ML20198C766
| ML20198C766 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/02/1998 |
| From: | Rainsberry J SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-97-04, GL-97-4, NUDOCS 9801080052 | |
| Download: ML20198C766 (8) | |
Text
.
,,m,,, m uou,em EDISON taf;27a-,,
An If)h0N f %)f h41ipsif a negen, January 2, 1998 U.S. Nuclear Regulatory Commission Attn Document Centrol Desk Washington, D.C.
30555-0001
Subject:
NRC Generic Letter 97-04: Assurance of Sufficient Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal Pumps San Onofre Nuclear Generating Station Units 2 and 3 Gentlement 1his letter provides, as 6n enclosure, the information requested in Generic Letter (GL)97-04. Current information for San Onofre Units 2 and 3 is provided which confirms the adequacy of the net positive suction head (NPSH) available for emergency core cooling (including decay heat removal) and containment heat removal pumps. This information is based on a review of the current San Onofre Units 2 and 3 design-basis analyses used to determine the available NPSH for these pumps, if you have any questions or would like additional information on this subject, please let me know.
Very truly yours, M
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before me, A 4s a _d h1 h >M 1U personally h
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personally known to me to be the person whose name is subscribed to the within instrument and acknowledged to me that he executed the same in his authorized capacity, and that by his signature on the instrument the person, or the entity upon behalf of which the person acted, executed the instrument.
WITNESS niy hand and of ficial seal.
1 nuwcesunummt commmane usuin Nctyy Metc-Casume I
sanomeocower Signature Ax *cM J Mi 44t C
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Enclosure cc:
E. W. Merschoff, Regional Administrator, NRC Region IV K. E. Perkins, Jr., Director, Walnut Creek field Office, NRC Reginn IV J. A. Sloan, NRC Senior Resident inspector, San Onofre Units 2 & 3 M. B. Fields, NRC Project Manager, San Onofre Units 2 and 3
Response to Generic Letter 97-04 Southern California Edison San Onofre Nuclear-Generating Station, Units 2 and 3 INTRODUCTION 1k In response to the NRC request in Generic Letter 97-04, " Assurance of Sufficient Net Positive Suction llead for Emergency Core Cooling and
- tainment Heat Removal Pump 3," Southern California Edison (SCE) has revicwed sne cur" w San Onofre Units 2 and 3 design-basis analyses used to determine
+ne avails e net ;'aittive section head (NPSH) for the emergency core cooling (including cure spray (CS) and decay heat removal) and containment heat B
removal pumps that meet either of the following criteria:
(1) pumps that take suction from the containmer sump or suppression pool fcilowing a design-basis loss of coola,.t accident (LOCA) or secondary line break, or; g
f (2) pumps used in " piggyback" operation that are nacessary for recirculation cooling of the reactor core and containment (that is, pumps that are supplied by pumps which take auction directly from the sump or suppression pool).
hE00ESTED INF0E",'Il0fl Based on the above review, the respense to the NRC specific information requests are provided below.
For the purposes of this resnonse, the ten ' Emergency Ccre Cooling System (ECCS) Pumps" includes the Low Pressure Safety Injection (LPSI), High Pressure Safety injection (HPSI), and Containment Spray Pumps.
These pumps meet criterion (1) above since they all take a suction from the containment sump.
Units 2 and 3 do not have any pumps that meet criterion (2) abovs Note; Since Unit I s no longer operating and has no fuel in the core, Generic Letter 97-04 does net apply.
1.0
. Specify the general methodolog; ased so calculate the head loss associated with the ECCS suction strainers.
Response
In general, the methodology used to determine the ECCS system head losses is based on the analysis methodologies in Crane Paper 410 s
(
Reference:
" Flow of Fluids through valves, fittings, and pipe,"
}
Technical Paper No. 410, publishcd by Crane Company) and testing of the ECCS sump configuratio').
San Onofre Units 2 and 3 ECCS Pumps, with 24 inch containment sump suction lines, do not contain in-line strainers (
Reference:
Updated
}
Final Safety Analysis Report (UFSAR), Section 6.2, Figures 6.2-52,
}
Sheets 1-4).
Debris is prevented from entering the sump and intakes by J
a trash rack and screens with an internal grating around the suction pipe that suppresses the formation of vortexes.
To meet the requirements of Regulatory Guide 1.79 and to ensure that this containment sump configuration would fully satisfy any demands put on it by the worst case LOCA, San Onofre contracted with Western Canada j!
Hydraulic Laboratories LTD to complete model studies, which included testing, on the containment sump design. The first study was repeated i
i at a later date to determine the limiting worst case level for the containment sump (20.5 feet minimum sump level (original worst case) to 18.9 feet minimum sump level (current worst case)).
The purpose of the tests was to determine the adequacy of design during a transient, trom these tests it was concluded that the containment sump design was adequate and could support a 50 percent blockage of the screens and a minimum suction pipe coverage of 4.2 feet above the intcke centerline I
at the design flow of 3900 g.p.m.
The design bcsis analysis of the head loss attributed to the suction piping and 4ts components was completed in 1979 and revised in 1984.
This ar.alysis calculated the head loss based upon the methodologies defined and developed in Crane Paper 410 utiliziag Darcy's formula and Bernoulli's thec-em ano equation.
2.0 Identify the required NPSH and the available NPSH.
Pesponse:
Required and available NPSHs for each pump are listed in Table 1 below.
This table shows the values for the pump; in their most limiting mode.
of operation, which is during recirculation with each pump at its runout limit.
Table 1 Required and Available NPSH Pump Flowrate NPSH NPSH Margin (9.p.m.)
Req.(ft.)
Avail.(ft.)
(ft. L HPSI 1000 23.0 24.9 1.9 LPSI m 5500 23.0 25.3 2.3 Contain.
2500 13.0 74.5 11.5 Spray l
The NPSn required is from pump manufacturer test curves, and the NPSH available is from calculations M12.10 and N-0024-006.
(1) The LPSI pump data is provided for completeness to be consistent with responses to NRC question 212.133.
However, a LPSI p' imp is not required to operate during recirculation.
3.0 Specify whether the current design-basis NPSH analysis differs from the most recent analysis reviewed and approved by the NRC for which a safety evaluation was issued.
Response
The current design basis is consistent with the methodology approved in the Safety Evaluatien Repert (SER).
Howev
, some of the specific data l
has been revised since the SER was issued discussed below.
The current design-basis NPSH analysis is calculation M12.1D,-Rev. 1-(issued May 1984).
The NPSH values from M12.10 are compared to the values in the NRC SER in the following discussion.
l-The history of the significant changes is the'following:
'The NRC SER, as required by NUREG-0712, was issued in February 1979.
The only written NPSH reference for -he ECCS pumps is in 3ection 6.2 of the SER, wherein the following statement is made: "The applicants' results show that the available NPSH for the containment 3 pray pumps in the injaction and recirculation modes are 36.5-and 26 feet, L
i
/
i
+
.respectively. The required NP3H for a spray pur.ip is 24 feet." These values appear in the response to Question 212.133 dated May 1978 as it appears-in Amendment 9 of the final Safety Analysis Report (FSAR) as shown in Table 2 below.
Table 2 FSAR Amendment 9 Data Pump Flow, ate NPSH NPSH. Avail.(ft.)
Margin (ft.)
(g.p.m.)
Req.(ft.)
SI Recirc.
SI Recirc.
HPSI 850 20.0 36.4 28.0 16.4 8.0 LPSI 5000 25.5 38,0 27.5 12.5 2.0 Contain.
2200 24.0 36.5 26.0 12.5 2.0 Spray The NPSH, was revised in FSAR Amendment 14 to the as built test values for the pumps, i.e., the NPSH for CS pumps is now 13 feet versus 24 feet as stated in the SER.
These revised NPSH, values are substantiated in the ECCS pump curves provided in figures 6.2-47 through 50 and 6.3-7 through 16 of the Updated FSAR, which were taken from the manufacturer's certified test curves.
The response to Q&R question 212.133 was revised in FSAR Amendment 14, which was issued in February 1979, as shown in Table 3.
Table 3 FSAR Amendment 14 Data Pump Flowrate NPSH NPSHAvail.(ft.)
Margin (ft.)
(g.p.m.)
Req.(ft.)
SI Recirc.
SI Recirc.
HPSI 850 19.0 35.7 28.3 16.7 9.3 LPSI 5000 23.0 38.1 28.6 15.1 5.6 Contain.
2200 13.0 36.4 27.1 23.4 14.1 Spray
- I l
____---__-______--___-_-____--_______-_A
Calculation M12.10, Revisior 1, issued in May 1984, incorporates runout flows versus design flows, and the results are shot.n in Table 4 below.
Table 4 a ta Including Runout flows Current Design a
Pump Flowrate NPSH NPSH Margin (g.p.m.)
Req.(ft.)
Avail.(ft.)
(ft.)
HPSI 1000 23.0 26.5 3.5 LPSI 5500 23.0 26.9 3.9 fontain.
2500 13.0 26.1 13.1 Spray M12.1D assumes a containment sump level of 26.5 feet plant elevation.
The post recirculation. tuation signal (RAS) containment inventory was revised in 199a in calculation N-0024-006 to 18.9 feet plant elevation.
This difference in plant elevation has been corrected for in the requirements presented in the response to qu stion 2.
As ncted in the response to question 1, the Western Canada sump hydraulic model was re-evaluated in resporse to this level change and was found to be-acceptable at the required flow rate.
4.0 Specify whether containment overpressure (i.e., containment pres,
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.
Rasponse:
No credit was taken in the design-basis calculation for overpressure above the saturated liquid pressure.
The guidance in Regulatory Guide 1.1 was used in calculation M12.1D as a design basis requirement.
. _ =.
_ E.
5.0, When containment overpressure is credited in the calculation of available NPSH, confirm that an appropriate containment pressure analysis was done. to establish the minimum containment pressure.
Response
Cont 31nment overpressure is not credited in the calculation of available NPSH, therefore, no confirmatory containment pressure analysis is applicable to the ECCS NPSH design basis.
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