ML20024B476
| ML20024B476 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 11/15/1978 |
| From: | Cartin L BABCOCK & WILCOX CO. |
| To: | Karrasch B BABCOCK & WILCOX CO. |
| References | |
| TASK-*, TASK-06, TASK-6, TASK-GB GPU-2703, STD-205-T3.17.2, NUDOCS 8307090001 | |
| Download: ML20024B476 (10) | |
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TPE Ur.5 COCK & WILCOX CC ANY POWER GENERATION GRO' P J
e;4 T-I B. A. Karrasch, Manager, Plant Integration I
From g C ___.
rL. R. Cartin.. Plant Integration (2835)
//~ sos 643.s Cust. C File No.
or Ref. 205/T3.17.2 All 205FA Plants STD Subj.
Date i
Risk Progrcm R-39: Forty Foot AW Level November 15, 1978
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Conclusions Analyses have been performed to. evaluate the impact of controlling auxiliary feedwater (AW) to a forty foot level within the steam generator during accident conditions where =ain feedwater is unavailable. The principal conclusions which can be drawn from the analyses results and other activit,ies are as follows:
1.
A high level setpoint (forty feet) cannot be used for moderate frequency events (loss of main feedwater, loss of offsite power; etc.).
Maintenance of the present si:: foot level control setpoint is required.
2.
A high level (forty feet) control setpoint can be used for faulted conditions (SLB, LOCA, etc.) where AW is actuated by the ESFAS.
3.
To achieve ite=s 1 and 2 above, a dual setpoint is required. Two forms of dual setpoint have been identified: a) forty foot' control on ESFAS only; six foot on SRCI, and b) forty foot when RC pumps are tripped; six foot when RCP temperatures are running. Further investigation is needad.
4.
An alternatative to controlling AW at a forty foot level has been identified.
Design upgrades (cavitating venturi, automatic piggyback operation, etc.) to the 205 HPI systems could enhance system perfor=ance to provide LOCA mitigation with a six foot AW control setpoint.
5.
Investigations to evaluate an intermediate level (between six feet and forty feet) do not appear to be warranted at this time.
6.
Future plants should consider an upgrade to the HPI system (more flow) to relax dependence on steam generator performance for small break mitigation.
Results Sutcmarv Table 1 presents a detailed overview of analysis activities and significant results which have evolved from forty foot A W control setpoint evaluations.
The principal analysis results are summarized below:
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Cartin to Karrasch Page Two Risk Program R-39: Forty Foot AFW L6 vel November 15. 1978 1.
Stress Impact: For moderats frequency even'es, control of AFW to a forty foot level results in ESEAS actuation of the HPI system, and 180 additional cycles of HPI nozzle usage is thus required.
Mt. Vernon results indicate that only 10 of the required 180 cycles can be accommodated on TVA before exceeding the limiting code usage factor of 1.0 (some other 205 plants can accommodate 50 of the required 180 additional cycles). OTSG stress impact is acceptable.
2.
Operation Impact: For moderate frequency events with AFW controlled to a forty foot level, ESEAS actuation of the HPI system on low RC pressure and a loss of indicated pressurizer level will occur. HPI will subsequently refill the RCS resulting in high RC pressures and water relief out the pressurizer safety and relief valves. The ab.'ve rest ts are unaccc t ::e fo'r events which will occur frequently during the lifetime of the plant.
l 3.
SLB Analysis with a Forty Foot AFU Level: Results indicate, a) no critical return to power, b) no subcritical return to power larger in magnitude than that proposed for TVA FSAR submittal, c) no defeat of FOGC, and d) no moisture carryover into the steam lines during 'he fill process t
or during the long term where the AFW 1evel is controlled at forty feet.
These results are derived from one SLB evaluation with specific single failure assumptions. Ct.:cr sing e failure as.tmptions will change the results. However, this evaluation shows generally favorable resutis for use cf the for:y foot level.
General Discussion The analyses and r:.=::lts identified in Table 1 show that the use of a dual setpoint for AFW control is a good fix for the small break problem. With AFR initiation by the SRCI and subsequent control at six feet during moderate frequency events, plant control can be maintained and no unacceptable stress levels would be imposed on FOB components. Maintenance of the present six foot level control setpoint (si opecssd to sc.a intermediate level between six and fer:y feo;) is requi.sc to limit consequences at power levels ;E 100%.
During non-LOCA ESFAS transient (SLB, FWLB, etc), addition and control of AFW rn a forty foot level is " conditionally" acceptable with little risk of a future position change. The principle problems anticipated for these events were found to be much less severe based on the results from the one steam line break (SLB) analysis performed by Safety Analysis. Because of time and ccde limitations, no accident other than the SLB was examined with a forty foot level; furthermore, a one-case SLB analysis cannot cover all possible detrimental effects. However, the results from the limited analyses available, indicate a large deal of margin relative to the acceptance criteria identified. Because of this margin, changes in the calculated results due to different initial conditions and assumptions or different accidents are expected to still remain l
acceptable. Conscquently, our present engineering opinion is that the forty j
foot AFW level during faulted conditions is acceptable. However, work should continue on the Safety Analysis area to evaluate single failure assumptions (F31*/ failure or stu:k open valve on good steam generator) and the need to evaluate a feedwater line break event.
':r *h_ : additir-c1 work act!"itics vf'.1 he identified s5--t!7
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Cartin to Karrasch Page Three Risk Program R-39: Forty Foot AFW Level November 15, 1978 to put outstanding safety analysis concerns to bed.
Additional Work Activities I.
Alternative Fixes The evaluation climate to date has centered on demonstrating that AFW addition and control to a forty foot level is acceptable in order to eliminate the need to recompute and relicense the small break topical.
This approach has disadvantages; two are the creation of future licensing risks in the Safety Analysis area and the deliberate reliance on steam generator performance to provide small break mitigation. Traditionally, solutions' to LOCA problems have been ECCS fluid ' systems fix (HPI),
LPI, and CFT's). Such a fix is potentially available for the present small break problem. With. incorporation of automatic piggyback and cavitating venturi in the HPI system design, and with the pump degradation strain defined in terms of total developed head instead of delivered flow, the HPI system perfor=ance may be enhanced to provide co=p,liance to the 10CFR50.46 for small breaks with a six foot AFW level control. Table 2 shows the potential positive impact of the design changes on the HPI system perfcrmance. The approximate 56 gpm increase in effective HPI system flow is assessed to provide approximately four feet of additional core mixture during the long term small break transient. Acceptable results (slight core uncovering might occur) are expected.
~
Table 3 is an atte=nt to highlight the potential advantages and disadvantages of the steam generator level and HP1 system fix. In my opinion, both fixes are acceptable from an engineering standpoint. The choice of one fix over the other should thus be based on evaluation of licensing con-sequences and costs. From a cost standpoint, no firm numbers are available; however, ballpark figures indicate that the HPI upgrade fix would be cheaper even with a revised ECCS topical submittal. From a licensing standpoint the following points must be considered:
1.
Will maintenance of the forty foot AFW level during post LOCA conditions provide long term validity of the small break topical?
2.
Is reliance on steam generator performance to provide small LOCA mitigation an acceptable position in light of the crudeness of present codels employed to simulate primary and secondary interaction?
3.
Will control of AFW to a forty foot level during non-LOCA faulted events degrade our ability to respond to long term accident analysis concerns already identified by the NRC?
Answers to the above are not easily obtained. Nevertheless, because of the large cost impact (approximately $135,000 per unit for dual setpoint instrumentation alone), the merit" of incorporating a fluid system design change should be examined. Further details on additional activities associated with both alternative fixes are provided below.
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Cartin to Karrasch Page Four Risk Program R-39: Forty Foot AFW Level November 15, 1978 II.
Anticipated Workscope For both alternative design fixes, future work activities are identified below to illustrate the workscope remaining. These activities are not scheduled; and resource requirements have not been developed and/or committed to.
A.
Steam Generator Level Fix:
Use of a dual setpoint has been identified as a potential fix for the small break problem. Remaining work activities include:
1.
ECCS: Perform containment pressure sensitivity study and analyze worst case small LOCA with new steam generator model and a forty foot AFW 1evel (500 manhours /8.5 CDC hours).
2.
C&I Integration: Finalize C&I instrumentation design, design re-quirement and issue CI/A's. Coordinate Equipment Engineering efforts to update C&I design.
3.
Control Analysis: Issue CI/A to update 1092 Functional Spec to.
indicate LOCA and SLB transients with a forty foot AFW 1evel.
4.
Plant Integration: Issue CI/A's to addition additional level taps on all 205 stead generators. Coordiante and schedule through Standard Plant Unit BSAR text change to reflect modified C&I desing for AFW control.
5.
Component Engineering: Initiate FOAK nozzle design effort for level sensing taps to be installed in the field. Devleope procedure to install additional taps in the field. Coordinate field installation through B&W Construction Company.
B.
HPI System Fix: The following are anticipated work activities associated with this alternative solution to the small break problem:
Initial Activities:
1.
Equipment Engineering:
i a.
Develop venturi design requirement.
b.
Secure vente quote for development and test program.
c.
Finalize HPI system performance with automatic piggyback and cavitating venturi.
l i
2.
ECCS: Evaluate worst case small break with upgraded HPI design.
Follow-on Activities:
(Required if results are acceptable) 1.
Equipment Engineering: Coordinate venturi design effort and upgrade MULPS System Description to reficct design upgrade.
T27.Fn0
e, Cartin to Karrasch Page Five
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Risk Program R-39: Forty Foot AFW Level November 15, 1978 2.
Plant Integration: Revise MU&PS Requirement document, upgrade BSAR.
3.
ECCS: Develop steam generator model change (400 mahours/16 CDC),
recompute small break topical (2000 mahours/80 CDC), submit model change and revised small break topical to the NRC.
III. Future Contracts ECCS analysis is a highly visable analytical endeavor subject to continued ~
scrutiny by the NRC, ACRS, and special interest groups. Maintenance of analysis margin, especially in the small break area, to accommodate future technological advances or past errors is highly desirable.
For B&W 205 plants, the HPI flow capacity is underdesigned. This fact was somewhat evident prior to the submittal of BAW-10074 in that ECCS design changes (HPI cross-connetets, LPI cross-connects, with cavitating venturi, and internal vent valves) had to be made to provide small break LOCA mitigation. The recent unacceptable results with a six foot AFW 1evel is even stronger evidence today; with a 100 gpm capacity increase, present small break problems would not exist.
Table 4 presents a comparison of important HPI system characteristics for B&W standard design and those of our competitors. The principal points shown are that: 1) all vendors utilize cross-connected HPI trains with cold leg injection, and 2)
B&W design flow capacity is significantly less than our co=petitors.
To maintain a competitive and licensable product, improvements in the ECCS must be made. Therefore, because of the small analysis margin available in the small break area, it is reco= mended that a higher capacity HP1 system be identified as a candidate for the B&W standard plant.
LRC:dh Att'ach cc:
B. L. Brooks J. R. Burris J. F. Cuvelier R. B. Davis S. H. Duerson B. H. Dunn R. C. Jones D. W. Labelle N. S. Shah E. W. Swanson R. O. Vosburgh E. A. Womack T21873
gtrinqY of ctstftTt Cent Sitnifteemt Scsulte Ceneeat tasponeible Analvste Werbeeope tinf t _
Core uncovering - vicisties of To provide g
Emanime weret case small break aml to kee 10CTR30.46.
tcpical we Small treak ECCS with AN actuated and controlled WCA Amatysts to a 4' level in the atene be contro.
level in a generators.
generator.
WCA cond.
(See ceae.
- 1) Actuation of ESTAS Pr!)
provide tranatent curves for and Icss of pressurtrer strese le Mt. Verne
$ trees impact Centrol less of MTV. loss of station level occurred f or e...lerate Analysis power, operious actuatica of frepency events ustus assusp-and thCA turbine bypass systee*
tiene conservative for stress assuming a 40' ATV lev d to impeirt evaluations.
Mt. Vernos.
(tlpdate to 1092 Spee)
- 2) Severe overcoeling et RC$r sinteneT,,5'approatmately 430F with 6 level.
Actuatie The code 11 tilt for a usage systen i Evaluate stress impact of 180 factnr of 1 allows only 10 Stress impact Mt. Vernos additional cycles of 1171 operation of the 180 additional cycles moderate (Behoka) as defined by transient results required for W A.
ensure i auet be provided to 86-2338.u%
integri CTSC st-CTSC etresses acceptable for Evolueted strese impict of revloed revised 1072 Spec transteet Stress lapect Mt. Vernos 1092 Spec transients, provided in with a 40' level.
(Brew) 86-2336-00, en the steam generaters.
Results fram 65-1338-00 and the Lose of Based on transient re nulte developed reanalysis of the LOMW event and EST Operability Centrol Analysis en st'ress analysis evaluatione indicate the fellowing conse-modera (86-2338-00) and subsequent reanalysis anacce:
e.eences.
ATV du of loss of main feedwater tranatent with realistic assumptiosa, eval-
- 1) Losa of pressuriter level be maat 6' lev mate plaat response during moderate 8
on 109 freguency event with a 40' level.
- 2) ESFn5 e6&lvetive of HFi proper systes due to low RC reduce pressure.
ed
- 3) Refill of pressuriser due te
{Q HPt injection resulting ta leh 8
3 high RC pressures acd water re11cf e ut safety and relief y
valves.
Ter realistic Lct3v case et 100%
power. ESTAS le acuated at se AfV level of 30' and pressuriser level is lost at an AN 1evel of 35.5*.
513 foot A W centrol for this case et 100% power is acceptable.
Wo cr For SLB. FVLB. LOMW and 14Cp Frevide impact assessment of a transieht the foll-vin potential esce Sefery Analysis 40' steam generator level os non-p oblems were identifiedt to b Espact es Chapter 13 14CA Chapter 15 over.te.
masa prob
- 1) Return to power.
prev heat
- 2) Moisture carryover.
tait to <
- 3) TDCC operation.
Identification of the effected stesa generatar during a tube rupture event would ales be
{
be.=tsed.
I Amt For case emanimed:
Analyse weret case overcooltag 313 ses Impact en Safety Amelysis (TVA) assumlag AN in teatrolled
- 1) ko critical reture to power.
foo es a 40' level.
cae
) No inere.ne in t t e sub-ana critic.I.-turn t-power far oesure..!..er ti...
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y }t? FF rESUt.TS Concluelene Deference Docueent_
S t an t i t e ent e rsu,1,,,t,e, t
Analvete Wethocepe Esamise worst rase small break Cete uncovering - vicisties of To provide IbcA mitigation
- 1) N14 Shah to DII Soy.
ami to hece small break
" Status of 2MFA 1etth A N actuated and contre 11ed 10CTR30.46.
Sea 11 3reak Analy.
topical valid. AW must to o 6' level in the steam ae controlled to a 40' ets." ffD-203/
73.4. 3/M/ 78.
generaters.
level in the steme generstern during poet 1DCA cend.ttons.
- 2) 32-7743-00.
Provide tranatent curves for
- 1) Actuatten of ESTAS W I)
(See concluelens free JR Burris to Mt lehnke.
Mt. Vernos related to
" Changes to RCS func.
end less of pressurirer loon of MTW, less of stettes level occurred for eoiletate strees 1spect) tional Spec Due to 40' AFW Level." E15-13/
powIr. epurteva actuattom of frequency events unlug asevep-T3.4. 9/29/78.
turbine bypase system, and 10CA tions conservative for strees (66-1338-00) assueing a 40' AFV level to 1spact evaluations.
Mt. Vernos.
(Upd:te to 1092 Spec)
- 2) Severe evercooltag ef RC33 minisma T.,5'apprestaately 433F with 4 sevel.
Actuation of the Mp1
!) LR Cartin to 34 Evaluate strees tapact of 180 The code limit for a usage Earrasch. "Hyl facter of 1 allows only 10 eystem (ESTAS) durlag Warrte Integrity."
adattional cycles of IlF1 operation of the 180 additional cycles moderate frequency evente STD-203/f3.33 se 4: fined by trenelent reentte must be prevented to provided'in 86-2338 4.i.
required for TVA.
ensure EF1 noaste 11/02/18.
integrity.
- 2) HW flehnke te JR CTSC stresses acceptable for CTSC strees acceptable.
Surris. " Integrity of airl Nezales."
E7stuated strees Impset of revised revised 1092 Spec traneteet 203 plante.
1092 Spec transients. provided in with a 40' level.
10/31/78, 86-2338-00, en the stema generaters.
Aesults from 86-2338-00 and the Loss of pressuriser level itD Sased on transient ru ette developed and ESFAS actuation during
>1) Jr c6vetter to reanalysta of the LOMTV event moderate frequency event is LR Cartin. lop ct en stress analysis ev sti.attens indicate the following conse-(86-2338-00) and subsequent reanalysis unacceptable. Control of of so' sceae cf less of mala feeduater transient quences.
A N during such events should Generator level."
eith realistic assuspriosa, eval.
- 1) Loss of pressuriser level be maintained at the present
$TD.205/T3.17.2.
mata plant response during moderate 6' level tp eliminate inyect 11/13/78.
(86-2642-00) frequency eveet with a 40' level.
- 2) s5Fas animetlem of 1171 proper system response at es 1092 Spas sad to ensure systes due to low RC reduced power levels.
- 2) JT Cuveller to pressure.
LR Cartin. "Ana.
lyste of 40'
- 3) Retall of pressuriser due to
$ team Generator HPI injection resulting is Level." 51D-205/
high BC pressures and water
'T3.17.2. 10/10/78 retter cut safety and relief valves.
For realistic LOPJV case at 100%
power. ESTAS is acuated at at AN level of 30' and pressurtser level te lost at an A N 1evel of 35.5'.
Six f oot AW control f or this case at 100% power is acceptable.
sis Frsvide 1spect assessnest of a For SLt. NLB. LOMN and LOOP No conclusions were drawn M. Liebean't to D.
40' steam generator levet on neo-s r.n.1.i.t tha fr.11 wing potential eveept that analysis neede tabelle. " Impact of to be performed to evastuate the 40' M= Level LOCA Chapter 13 events.
protilens were identified:
magnitude of potential Control on the 5sope i
- 1) Beturn to power.
problems. Code limitations of Safety Analyste."
35AA-203/T3.83, provost smalyste of over-beating transients, therefore.
9/20/78
- 2) Moisture carryever.
initial analyste efforts are to concentrate og SLB.
- 3) TOCC operation.
Identification of the affected stese generster during a cube rupture event would alee be be.n red.
u (is Analyse weret case evercooltas $12 For case esseined:
Anticipate probless are Ie.e D.E. Eupture of Mata severe tham espei:ted. Fort, Steam Line With 40' I
(TVA) aseming AN 14 centrolled I
se a 40' lavs1.
- 3) No crit 3 cal return to power.
foot level le preu bly accc Level Cont rol.
table. With knowirJac of >La (et-2b s-ud.
- 2) No inerene in it e sub-analysis...-ntinur warh to cen.
11/15/7s1 l
c a ttic.1 uture t-Power firm worst ne im t-cn oesur e. '. s er et..' profv-ed emarined t.;,g:e siti.ve fr. h te
.halttal.
as...,it ive. etc.).r.J eve! age
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...alyste.
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TABLE 2 HPI SYSTEM FLOW CHARACTERISTICS HPI SYSTEM FLOW With Venturiis Increase In RC Pressure Present Analysis Piggyback, add Effective HPI (psig)
Assumptions
-10% TDH Margin System Flow (gpm)
(gpm)
(gpm) 2000 420 505 59.5 1600 515 595 56 1200 590 670 56 800 650 700 35 600 670 700 21 Notes:
- 1) Based on one operative pump and four injection points.
- 2) Estimate flow from Equipmen't Engineering.
3) 70% of the total increase in system flow with modified design features.
s e
e T2.ts*76
-7
~ ', ' ' ' ' <e TABLE 3 STEAM CENERATOR LEVEL versus HPI SYSTEM FIX Advantages Disadvantaces Steam Generator Level
- 1) Small break topical remain
- 1) Additional taps required Dual Setpoint valid and ECCS licensing on steam generator (field position remains intact.,
installation required on WPPSS, PGE).
- 2) Impact on Chapter 15 event conditionally acceptable
- 2) C&I changes for TVA dual based.cnt analyses to date.
setpoint required (appre::-
imately $135,000/ unit)
- 3) LOCA problem spreads to other Chapter 15 events.
- 4) LOCA mitigation has large dependence on steam generat performance.
HPI System Upgrade
- 1) Could provide ECCS success
- 1) Additional ECCS analysis (Cavitating Venturi, at 6'.
required to evaluate pro-Auto Piggyback, and posed fix.
Us2 of TDH Margin
- 2) Would ele =inate HPI system Instead of Flow Margin) pump runout concerns.
- 2) FOAK venturi design and tes program possible required
- 3) Could provide HP1 break (approximately $80-100,0:.
mitigation with no operator action.
- 3) Must purchase (approximate 1-
- 4) Would eliminate impact on
$5,000/ venturi) four ven ::
non-LOCA events.
per unit and install (BOP cost?)
- 5) Delete requirement for steam genor.ncr level taps and CSI chan es.
s 6)
ECCS Problems get an ECCS Fluid Systems fix.
E T22."n?
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TABLE 4 HPI SYSTDI CHARACTERISTICS CE W
B&W SYSTDt 80 RESAR 414 BSAR 205
)
Number of Pumps 2
2 3
Desing Flow (gpm) 850 1200 700 D2cign Head (ft) 2850 2750 2600 Suction Points EWST i BWST &
BWST &
I RB Sump RB Sump LPI Discharge Cross-Connected ( }
Yes Yes Yes Injection P'oints Cold Leg Cold Leg Cold beg Notes:
- 1) Flow from each HPI can enter RCS at 4 penetration points.
- 2) Two HPI pumps are available upon ESTAS actuation. Third pump is an installed spare.
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T2.1970
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