ML20077L250
| ML20077L250 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 07/30/1991 |
| From: | Creel G BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9108120146 | |
| Download: ML20077L250 (6) | |
Text
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BALTIMORE I
GAS AND ELECTRIC CHARI ES CENTER
- 9.O. BOX 1475
- BALTIMORE, MARYLAND 21203-1475 Gromot C CRttL Vict Pets @CNT N./C4 C Ap (ms mov
( 308) 26 0- d 4 5$
i July 30,1991 U. S. Nuclear Regulatory Commission Washington,DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50 317 & 50-318 Oneration With Elevated Chesancake Pay Temocrature Gentlemen:
At our request, a telephone conference call was held with members of your staff at 3:30 p.m. on July 24,1991, to discuss actions Baltimore Gas and Electric (BG&E) Company was taking to assess the safety implications of Calvert Cliffs operation in the event that Chesapeake Bay water temperature should exceed 850F. Baltimore Gas and Electric Company and NRC staff members participating in this conference call are listed in Attachment 1. The purpose of this letter is to document BG&E's findir.g. as presented during the July 24 conference call, that periodic operation in the short-term with inlet temperatures up to and including 87('F does not constitute a significant hazard to public health and safety.
An evaluation completed to support this determination is summarized below. This evaluation was resiewed and approved by our Plant Operations and Safety Review Committee on July 24,1991, and provides our basis for continued plant operations until final design work can be completed to increase the design inlet temperature pursuant to 10 CFR 50.59.
10 CFR 50.59 analyses are expected to be completed and approved by August 16,1991. If the results of these analyses indicate that a permanent increase in design inlet temperature above 850F cannot be supported, we will immediately restore the 850F limit.."or your information, we did not actually experience inlet temperatures above 850F subsequert to the July 24 telephone call, and do not expect to see such temperatures before completion of er design aethities.
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. Document Control Desk July 30,1991 Page 2 IIACKGilOUNI)
His summer we have experienced an unusual combination of ensironmental conditions resulting in an unexpected rise in the temperature of the cooling water drawn from the Chesapeake Bay. De combination of a hot, stagnant air mass, combined with tidal effects and an casterly wind flow have created a condition where we are drawing warm,:r water than normalinto the plant. His condition is causing the inlet temperature to approach the design maximum temperature of 85oF for the saltwater cooling system. Operation with inlet temperatures above this design temperature limit would place the plant in an unanalyzed condition.
Consequently, we are evaluating the effect a slightly higher inlet temperature would have on the l
cooling capability of the saltwater system. At the completion of this evaluation, we willimplement a
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l 10 CFR 50.59 safety evaluation that supports a permanent 6 crease in the design basis inlet temperature of the saltwater system. While the 50.59 evaluation is being completed, we have temporarily relaxed the design constraints for the inlet saltwater temperature to allow a maximum temperature of 870F. This relaxation was based upon favorable preliminary results from which we were able to confidently draw the conclusion that the remaining analyses would not lead to any safety concerns.
l ENViltONMENTAL CONSEOUENCES Operation of the plant with an inlet bay temperature of 87oF will not result in any irreversible environmental consequences. There are no emironmental limitations on maximum inlet or discharge temperature to the Chesapeake Bay in either the operating license or the NPDES permit issued by the State of Maryland. As di.; cussed in the NRC Environmental Impact Appraisal for License Amendment Nos. 23 and 7 (Unit 1 and 2. respectively), a limit on maximum discharge j
temperature was considered during initial plant licensing, but was determined to be unnecessary and l
was rejected in favor of a limit on the saltwater temperature rise across the main condensers. This limit was established as 12oF delta T, and is contained in the NPDES permit.
DISCUSSION In the analyses used to support the UFSAR, the inlet temperature to the saltwater system was assumed to be no greater than 85oF. All subsequent analyses, including the containment response to design basis events, are based on this saltwater temperature. We are evaluating the effect that a l
temperature increase (above 85oF) will have on the results of these design calculations. Of the l
components serviced by the saltwater system, we have determined that there are some requiring additional analysis to demonstrate acceptability. They are: (1) peak containment pressure and temperature fol'owing a Design Basis Event; (2) post-Loss of Coolant Accident (LOCA) l containment pressure / temperature profile; (3) emergency diesel generator cooling requirements; l
(4) ECCS pump room cooling; (5) normal operating containment temperature; (6) senice water heat exchanger room cooling and (7) component cooling water heat exchanger room cooling. The current status of these evaluations is as follows:
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. Document Control Desk July 30,1Wl Page 3 l
1.
Peak Contninment Pressure and Traperature This analysis is complete to the point where we underr.tand that the peak containment pressure and temperature is not sensitive to small increases in the saltwater inlet temperature. The peak containment temperature is init.*Cy mitigated by the passive heat sinks in containment, as opposed to the c.oling action of the air coolers.
2.
Post l.OCA Co..tainment Pressurefremperature Pronte tilthough the analysis of this item is not complete for ther.c profiles, we exp:ct the nc v temperature profile to be bounded by the existing temperature pronte anJ, thus, the emironnenta i qualificainn of the safety related equipment should not be affected.
3.
Emercency Diesel Ovattalon This evaluation is complete. %c existing service water heat exchanger monitoring program has been revised to ensure that adequate cooling will be available to the emergency diesel f
generators given a rise in saltwater inlet ternperature. Therefore, diesel operability is not affected by the increase in saltwater inlet temperature.
4.
ECCS Pump them Cooling
%is evaluation is complete. There is.;nple margm in the cooling capability of the ECCS pump room heat exchangers. Tbc postulated saltwater inlet tem impact the ability of the heat exchangers to adequately cool this room.perature 5.
Normal Containment Operating Temperature This evaluation is complete. On July 24, the average containment temperature was reading about 1130F, which is below the limit of 1200F in Technical Specification 3.6.1.5. uls is considered a normal sensor.al reading even with the unusually high saltwater inlet temperatures. We do not foresce a problem in meeting the normal containment temperature limit.
Service Water IIcat Exchancednen
' The room temperature has been calculated to stay below 130"F, as long as manual actions are taken to supply forced cooling within 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> 1mst LOCA. The preliminary results of new calculations for an increase in postulated saltwater temperature of indicate that the operator action time may decrease to approximate., seven hours to provide the same cooling. The equipment and proce tures are already in place to permit the operators to take the required nettons. Modifications to the procedures will be made as necessary, ba cd on the final calculational results.
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. Document Control Desk July 30,1991 Page 4 7.
Comoonent Cooling Wnter llent Exchangedhel Tiis evaluation is complete. 1he evaluation shows that temperatures in the component cooling water heat exchanger room will not increase beyond the design values.
CONCI.USION As described above, analyses are being completed to determine the effect that a temperature risc (above 85"F) will have on the ability of the saltwater splem to '" rform its safety.rclated function.
1hc preliminary results of these evaluation indicate that the im
.c in saltwater in!ct temperature will not have a detrimental impact on the ability of various hu.n re.noval systems to perform their l
functions. We expect the 10 CFR 50.59 cvaluation, which is being prepared, will indu :te that this increase does not consti'.
3 areviewed safety question. If during the counc of these evaluations we discover that the u m analyses do not support this determination, we will immediately revert to the original 4 m:
ature of 85"F.
1his atoposed char aluated broadly against the standards set forth in 10 Cim 50.92
.v and (etermined not i.ontuu. a significant nazard to the health and safety of the public. The actions described above do not an increase in the probability or consequences of an accident previously evaluated. We will not be operating the plant in a different fashion than before. Thus the changes will not increase the probabihty of failure of other plant components. We are performing evaluations to determine the exact impact of an increase in saltwater inlet temperature on the operation of safety.rclated systems, To date, these evaluations have shown that there is no increase in the consequences of a previously evaluated accident.
The possibility of new or different tyg m of accidents f rom an> accident previously evaluated has not been created. This design input change will not affect the operation of the plant beyond some minor procedure changes involving the service watet ocal c.uhanger differential pressure limits. Other plant components will not be operated differen"y than betare.
The margin of safety will not be reduced. The evaluations inacate that the existing margin of safety will be preserved. The containment response calculations have shown that we do not exceed our peak containment pressure or temperature design limits based on an increase in saltwater inlet temperature. _ Additionally, the long. term pressure / temperature response calculations are expected to show that we will not challenge the existing environmertal qualification of the safety.related equipment inside containment. As noted above, the other sys ems which are impacted by this change remain operable and capable of performing their safety function.
Should you have any further questlans regarding this matter, we will be pleased to discuss them with you.
Very truly yours, i
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Document Control Desk July 30,1991 Page 5 cc:
D. A. Brune F2 quire J. E. Silberg, Esquire R. A. Capra, NRC D. O. hicDonald, Jr., NRC T. T. hiartin, NRC L E. Nicholson, NRC R.1. hiclean, DNR J.11. Walter, PSC l
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NITAGlill2il TELEl'IlONE CONI'ERENCE PARTICIPANTS
.luly 24,1991 NRC Office of Nuclear Reactor ReculatJnn NRC Regimi D. O. Mcdonald, Jr.
C. J. Cowgill W. T. LeFave K. N. Jabbour D. O.11rinkman P. K. IIapen D.11. Oudinot 1
NRC lh t gnt inspectors' Of firs flaitimore Oas & Electric Company A. O, llowe R.11. Denton C. F. Lyons R. L Wenderlich S.11.13rewer J.R.11i11 W. J.1.ippold l
L J. Tucker G. L Detter P. E. Katz
- 13. S. Montgomery E. R. Zumwalt S. T. O'Connor J. L Oines K. R. Ikone 1
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