ML20204H676
| ML20204H676 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 08/04/1986 |
| From: | Wilson R GENERAL PUBLIC UTILITIES CORP. |
| To: | Zwolinski J Office of Nuclear Reactor Regulation |
| References | |
| 5000-86-0972, 5000-86-972, NUDOCS 8608080175 | |
| Download: ML20204H676 (5) | |
Text
GPU Nuclear NggIgf 100 Interpace Parkway Parsippany, New Jersey 07054 201 263-6500 TELEX 136-482 August 4, 1986 e s Duect Dal Numben 5000-86-0972 Mr. John A. Zwolinski, Director BHR Project Directorate #1 Division of BWR Licensing U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Zwolinski:
Subject:
Oyster Creek Nuclear Generating Station (OCNGS)
Docket No. 50-219 Core Spray NPSH Calculations Supplemental Information In response to your May 5, 1986 letter, GPU Nuclear has reviewed the NPSH calculations for the core spray system pumps for both a small break and design basis LOCA.
For both cases, the calculations have reconfirmed that adequate NPSH margin is available for the expected torus conditions over the full range of pump operation.
For your review we have included Attachment I which answers your specific questions about the calculation assumptions, and also provides the physical characteristics of the suction strainers, temperature monitors, and relief valve quenchers.
If you have any questions during the course of your review, please contact M. Laggart, Manager, BHR Licensing, at (201) 299-2341.
V ry ruly yours, 8608080175 860004 ADOCK0500g9 PDR Vice President Technical Functions RFH/pa cc: Dr. Thomas E. Murley, Administrator Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406 l
NRC Resident Inspector l
Oyster Creek Nuclear Generating Station Forked River, NJ 08731 l
Mr. Jack N. Donohew, Jr.
U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Phillips Building, Mail Stop 314 o\\
Bethesda, MD 20014 0
l GPU Nuc' ear is a part of the General Pubhc Utihties System
)
ATTAC MENT 1 1.
Q.
Discuss the highest torus suppression pool temperature assumed in the Loss-of-Coolant Accident (LOCA) analysis and net positive suction head (NPSH) of the core spray pumps.
The statements made by the licensee are that these pumps would be the first safety pumps which would experience loss of NPSH as the pool temperature rises. Was the initial LOCA pool temperature based on the suppression pool temperature limits in the station Technical Specifications (TS).
The initial temperature should be the most conservative limits allowed by the TS for any extended period of time.
A.
For calculating the NPSH available for the Core Spray Pumps, two conditions were analyzed:
(1) a small break (SB) LOCA with relief valve blowdown; and (2) a Design Basis Accident (DBA) LOCA which assumes a complete circumferential break of a recirculation loop.
Both calculations assumed a maximum torus pool water temperature coincident with maximum pump flow. The results were as follows:
I.
- 1) Max Torus Water Temp 139.9'F
- 2) Torus Pressure at Max Temp 16.2 psia
29.1 ft.
NZO18 20 ft.
28.4 ft.
NZ01C 20 ft.
24.7 ft.
NZ010 20 ft.
29.0 ft.
- 1) Max Torus Water Temp 148.7*F
- 2) Torus Pressure at Max Temp 16.3 psia
- 3) Max Pump Flow 5000 GPM b) Results Pump No.
NPSH Reg'd NPSH Available NZ01A 20 ft.
28.1 ft.
NZ01B 20 ft.
27.4 ft.
NZO1C 20 ft.
23.8 ft.
NZO10 20 ft.
28.0 ft.
I 3388f
The initial torus water temperature assumed for both calculations was 95'F.
This temperature is the OCNGS Limiting Condition for Operation (TS 3.5) for the torus water.
If this temperature is exceeded, except as allowed for testing (105*F), the unit shall be placed in Cold Shutdown within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (TS 3.5.A.7).
2.
Q.
Describe the core spray pump suction header locations in the suppression pool in relation to the relief valve (RV) quenchers, to the suppression pool bulk temperature monitors, and the pool water level.
A.
The locations for the core spray pump suction strainers and RV quenchers are delineated on FSAR Table J.3-3 and attached Figure 1-1.
The five electromatic relief valves (EMRVs) discharge to the torus via two piping systems. For each system, 8-inch discharge Ifnes from the individual valves join in a 14 inch discharge header. The header reduces to 12-inches as it enters the vent pipe to the torus. The 12-inch pipe penetrates the elliptical cap of the vent pipe and teminater, in a two am Y-quencher. The Y-quencher which has numerous small holes is anchored to the bottom of the torus. The two Y-quenchers are located between azimuths 117* and 153*, 207* and 243*.
The suppression pool bulk temperature is monitored by two pairs of themocouples at azimuths 0* and 180*.
For each azimuth location, the themocouples are separated by a vertical distance of 4'-9" with the highest located at site El. (-) 8'-4".
The suppression pool water levels for the minimum and maximum volumes (TS 3.5 A.1.a.,b.) are 143 inches and 155 inches respectively above the Torus bottom (E1.-17'-6").
3.
Q.
Discuss the representativeness of the suppression pool temperature monitors for measuring the temperature at the core spray suction in the pool during RV blowdown.
A.
Two of the four temperature themocouples are located at azimuth 180*
which also corresponds to the location of one of the three suction strainers. The other two temperature monitors are located at azimuth 0* which is centrally located between the two remaining suction strainers. For each azimuth location, the thermocouples are approximately 3' and 8' respectively below the minimum water level.
To detemine the suppression pool bulk water temperature (Procedure 106-Conduct of Operations), an average is calculated from the four themocouple readings.
If the temperature difference between the highest and lowest is greater than 10*F, then the highest temperature is used for the suppression pool bulk water temperature. Since these three suction strainers feed a common header to the core spray pumps, the four themocouples would provide a representative profile of the torus water temperature during a RV blowdown.
4.
Q.
Discuss any assumptions made in the calculation of the temperature at core spray suction in the pool that take credit for pool mixing during RV blowdown to the torus.
3388f J
A.
The assumptions made that support the use of a bulk average temperature at the core spray suction are:
- Two of the three suction strainers are physically separated from the RV Y-quenchers and would provide cooler water for therwal mixing in the suction header.
- The containment spray pumps which take suction from the same header would be recirculating flow to the torus during RV blowdown.
5.
Q.
What is the maximum temperature at the core spray stetion header during RV blowdown in the LOCA, and what are your bases?
A.
RV blowdown occurs during the actuation of the Automatic Depressurization System (ADS) following a SB LOCA.
The maximum temperature assumed in the core spray suction header for this case is equal to the maximum bulk Torus water temperature calculated as the result of a RV blowdown (139.9'F). The basis for this calculation assumed an initial water temperature of 95'F which is the OCNG3 LCO for normal power operation. During the actuation of the ADS, the RV blowdown would be directed to the 2nd (90*-180*) and 3rd (180*-270*)
quadrants of the suppression pool (Figure 1-1).
Since two out of the three suction strainers are located in the first and fourth quadrants, the core spray suction header would receive cooler water from these quadrants to reduce the local temperature effects between the second and third quadrants during the RV blowdown.
6.
Q.
Compare your assumptions in your calculations for NPSH to the Regulatory Fosition in Regulatory Guide 1.1, Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal System Pumps,"
dated November 1970.
A.
The NPSH calculations at maximum pump flow and maximum torus water temperature presented in response 1 A assumed an overpressure in the torus.
In comparison with the Reg. Guide 1.1 guidelines, this overpressure would be omitted and the results would be as follows:
i Pump NPSH NPSH Available No Reg'd SBA DBA NZ01A 20 ft.
25.6 24.5 NZ018 20 ft.
25.0 23.8 NZ01C 20 ft.
21. 3 20.1 NZ010 20 ft.
25.6 24.4 I
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