05000423/LER-2013-005, Regarding Loss of Containment Integrity Due to Failed Airlock

Regarding Loss of Containment Integrity Due to Failed Airlock

ML13248A449
Person / Time
Site:	Millstone
Issue date:	08/21/2013
From:	Scace S Dominion Nuclear Connecticut, Dominion
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
13-397A LER 13-005-00
Download: ML13248A449 (6)

LER-2013-005, Regarding Loss of Containment Integrity Due to Failed Airlock

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
4232013005R00 - NRC Website

text

' Dominion Dominion Nuclear Connecticut, Inc.

Millstone Power Station Rope Ferry Road, Waterford, CT 06385 AUG 2 12013 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.

MPS Lic/TGC Docket No.

License No.

13-397A RO 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 LICENSEE EVENT REPORT 2013-005-00 LOSS OF CONTAINMENT INTEGRITY DUE TO FAILED AIRLOCK Licensee Event Report (LER) 2013-005-00, documenting an event at Millstone Power Station Unit 3 that occurred on May 15, 2013, was inadvertently sent on July 15, 2013 with an incorrect report date entered in block 7 on NRC Form 366. This letter forwards a corrected copy of the LER that includes the correct report date.

If you have any questions or require additional information, please contact Mr. William D. Bartron at (860) 444-4301.

Sincerely,

/St h

ae c&U Site Vice President - Millstone Attachments: 1 Commitments made in this letter: None

Serial No. 13-397A Docket No. 50-423 Licensee Event Report 2013-005-00 Page 2 of 2 cc:

U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 J. S. Kim Project Manager - Millstone Power Station U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 C2A Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No. 13-397A Docket No. 50-423 Licensee Event Report 2013-005-00 ATTACHMENT LICENSEE EVENT REPORT 2013-005-00 LOSS OF CONTAINMENT INTEGRITY DUE TO FAILED AIRLOCK MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.

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

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

3. PAGE Millstone Power Station - Unit 3 05000423 1 OF 3

4. TITLE Loss of Containment Integrity Due to Failed Airlock

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED S

FACILITY NAME DOCKET NUMBER ISEQUENTIAL REV MNH DY YA 50 bMONTH DAY YEAR YEAR NUMBER NO.

MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 05 15 2013 2013-005-00 07 15 2013 05000

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR :_Check all that apply)

9. OPERATING MODE 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 4 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1 )(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)

10. POWER LEVEL 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71 (a)(5) 000 20.2203(a)(2)(v) 50.73(a)(2)(i)(A)

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

OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)

Specify in Abstract below or in

1.

EVENT DESCRIPTION

On May 15, 2013, at 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br />, with the Millstone Power Station Unit 3, (MPS3) in MODE 4 at 0%

power, it was discovered that an equalizing valve for the outer containment door was leaking by its seat rendering the outer containment door inoperable. This condition was discovered by maintenance personnel as they were exiting containment through the inner containment door. The inner containment door was open for transit at the time the leaking equalizing valve was discovered. The outer containment door was declared inoperable 0620 hours0.00718 days <br />0.172 hours <br />0.00103 weeks <br />2.3591e-4 months <br /> on May 15, 2013 and the appropriate technical specification action statement was entered. Subsequent to the completion of troubleshooting activities, the outer containment door was declared operable 1720 hours0.0199 days <br />0.478 hours <br />0.00284 weeks <br />6.5446e-4 months <br /> on May 15, 2013.

With the inner containment door open and the equalizing valve also open (leaking), this provided a direct path from inside containment to the outside and thus a loss of containment integrity. This event was reported as a prompt report (event report #49034) in accordance with 10 CFR 50.72(b)(3)(v), as an event that could have prevented the fulfillment of the safety function of structures or systems that are needed to: (C) Control the release of radioactive material. This event is being reported in accordance with 10 CFR 50.73(a)(2)(v), as an event that could have prevented the fulfillment of the safety function of structures or systems that are needed to: (C) Control the release of radioactive material.

Background Information

The personnel air lock is a double closure penetration of the containment wall and liner. Each closure head is hinged and double gasketed with a leakage test tap between the "0" rings. The enclosed space between the "0" rings is pressurized to containment design pressure to test for leakage through the access door when it is locked in place. The personnel access lock can be independently pressurized up to containment design pressure for testing. Both doors are hydraulically latched and hydraulically swung. Both doors are interlocked so that in the event one door is opening the other cannot be actuated. Since the containment is slightly sub-atmospheric, both doors are furnished with a pressure equalizing connection. The equalizing valves are operated by the person entering or leaving the personnel access lock.

2.

CAUSE

The investigation determined the most likely cause of the leaking equalizing valve on the MPS3 outer containment door was personnel error. The equalizing valve was most likely inadvertently bumped by personnel in transit causing it to be slightly open.

3.

ASSESSMENT OF SAFETY CONSEQUENCES

The containment was maintained at a slight vacuum consistent with plant Technical Specifications throughout the period. This maintained the initial conditions assumed in the accident analysis and would have provided a treated release path for incidental releases. Additionally, as soon as the condition was noted, the safety function was reestablished by closing the inner airlock door.

The design basis analysis incorporates an allowance for containment leakage. In the most recent (2011) Integrated Leak Rate Test, actual leakage was less than 20% of the analysis assumptions. The very limited additional leakage which could have occurred past the seat of the pressure equalizing valve would most likely not have resulted in actual containment leakage beyond that currently analyzed.

1

IEET It is also noted that the leakage occurred as MPS3 was in the initial heat up following a reload. The core consisted of fresh, once and twice burnt fuel assemblies. Should an accident actually have occurred, the radiological source term present was significantly smaller than that used in design basis accident calculations. Therefore, the event had minimal safety significance.

4.

CORRECTIVE ACTION

The inner containment door was immediately closed. Subsequently maintenance personnel verified the equalizing valve handle was in the closed position, inspected the containment door seals, and tested both the inner and outer containment doors with satisfactory results. Additional corrective actions are being taken in accordance with the station's corrective action program.

5.

PREVIOUS OCCURRENCES

None

6.

Energy Industry Identification System (EIIS) codes

" Valve-V

• Containment Building - NH

• Air Lock - AL

• Door-DR