IR 05000277/2004010

IR 05000277-04-010, 05000278-04-010; 09/13/2004 - 09/17/2004; Peach Bottom Atomic Power Station Units 2 and 3; Supplemental Inspection

ML043020004
Person / Time
Site:	Peach Bottom
Issue date:	10/27/2004
From:	Rogge J NRC/RGN-I/DRS/EB
To:	Crane C Exelon Generation Co, Exelon Nuclear
References
IR-04-010
Download: ML043020004 (10)

Text

ber 27, 2004

SUBJECT:

PEACH BOTTOM ATOMIC POWER STATION - NRC SUPPLEMENTAL INSPECTION REPORT 05000277/2004010 AND 05000278/2004010

Dear Mr. Crane:

On September 17, 2004, the US Nuclear Regulatory Commission (NRC) completed an inspection at your Peach Bottom Atomic Power Station Units 2 and 3. The enclosed supplemental inspection report documents the inspection findings, which were discussed on September 17, 2004 and October 26, 2004, with Mr. Robert Braun and other members of your staff.

The inspection examined activities conducted under your license as they relate to safety and compliance with the Commissions rules and regulations and with the conditions of your license.

The inspectors reviewed selected procedures and records and interviewed personnel.

Based on the results of this inspection no findings of significance were identified.

In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter, its enclosure, and your response (if any) will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records (PARS) component of NRC's document system (ADAMS). ADAMS is accessible from the NRC Website at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).

Sincerely,

/RA/

John F. Rogge, Chief Electrical Branch Division of Reactor Safety Docket Nos.: 50-277, 50-278 License Nos: DPR-44, DPR-56 Enclosure: Inspection Report 05000277/2004010 and 05000278/2004010 w/Attachment: Supplemental Information

Mr. Christopher

SUMMARY OF FINDINGS

IR 05000277/2004010, 05000278/2004010; 09/13/2004 - 09/17/2004; Peach Bottom Atomic

Power Station Units 2 and 3; Supplemental Inspection.

Cornerstone: Mitigating Systems

The U.S. Nuclear Regulatory Commission (NRC) performed this supplemental inspection to assess Exelons evaluation associated with the failure of the E2 emergency diesel generator (EDG) on September 15, 2003. This performance issue was previously characterized as having low to moderate risk significance (white) in NRC Inspection Report 50-277&278/03-13.

During this supplemental inspection, performed in accordance with Inspection Procedure 95001, the inspectors determined that Exelon performed a comprehensive evaluation of the failure of the E2 EDG during a partial loss of offsite power event on September 15, 2003.

Exelons evaluation identified the primary root cause of the performance issue to be lack of proper controls for installation of cylinder liner adapter gaskets during installation in 1992. The lack of adequate gasket crush, along with gasket relaxation, led to leakage of combustion gasses into the cooling water system, and subsequent trip on low cooling water pressure.

Exelons performance is acceptable in addressing the diesel generator failure, therefore, the white finding associated with this issue will only be considered in assessing plant performance for a total of four quarters in accordance with the guidance in IMC 0305, Operating Reactor Assessment Program. Implementation of Exelons corrective actions will be reviewed during a future inspection.

ii

REPORT DETAILS

INSPECTION SCOPE

The U.S. Nuclear Regulatory Commission (NRC) performed this supplemental inspection to assess Exelons evaluation associated with the failure of the E2 EDG during a partial loss of offsite power event on September 15, 2003. This performance issue was previously characterized as white in NRC Inspection Report 50-277&278/03-13, and is related to the mitigating systems cornerstone in the reactor safety strategic performance area.

EVALUATION OF INSPECTION REQUIREMENTS 02.01 Problem Identification a.

Determination of who (i.e., licensee, self-revealing, or NRC) identified the issue and under what conditions The issue was self-revealing, and was identified when the E2 EDG tripped on low jacket water pressure approximately one hour after starting and loading during the partial loss of offsite power event on September 15, 2003.

b.

Determination of how long the issue existed, and prior opportunities for identification Exelon determined that the issue existed since the cylinder liners were replaced on the engine in 1992. Exelon determined that the condition could have been identified on two occasions in the spring of 2003 when low jacket water pressure was noted during test runs of the E2 EDG but was not fully investigated or resolved.

c.

Determination of the plant-specific risk consequences (as applicable) and compliance concerns associated with the issue Exelon performed a risk assessment using the Phase 2 worksheets from Risk-Informed Inspection Notebook for Peach Bottom Units 2 and 3. Exelon estimated change in core damage frequency (CDF) in the very low risk (Green) range.

NRC performed a phase 2 evaluation and determined the EDG failure had low to moderate risk and that further refinement of the results was warranted. NRC performed a Phase 3 evaluation using SPAR Model 3.01 for Peach Bottom and calculated CDF and LERF values of White for Unit 2 and Green for Unit 3. The difference between the results for Unit 2 and Unit 3 is due to differences in loads on the electrical busses.

02.02 Root Cause and Extent of Condition Evaluation a.

Evaluation of methods used to identify root cause and contributing causes.

Exelon used Event and Causal Factor Charting and Barrier Analysis to determine why the E2 EDG failed to continue to run and carry load.

b.

Level of detail of the root cause evaluation The root cause evaluation assessed multiple potential causes for the loss of cooling water pressure on the E2 Emergency Diesel Generator. Troubleshooting activities were conducted and were able to replicate the performance observed during the event and identified the presence of combustion gasses in the coolant system.

c.

Consideration of prior occurrences of the problem and knowledge of prior operating experience During the evaluation of the cause of the combustion gas leak, Exelon determined that on two occasions in the spring of 2003, low cooling water pressure was observed.

Subsequent troubleshooting identified no abnormalities, and the cause of the observed low pressure was never identified.

d.

Consideration of potential common cause(s) and extent of condition of the problem During repairs to the E2 EDG following the September 15, 2003, event, Exelon determined that leaking cylinder liner adapter gaskets allowed combustion gasses to enter the cooling system as a result of not achieving adequate gasket crush on initial installation in 1992. Exelon determined that inadequate procedural guidance for performing maintenance resulted in the faulty installation. Exelon also found that because the same procedure was used at both Limerick and Peach Bottom, by the same work group that the problem could potentially apply to the engines at both sites. Exelon performed monitoring to determine if there was evidence of gas leakage into the cooling systems of all the engines. In addition, Exelon performed a review to determine if solid metallic gaskets were used elsewhere and whether adequate guidance existed for their installation.

02.03 Corrective Actions a.

Appropriateness of corrective actions Exelon has reviewed the manufacturers guidance for the installation of cylinder liner adapter gaskets and revised procedures to incorporate the recommended method.

Exelon has also obtained special tools necessary for the installation and trained maintenance personnel on the installation method and use of the tools. Exelon has also implemented enhancements to troubleshooting and corrective action guidance to ensure that, in the future, resolution of identified problems is more rigorously pursued. Exelon also scheduled reviews of all the EDG manufacturers service advisories to ensure that all appropriate recommendations had been incorporated.

b.

Prioritization of corrective actions Exelon took actions to ensure that the installation procedure revisions and technician training were completed before the next scheduled EDG inspection and overhaul. Exelon also implemented monitoring of the engines for evidence of gas leakage into the cooling systems and prompt correction of any leakage observed.

c.

Establishment of schedule for implementing and completing the corrective actions Exelon initiated activities to ensure the updated maintenance procedures were in place at all the sites using the same EDGs prior to the next occurrence of inspection and overhaul of the engines at each site.

d.

Establishment of quantitative or qualitative measures of success for determining the effectiveness of the corrective actions to prevent recurrence Exelon performed an effectiveness review of the corrective actions for the low cooling water pressure. In their review, Exelon identified several additional enhancements and initiated steps to implement them. In addition, Exelon has added coolant system monitoring activities during each engine run to provide early detection of any combustion gas leakage which might occur.

03. MANAGEMENT MEETINGS

Exit Meeting Summary

The inspector discussed the results of the inspection with Mr. R. Braun and other members of the Peach Bottom staff at a meeting on September 17, 2004 and October 26, 2004.

Some of the information reviewed during the inspection was marked as proprietary. All proprietary information was returned to Exelon at the end of the inspection. This report contains no proprietary information.

ATTACHMENT

SUPPLEMENTAL INFORMATION

KEY POINTS OF CONTACT

Exelon personnel

R. Braun, Site Vice President

J. Grimes, Plant Manager

P. Cowan, Nuclear Oversight Manager

J. Mellor, Regulatory Assurance Manager

D. Foss, Licensing Engineer

J. McLaughlin, System Manager

J. Rogenmuser, System Manager

NRC personnel

C. Smith, Senior Resident Inspector

D. Orr, Senior Resident inspector (Salem)

LIST OF ITEMS OPENED, CLOSED, AND DISCUSSED

Opened

None

Opened and Closed

None

Closed

05000277/2003013-01 AV Failure to adequately maintain the E2 Emergency Diesel Generator

05000278/2003013-02 AV Failure to adequately maintain the E2 Emergency Diesel Generator

Discussed

NONE