05000271/LER-2007-003, Reactor Trip Caused by Turbine Stop Valve Closure Due to Inadequate Preventative Maintenance

Reactor Trip Caused by Turbine Stop Valve Closure Due to Inadequate Preventative Maintenance

ML073050318
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	10/25/2007
From:	Ted Sullivan Entergy Nuclear Operations, Entergy Nuclear Vermont Yankee
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
BVY 07-073 LER 07-003-00
Download: ML073050318 (5)

LER-2007-003, Reactor Trip Caused by Turbine Stop Valve Closure Due to Inadequate Preventative Maintenance

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(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
2712007003R00 - NRC Website

text

r SEntergy Entergy Nuclear Operations, Inc.

Vermont Yankee P.O. Box 0500 185 Old Ferry Road Brattleboro. VT 05302-0500 Tel 802 257 5271 October 25, 2007 BVY 07-073 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Vermont Yankee Nuclear Power Station License No. DPR-28 (Docket No. 50-271)

Reportable Occurrence Number: LER 2007-003-00

Dear Sir or Madam,

As defined by 10 CFR 50.73(a)(2)(iv)(A), we are submitting the attached revised Licensee Event Report, LER 2007-003-00, for a Reportable Occurrence that was discovered on August 30, 2007.

There are no regulatory commitments contained within this correspondence.

If there are any questions regarding this letter please contact Mr. David Mannai at (802) 258-5422.

Sincerely, Ted A. Sullivan Site Vice Presid Vermont Y4 Nuclear Power Station cc: (next page)

BVY 07-073 / page 2 of 2 cc:

Mr. Samuel J. Collins Regional Administrator, Region 1 U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406-1415 Mr. James S. Kim, Project Manager U.S. Nuclear Regulatory Commission Mail Stop 08C2A Washington, DC 20555 USNRC Resident Inspector Entergy Nuclear Vermont Yankee, LLC P.O. Box 157 Vernon, Vermont 05354 Mr. David O'Brien, Commissioner VT Department of Public Service 112 State Street - Drawer 20 Montpelier, Vermont 05620-2601

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007 (6-2004)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE VERMONT YANKEE NUCLEAR POWER STATION (VY) 05000 271 1 OF 3

4. TITLE Reactor Trip Caused by Turbine Stop Valve Closure due to Inadequate Preventative Maintenance

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED I

FACILITY NAME DOCKET NUMBER MNH DY YA YER SEQUENTIAL REV MNH DAY YEAR N/A FACILITY NAME DOCKET NUMBER 08 30 2007 2007 003 00 10 25 2007 N/A

9. OPERATING MODE

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

.E) 20.2201(b)

E] 20.2203(a)(3)(i)

E] 50.73(a)(2)(i)(C)

Q] 50.73(a)(2)(vii)

N

[] 20.2201(d)

[

20.2203(a)(3)(ii) j] 50.73(a)(2)(ii)(A) jJ 50.73(a)(2)(viii)(A)

E] 20.2203(a)(1)

[

20.2203(a)(4)

[

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

[

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

E] 20.2203(a)(2)(i)

[

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

[

50.73(a)(2)(iii)

[

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

10. POWER LEVEL

[

20.2203(a)(2)(ii)

[

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

El 50.73(a)(2)(iv)(A)

[

50.73(a)(2)(x) o 20.2203(a)(2)(iii)

Q 50.36(c)(2)

[

50.73(a)(2)(v)(A) 7 73.71(a)(4) 62 E] 20.2203(a)(2)(iv)

[

50.46(a)(3)(ii)

[

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

E] 73.71(a)(5)

O 20.2203(a)(2)(v)

E] 50.73(a)(2)(i)(A) 5 50.73(a)(2)(v)(C) 5 OTHER

[]

20.2203(a)(2)(vi) iJ 50.73(a)(2)(i)(B) 5 50.73(a)(2)(v)(D)

Specify in Abstract below dr in

CAUSE

Root Cause:

The reactor trip was attributed to the lack of adequate preventative maintenance on the TSV Bell Crank Mechanism.

There was no preventive maintenance activity to inspect, rebuild and lubricate the Bell Crank Mechanism on a periodic basis.

ASSESSMENT OF SAFETY CONSEQUENCES

The safety objective of the RPS is to provide timely protection at the onset of conditions that could challenge the integrity of the fuel barrier and nuclear system process barriers. The RPS prevents the release of radioactive material from the fuel and nuclear system process barriers by terminating excessive temperature and pressure increases through the initiation of an automatic plant shutdown. The TSV closure signal inputs to the RPS are from limit switches mounted on the four TSVs. Each of the switches is arranged to open before the valve is more than 10% closedto provide an early positive indication of valve closure. The logic is arranged so that closure of any three or more valves initiates an automatic plant shutdown.. For this event, all four valves closed and the RPS and plant safety systems functioned as designed. Plant safety analyses includes analyses of events that bound the experienced automatic shutdown and demonstrate that fuel and nuclear system process barriers remain intact.

Consequently, the event did not have an-adverse impact on the health and safety of the public.

CORRECTIVE ACTIONS

Immediate Actions

1) Notified the NRC per 10CFR50.72(b)(2)(iv)(B) and 10CFR50.72 (b)(3)(iv)(A).

2) Troubleshot and corrected failure of TSV-2 to open.

3) Lubricated and tested the TSV-2 Bypass Control Mechanism.

4) Completed post trip report prior to resuming plant operation.

Corrective Actions to Prevent Recurrence (CAPR)

1) Create a preventative maintenance activity to rebuild the Bypass Control Mechanism at the same interval as other turbine valve maintenance.

Long Term Corrective Actions

1) Lubricate TSV-2 Bypass Control Mechanism Bell Crank on a periodic basis until refurbishment during Refuel Outage (RFO 27) (scheduled for fall of 2008).

2) Inspect, rebuild, refurbish and lubricate the TSV-2 Bell Crank and Bypass Control Mechanism during RFO 27.

3) Evaluate TSV vendor testing recommendations and determine the appropriate testing frequencies.

ADDITIONAL INFORMATION

No similar events where a reactor trip was caused by turbine stop valve closure have occurred at VY within the past five years.