iiJ D

50.36(c)(1)(ii)(A)

D 50.73(a)(2)(v)(A)

D 13.11(a)(4)

D 20.2203(a)(2J(iii)

D so.36(c)(2)

D 50.73(a)(2)(v)(B)

D 13.11(a)(si D 20.2203(a)(2)(iv)

D so.46(a)(3J(iiJ D

50.73(a)(2)(v)(C)

D 13.11(a)(1 i 100 D 20.2203(a)(2)(v)

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

D 50.73(a)(2)(v)(D)

D 13.11(a)(2)(i)

D 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 73.77(a)(2)(ii) j 1';;;'.'.t~f !i

.*.. ? ' *: 5'{/.*

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

D OTHER Specify in Abstract below or in nvestigation after the LER-2016-001-00 event conservatively determined that XHX0001A-VU was not capable of performing ts design basis function for 57 days, from July 24 through Sept 17, 2015. The investigation also found that XHX0001A-VU was intermittently operating as the only chiller on A Train while unable to remove the design basis heat load during the tallowing time frames:

Placed In Service Removed From Service Total Time 07/29/2015 at 00:18 08/18/2015 at 1 :18 20.05 days 08/19/2015 at 17:04 08/26/2015 at 22:41 7.23 days 08/26/2015 at 23:20 09/03/2015 at 00:06 7.03 days During the 34.31 day p'eriod, XHX0001 C-VU was not aligned on the A Train of VU. The A Train of VU was unavailable for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> which exceeds the TS 3/4.5.2 action requirements for XPP0043A-CS, Charging/Safety Injection Pump

~-

rrhe failure to provide design basis heat load cooling capacity was caused directly by low refrigerant on Circuit 2. The initial apparent cause evaluation (ACE) determined that the low refrigerant on Circuit 2 was due to a refrigerant leak around the hreaded connection of the Chilled Water Liquid Injection Solenoid Inlet Valve for Circuit 2.

bn February 24, 2016, interim actions were completed as part of the initial ACE for LER-2016-001-00. The corrective maintenance and troubleshooting efforts performed by a subsequent ACE indicated an additional leakage path at the evaporator. The evaporator is common ta* both Circuit 1 and Circuit 2 on the XHX0001A-VU design. The evaporator heat exchanger is designed with two circuits and the passes separated by eighth of an inch thick and a quarter of an inch wide heoprene gasket. Pressure testing supported that the gasket region of the evaporator heat exchanger was allowing efrigerant leakage. The initial apparent cause was reevaluated and determined that the gasket leakage was due to nadequate compression of the neoprene gasket and inadequate evaporator head gasket design. Therefore, both the hreaded connection and gasket leakage allowed refrigerant leakage which resulted in the event.

~.O SAFETY SIGNIFICANCE rrhe Final Safety Analysis Report (FSAR) 9.4.7.2.4 describes the Safety Class Chilled Water System. This section states hat continuous operation of one of the three chillers and chilled water pumps is required during normal and emergency periods to provide 45 degrees Fahrenheit water to the chilled water coils. The availability of three chillers and three chilled Nater pumps permits one unit to undergo extended maintenance. When all three chillers and pump sets are available, one is

~esignated as a spare and its breaker(s) is racked out. All chillers may be started locally.

The impact of this event was not risk significant. The VU system is not modeled in the Probabilistic Risk Analysis (PRA) model, and would have minimal impact, but can be conservatively modeled by taking Charging Pump A (XPP0043A-CS) out of service during the period that XHX0001A-VU was non-functional.

The past risk impact of both the 57 day period and the 34.31 day period (each conservatively modeled by the same basic event of removing XPP0043A-CS from service) on the PRA is found using EOOS. Since the Charging Pumps are modeled n the baseline PRA, the total change in CDF is conservatively found as the impact of taking XPP0043A-CS out of service for he entire 57 day period of interest.

The delta CDF for the 57 day period out of service is 4.61 E-08/yr The delta LERF for the 57 day period out of service is 5.82E-10/yr 14.0 PREVIOUS OCCURRENCE Pn October 24, 2011, a refrigerant leak on Circuit 1 of XHX0001A-VU was observed. The leak was identified as coming "ram XVR16482A-VU, Chilled Water Chiller "A" Condenser Vessel Relief Valve Circuit 1 A. XVR16482A-VU was reinstalled With new sealant and a follow up leak check was completed satisfactorily.

5.0 CORRECTIVE ACTIONS

!=or the refrigerant leak around the threaded connection of XVM16506A-VU, Chilled Water Chiller "A" Liquid Injection Solenoid Inlet Valve Circuit 2, XVM16506-VU was replaced.

The gaskets were replaced on the north and south side of the evaporator per maintenance procedures. Post maintenance esting was conducted satisfactory to ensure the inter circuit leak was resolved. Page 4

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