ML063340439
| ML063340439 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 11/29/2006 |
| From: | David Lew Division Reactor Projects I |
| To: | Epstein E - No Known Affiliation |
| Bellamy R Rgn-I/DRP/Br7/610-337-5200 | |
| References | |
| DER-42957 | |
| Download: ML063340439 (5) | |
Text
November 29, 2006 Mr. Eric Epstein 4100 Hillsdale Road Harrisburg, PA 17112
Dear Mr. Epstein:
I am responding to the joint letter from TMI Alert and the Union of Concerned Scientists dated November 6, 2006. Your letter discussed concerns you had with potential indications of inadequate operator training and/or operating procedures at Three Mile Island Unit 1 following the reactor trip on November 2, 2006, as described in Nuclear Regulatory Commission (NRC)
Daily Event Report No. 42957. You stated that, based on the licensee reports, you were concerned that plant operators did not appear to understand the operating characteristics of the Main Steam Safety Valves (MSSVs). You also urged the NRC to rigorously examine the operator training and operating procedures at TMI to determine why operators mistakenly concluded that the steam generator safety valves were stuck open.
The NRC staff evaluated plant operator response starting with the Resident Inspectors, who responded to the control room within five minutes of the event, monitoring the operators immediate actions to place the plant in a stable condition. The NRC continued to evaluate the licensees followup actions including the identification of appropriate corrective actions. The NRCs review determined that the plant operators responded to the event safely and in accordance with plant procedures. Operators accurately assessed plant conditions following the trip and noted that two MSSVs remained open. They determined that excessive reactor coolant system overcooling was not occurring and thus, the plant did not meet criteria to enter the emergency operating procedure that would have directed immediate actions to shut the MSSVs. Operators performed vital system status verifications, leading to their actions to maintain steam generator pressure and to stabilize reactor coolant system temperature. The operators continued to follow the procedure which later directed the operators to lower steam generator pressure to reseat any open MSSV(s). Plant procedures properly specified these actions commensurate with existing plant conditions during the post trip response.
The MSSVs are designed to reseat within a range of pressure somewhat below lifting pressure.
The B MSSV reseated five minutes after the reactor trip with no operator action due to steam generator pressure dropping as decay heat was removed. When the A MSSV did not reseat, the operating crew manually reduced A steam generator pressure in accordance with procedures. The A MSSV reseated 34 minutes after the trip in response to this operator action. Both valves reseated as designed, but near the lower end of the reseat pressure tolerance band. The NRCs review determined that TMIs operators expect the MSSVs to reseat high in the reseat pressure tolerance band with no operator action. Some operators at TMI described the MSSV not reseating as expected as being stuck open, although they were aware that the MSSVs have a reseat pressure tolerance band, and they did not believe the MSSVs had malfunctioned. They use this term for this condition because the procedure directs
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operators to evaluate the effect of the MSSV not being reseated on plant cooldown, and directs actions to be taken when MSSVs do not reseat.
The NRC Resident Inspectors were present in the control room during the reactor trip response and observed post trip event assessment activities. The Resident Inspectors independently determined that the MSSVs had not stuck open and that the operators did not believe the MSSVs were actually stuck in a fixed open position. The operators took appropriate actions in accordance with the station operating procedures based on the symptoms with which they were faced. The procedures are designed to maintain critical safety functions without assuming the cause of the symptoms. This was a key lesson learned from the TMI-2 accident.
Following receipt of the initial 50.72 notification, the NRC Resident Inspectors questioned whether use of the term stuck open accurately described MSSV performance during the trip.
AmerGen immediately responded that this term was not technically accurate and should not have been included in the 10 CFR 50.72 report. AmerGen subsequently updated the 10 CFR 50.72 report to more accurately describe the condition of the MSSVs following the plant trip.
In conclusion, the NRCs review of the event showed that the operators were aware of plant conditions throughout the event, entered and carried out the appropriate procedures in response to the event, and the procedural guidance and quality were appropriate. The NRC determined that the licensee could have been more accurate in their terminology in the initial 10 CFR 50.72 report for this event. The licensee updated the 10 CFR 50.72 report to clarify the condition of the MSSVs, and the licensee has initiated additional corrective actions to improve the accuracy of their reporting in external communications.
The NRCs review of this matter will be documented in NRC Inspection Report 05000289/2006006. We will send you a copy of this report when issued. TMI Alert will receive a copy of this report through normal distribution. If you have any further questions regarding these issues, please call the NRC Regional Branch Chief for Three Mile Island, Dr. Ronald Bellamy, at 610-337-5200.
Sincerely,
/RA/
David C. Lew, Director Division of Reactor Projects Docket Nos.: 50-289 (Unit 1)
License Nos. DPR-50 (Unit 1)
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cc:
Chief Operating Officer, AmerGen Site Vice President - TMI Unit 1, AmerGen Plant Manager - TMI, Unit 1, AmerGen Regulatory Assurance Manager - TMI, Unit 1, AmerGen Senior Vice President - Nuclear Services, AmerGen Vice President - Mid-Atlantic Operations, AmerGen Vice President - Operations Support, AmerGen Vice President - Licensing and Regulatory Affairs, AmerGen Director Licensing - AmerGen Manager Licensing - TMI, AmerGen Vice President - General Counsel and Secretary, AmerGen T. ONeill, Associate General Counsel, Exelon Generation Company J. Fewell, Esq., Assistant General Counsel, Exelon Nuclear Correspondence Control Desk - AmerGen Chairman, Board of County Commissioners of Dauphin County Chairman, Board of Supervisors of Londonderry Township R. Janati, Director, Bureau of Radiation Protection, State of PA J. Johnsrud, National Energy Committee D. Allard, PADEP
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Distribution:
S. Collins, RA M. Dapas, DRA R. Bellamy, DRP R. Fuhrmeister, DRP A. Rosebrook, DRP D. Kern, DRP, Senior Resident Inspector J. Brand, DRP, Resident Inspector B. Sosa, RI OEDO H. Chernoff, NRR F. Saba, PM, NRR J. Boska, NRR E. Miller, NRR K. Farrar, ORA R. Barkley, ORA M. Sykes, DRS D. Screnci, PAO Region I Docket Room (with concurrences)
An identical letter sent to: see next page Response Letter ADAMS Accession Number: ML063340439 Incoming Letter ADAMS Accession Number: ML063340694 SUNSI Review Complete: RRB (Reviewers Initials)
DOCUMENT NAME: C:\\FileNet\\ML063340439.wpd After declaring this document An Official Agency Record it will be released to the Public.
To receive a copy of this document, indicate in the box: "C" = Copy without attachment/enclosure "E" = Copy with attachment/enclosure "N" = No copy OFFICE RI/DRP RI/DRP RI/DRS RI/DRP NAME ARosebrook/AAR RBellamy/AAR for MSykes/MDS DLew/DCL DATE 11/17/06 11/17/06 11/20/06 11/29/06 OFFICE RI/ORA RI/RC NAME RBarkley/AAR for KFarrar/KLF DATE 11/17/06 11/27/06 OFFICIAL RECORD COPY
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Mr. David Lochbaum Director, Nuclear Safety Project Union of Concerned Scientists 1707 H Street NW Suite 600 Washington, DC 20006-3919