ML20236C218
| ML20236C218 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/15/1989 |
| From: | Russell L BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8903220029 | |
| Download: ML20236C218 (2) | |
Text
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BALTIMORE GAS AND ELECTRIC CHARLES CENTER. P.O. BOX 1475 BALTIMORE, MARYLAND 21203
- LEON D. RUSSELL.
MANAGER CALVERT CLHS NUCLEAR POWER PLANT DEPARTMENT March 151989 -
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l U. S. Nuclear Regulatory Commission -
l Washington, DC 20555 l
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ATTENTION:
Document Control Desk.
1 J
SUBJECT:
Calvert Cliffs Nuclesr Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 10 CFR 50.9 Report; Loss of Shutdown Cooling Implications for Low Temperature Overpressure Protection i
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Gentlemen:
We have determined that some postulated loss ~ of l shutdowni cooling (LOSDC) scenarios -
result in excessive reactor coolant system pressure : transients - and the possible-violation of reactor pressure ' vessel pressure-temperature Llimits. All analyses ' assume -
and require a LOSDC followed ' by ' a single failure. ' Initial conditions. require - the -
plant to be.in COLD SHUTDOWN,.with the pressurizer partially filled and the steam generators drained with the tubes dry. Without the steam generators for decay heat removal, the LOSDC with single failures can' result in RCS overpressurization.
The initiator for these scenarios is a LOSDC. A LOSDC can occur i from air entrainment, suction line valve closure and loss.of. offsite ' power, for example. After -
- i a LOSDC, the RCS will pressurize until sufficient decay heat is l removed by steam
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generator heat transfer or through a vent.
-In COLD SHUTDOWN (MODE 5), an operable steam generator 'is not required by our Technical Specifications. If steam- - generators are ~available, they.may not ' provide effective heat transfer following ~ LOSDC if. the primary ! side : tubes - are ' drained ' and there 'is not a clear steam flow path to the tubes. Vent pressure : may violate' operating
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limits unless the operator restores - inventory ' losses and ' maintains subcooling by coolant f injection. Technical Specifications'. require E one diesel generator, two' PORVs, and a boric ncid injection pump' (either a ' charging or High Pressure Safety Injection (HPSI) pump). Loss of shutdown cooling with failures of these components can prevent effective operator action and cause - overpressurization.
The worst. case scenario - assumes a loss of ' offsite power ' during MODE 5' with. the RCS partially filled and' one diesel generator operable. With the single. failure L of the lone diesel generator, the affected unit will' ' experience a loss of all ' AC power.
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This : will render the PORVs inoperable and no coolant injection will be' available.
l Peak equilibrium pressures will reach' -the pressurizer safety valve setpoint (2,500 psi) for-this case. 'This scenario bounds all other scenarios we have analyzed.
8903220029 8903 g
{MM ADOCK 0500 gDR
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Document Control Desk
' March 151989 '
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l We will evaluate the capability of the steam generators to remove decay heat with drained tubes. We have conservatively assumed in our initial analyses' that the steam generators provide no heat removal. Should our evaluation. conclude that the steam generators can indeed ' remove some heat, our analyses will be revised.
Until our investigation is complete, we will maintain during MODE 5 two diesel generators operable and two HPSI pumps available until the. RCS is vented by the
' removal of the pressurizer safety relief valves or manway. The HPSI ' pumps are required for. decay heat removal for the first few days after reactor ' shutdown. This will be done only when the steam generators are unavailable for decay heat removal.
f These actions provide the operators with redundant decay heat removal capabilities and ensures a single failure will not lead to RCS overpressurization.
l We have evaluated these scenarios for deportability under 10 CFR 50.72 and 50.73-and we have determined that reporting is. not required. We have contacted our owner's group and information pertaining to this issue will be disseminated to the appropriate licensees for PWRs.
This letter confirms the information provided to the Resident Inspector's Office on l
March 8,1989, under-10 CFR 50.9. Should you have any further questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, Qin bl4 LBR/SRC/ dim i
cc:
D. A. Brune, Esquire 1 E.
Silberg, ' Esquire R. A.Capra, NRC S. A. McNeil, NRC W. T. Russell, NRC H. Eichenholz/V. L. Pritchett, NRC T. Magette, DNR
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