ML20198H751
| ML20198H751 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 01/05/1998 |
| From: | Roche M GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 6730-97-2295, GL-97-04, GL-97-4, NUDOCS 9801130387 | |
| Download: ML20198H751 (8) | |
Text
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j GPU Nucleef !ac.
(
U s Route #9 south NUN Ior$e[$v*e N MUl@88 Tel 609 9714030 January 5,1998 6730-97-2295 U. S. Nuclear Regulaiory Commission Attn: Documem Control Desk Washington DC 20555
Dear Sir:
Subject:
Oyster Creek Nuclear Generating Station Docket No. 50 219 Generic Letter 97-04; 90 Day Response On October 7,1997, the NRC issued Generic Letter 97-04, " Assurance of Sufficient Net Positive Suction IIcad for Emergency Core Cooling and Containment lleat Removal Pumps". This Generic Letter contained both a 30 day and a 90 day required written response. Attachment I to this cover letter provides the requisite 90 day response for the Oyster Creek Nuclear Generating Station.
If any additional information or assistance is required, please contact Mr. John Rogers of my staff at 609.971.4893.
Very tmly yours, h
h 4
Michael D. Roche Vice President and Director 7
Oyster Creek Ao%g i
MBR/JJR Attachment cc:
Administrator, Region 1 NRC Project Manager
- Senior Resident inspector
{ l" g
t Sworn to and subscribed before me this 6S day of January 1998.
LD N [
My commission expires:
b'Ivm30 A Notary Public of NJ 9001130387 990105 i
PDR ADOCK 05000219 P
ATTACHMENT I
References:
1.
Generic Letter 97-04, " Assurance of Sufficient Net Positive Suction Head j
for Emergency Core Cooling and Containment Heat Removal Pumps",
{
date 10n/97 2.
C-1302 212 E610101, Rev. O " Documentation of Core Spray Available NPSH following DBA LOCA" 3.
FDSAR Amendment 68, Section 3.1 " Safety Guide No.1" 4.
Oyster Creek Nuclear Generating Station Inspection Report 50 219/89 80; Response to Notice of Violation and Deviations.
5.
_ NRC Bulletin 96-03, Potential Plugging of Emergency Core Cooling Suction Strainers by Debris in Boiling Water Reactors" Oyster Creek is a BWR2 with a Mark I containment. The drywell and wetwell (suppression chamber) are pressurized to approximately 15.9 psia during normal
' operation. The plant is provided with two sets ofindependent containment and core spray systems. Three suction strainers supply a common ring header (depicted below)
. that services the containment and core spray pumps.
Ring Header NZoln N7Dic DIU N7Di A -
l f
w e
es i.
- e-cs 13a4 cs12 *
/
1
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X68A; X68B, X69 Current Suction Strainers LNZ01 A/B/C/D... - Cere Spray Pumps CSI 1/2/3/4-Containment Spray Pumps i
6730-97-2295 Page 2 Containment Spray The containment sprey pumps are divided between two systems. Refer to the figure below for a schematic diagram of a single system configuration. Each system is initially aligned to cool the suppression pool. The control room operators manually start the pumps in accordance with the Emergency Operating Procedures (EOPs).
NC To Drywell Atenosphere NC p
To Wetwell Atniosphere X
To suppresolon Pool NO From Suppression Pool Heat Eschenger p, p
'W Dv
\\
From Suppressnan Pool Heat Eschenger p,p Y'
l'
. 4-Contelament Qrey System Arrangement (Oue of Tm o)
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6730-97-2295 Page 3 Core Spray The Core Spray System contains two completely independent systems each containing two sets of pumps, one pump can supply 100% rated flow for the system. For the purposes of meeting 10 CFR 50 Appendix K analyses, two main pumps and one booster pump are required. Either low-low reactor water level or high drywell pressure simultaneously actuates both loops.
1' NC l
-+
To RPV NC To Suppression Pool NC
- (
e From Suppression Pool J
Booster Pump p,,p
-o O
From Suppression Pool Booster Pump l' ump m
A
\\/
V Core Spray System Arrangement (One of Two) 1 m
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6730-97-2295 Page 4 The following is the GPU Nuclear response to GL97-04. When evaluating NPSH for the aforementioned pumps, the system configuiations and operator actions were included in the analysis.
1.
Specify the general methodology used to calculate the head loss asscciated with the ECCS suction strainw.
The ECCS suction head loss was calculated based upon pressure drop relationships associated with the piping, fittings, and suction strainers currently installed in the Oyster Creek Nuclear Generating station. The losses were calculated for each of the individual core spray pumps. The containment spray pump NPSH is bounded by the core spray pump NPSh. The losses associated with the containment spray system were less than that for the core spray pumps.
Therefore, the available NPSH is greater than that for the core spray system.
Additionally, as is evident from the table which follows, the required NPSH was several feet less than that for the core spray pumps. As a result, the containment k
spray pumps were not specifically evaluated for any change to the conditions
-4 associated with the NPSH evaluations. However, their flow rate is included when evaluating the core spray head loss. This is required since the core and m
"5 containment spray pumps share common suction stramers and header piping as depicted previously. Similarly, the booster pump NPSH is not specifically evaluated. These pumps are always run in conjunction with the main core spray pumps. As a result, the suction head of these pumps (>200R) exceed that r. quired for adequate NPSH (24R). They are, however, considered to operate as part of the NPSH evaluation of the core spray main pumps since they automatically start and cause the main pumps to operate at higher flows.
The NPSH of the pumps was evaluated as the ditTerence between that available and that required by the pump.
NPSH = NPSHAvdaN. - NPSHa,quir,a The NPSHava u. was calculated using the following relationship.
NPSH,,,a = h,, + h,,
.%, - h,,
- ~
6730-97 2295 Attachment i Page 5 h is the atmospheric pressure above the surface of the suppression pool that provides the source of fluid to the pumps under evaluation.. When evaluating tha NPSH for,: ore spray and containment spray pumps this value was assumed to be 14.7 psia. This corresponded to zero containment over pressure and was less than both the normal operating pressure (15.9 psia) as well as the ;ntainment spray pump trip set-point (15.3 psia).
- h. is the static fluid pressure associated with the pumps. It represented the pressure associated with the weight of water above the inlet to the pump. It was calculated based upon an initial suppression pool level that corresponded to the minimum LCO volume for Oyster Creek (82,000ff) and the maximum pool temperature (95*F). The NPSH analysis evaluated suppression pool level and temperature as a function of time.
h,,,,,, is the saturation pressure of the suppression pool fluid that provioes suction flow to the core and containment spray systems. The vapor pressure was calculated based upon a conservative assessment of the suppression pool heatup, he, is the head loss associated with the flow through the system. The head loss calculation was an evaluation of the piping length, geometry and fittings that in:lude the existing suction strainers. The frictional factors, geornetry and fitting loss coeflicients were established using standard engineering methods.
2.
- identify the required NPSH and the available NPSH, The required NPSH was based upon the pump manufacturers NPSH curves provided for the pump type installed at the site.
NPSH Required comment Pumps Flow NPSHR NPSHA Main Core Spray 5000gpm 19.98R Refer to tables provided (NZ01 A,H,C,D) below.
4200gpm 16.68fl Refer to tables provided below.
Booster Core Spray 5000gpm 24.00R in excess of 200R as (NZO3 A,B,C,D) discussed above in item 1.
4200gpm 21.00R In excess of 200ft as discussed above in item 1.
Containment Spray 3500gpm
?2.50R Not specifically evaluated (CS 1-1/2/3/4) as discussed in item 1.
r t
6730 97-2295 Page 6 The available NPSH was calculated for each pump based upon the total strainer flow (ring header plant) and the specific piping configuration for the individual pumps.
The static head associated with the calculation was based upon the minimum LCO suppression pool levd. Containment over pressure was not currently assumed..
The puol level is compared with the pump NPSH datum, which is located at the pump suctica inlet centerline.
For the large break LOC A evaluation with the feilure of a diesel to start, the available NPSH for the limiting core spray pumps (main pumps) is provided in the following table (Reference 2).
NPSilAvailable Flow NPSHA (minimum)
Pump NZO1B 5000 gpm 20.048 R NZOIC 4200 gpm 21.412 R For the large break LOCA evaluation with the failure of a primary core spray pump (NZ01 A) the available NPSH is provided for the limitir:3 pumps in the following table (Reference 2).
NPSilAvullable Pump Flow NPSHA (minimum)
NZolB 5000 gpm 22.955 A NZOIC 5000 gpma 20.016 R NZOIC 4200 gpm.a 24.318 A 3.
Specify whether the current design-basis NPSel analysis differs from the most recent analysis reviewed and approved by the NRC for which a safety evaluation was issued.
The current design basis NPSH analysis was performed to address the concerns det-iled in 10 CFR 50, Appendix K. It was reviewed and approved by the staff and is centained in the Oyster Creek FSAR. To address concerns associated with pump run-out flows a new calculation, which is more conservative than that most recently reviewed by the NRC (Reference 3 and 4), has been performed. The change to a more conservative analysis was done to ensure that the run-out pump conditions would not result in pump cavitation. Finally, to bound all measured heat sink temperatures, a cooling water temperature of 95*F was assumed..
A separate submittal associeted with the close out orNRC Bulletin 96 03 (reference 3) for the new suction strainers to be installed ha the next refheling omage is being prepar ed and will request credit ror containment overpressure.
Mininem NPsH st 23 minutes. Operator action to trip booster pump is required by the EoPs.
AAer operator action to tr:p booster purnp as rcr EOPs, 1
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6730-97-2295 Page 7 1
4.
Specify whether containment overpressure (i.e., containment pressure above the vapor pressure of t6.esump or suppression pool fluid) was credited in the calculation of available NPSil. Specify (Se amount of overprewure needed and the minimum overpressure available.
The current NPSIDv Jysis does not take credit for containment over pressure.
Ilowever, a separate submittal associated with the close out of NRC Bulletin 96-03 (reference 5) for the new suction strainers to be installed in the next refueling outage is being prepared and will request credit for containment overpressure.
5.
When containment overpressure is credited in the calculation of availaide NPSil, confirm that an appropriate containment pressure analysis was done to establish the minimuin containment p.mure.
As indicated in the response to question 4, the current NPSH analysis does not take credit for containment over pressure.
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