ML20150B049
| ML20150B049 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 07/05/1988 |
| From: | Tiernan J BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| IEB-88-004, IEB-88-4, NUDOCS 8807110242 | |
| Download: ML20150B049 (7) | |
Text
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B ALTIMORE GAS AND ELECTRIC CHARLES CENTER P. O. BOX 1475. BALTIMORE, MARYLAND 21203 JOSEPH A.T4ERNAN vice PmtslOENT NUCLEAR Engmov July 5,1988 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos. I & 2; Docket Nos. 50-317 & 50-318 Response to NRC Bulletin 88-04: Potential Safetv-Related Pumo Loss
REFERENCE:
(a) NRC Bulletin No. 88-04; Potential Safety-Related Pump Loss Gentlemen:
The attachment to this letter provides the information you requested in Reference (a).
Based on our investigation into your concerns regarding miniflow design, we have determined that the current Calvert Cliffs design and operation (upon completion of noted action items) provide adequate flow.
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8807110242 880705ADOCK 050C0317 PDR PDC Q
Document C:ntr:1 Desk July 5,1988 Page 2 Should you have any further questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours,
&w STATE OF MARYLAND TO WIT:
I h re y certify that on the f d day of
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, before me, the r'ber, a Notary Public of the State of %rylane( in and for
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, personally appeared Joseph A. Tiernan, being duly sworn, and states that Ve is Vice President of the Baltimore Gas and Electric Company, a corporation of the State of hiaryland; that he provides the foregoing response for the purposes therein set forth; that the statements made are true and correct to the best of his knowledge, information, and belief; and that he was authorized to provide the response on behalf of said Corporation.
WITNESS my liand and Notarial Seal:
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[' ' Notary Pab)fe hiy Commission Expires:
d>!# / /fN 6 ate JAT/GLB/WCli/ dim Attachment ec:
D. A. Brune, Esquire J.
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Silberg, Esquire R. A.Capra, NRC S. A.hicNeil, NRC W. T. Russell, NRC D. C. Trimble, NRC T. hiagette, DNR
ATTACHMENT (1)
RESPONSE to NRC BULLETIN 88-04 POTENTIALSAFETY-RELATED PUMP LOSS Response to Bulletin Action items ITEM I NRC Reauest Determine the existence of any safety-related system with a configuration which could allow for dead-heading or inadequate miniflow for pumps.
BG&E Response Calvert Cliffs Nuclear Power Plant has two systems with pump recirculation lines sharing common return headers. These systems are the Auxiliary Feedwater (AFW) and Emergency Core Cooling (ECCS) Systems. Both of these systems were designed to operate with this configuration and therefore, there are no adverse consequences when all pumps are simultaneously operating during miniflow conditions. Specific discussion is as follows:
A.
Auxiliary Feedwater System Each of the units has two Steam-Driven Auxiliary Feedwater Pumps (SDAFWP) and one Motor-Driven Auxiliary Feedwater Pump (MDAFWP). One SDAF'n'P is placed in stand-by by manually isolating its turbine steam supply, thus only two pumps automatically start when an Auxiliary Feedwater Actuation Signal is received. Both pumps deliver flow to two discharge legs where all flow control valves fail open. The pumps are sized to allow flow delivery to the steam generators at any pressure.
Thus, the probability of these pumps being in a condition of having only miniflow during automatic operation is sery low. Nevertheless, in order to allow for operational flexibility and provide a prudent design, each pump was supplied with a miniflow recirculation line.
The SDAFWP recirculation for each pump is controlled by flow restriction orifices located between the pump and the common return header. The MDAFWP recirculation is controlled by a combination of an orificed recirculation valve and an orifice. The MDAFWFs were added as part of our response to the Bulletins and Orders Task Force Recommendations. The MDAFWP recirculation lines were tied into their respective unit's SDAFWP recirculation lines, with restriction orifice sizing design being based on simultaneous pump operation.
Both units' recirculation lines tie together with a common run prior to entering the Condensate Storage Tank.
In response to this Bulletin, a confirmatory analysis was performed to re-verify the original design. This analysis factored in actual pump performance, ASME Section XI tolerances, gauge accuracy and running all four pumps (two from each unit) simultaneously. This analysis demonstrated that the original design was correct; i.e.,
there is adequate miniflow to protect the pumps under all operating conditions.
n I
ATTACHMENT (1)
RESPONSE to NRC BULLETIN 88-04 POTENTIALSAFETY-RELATED PUMP LOSS During a recent disassembly of a SDAFWP, no damage due to internal flow recirculation was detected.
B.
Emereency Core Coalian System Each of the units has three liigh Pressure Safety injection (IIPSI) pumps (a maximum of two will automatically start), two Low Pressure Safety Injection (LPSI) pumps and two Containment Spray (CS) pumps. All of the individual pumps' miniflow recirculation lines tie together into a comm '.n header back to the Refueling Water Tank (RWT). During initial design, the Nuclear Steam Supply System vendor sized an individual restriction orifice for each pump according to its miniflow requirements. They provided the architect engineer with a maximum miniflow recirculation line pressure loss. A confirmatory analysis was performed to demonstrate that with all pumps running simultaneously, the flow orifices would be the determining factor for individual pump flow rather than the piping pressure losses.
C.
Conclusions Based upon our research and confirmatory analyses, we have determined that the original Calvert Cliffs design properly factored in the effects of simultaneous pump operation. During miniflow operation all AFW and ECCS Pumps will have adequate flow.
ITEM 2 NRC Reauest Evaluate system flow if the condition described in Item I exists.
BG&E Resocnse Not applicable.
ITEM 3 NRC Reauest Evaluate the adequacy of the minimum flow bypass lines for safety-related centrifugal pumps with respect to damage resulting from operation and testing in the minimum flow m oc e.
A*ITACHMENT (1)
RESPONSE to NRC BULLETIN 88-04 POTENTIALSAFETY-RELATED PUMP LOSS BG&E Response The following is a list of all safety-related pumps with a discussion of the adequacy of their miniflow bypass lines.
A.
High Pressure Safety Iniection Pumos The pump supplier has verified the adequacy of the original miniflow design value.
B.
Low Pressure Safety Iniection Pumos The pump supplier has recommended monitoring vibration levels during miniflow conditions. This is accomplished as part of our ASME Section XI pump monitoring program. No augmented pump inspection is required if vibration levels remain unchanged.
With acceptabic stable vibration levels at the miniflow level, performance and reliability will be acceptable. The inlet velocity is relatively low and the impeller material is stainless steel, therefore, any resulting damage due to recirculation is expected to be negligible.
C.
Containment Sorav Pumos The pump supplier did not recommend any changes in miniflow quantity. They provided an inspection interval based on calendar time and cumulative time in low flow operation. Based on the small amount of time the pumps are operated in miniflow conditions, we are implementing a calendar-based inspection requirement into our Preventive Maintenance Program.
D.
Steam-Driven Auxiliary Feedwater Pumos Same response as for CS Pump.
E.
Motor-Driven Auxiliary Feedwater Pumos These pumps were installed with adequate miniflow capacity.
F.
Saltwater Pumos There is no miniflow line installed, flowever, since we have noted that operation at low flow results in a recirculation condition, operating controls are being revised to ensure adequate minimum flow. Even so, during shutdown operation, it may not be possible to maintain the required flow. We will be working with the pump supplier to determine any atigmented maintenance inspection requirements.
G.
Service Water Pumos There is no miniflow line installed. We are reviewing our Operating Instructions and will revise them as necessary to ensure adequate flow through the pump.
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RESPONSE to NRC BULLETIN 88-04 POTENTIALSAFETY-RELATED PUMP LOSS H.
Comoonent Cooline Water Pumos There is no miniflow line installed. Minimum plant heat loads ensure that adequate flow will be delivered by the pump.
J.
Soent Fuel Coolina Pumos These are 100 hp pumps. An article published in Power and Fluids, Worthington Group,1982, Volume 8, Number 2, "Flow Recirculation in Centrifugal Pumps", and training material provided by a pump vendor, indicates that the energy levels are not sufficient to cause damage or operational prcblems even though the pumps are operated in the recirculation zone. These pumps were provided with an orificed miniflow line back to their respective suction lines. Based on the low susceptibility to recirculation damage, evaluation of miniflow capacity was not necessary.
J.
Boric Acid Pumos These are 25 hp pumps. They were installed with independent miniflow recircula-tion lines back to their respc etive Boric Acid Storage Tanks. Based on the discussica for the Spent Fuel Cooling Pumps, evaluation of miniflow capacity was not necessary.
ITEM 4 NRC Reauest Within 60 days of the receipt of the Bulletin, provide a written response to the requested information.
BG&E Response The information requested by this item is provided by our response to Items I, 2, 3, 5 and 6, except for the implementation of the following. All actions will be completed by December 31, 1988. Based upon the information provided, justification for continued operation is not necessary.
A.
Containment Sorav Pumos The pump Preventive Maintenance instructions will be modified to reflect the augmented inspection.
B.
Steam-Driven Auxiliary Feedwater Pumos
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The pump Preventive Maintenance instructions will be modified to reflect the augmented inspection.
ATTACHMENT (1)
RESPONSE to NRC BULLETIN 88-04 POTENTIALSAFETY-RELATED PUMP LOSS C.
Saltwater Pumos Vendor recommendations will be finalized and implemented as appropriate and operating instructions will be modified as necessary.
D.
Service Water Pumos Changes to Operating Instructions for maintaining minimum flow will be finalized.
ITEM 5 NRC Reauest Within 30 days of the completion of the long-term actions, provide a written response describing the actions takea.
BG&E Response Not applicable.
ITEM 6 NRC Reauest An evaluation of your actions in response to this Bulletin should be documented and maintained at the plant site for a minimum of two years.
BG&E Response Our evaluation in response to this Bulletin will be documented and maintained at Calvert Cliffs for a minimum period of two years.
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