ML18065B139
| ML18065B139 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 01/05/1998 |
| From: | Thomas J. Palmisano CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-97-04, GL-97-4, NUDOCS 9801140203 | |
| Download: ML18065B139 (10) | |
Text
A CMS Energy Company January 5, 1998 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert. Ml 49043 DOCKET 50-255 - LICENSE DPR PALISADES PLANT Tel: 616 764 2296 Fax: 616 764 2425 11Joma* J. Palml1111ao Site Vice President 90-DAY RESPONSE - GENERIC LEITER 97-04, "ASSURANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS" Generic Letter (GL) 97-04, "Assurance of Sufficient Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal Pumps", issued October 7, 1997, requests that licensees provide certain information for their facilities. This information concerns the design-basis analyses used to determine available net positive suction head (NPSH) for emergency core cooling system (ECCS) and containment spray system (CSS) pumps.
This letter provides the requested information in the attachment.
SUMMARY
OF COMMITMENTS This letter contains no new commitments and*no revisions to existing commitments.
Thomas J. Palmisano Site Vice Presiderif -
CC Administrator, Region Ill, USNRC Project Manager, NRR, USNRC NRC Resident Inspector - Palisades Attachment
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CONSUMERS ENERGY COMPANY To the best of my knowledge, the contents of this 90-day response to Generic Letter 97-04, are truthful and complete.
By~~
Th~JOPalmisano Site Vice President Sworn and subscribed to before me this
~-flt. day of ~
1998
~~~
Mary Ann Engle, Notary Public Berrien County, Michigan (Acting in Van Buren County, Michigan)
My commission expires February 16, 2000
[SEAL]
ATTACHMENT _
CONSUMERS ENERGY COMPANY PALISADES PLANT DOCKET 50-255 90-DAY RESPONSE - GENERIC LETTER 97-04 "ASSURANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS" 7 Pages
90-DAY RESPONSE - GENERIC LETTER 97-04 "ASSURANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS" INTRODUCTION Generic Letter (GL) 97-04, "Assurance of Sufficient Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal Pumps", requests that licensees provide the information outlined below for their facilities. Specifically, the licensees are requested to review the current design-basis analyses used to determine available net positive suction head (NPSH) for emergency core cooling system (ECCS) and containment spray system (CSS) pumps that meet one of the following criteria:
- 1.
pumps that take suction from the containment sump following a design-basis LOCA or secondary line break, or
- 2.
pumps that are supplied by pumps which take suction directly from the containment sump (piggybacking).
For Palisades, the high pressure safety injection (HPSI), low pressure safety injection (LPSI), and containment spray (CS) pumps fit the criteria for review.
Following is the information requested for the 90:.day response to GL 97-04:
NRC REQUESTED INFORMATION (1)
Specify the general methodology used to calculate the head loss associated with the ECCS suction strainers.
CONSUMERS ENERGY COMPANY RESPONSE (1). The head loss for the sump screens (i.e. suction strainers) is calculated by the computer program used to evaluate the recirculation mode flow rates at Palisades.
The program uses the Darcy-Weisbach equation for head loss:
where K is the total resistance coefficient for each pipeline in the system. The K value for the pipeline containing the sump screens includes the K value for the sump scre~ns: *The fluid *velocity (v) is calculated from the predicted flow rates:
The K value for the sump screens is calculated using an equation from the "Handbook of Hydraulic Resistance, Coefficients of Local Resistance and of Friction" by I.E.
ldel'chik.
- The sump screen K value is calculated assuming 10% of the open screen area is blocked by debris. The resistance coefficient of each sump screen has a value of 1.0 in the current analysis-of-record.
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90-DAY RESPONSE - GENERIC LETTER 97-04 "ASSU'RANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS" The determination of screen head loss is part of the overall calculation of ECCS and containment spray (CS) net positive suction head (NPSH) margins. This calculation uses the following equation to determine the available NPSH (NPSH.J for each ECCS and CS pump following the initiation of recirculation following a large break loss of coolant accident (LBLOCA):
where:
hA = absolute pressure on containment water surface h5r = static head of water above pump suction elevation hvp = vapor pressure of water @ pump suctions ht= frictional head loss in the suction piping, sump screens, etc.
The current analysis assumes, in accordance with Reg Guide 1.1 and NUREG-0800, that the pressure on the water inside containment equals the vapor pressure of the water at the pump suction, (i.e. these two terms cancel each other). Thus, available NPSH is assumed to be the static head minus the friction losses in the suction piping.
A computer program is used to evaluate a model of the ECCS and CS systems in the various recirculation mode configura~i()ns. The pressure predicted by the model at the pump suction nodes is converted to feet of water and taken to represent the available NPSH for the pumps in each configuration.
Factors incorporated into the model and the analysis include the following:
a)
The containment water level, which determines h5r, is conservatively assumed to be less than the predicted minimum water level following a LBLOCA.
b)
The friction losses between the containment sump and the pump suction inlets account for pipe roughness, the nominal piping lengths, the losses created by the various valves and fittings in the system, and the effect of fluid velocity through the piping. The fluid velocity is determined from the predicted flow rates generated by the computer model.
c)
The current ECCS and CS pump NPSH analysis evaluates the LBLOCA
- scenario.- This is the only FSAR accident that is evaluated for the recirculation mode of ECCS operation. Secondary side pipe breaks and smaller LOCAs a*re not analyzed for ECCS and CS pump NPSH.
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90-DAY RESPONSE - GENERIC LETTER 97-04 "ASSURANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS" NRC REQUESTED INFORMATION (2) Identify the required NPSH and the available NPSH for each pump.
CONSUMERS ENERGY COMPANY RESPONSE (2)
Due to Palisades' ECCS configuration, assumed single failures, and operational lineups, several recirculation mode lineups are analyzed for ECCS pump and CS pump NPSH. The first distinction between lineups involves the assumed single failure. Palisades evaluates two single failures: Failure of Left Channel Safety Injection and Failure of Right Channel Safety Injection. The Left Channel Failure scenario leaves one High Pressure Safety Injection (HPSI) pump, one Low Pressure Safety Injection (LPSI) pump, and one Containment Spray (CS) pump available for mitigating an accident. The Right Channel Failure scenario leaves one HPSI pump, one LPSI pump, and two CS pumps available for mitigating an accident.
The second distinction between lineups involves the various operational configurations of the system following the initiation of recirculation. The cases evaluated include:
a) immediately after recirculation begins (HPSI and CS pumps only) b)
recirculation mode with subcooling (or piggyback operation) in-service c) recirculation mode with subcooling and hot leg injection in-service d) recirculation mode with subcooling and a LPSI pump in-service for sampling In each evaluated case, the operating pumps are predicted to either have sufficient NPSH available (i.e. available NPSH (NPSHJ is predicted to be greater than the required NPSH (NPSHR)) or operate for an acceptably short time period when NPSHA < NPSHR.
(Case 1) Left Channel Failure of Safety Injection Operation of CS Pump P-54A, HPSI Pump P-66A, & 2 spray headers just after the initiation of recirculation.
Pump Flow Rate, gpm NPSHA, ft NPSHR, ft CS Pump P-54A 2400
<19.5 21.0 HPSI Pump P-66A 695
<19.5 20.8 The available NPSH is listed as less than 19.5 feet because the case used for this data assumed a containment water elevation of 595 feet. Using the minimum acceptable water elevation of 593 feet, the available NPSH would 3
90-DAY RESPONSE - GENERIC LETTER 97-04
,;ASSU'RANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS" be approximately 17.5 feet. This mode of operation exists from the time of suction switchover until the operators place the subcooling lineup in service (i.e. several minutes). The CS and HPSI pump manufacturers have approved operation of the pumps in this mode for the required period of time.
(Case 2) Left Channel Failure of Safety Injection Operation of CS Pump P-54A, HPSI Pump P-66A, 1 Spray Header, subcooling in service.
Pump Flow rate, gpm NPSHA, ft NPSHR, ft CS Pump P-54A 2123 18.0 17.2 HPSI Pump P-66A 727 331.8 22.5 This is the design case for Palisades. This is the lineup established quickly after a recirculation actuation signal (RAS) when the operators take manual action to isolate one containment spray header and open the subcooling valve to the HPSI pump.
(Case 3) Left Channel Failure of Safety Injection Operation of CS Pump P-54A, HPSI Pump P-66A, 1 Spray Header, subcooling in service, hot leg injection in service.
The NPSH margins for the hot leg injection with subcooling case.are not explicitly calculated in the current analysis. Because HPSI pump flow is less in this case (z590 gpm) than predicted for Case 2 (above), the NPSH margins will be larger for both pumps.
(Case 4) Left Channel Failure of Safety Injection Operation of CS Pump P-54A, HPSI Pump P-66A, 1 Spray Header, subcooling in service, LPSI Pump P-67A in service for Primary-Coolant System (PCS) sampling.
- -- This case analyzes the lineup when a LPSI pump is used to sample the PCS/Containment water. The LPSI pump flow rate is limited to-2000 gpm.
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90-DAY RESPONSE - GENERIC LETTER 97-04 "ASSURANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS" Pump Flow rate, gpm NPSHA, ft NPSHR, ft CS Pump P-54A 2123 18.3 17.2 HPSI Pump P-66A 726 332.3 22.5 LPSI Pump P-67 A 2000
. 19.0
<10-12 ft.
estimated The NPSHR for the LPSI pump is estimated because a flow rate of 2000 gpm is less than the lowest flow rate on the manufacturer's NPSHR curve.
(Case 5) Right Channel Failure of Safety Injection Operation of CS Pumps P-548 & P-54C, HPSI Pump P-668, & 2 Spray Headers just after the initiation of recirculation.
Pump Flow rate, gpm NPSHA, ft NPSHR, ft CS Pump P-548 1686 17.9 13.2 CS Pump P-54C 1629 17.9 13.2 HPSI Pump P-668 688 17.0 21.6 This is the lineup immediately after RAS, before the operators take manual action to open the subcooling valve for the HPSI pump. This lineup would be in service for only a few minutes. The HPSI pump manufacturer has approved operation of the pump in this mode for the required period of time.
(Case 6) Right Channel Failure of Safety Injection Operation of CS Pumps P-548 & ~-54C, HPSI Pump P-668, 2 Spray Headers, subcooling in service.
Pump.
Flow rate, gpm NPSHA, ft NPSHR, ft
.. _ C~ Pump P-548 1914 17.7 14.7 CS Pump P-54C 1855 17.7 14.7.
HPSI Pump P-668 722 359.0 23.6 5
l fJ 90-DAY RESPONSE - GENERIC LETTER 97-04 "ASSURANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS" This is the design case for Palisades. This is the lineup established after the operators take manual action to open the subcooling valve to the HPSI pump.
(Case 7) Right Channel Failure of Safety Injection Operation of CS Pumps P-548 & P-54C, HPSI Pump P-668, 2 Spray Headers, subcooling in service, hot leg injection in service.
The NPSH margins for the hot leg injection case with subcooling were not explicitly calculated. Because HPSI pump flow is less in this case ( ~ 585 gpm) than predicted for Case 6 (above), the NP$H margins will be larger for the three pumps.
(Case 8) Right Channel Failure of Safety Injection Operation of CS Pumps P-548 & P-54C, HPSI Pump P-668, 2 Spray Headers, subcooling in service, LPSI Pump P-678 in service for PCS sampling.
This case analyzes the lineup when a LPSI pump is used to sample the PCS/Containment water. The LPSI pump flow rate is limited to 2000 gpm.
Pump Flow rate, gpm NPSHA, ft NPSHR, ft CS Pump P-548 1818 17.4 14.7 CS Pump P-54C 1762 17.3 14.6' HPSI Pump P-668 677 358.8 23.6 LPSI Pump P-678 2000 17.4
<10-12 ft.
estimated The NPSHR for the LPSI pump is estimated because a flow rate of 2000 gpm is less than the lowest flow rate on the manufacturer's NPSHR curve.
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90-DAY RESPONSE - GENERIC LETTER 97-04 "ASSURANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS" NRC REQUESTED INFORMATION (3)
Specify whether the current design-basis NPSH *analysis differs from the most recent analysis reviewed and approved by the NRG for which a safety evaluation was issued.
CONSUMERS ENERGY COMPANY RESPONSE (3)
The current NPSH calculation was completed in November 1996. A 10 CFR 50.59 Safety Evaluation was completed in accordance with plant procedures for this analysis with the determination that an unreviewed safety question does not exist. This latest analysis has not been submitted for review and approval by the NRC..
Except for the reviews performed on the original plant design and those system level reviews performed as part of the Systematic Evaluation Program (SEP) for the Palisades Plant, no evidence exists that the NRC documented their reviews of NPSH analyses in an SER. Our reviews of the SER's issued by the NRC for the Palisades Plant support this evidence as no SER specific to ECCS or CSS pump NPSH was
- identified.
NRC REQUESTED INFORMATION (4)
Specify whether containment overpressure (i.e. containment pressure above the vapor pressure of the sump or suppression pool fluid) was credited in the calculation of available NPSH. Specify the amount of overpressure needed and the minimum overpressure available.
CONSUMERSENERGYCOMPANYRESPONSE (4)
Containment overpressure is not credited in the current NPSH analysis. The methodology used in the current analysis assumes the containment pressure is equal
. to the vapor pressure of the pumped fluid. See Consumers Energy Company response to Item 1 for more details.
NRC REQUESTED INFORMATION
. (5). When containment overpressure is crf}difed in the_ calculation of available NPSH, confirm that an appropriate containment pressure analysis was done to establish the minimum containment pressure.
CONSUMERS ENERGY COMPANY RESPONSE (5)
Based on the response to Item 4, a response is not required for this item.
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