ML20214J944

Proposed Tech Specs,Reducing Min Flow Rate Requirements for Safety Injection & Centrifugal Charging Pumps.Related Documentation Encl

ML20214J944
Person / Time
Site:	Sequoyah
Issue date:	08/08/1986
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20214J938	List: ML20214J934 ML20214J944 ML20214J952
References
NUDOCS 8608150240
Download: ML20214J944 (11)

Text

{{#Wiki_filter:- _ _ . EMERGENCY CORE COOLING SYSTEMS (ECCS) SURVEILLANCE REQUIREMENTS (Continued)

h. By performing a flow balance test during shutdown following completion of modifications to the ECCS subsystem that alter the subsystem flow characteristics and verifying the following flow rates:

1. For safety injection pump lines with a single pump running:

a. The sum of the injection line flow rates, excluding the highest flow rate is greater than or equal to M gpm, and 444-

b. The total pump flow rate is less than or equal to gpm.

2. For centrifugal charging pump lines with a single pump running:

a. The sum of the injection line flow rates, excluding the highest flow rate is greater than or equal to g gpm, and

b. The total pump flow rate is less than or equal to 555 gpm.

3. For all four cold leg injection lines with a single RHR pump running a flow rate greater than or equal to 3976 gpm.

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SEQUOYAH - UNIT 1 3/4 5-8 l l _ _ _ _ _ _ - . , . _ _ - - - u1%

O EMERGENCY CORE COOLING SYSTEMS SURVEILLANCE REQUIREMENTS (Continued)

h. By performing a flow balance test during shutdown following completion of . modifications to the ECCS suosystem that alter the subsystem flow characteristics and verifying the following flow rates:

1. For safety injection pump lines with a single pump running:

a. The sum of the injection line flow rates, excluding the highest flow rate is greater than or equal to 464:gpm, and Mt

b. The total pump flow rate is less than or equal to 4kd[gpm.

2. For centrifugal charging pump lines with a single pump running:

a. The sum of the injection line ' low rates, excluding the righest flow rate is greater than or equal to 4>hv gpm, and J/6

b. The total pump flow rate is less than or equal to 555 gpm.

3. For all four cold leg injection lines with a single RHR pump running a ficw rate greater than or equal to 3976 gpm.

! SEQUOYAH - UNIT 2 3/4 5-8 i . XW -l , 8 + ~ . zdkl;

ENCLOSURE 2 Proposed Technical Specification Change SEQUOYAH NUCLEAR PLANT Docket Nos. 50-327, -328 (TVA SQN TS 73) Description and Justification for Proposed Changes to Flow Rate Requirements For ECCS Pumps i i 1 uk ;

 ,     #. .                                            ENCLOSURE 2 5,

Stradard Practice Page 5 SQA30 Rev. 2 ATTACHMENT 1 SEOUOYAH NUCLEAR PLANT UNIT 1 AND 2 PROPOSED APPENDIX A OR B TECHNICAL SPECIFICATION CHANGE NO. 127 Description of Change (Use additicnal pages as necessary) This change will revise (ECCS) flowrate values as follows: Reduce the flowrate value in Surveillance Requirement (SR) 4.5.2.h.1.a to 444gpm; Increase the flowrate value in SR 4.5.2.h.1.b to 675gpm; and Reduce the flowrate value in SR 4.5.2.h.2.a to 316gpm. For resultant SR 4.5.2.h, see attached marked-up pages. Reason for Change (Use additional pages as necessary) The requested change in flowrate values for these Sks will update requirements to reflect actual system capabilities and the assumptions used in the current safety analysis. See attached pages for additional details. Justification for Chang (Use additional pages as necessary) Westinghouse analysis has evaluated that operation within the proposed limits meets all applicable 10CFR50.46 limits. APPROVED: 2 7 Plant Operations Review Committee JUL 0 81986 Date O'R. Ot h < - 7/slac, Plant Manager iDalte ff $ll Wh//)V l b Site Director ' 'Date N l g Radiological Health Staff (Radiological)1 Date

                                                  ^>/A Assistant Manager of Natural Resources'                                Date (Environmental) l NOTE: All changes made to the above proposal shall be coordinated with the original signers.

1 As required. 1 _k

Attachment , Reason for Change (continued) Full flow testing of the safety injection pumps (SIPS) and centrifugal charging pumps (CCPs) performed each refueling outage (in response to Westinghouse Technical Bulletin NSD-TB-80-ll) indicated deficient pump performance when compared to Technical Specification SR 4.5.2 requirements and/or the FSAR minimum pump performance curves. Westinghouse, at the request of Sequoyah Nuclear Plant (SQN), performed an Appendix K analysis utilizing reduced pump flows with the current system hydraulics; the analysis yielded acceptable results. Revised minimum emergency core cooling , system (ECCS) performance curves and ECCS Technical Specification SRs were provided to reflect assumptions used in the new safety analysis. The requested change to SR 4.5.2.h.l.a and SR 4.5.2.h.2.a incorporates the revised surveillance requirements provided by Westinghouse letter, reference 1. A subsequent evaluation of this analysis was performed to assess the effect of increasing the assumed reactor coolant pump seal injection flowrate. The results of the evaluation did not affect the previous analysis, and the same proposed ECCS technical specification revision was attached to the resulting Westinghouse letter, reference 2. l Additionally, SQN requested Westinghouse to evaluate the current SR value for maximum SIP flowrate to determine the available margin to pump runout. The Westinghouse Pump Group, in coordination with the pump manufacturer, Pacific Pump, determined acceptable tested pump performance had been achieved at a test point of 675gpm. Accordingly, the requested change to SR 4.5.2.h.l.b incorporates the revised surveillance requirement transmitted by Westinghouse letter, reference 3. n: ~

                                                                                                                               's s Apparent CCP and SIP performance deficiencies, relative to certified vendor performance and/or trending pump degradation, have in the past resulted in difficulty in meeting the FSAR minimum performance curves and/or the technical specification requirements for maximum allowable pump flow (pump runout protection) and minirsum injection flow (sum of three lowest branch injection lines). The maximum and minimum limits define an allowable band of acceptable system performance which must be satisfied for either the A-                                            ,

or B-train pump supplying a common injection path. Any differences in A- and P-train pump performance exacerbate difficulty in balancing, resulting in the weaker pump being left at the lower end of the band in order to keep the stronger train below the .naximum allowable flowrate. Relaxation of the band boundaries (upper or lower) without compromising nuclear safety, provides greater flexibility for balancing, greater margin for performance degradation, and more realistically reflects actual system capabilities and performance constraints. In summary, the requested changes to SR 4.5.2.h.1.a and SR 4.5.2.h.2.a will update the technical specifications to reflect the assumptions used in the latest safety analysis. The reduced minimum flow requirements are necessary to accommodate actual pump and system hydraulic performance and provide adequate margin for performance degradation. i i l t,b ak i

Justification for Change (continued) A nuclear safety evaluation has been performed by Westinghouse to evaluate the impact of reduced pump flowrates on the large break and small break LOCA analyses (see reference 1). For large break LOCA's, Westinghouse evaluated that the reduced safety injection flow could be accommodated within the existing analysis due to built-in conservatism. This is due to the relatively low importance of these pump's injected flow during the blowdown phase of large break LOCA's. For the small break LOCA analysis, the effect of reduced safety injection flow was to be evaluated for 4, 6, and 8-inch breaks. Existing LOCA FSAR analysis indicated the 6 and 8-inch breaks resulted in more than 400 F higher calculated PCT; therefore, only the 6 and 8-inch breaks were further evaluated as limiting cases. This evaluation consisted of using a correlation developed by a sensitivity study performed as a part of and documented by Westinghouse WCAP-9600, " Report on Small Break Accident for Westinghouse NSSS System." This study showed that for each percentage reduction of safety injection flow that the calcalated peak clad temperatuer increased approximately 15 F. For the case of SQN, an additional i 5-degrees per percent reduction in flow was added for conservatism due to the presence of the upper head injection system. This results in e factor of 20 F per percentage SI flow reduction. TVA asked Westinghouse to analyze the effects of a 10-percent reduction in SI flow in order to bound j the current situation. The results of the evaluation identified the 6-inch l l s .,

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                                                -4 break as the most limiting, yielding a maximum 200*F increase in PCT resulting from the reduced injected flow. This increase would still result in PCTs well below the 2200*F 10CFR$0.46 limit since existing calculated PCTs were less than 1500*F for all SQN small breaks. See reference 1 for Westinghouse nuclear safety evaluation check list and additional details.

Westinghouse review of the safety injection system and applicable SIP pump curves, supported by conference with Pacific Pumps, confirmed adequate NPSH is available to operate beyond the current 660gpm technical specification limit. Acceptable test data was available to 675 gps. The actual requirements are not expected to be as conservative as represented beyond 675gpm by the NPSH required curve, however, Pacific Pump would not authorize operation beyond 675gpm due to lack of test data. See reference 3 for additional details. The requested change to SR 4.5.2.h.1.b will increase the maximum allowable SIP flowrate to more accurately reflect actual pump limitations. By i increasing the maximum ellowable flowrate, the acceptable operational band is widened, thereby allowing the SIPS to be balanced at an overall higher level. This can result in increased available SI flow and increased available margin for degradation. I I

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References

1. Westinghouse letter TVA-84-057 with attachments from R. S. Howard to J. A. Raulston dated March 16, 1984 (copy attached).

2. Westinghouse letter TVA-86-671 from L. L. Williams to J. A. Raulston dated June 27, 1986 (copy attached).

3. Westinghouse letter TVA-86-510 with attachments from L. L. Williams to C. C. Mason dated January 16, 1986 (copy attached).

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C 2:x 27N mi<ania 15230-2728 gyg.iC ccpy CF THIS Lli iER c-' g; T'~' *' " gb TVA-84-057 W*~ rch 16, 1984 Mr. John A. Raulston, Chief Nuclear Engineer = , Tennessee Valley Authority rn 400 West Summit Hill Drive c, W10C126 c4 ,; . . Knoxville, Tennessee 37902 --:-

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Dear Mr. Raulston:

ca Attached for TVA's information and use is an evaluation of the "

           /-                                Sequoyah Unit II Centrifugal Charging Pump (CCP) and Intermediate High

_ Head Safety Injection Pumps Test Data. Westinghouse performed this 3 ,- -

 .                                           evaluation at the request of TVA.                                                                                                                             4T5 The Appendix K Analysis was performed and found acceptable using the If the system hydraulics is changed, (such as a repositioning of the reduced                       pump              flows                                and ofsystem                                                          '"* o wco branch line throttle                valves)        an evaluation                               the system hydraulicsperformance wil establishe                              '

be needed to determine the effect to the Appendix K. Analysis. ,, l The CCP mini-flow path was analyzed as being open during the fl uay 7 h4 injection phase. Note,thecomponentcoolingwater(CCW)tosealwaterb wi"r 4fE heat exchanger must be assured. The CCW is to be supplied, assuming a -i$ single active failure in the CCW system. .s. iTae , IfTVAhasanyquestionsconcerningthisevaluation,Pleasecontact1* -l us. .c, t (,Pe v s, i:g.x E Very truly yours, ,' E' Ws Tacincc< , l 'N WESTINGHOUSE ELECTRIC CORPORATION

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                          -J. A. Raulston                                       March 16, 1984 cc:    J. A. Raulston IL, 1A J. A. Coffey 11, IA C. C. Mason IL, 1A R. E. Alsup IL, IA R. U. Mathieson IL, IA S. A. Moser IL, TA 1 /lJAR:CJS:JLA - 5/3/84 C

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                           *Per telecon between your Gary Terpstra and our Jeff Schermerhorn, we understand that this evaluation, including accumulation of additional pump head capacity data, is being handled by NUC PR. We have noted several editorial comments on this evaluation as shown on the marked copy.

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