ML17146A811
| ML17146A811 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 05/18/1987 |
| From: | Butler W Office of Nuclear Reactor Regulation |
| To: | Keiser H PENNSYLVANIA POWER & LIGHT CO. |
| References | |
| NUDOCS 8705260154 | |
| Download: ML17146A811 (6) | |
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++**4 Docket No.: 50-388 UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 May 18'987 Mr. Harold M. Keiser Vice President Nuclear Operations Pennsylvania Power 5 Light Company 2 North Ninth Street Allentown, Pennsyl vania 18101
Dear Mr. Keiser:
SUBJECT:
INADEQUATE TORQUE ON HPCI VALVE RE:
Susquehanna Steam Electric Station, Unit I This will confirm our telephone agreement with Mr. R. Sgarro of ynur staff on May 15, 1987, for the reopening of the inboard containment isolation valve (HV-155F003) on the HPCI steamline of Susquehanna, Unit 1, as you requested in your letter of May 14, 1987.
It also documents the bases for the agreement.
In your letter, dated May 14, 1987, from Mr. Bruce D. Kenyon to the Director of Nuclear Reactor Regulation, you requested relief from the requirements of Technical Specification Section 3.6.3 for the Susquehanna Steam E1ectric Station Unit 1, relative to High Pressure Coolant Injection (HPCI) system valve HV-155F002.
The relief is needed because the valve HV-155F002 was declared inoperable after it was found to have an incorrect torque switch setting.
In addition, you requested an expeditious approval for openino the HPCI valve HV-155F003 which was isolated after valve HV-155F002 was declared inoperable.
This letter responds to that part of the request seeking approval to reopen the HPCI isolation valve HV-155F003.
The remainder of your request involving a change to the Technical Specifications will be addressed in a separate action.
In your letter, by way of background, you stated that the incorrect torque setting for valve HV-155F002 was discovered on May 7, 1987 during a records search pursuant to NRC Bulletin 85-03.
The error was made during the second refueling outage in March, 1986.
Your subsequent evaluation of the incorrect torque setting showed that the valve would close fully at differential pressures of 140 psid or less.
However, the valve would close to only 97K of full closure for differential pressures greater than 140 psid.
You stated that the valve HV-155F002 was conservatively declared inoperable because it was found to be included in Table 3.6.3-1 for primary containment isolation valves.
These valves are required to isolate and ensure that the containment atmosphere will be isolated from the outside atmosphere in the event of any release of radio-active material to the containment atmosphere or pressurization of the contain-ment atmosphere due to a loss of coolant accident inside the containment.
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valve HV-155F002, although included in Table 3.6.3-1, does not provide communication between the containment atmosphere and outside atmosphere when the reactor is in an operating
- mode, and therefore need not be declared inoperable for the purpose of isolating the containment atmosphere-from the outside atmosphere.
Additionally, because the valve would close fully at LOCA pressures (less than 140 psid) and since it satisfactorily passed the local leak rate test even with the incorrect torque setting durinq March,
- 1986, we find it need not have been declared inoperable.
The analysis presented in your letter compared the potential risk from accidents with valve HV-155F003 in the open position with the risk if that valve were to remain closed.
Your analysis indicates that if, as requested, valve HV-155F003 were to be left open and a
HPCI steam line break coincident with a failure of HV-155F003 to close were to occur, the consequences of such an event will be small (a small fraction of the dose guidelines of 10 CFR 100).
On the other hand, if valve HV-155F003 were left isolated, the affected HPCI train will be unavailable.
Your analysis shows that for the anticipated transients without scram (ATMS) the unavai)able HPCI train contributes an estimated core melt frequency of 5.6 X 10
/RY, which is similar to the frequencv for the HPCI line break described above; but, because of the significant damage to the core, the sequence will result in substantially higher risk.
Another dominant sequence evaluated by you is the Station Blackout sequence.
For that
- sequence, the isolated HPCI train will contribute a frequency of almost 2
X 10
/RY to the population of core melt sequences, Although the staff is unable to verify your analysis in the time available, the insights gained by the staff from risk assessments performed for other plants and staff's engineering judgement indicate that overall plant safety is improved if valve HV-155-F003 were left in the open position.
This derives from our understanding that the risk of leaving the HPCI system isolated would be sub-stantially higher than the risk of a HPCI steam line break occurring with valve HV-155-F003 failing to close.
In addition, as stated above, the valve need not have been declared inoperable, if the underlying isolation function of the valve as discussed in the bases Section 3/4.6.3 had been the determining factor.
Based on the above considerations, your proposal to reopen valve HV-155F003 is approved unti 1 May 23, 1987, or until the staff completes its action on your request for interim relief in the form of a change to the Technical Specifications.
Sincerely,
~
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Malter R. Butler, Director Project Directorate PDI-2 Division of Reactor Projects I/II cc:
See next page
Mr. Harold W. Keiser Pe.,nsylvania Power
& Light Company Susquehanna Steam Electric Station Units 1
& 2 CC:
Jay Silberg, Esq.
Shaw, Pittman, Potts
& Trowbridge 2300 N Street N.W.
Washington, D.C.
20037 Bryan A. Snapp, Esq.
Assistant Corporate Counsel Pennsylvania Power
& Light Company 2 North Ninth Street Allentown, Pennsylvania 18101 Mr. E. A. Heckman Licensing Group Supervisor Pennsylvania Power
& Light Company 2 North Ninth Street Allentown, Pennsylvania 18101 Mr. Loren Plisco Resident Inspector P.O.
Box 52 Shickshinny, Pennsylvania 18655 Mr. R. J.
Benich Services Project Manager General Electric Company 1000 First Avenue King of Prussia, Pennsylvania 19406 Mr, Thomas M. Gerusky, Director Bureau of Radiation Protection Resources Commonwealth of Pennsylvania P. 0.
Box 2063 Harrisburg, Pennsylvania 17120 Robert W. Alder, Esquire Office of Attorney General P.O.
Box 2357 Harrisburg, Pennsylvania 17120 Mr. Jesse C. Tilton, III Allegheny Elec. Coorperative, Inc.
212 Locust Street P.O.
Bxo 1266 Harrisburg, Pennsylvania 17108-1266 Mr.
W. H. Hirst, Manager Joint Generation Projects Department Atlantic Electric P.O.
Box 1500 1199 Black Horse Pike Pleasantville, New Jersey 08232 Regional Administrator, Region I U.S. Nuclear Reoulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406
valve HV-155F002, although included in Table 3.6.3-1, does not provide communication between the containment atmosphere and outside atmosphere when the reactor is in an operating
- mode, and therefore need not be declared inoperable for the purpose of isolating the containment atmosphere from the outside atmosphere.
Additionally, because the valve would close, fully at LOCA pressures (less than 140 psid) and since it satisfactorily passed the local leak rate test even with the incorrect torque setting during March,
- 1986, we find it need not have been declared inoperable.
The analysis presented in your letter compared the potential risk from accidents with valve HV-155F003 in the open position with the risk if that valve were to remain closed.
Your analysis indicates that if, as requested, valve HV-155F003 were to be left open and a HPCI steam line break coincident with a failure of HV-155F003 to close were to occur, 'the consequences of such an event will be small (a small fraction of the dose guidelines of 10 CFR 100).
On the other hand, if v'alve HV-155F003 were left isolated, the affected HPCI train will be unavailable.
Your analysis shows that for the anticipated transients without scram (ATWS) the unavai)able HPCI train contributes an estimated core melt frequency of 5.6 X 10
/RY, which is similar to the frequency for the HPCI line break described above; but, because of the significant damage to the core, the sequence will result in substantially higher risk.
Another dominant sequence evaluated by you is the Station Blackout sequence.
For that
- sequence, the isolated HPCI train will contribute a frequency of almost 2
X 10
/RY to the population of core melt sequences.
Although the staff is unable to verify your analysis in the time available, the insights gained by the staff from risk assessments performed for other plants and staff's engineering judgement indicate that overall plant safety is improved if valve HV-155-F003 were left in the open position.
This derives from our understanding that the risk of leaving the HPCI system isolated would be sub-stantially higher than the risk of a HPCI steam line break occurring with valve HV-155-F003 failing to close.
In addition, as stated
- above, the valve need not have been declared inoperable,
'f the underlying isolation function of the valve as discussed in the bases Section 3/4.6.3 had been the determining factor.
Based on the above considerations, your proposal to reopen valve HV-155F003 is approved until May 23, 1987, or until the staff completes its action on your request for interim relief in the form of a change to the Technical Specifications.
Sincerely, cc:
See next page PDI-M MThadani;ca 05/IS/87
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