ML051050063
| ML051050063 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 04/30/2004 |
| From: | Karjala D NRC/RGN-III |
| To: | Chernoff H, Louden P Office of Nuclear Reactor Regulation, NRC/RGN-III |
| References | |
| FOIA/PA-2004-0282 | |
| Download: ML051050063 (9) | |
Text
Harold Cheoff - AFW Pump Operabilty . Page 1 I -
0011, From: "dak2@nrc.gov" <dak2@nrc.gov> (y&V¶) AdC)
To: f9 fPPLL@ NRC.GOV' <p1l @nrc.gov>, "HKC@ NRC.GOV <hkc @nrc.gov>
Date: Fri, Apr 30, 2004 4:11 PM V v ,
Subject:
AFW Pump Operability \ft
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Evaluate the effects of the condition, including potential 1s perform its speci fled safety, or safety support, functionts)
The most limuiting requirement for the MDAFW pump (interms of flowj is to provide 200 gpm to a single SG [See'Note 2]
min following a LONF or a LOAC. The ability to provide this flow is dependent on the following items:
- The pump suction pressure - This is controlled by CST level. The CST minimum level is'based on'Tcch Spec level less tankrdrawdown for 30 ruindies of pump operation at 200 gprm. A lower CST level is used in this evaluation than was used in OPR00004. Lower CST level resulti'in lower flow to the SG.
- The AFNV pump capacity - This is evidenced bythe degree ordegridation from the design pump curve. Ifthe AFWV pump performance is degraded from its design operating conditioris, 'the pump %willprovide less flow for the required TDH to overcome downsteam resistance and baclipressure. The amount of allowable degradation is now specified by the Inservice Testing program (IT-10). This is an issue boib in this OPR and OPR000044.
A_ __ .:__ %ITlMU A ,. .e,. n nl ixvp-it tn limit AFWn flqjTrom a banicular turrzi both for Is the SSC In Its present condition capable of performing its safety or safety support function(s)? Explain basis.
(Use engineering analysis or engincering judgment to determine whelthcr the design function can be provided given the existence of the deficiency. When using engineering judgment, provide supporting inrormation from sources such as field walkdowns, industry expericncc, proven system'component performance under similar service conditions, etc.)
The AIDAFRV pumps in their present condition are capable Of performing (heir safety function.
Analysis or Flow Capability Using Current riant Conditions (prior to uncertainty application):
AFW flow problems can be analyzed using'the Proto-Flo model (Calc 97-114. Rev. 2) Ewith some minor corrections currently
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,lr.t- t'fOPERABILITY RECOMMENDATION FO0RM6 2 i -'
(The information concerning the NISSs is included because of its relerance to OPR000044 The information concerning the turbine - driven pumps is included only because the source documents refer to both typcs orpumps.).
Tech Spec Survcillance Requurcment. -SR 33.6.1 Evaluate thc effccts of the condition, including potential failure modes, on the ability of the SSC to perform its specified safety, or saretytsupport, 'function(s)
The most limiting rcquirement for thc MDATV pump' (in terms of flow) is to provide 200 gpm io a single SG [cSe Note 2]
5 min following a LONF or a LOAC. -Thc ability to provide this flow is dependent on the followving items:
- Thc pump suction pressurc -This is contrbllcd by.CST lcvcl. 'The CST minimum levcl is based on Tcch Spec leveI less Usnk dravdown fnor30 tLnuwtes of pump operation at 200 gpm. A lower CST level is used In this evaluation than Tvas used in OPR00044. Lower CST levcl results in lower flow to the SG.
0 The AFWV pump capacity -- This is evidenced by the degree ofdegradation from the design pump curve. If thc AF1 pumrp perfornunce is degraded from its design opera ing conditions,'the pump "ill provide less fow for thc Tequired TDIH to overcome downstream resistance and backpressure. The'anount of alloi-able degradation is now specified by thc Insernice Tesiing program (IT- I 0). This is an issue both in this OPR arid OPR000044.
- The function bf the MDAFWV pump pressure control valve-is to limit AFW flow fr6m'a particular purnp both for runout and for containment pressurization from a ruptured steam line. This valve whein functioning as designed, limits the MDAFWV pump outlet pressure to 1200 psig. 'The ow associated wiih this pressure is dependent both on the pump suctioti pressure and the amount of pump degradation. This was not an 'issue in OPR000044.
- The rcmainder of the system flow resistance-This is constant and is not an issuc in this OPR and 0PR000044.
- The leakage out orthe sysitcm-This leakege is posruhited to occur through the muin feedwater check valves and is testedby IT 300 & 305. Although the allowable limit is 5 gpm, the current test results show no'lcakage and that will be used in this OPR and OPR000044.
- The SteamicneratorBackpressurc-Thisis a function ofthe decayhcat inpui and the MSSV seteings. 1-lowever, the lowvest Mssv setting (and its reseat pressurc) dominates. Recent plant data have sbown an averagc setting 'of 0SS psig with a iinglc standard deviation of0.8%, of sctpoint. Doubling that number to achieve a 2O value (ror a 95/95 confidencec1l) atid then multiplying by thc standard factoroft.5867 to achieve a 75.'75 confidence level (which is appropriat forithis application) rcsults in a maximum SO backpressure oa 10952 psi5 (1109.9 psia). This back-prcssurc is I psi belo'lhe valut used in OPRQ00044. However, becausc orthe PCVopcration, ihe SG backpressurc is not controlling and the evaluation done in OPR000044 is bounded by this evaluation.
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Point Beach Nuclear Plant N1 MCr i¢4vi27Z'vPERABtilCYRCMEDTO 4 4. FORM ;_'z> t2" Is the SSC In Its present condition capable of performing its safety or safety support function(s)? Explain basis.
(Use engineering analysis or enginCering judgment to deiemrinc whether the design function can be prov ided given the existence of the deficiency, When using engineering judgminct, provide supporting iuiformation 'from sources such as field valkdowns, industry expcricncc, proven systemfcomponrnt performance under similar serv6ice conditions,:etc.)
The MIDAFAV pumps in their present condition are capable of performing their safety function.
Analysis of Flow Capability Using Current Plant Conditions (prior to uncertainty application):
AFWfilow problems can be analyied using theProto-Flo rnodel (CaIc 97-114. Rev. 2) with some minor corrections currently being incorporated. A case was run usinr the current plant conditions (including the allowable AFWV pump degradation per IT-
- 10) to detcrmine the flow to the SGs and to see whether the PCVs vere throttling flow to maintain pressuie. (When the valves are throttling, the PCVs are controlling foi, wheh thiy'are 100% open flow is primarily controlled by the SG backpressure.)
Theconditions bound those describcd in OPRoo0044 including the PCV operation and the lower CST level. The followins inputs were used:
CST lcvel -33.S fet (plant eclvation) Tech Spec level less tani drawdonn for 30 ninutes of pump operation at 200 gpm Pump curves - degraded curves as specified by IT-10 PCV -controlling to a pump discharge pressurc 6r 1200 psig SG backpressure - corresponds to current MSSV setting described earlier The results of this analysis showed that the P38A would proi:ide 19S spm and P38B would provide 192 gpm.
Flow Capabilityincluding Uncertainty Application:
The estimated unccrieinryassociated withtis flow ialu to thie SGs'is -7 gpnu iSce Note 4 for more detil on uncenrtanties uscd in this evalualion]. The estimaied uncertainty associated with the prcssure control valve setting is -18 gpm. Combining these two values of uncenainsy using the standard square root of the sum of the squares of the independent variables Yields -20 gpm. Applying the uncertainties, results in a worst case predicied flows of 178 gpm and 172 gpm, respectively. Although the value of 172 gpm (192 -20 for worst case pump) does not meet the stated design requirement of 200 gpm, the AFV pumps will perform their intended functions for the following reason:
Conservntisms In the determination of the FSAR Requirements (Initiation time)
FSAR Delivery The lirliting License Basis analyses for'the'required delivered flow from AFWV arc the previously mentioned LONF and LOAC transients. In both cascs an analytica3 assumptioniofa 5 ninute delay [Sec Note I) in initiation orAFI horwis made.
As clarified in sections 10.2.'14.10.1.and 14.10.2 of he FSAR (as updated by approved FSAT Change Request FCR 03-042; pcnding incorporation). the 5 minutc dcl3y is an arbitrary one [Sec 1sote l1and is not rcflcctiec ofrthe plant dcsign or response. Both ofthcse events use the CST as a suction source and already incorp)rate single active fail ecs of pumps to start. Therefore, no nanual rc-aligiment of the AFWVsystcm is requircd and thc remaining pump(s) start automatically and deliver their pre-sc flow raie automatically.
Actual Delivery In the casceof a LONF. automatic pump start will occur inmmediately upon receipt oran AFW stars signal beciuse otfishe power is still available. In the more limiting case ofa U)AC, off site power is lost and ilte AF1' pumps sequence on with the EDGs. This occurs in less than one minute from initiation.
'There Is an additional 45 second delay before the minimum recirculation nfow control valvc shuts and all flow is delivered to the S.G. During this period, approximately75 cpm is diverted lrom thelpump disclhrge back to the CST via the recirculation line.
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OMMENDATION FORM ;
Consertalism Tberefore, despite the arbitrarily assumed delay of 5 minutcs used in Ihe analysis, it can be conservatively stated that 100 gpin of flow is delivercd starting at I minute, with -172 gpm delivered at 2 minutes in both the LOAC and LONF cascs.
Operator Action Tinting Considerations' The crmxof this issue ot reduced AFW flow to the SG centers around the conservatively interpreted statement in the FSAR that The AF system shall automatically start and deliver adequate AF system flow to maintain adequate steam gencr'tor levels during accidents which may result in main steam sifey 'ValVe opeujing". Jhiis implies no operator action. It is clear, however, from the Emergency Operating Procedures that iddrcss the'tw6 limiting scenarios, LONXF and LOAC, that one of the earliest steps inthese response procedures is to manually ensure proper AFNN flow to the SG(s). As noted earlier, therc are nctually approximately 4 minutes of additional AF\V pump run time that can be credited because of the design'features of the actuation sequenice. Therefore, the actual lowv (using the additional 4 minutes) totaled over time for a degraded flow would inject the sarne rnass of wvatcr as a flow Initiated later Intime (atftime - 5 minutes) for some time following accident initiation.
Using the time analysis discussed earlier in this recommcndation, rcsults in a flow of-I 00 ppm for I minute followed by a flow of 172 gpm until the operator could takie manual control. This mass is equivalent to thc mass injected for an AFW flow of 200 gpm lasting 22 minutes. This occurs at 27 minutcs from cvcnt Initiation. This time period is more than sufficient for the operator to implement the SG control steps in the response procedures ivhich occurs 2 stcps a fer the verification of immediate actions in EOP 0. 'Reactor Trip or Safety Injection".
Conclusion:
This analysis swas perforned using the current allow'able pump degradation allowed by IT-10 and tierefore the currcnt acceptance criteria it contains supports this OPR.
Therefiore critical plant parameters in this postulated scenirio would be bounded by the FSAR analyses and thus'the'NMDAFW pumpscould be relied onto perform ihcirintended function. Howcver, theyarc not in conformance withSectionl4.110 and Section 14.1. 1lihich state the system provides 200 gpm to the steam generators for a LONF and a LOAC The status is therefore OPERABLE but NONCONFORIMING.
Thecresults of this OPR do not invalidate the conclusions of OPR000044 and bound the conditions evaluated thcrcin.
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'Point Beach Nuclear Plant NMC A '-^ :rOpERABLY RECOMMENDATION 'FORM If the SSC is ot fuly capable (FllQualifcaion)of performing Its safety or safety support function(s), then determine"'f Compensatory Measures are required to maintain OPERABILITY.
(Describe the Compensatory Measures, basis for which the Compensatory Measures maintain OPERABILITY, implementation mechanism (procedure, temp mod, etc.). and under what conditions the Compensatory Measures may be terminated.)
No compensatory measures are required.
Ifthe SSC is not capable'of performing Its safety or safety support function(s), then provide an Aggregate Review of the condition. Identify related Action Requests (CAP numbers).
NA Equipment recommended to be:
o OperableO Operable, But Degraded 0 Nonconforming D Inoperable Engineering Management Approval Required /4lotify Shift Manager immediately Responsible Engineer: t.// -a/ Date: S ~xt:7698 Verifier: C Date: - Ext: 7636 Cognizant Engineering supervisor. Date: JD Ext 7416 Approval Recommendation CognizantlnEiineering Manager. .,
Date: '11//>.5 E NIA Shift Manager Concurrence and Approval: ' ' Gil. ..
Date and Time: t(, {x
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Point Beach Nuclcar Plant NMC 6PERABIL TY.RECOMMENATIONF Identify references used. (Reference Name and Section (s))
- 1. PBNP FSAR 102 (06103), '"Auxiliary Feedwatcr System (Al"
- 2. PBNTP FSAR 14.1.10 (06103), "Loss or Normal Fcedi ater'
- 5. IT 10, Rev. 48, "Test of Elccirically Driven Auxiliary Feed Pumps and Valves (Quarterly)
- 6. CIM000265 BYRONJ, "AFW Pump Pcrrormance Curves"
- 7. IT 300(305), Rcv. 16, "Main Fced Line Chece'Valves Unit 1(2)"
S. TLB 34, Rev. 5, "Condensatc Storage Tank (T-34 AIBr'
- 9. 'STPT 14.11, Rev. 17, "Auxiliary Feed amtef
- 10. Calculation 97-114, Rev 2 "Development of Point Beach Auxiliary rcedwaterSystemProto-lo Hydraulic 10odel" Continuation. (Notes)
This section is being used to providc amplification of some portions of the text.
- 1. The Sminute time delay for initiation of AFW in theanalysis appears to cone from a consideration ortlcfime required to transfer AF`V pump suction to the Ser'ice Water (SW) System following a seismic event. SW suction is
- not th limiting case because thc inlet pressure of SW issmuch greater than that availablc from the CST. It is irrelevant in this evaluation because the CST is the more limniting suction source. Nonetheless, the value remains in the FSAR analyses as a conservatism.
,2. The Westinghouse analyses consider the'split nlow configuration (onc MDAFIVlpump fe'eding two SGs) to be more limiting but this is from an RCS response perspective. For purposes of this evaluation, this is immaterial because the acceptance criteria of the analysis is salisfied in cither case. Both casesues 200 gpm as their acceptance criteria.
Therefore this evaluation focuses on the 200 gp'm flow to the SG because it is more limiting hydraulically.
- 3. The cquivalent mass injection calculation is done by dcfining the timc Ct) that the AFU low is Icss'than200gpm An equation can be developed that equates mass injected in the degraded flow case to the 200 gipm case. The'degraded
'flow case consists of 100 gpm from T- I min to 2 min (T is the time from event initiationj plus the degraded flowriate (Q) multiplied byt. The 200 gpm case consists bf the time (t) that is credited for the degraded condition less the 3 min difference between full flow in the degraded case and the 5 min start time.
.100 + Qt = 200 (i.3) Inserting the value for Q (172 gpm - based on the most limiting pump) and sbliin; for I yields 25 minutes.
Therefore T,,, - I + 2 27 min from event initiation. Thc followSing chart helps show the relaioanship betvccn T and r:
(7)nie from event initiation Degraded F16w.Casc(OPR) Totalized DcsignFlw r(FSARcasc) Totalized p min ' 0 Sgpm O gal 0Oupm Ogal I nimn 100 ypm 0 gal 0 spm Ogal
,2min 172 Epm 00 gal 0 gpm ° gal 3 min 172 gpm 272.gal 0 gpm 0 gal 4 rnin 172 gpm 444 gal Ogpm 0 gal 5 min 172 gpni 616 gal 200 gpm 0 gal 6 min 172 gpm 78S gal 200 spm 200 gal 7 min 172 gpm 960 gal 200 gpm 400 gal 27 mill 172 gpmn 4400 Pal 200 gpm 4400 gal
- 4. There are two contributors to the uncertainty of the AFIv' nfav to hlic SG. The values associated iith these contributors arc determined usine a 75/75 confidence level (which is ar'ronriate for this a1ntiCatitn)l Thu first PntF-S1.'3
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Point Beach Nuclear Plant NMC *~ - ~ A.~3/4 VPERbILTYMECOMMENDATION FORM SSCntiffeeted bi condition: OPROOOI09 The motor-driven auxiliary feedwatzer(MDAFW) pumps P38A and P38B are the SSCs afl'cctcd by this condition. The condition is described in CAP056170. 'IT-10 acceptancc criteria does not cnsure adequatc AFW svithout operatoraction' and followed up with OPR000109. In addition to the condition described below. the motor-driven AFMV pumps are also currently considered operable but nonconforming under OPR060044 and the rclationship between the tvo operability determination/recommeidations will be addressed in this OPR.
Identify the oveireIl scope of the condition that calls OPERABILITY into question.
The condition that calls OPERABILITy into question is the potcntial for AFW flow to the SGs to fall below 200 gpm (the FSAR stated minimum) at certain lCYCs of pump degradation which are currently within the lST acceptance critcria for the NlDAFW pumps. 'This is due to the manner in which thc motor-driven AFW (MDAFW) pump outlet pressure control valves (AF-4012 and AF4019) are set up. This issue does not apply to the turbine-driven pumps because their flow is not controlled by an automatic pressure control valve.
The NIDAFW pump outlet PCVs are set up to maintain a constant prcssure of 1200 psig upstream of the valve (i.e the pump outlet pressure). The outlet pressure oftie AFW pump is equal to the total developed hcad (TDII) of the pump at the flow added to the suction pressure of the pump (as developed by the CST level). The TDH of the pump as a function of flow through the pump is shown on the pump curve. When solving for 1200 psig pump outlet pressure (using the Technical Specification limit far minimum CST level and thc pumip design curve), the pumps wcre able to just produce the required flow.
However, when uncertainty was added and allowable degradation was applied. the pumps could no longer reach their licensing basis flow.
Describe the specified safety, or safety support, function(s) of thc SSC. Identify the Licensing Basis functions and pesforinance requirements, including Technical Specifications, FSAR, NRC Commitments? or other appropriate Information (refercnceSCOPEsection 5.3).
TS 3.7.1 Four MSSVs per stcam gecncrator shall be OPERABLE.
TS SR 3.7.1.1 Vcrify each required ?.ISSV lift setpoint per Tablc 3.7.1-2 iin accordance tith the Inscrvice Testing Program.
Followingtesting, lift settingslall be ithin tt--1%.
TS Table 3.7.1.2 states that the lift setpoint for the lowest 5et iilves is 1035 psig +1-3%.
TS 3.7.5: The AFWV System shall be OPERABLE with; one turbine driven AFW pump system and two motor driven AFW pump systems. Applicability: Modes 1.2, and 3, MODE 4 when steam generator is relied upon for heat removal.
FSAR 10.2 The AF system shall automatically start and dcliver adequate AF system flow to maintain adequate steam generator levels during accidents which tmy result in main steam safcty valve'opening. Such accidents include; LOSS OF NORMAL FEEDWVATER (LONFI), FSAR Chapter 14.1,10, and LOSS OF ALL AC POWERTO THE STATION AUXILIARIES (LOAC), FSAR Chipter 14.1.11. events. LONF and LOAC are time-sensitive to AF system start-up.
FSAR 14.1.10 The auxiliary feedwater'system provides 200 gpm of flow split to two steam generators. S rrinutcs follouing receipt of a low-low steam gencrator wvatcr level setpoint sign'al.
The capacity of thc auxiliary feedwaler system is such that the uatcr level in the steam generaiors does not rcccde below the lowest level at which sufficient heat trtahscr area is available to dissipate core residual heat nwithout uwater relief from the RCS relief or sarety valves.
FSAR 14.1.11 The auxiliary feedwater system insures feedwaicr supply of at least 200 gpm upon loss ofpower to the station au~xiliaries. since the stean turbine driven atxiliary feedwater pump has a capacity of 400 gpm and the motor driven auxiliary feedwatcr pumps have a capacity of 200 gpm each.
1ST ProcramrThe auxiliary fcedwater pumps and MSSVs arc included in the program.
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runout and for containment pressurization from a ruptured steam line. This valve when functioning as designed, limits the MDAFW pump outtet pressure to 1200 psig. The flow associated wiih this pressure is dependent both on the pump suctioni pressure and the amount of pump degradation. This was not an issue in OPR000044.
- The remaindcr of the system flow resistance-This is constant and is not an issue in this OPR and OPROO0044.
- The leakage out of the sysiem- This leakage is postulated to occur through the main feedwater check valves and is tested by IT300 &:305. Althou'sh the alloivable limit is S gpm, the current test results show no leakage and that will be used in this OPR and OPR000044.
- The Steam Gcnerator Backpressure-Tlsisi a function ofthe decay heat input and the MSSV setcings. flowever, the lowest MSSV setting (and its rcseat pressure) dominates. Recent plant data have shown an avera'c setting of 1085 psig with a iingle standard deviation of 0.8% ofsetpoint. Doubling that number to achieve a 2O value (for a 95/95 confidence Ivel) and then multiplyin; by thestandard factor of0.5867 to achieve a 75,175 confldencc level (which is appropriate for 'this apilication) results in a maximum SG backpressure of 10952 psig (1 109.9 psia). This
'backpressure is I psi below tbhe a!uc used in OPR000044. Hlowever, because orthe PCv operation, the SG backpressure is not controllinc and the evaluation done in OPR000044 is bounded by this evaluation.
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