05000336/LER-2014-003, Regarding Loss of Safety Function Due to Inoperable Enclosure Building

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Regarding Loss of Safety Function Due to Inoperable Enclosure Building
ML14157A300
Person / Time
Site: Millstone Dominion icon.png
Issue date: 06/02/2014
From: Scace S
Dominion Nuclear Connecticut
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 14-003-00
Download: ML14157A300 (6)


LER-2014-003, Regarding Loss of Safety Function Due to Inoperable Enclosure Building
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(v), Loss of Safety Function

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)(i)(B), Prohibited by Technical Specifications
3362014003R00 - NRC Website

text

Dominion Dominion Nuclear Connecticut, Inc.

Rope Ferry Rd., Waterford, CT 06385 Mailing Address: P.O. Box 128

\\Varfrfird, CT 06385 dorncorn JUN 0 2.2014 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.

MPS Lic/TGC Docket No.

License No.14-253 RO 50-336 DPR-65 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2 LICENSEE EVENT REPORT 2014-003-00 MILLSTONE POWER STATION UNIT 2 LOSS OF SAFETY FUNCTION DUE TO INOPERABLE ENCLOSURE BUILDING This letter forwards Licensee Event Report (LER) 2014-003-00 documenting a condition at Millstone Power Station Unit 2 on April 5, 2014. This LER is being submitted pursuant to 10 CFR 50.73(a)(2)(v)(C) as a condition that could have prevented the fulfillment of the safety function of structures or systems to control the release of radioactive material and 10 CFR 50.73(a)(2)(v)(D), mitigate the consequences of an accident.

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

Sincerely,

/S teph en E. S c acel Site Vice President - Millstone Attachments: 1 Commitments made in this letter: None

Serial No.14-253 Docket No. 50-336 Licensee Event Report 2014-003-00 Page 2 of 2 cc:

Nuclear Regulatory Commission, Region I Regional Administrator 2100 Renaissance Blvd.

Suite 100 King of Prussia, PA 19406-2713 M. C. Thadani NRC Senior Project Manager Millstone Units 2 and 3 U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 C 2A 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

ATTACHMENT LICENSEE EVENT REPORT 2014-003-00 MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01131/2017 (02-2014)

(02-2014)

=*

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.

0 4 S Send comments regarding burden estimate to the FOIA, Privacy and Information Collections

'7NjSEE EVENT REPORT (LE Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by LCE E

E N Rintemet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and (See Page 2 for required number of Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC digits/characters for each block) 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE Millstone Power Station Unit 2 05000336 1 OF 3
4. TITLE Loss of Safety Function Due to Inoperable Enclosure Building
5. EVENT DATE
6. LER NUMBER
7. REPORT DATE
8. OTHER FACILITIES INVOLVED 7

7I FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR NUMBER NO.

05000 FACILITY NAME DOCKET NUMBER 04 05 2014 2014 -

003

- 00 06 02 2014 05000
9. OPERATING MODE
11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

E 20.2201(b)

D 20.2203(a)(3)(i)

[1 50.73(a)(2)(i)(C)

Ej 50.73(a)(2)(vii) 20.2201(d)

E 20.2203(a)(3)(ii)

[I 50.73(a)(2)(ii)(A)

[I 50.73(a)(2)(viii)(A)

Lj 20.2203(a)(1)

[

20.2203(a)(4)

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

[I 50.73(a)(2)(viii)(B)

El 20.2203(a)(2)(i)

[1 50.36(c)(1)(i)(A)

EI 50.73(a)(2)(iii)

LI 50.73(a)(2)(ix)(A)

10. POWER LEVEL LI 20.2203(a)(2)(ii)

L] 50.36(c)(1)(ii)(A)

LI 50.73(a)(2)(iv)(A)

LI 50.73(a)(2)(x)

LI 20.2203(a)(2)(iii)

LI 50.36(c)(2)

LI 50.73(a)(2)(v)(A)

LI 73.71(a)(4) 10 20.2203(a)(2)(iv)

[1 50.46(a)(3)(ii)

EL 50.73(a)(2)(v)(B)

LI 73.71(a)(5) 1L 20.2203(a)(2)(v)

LI 50.73(a)(2)(i)(A)

[

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

LI OTHER

,I 20.2203(a)(2)(vi)

[I 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D) specify in Abstract below or in

1. EVENT DESCRIPTION

On April 5, 2014, with Millstone Power Station Unit 2 (MPS2) at 100% power in Mode 1, the Enclosure Building was rendered inoperable during a maintenance activity. The condition was created at approximately 1025 and restored to operable status at 1300 on April 5, 2014. Plant Technical Specification (TS) 3.6.5.2 requires that the Enclosure Building shall be operable in Modes 1, 2, 3, and 4. The TS 3.6.5.2 Action is to restore the Enclosure Building to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in cold shutdown within the next 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Therefore, the TS 3.6.5.2 Action requirements were met.

Since the Enclosure Building was inoperable from approximately 1025 until restored at 1300, the safety function of the Enclosure Building to limit radiological releases or mitigate the consequences in the event of a design basis accident could not be assured.

This condition is being reported pursuant to 1 OCFR50.73(a)(2)(v)(C) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material and 10CFR50.73(a)(2)(v)(D), mitigate the consequences of an accident.

2. CAUSE

The condition was created as the result of a human performance error while performing a maintenance activity associated with the Enclosure Building boundary. Flexible boots are installed on the main steam safety valve vent pipes that extend through the Enclosure Building boundary. There are two sets of boots, upper and lower, on each main steam safety valve vent pipe. The upper boots are credited as the Enclosure Building boundary. Maintenance workers were sent out to remove the lower boots on eight main steam safety valve vent pipes to support a planned surveillance. The procedure also required that the upper boots be inspected to ensure they are installed. The workers were inattentive to the scope of the work activity and removed both the lower and upper boots.

Removal of the upper boots rendered the Enclosure Building inoperable.

3. ASSESSMENT OF SAFETY CONSEQUENCES

The purpose of the Enclosure Building is to contain, collect, and process potential containment leakage prior to its release to the environment to minimize radioactivity levels and resulting dose consequences from a design basis loss-of-coolant-accident. The Enclosure Building Filtration System (EBFS) is designed to establish and maintain the required negative pressure of -0.25 inches wg within the Enclosure Building (secondary containment).

The flexible boots were removed from eight main steam safety valve vent pipes. Each main steam safety valve also has a sliding bushing that can be credited for sealing the associated boundary, if the bushing is properly seated. Proper seating of the sliding bushings has not been completely reliable historically (as described in LER 2011-001-00). The pipes were inspected to assess the condition of the sliding bushings and five of the eight were seated.

Therefore, three of the main steam safety valve pipe boundaries were compromised. An Engineering Technical Evaluation was performed to estimate the system response based on the as-found condition of the main steam safety valve pipe boundaries. The Engineering Technical Evaluation concluded that the aggregate impact of the openings was too close to assure that the required negative pressure of -0.25 inches wg would be achieved. The condition existed for less than three hours.

NRC Branch Technical Position CSB 6-3 defines the secondary containment as "positive" for pressures less negative than -0.25 inch wg. This criterion accounts for wind loads and uncertainties in pressure measurements. With differential pressures less negative than -0.25 inch wg, a conservative assumption, consistent with design basis, is made that all primary containment leakage is released directly to the environment. Although NRC Branch Technical Position CSB 6-3 defines the secondary containment as "positive" for pressures less negative than -0.25 inch wg, it is estimated that a negative pressure close to -0.25 inches wg would have been achieved based on the as-found condition. Since this condition existed for less than three hours and estimated pressure would have been close to the -0.25 inches wg pressure acceptance criteria, the safety consequences are considered low.

4. CORRECTIVE ACTION

The Enclosure Building was restored to operable status. Since this was a human performance error, the event and lessons learned were communicated to the Millstone Site as a Station Human Performance Clock Reset.

Additional corrective actions are being taken in accordance with the station's corrective action program.

5. PREVIOUS OCCURRENCES

LER 2011-001-00 describes a condition in which the Enclosure Building was rendered inoperable due to failed barriers. The corrective action associated with LER 2011-001-00 was to modify the barrier design to credit the upper flexible boots described above.

6. ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) CODES Enclosure Building Filtration System (EBFS) [BD]