05000374/LER-2009-002

LER-2009-002, , Completed Plant Shutdown Due to Unidentified Leakage in Excess of Technical Specification Limits

Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No.
Event date:	10-12-2009
Report date:	12-11-2009
Reporting criterion:	10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown
Initial Reporting
ENS 45426	10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown
3742009002R00 - NRC Website

A. PLANT AND SYSTEM IDENTIFICATION

General Electric Boiling Water Reactor, 3489 Megawatts Thermal Rated Core Power

CONDITION PRIOR TO EVENT

Unit(s): 2 Event Date: 10/12/2009 Event Time: 1405 Reactor Mode(s): 1 Power Level(s): 100 Mode(s) Name: Power Operation

B. DESCRIPTION OF EVENT

On October 11, 2009, at 2333 CDT, unidentified leakage on LaSalle Unit 2 exceeded the Technical Specification (TS) Limiting Condition for Operation (LCO) 3.4.5.d limit of less than or equal to a two gallon per minute (gpm) increase in the previous 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period while in Mode 1. Required Action (RA) B.1 requires that the increase in unidentified leakage be reduced below the limit within four hours. If RA B.1 can not be met, RA C.1 and C.2 require that the unit be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

At 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br /> on October 12, 2009, a plant shutdown was commenced. At 0333 hours0.00385 days <br />0.0925 hours <br />5.505952e-4 weeks <br />1.267065e-4 months <br />, unidentified leakage was still in excess of the TS LCO 3.4.5.d limit. The unit entered Mode 3 at 1405 hours0.0163 days <br />0.39 hours <br />0.00232 weeks <br />5.346025e-4 months <br /> on October 12, and reached Mode 4 at 0005 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> on October 13, 2009.

The unidentified leakage was determined to be from a packing leak on the Inboard Main Steam Isolation Valve (MSIV) Drain Line Isolation Valve (2B21-F016) (NB)[AD]. The packing leak was repaired and the unit was restarted on October 14, returning to full power on October 17, 2009.

The event was reportable under 10 CFR50.72(b)(2)(i) as an initiation of a nuclear plant shutdown required by TS. An ENS call (EN# 45426) was made on October 12, 2009, at 0433 CDT. The event is also reportable under 10 CFR 50.73(a)(2)(i)(A), as the completion of a nuclear plant shutdown required by TS.

C. CAUSE OF EVENT

The cause of the event was a packing leak on the Inboard MSIV Drain Line Isolation Valve (2B21-F016).

The leak occurred when the 2B21-F016 valve was stroked closed and then full open during a 2B Reactor Protection SyStem (RPS) bus transfer.

A root cause investigation determined that there was a body-to-bonnet misalignment at the completion of the 2005 valve installation that was not noticed by the workers. The misalignment was due, in part, to a lack of clarity and specificity in the work package and vendor manual instructions. Additionally, the misalignment was masked by the fact that a graphite gasket.was used, which was more malleable than the iron gaskets commonly used, and did not leak immediately following the work despite the misalignment.

• NRC FORM 366A (9-2007) PRINTED ON RECYCLED PAPER �NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSIONLICENSEE EVENT REPORT (LER)(9-2007)

CONTINUATION SHEET

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D. SAFETY ANALYSIS

The safety significance of the event was minimal. Makeup capability was adequate to compensate for the leak, which was approximately 2.3 gpm. All Emergency Core Cooling Systems (ECCS) were operable and capable of fulfilling their intended safety function during the period of excessive leakage.

The event did not constitute a safety system functional failure.

Corrective Actions:

• The 2B21-F016 valve was repacked and repaired.

Corrective Action to Prevent Recurrence:

• Mechanical Maintenance personnel and supervisors will be trained on the different types of gaskets used on pressure seal valves and their installation requirements.

• A maintenance procedure will be developed specifically for the Inboard and Outboard MSIV Drain Line Isolation Valves (1/2B21-F016 and 1/2B21-F019) to incorporate vendor manual instructions, including ensuring proper alignment by installing the valve operator in order to pull up the inner bonnet prior to tightening.

• Other pressure seal valve maintenance procedures will be revised as necessary to incorporate vendor manual instructions for ensuring proper body-to-body alignment.

F. PREVIOUS OCCURENCES

A document review covering the previous three years found no previous occurrences of a plant shutdown required by excessive unidentified leakage.

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G. COMPONENT FAILURE DATA

Velan Pressure Seal Gate Valve (Forged) 3"