ML20024E122
| ML20024E122 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 08/05/1983 |
| From: | Bradley E PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.D.1, TASK-TM NUDOCS 8308090237 | |
| Download: ML20024E122 (15) | |
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PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.19101 CDW ARD G. B AU ER, J R.
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E'UG ENE J. BR ADLEY associava esmanah coussak DON ALD BLANKEN RUDOLPH A. CHILLEMI E. C. KIR K H ALL UguSt 5, 1983 T. H. M AMER CORN ELL PAUL AUERBACH mesesvant samanah counsuL EDW ARD J. CULLEN JR.
THOM AS H. MILLER, JR.
IR EME A. McKENN A assesvant counsak Mr. A. Schwencer, Chief Licensing Branch No. 2 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C. 20555
Subject:
Limerick Generating Station, Units I and 2 Additional Information for Equipment Qualifi-cation Branch Re ference: Letter from NRC (A. Schwencer) to Philadelphia Electric Company (E. G. Bauer, Jr.), dated June 27, 1983 File: GOVT l-l (NRC)
Dear Mr. Schwencer:
The referenced letter asked 4 questions related to NUREG-0737 Item II.D.1 arising from the staffs' review o f report NEDE-24988-P.
The responses to these questions are attached.
Sincerely, Eugene J. adley JTR/gra/67 Attachment Copy to: See Attached Service List
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8309090237 830805 PDR ADOCK 05000352
'd A PDR
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e cc: Judge Lawrence Brenner (w/ enclosure)
Judge Richard F. Cole (w/ enclosure)
Judge Peter A. Morris (w/ enclosure)
Troy B. Conner, Jr., Esq. (w/ enclosure)
Ann P. Hodgdon, Esq. (w/ enclosure) -
Mr. Frank R. Romano (w/ enclosure)
Mr. Robert L. Anthony (w/ enclosure)
-Mr. Marvin I. Lewis (w/ enclosure)
Judith A. Dorsey, Esq.
(w/ enclosure)
Charles W. Elliott, Esq. (w/ enclosure)-
Jacqueline I. Ruttenberg (w/ enclosure)
Thomas Y. Au, Esq. (w/ enclosure)
Mr. Thomas Gerusky (w/ enclosure)
Director, Pennsylvania Emergency Management Agency (w/ enclosure)
Mr. Steven P. Hershey (w/ enclosure)
Angus Love, Esq. (w/ enclosure)
Mr. Joseph H. White, III (w/ enclosure)
David Wersan, Esq. (w/ enclosure)
Robert'J. Sugarman, Esq. (w/ enclosure)
Martha W. Bush, Esq. (w/ enclosure)
Spence W. Perry, Esq. (w/ enclosure)
Atomic Safety and Licensing Appeal Board (w/ enclosure)
Atomic Safety and Licensing Board Panel (w/ enclosure)
Docket and Service Section (w/ enclosure)
3 Docket Nos. 50-352 50-353
)' 611agb3 ggi Limerick Generatino Station NUREG-0737, Item II.D.1
[ NRC QUE ST ION 1 y . ,
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- The test pr ogram util ized a " rams head" discharge pipe
- g configuration. Limer ick util izes a " tee" quencher configuration 5' at the end of the di schar ge line. Describe the discharge pipe configuration used at Limerick and corpare the anticipated loads W. on valve internal s in the Limerick configuration to the measured y loads in the test prcgram. Discuss the impact of any differences in loads on valve operability.
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)[, , R{S ggNS g_Ig_QQg SilgN __1 rL 5f The safety / relief valve discharge piping configuration at Limerick util izes a " tee" quencher at the discharge pipe exit.
The average length of the fourteen SRV discharge lines (SRVOL) is 132' of 12" diareter pipe and the subrergence length in the suppression pool is approximately 18- 6" . The SRV test program A. utilized a ramshead at the discharge pipe exit, a pipe length of
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T' 112', a diameter of 10" and a subrergence length of approximately 13'. Loads on valve i nte rnal s in the Lir.erick configuration are fC within acceptable limits for the following reasons. b j 1. No dynamic mechanical load originating at the " tee" l_" , quencher is transmitted to the val ve in the Limerick
) configuration'because there is at least one anchor point between the valve and the tee quencher.
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- 2. The length of the fi rst segment of piping downstream of
.the SRV in the test f acili ty was selected to resul t in 1 the test program hav ing a bounding dynamic mechanical }4 load on the valve. The Lirerick SRVDL piping Configurat ion di f f er s from the test facility in that the E first line segment does not terminate in a 900 elbow and )j -
the pipe size increases in the first segment. An 1- 1 r
D. - p-assessnent of the Limerick con figuration has confi rmed that the mechanical loads imposed on the Limerick valves D by the l ow pressure water f l ow are enveloped by the hign pressure steam loads.
- 3. Dynamic hydraulic loads (backpressure) are experienced by the valve i nt er na l s in the Limerick configuration.
k The backpressure loads may be either (i) transient ), backpressures occurr ing during valve actuation, or (ii) l3 steady-state bac kpressures occurring dur ing steady-state flow following valve actuation. I (a) The key parameters affecting the transient _U backpressures are the fluid pressure upstream of g the valve, tne valve opening time, the fluid M inertia in the submerged SRVOL and the SRVOL air ft vol ume. Tr ansi en t backpressures increase with g~ higher upstream pressure, shorter val /e opening times, greater line submergence, and smaller SRVOL d2 air volume. The tr ans ien t backpressure in the test $7 program was max imized by utilizing a submergence of f rp ; 13' and a pipe length of 112'. The Limerick configuration d i f fers f rom the test facility with $ of f setting parameters of greater submergence and f larger SRVDL ai r volume. An evaluation of these it dif ferences has confi rmed that the test facility $, and the Limer ick configur ation have comparable backpressures. The maximum transient backpressure cccurs with high pressure steam flow conditions. g; The tr ans ient oac kpre ssur e for the alternate j shutdown cooling mode of operation is always much f less than the des ign for steam flow conditions g- , because of tne lower upstrean pressure and the g Icnger val ve op ening t ime. s a g;" (b) The steady-state backpressure in the test program was max imiz ed by util iz ing an or ifice plate in the SRVDL above the water level and before the g ramshead. The orifice was sized to produce a backpressur e gr eater than that c al cu l a ted for'any i of the Limerick SRVOL's. p 4 An additional cons i der at ion in the selection of the ramshead for the test facility was to allow more direct measurement of the g; thrust load in the final pipe segment. Util ization of a " tee"
... , quencher in the tes t pr og ram woul d have required quencher
] supports that would unnecessarily obscure accurate measurement of g- the pipe thrust loads.
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i The.dif f erencesf in the line configuration between the D.. - L imer ickj p1 ant." and'. the test - p rogram as'discussedcabove result in-
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) . NRC QUESTION 2 ) ) The test conf igurat ion ut il iz ed no spring hangers as pipe supports. Plant spec ific con figurations do use spring hangers in g ccnjunction with snubber 3nd rigid supports. Describe the safety f- relief valve pipe supports used at Limerick and compare the
' c2 anticipated loads on valve internal s for the Limerick pipe g5 supports to the measured lo ad s in the test program. Describe the l' impact of any differences in loads on valve operability.
Q-g' RESPONSE TO CUESTION 2 Ts . s h) y fif The Limerick sa f e ty-r el ie f valve di scharge lines (SRVOL's) are supported by a combination of s nu bb e r s , rigid supports, and '4 spring hangers. These suppor ts were des igned to accommodate ); combinations of l oads resul ting f ron piping, dead weight, thermal { conditions, seismic and suppr ession pool hydrodynamic events, and
$~ a high pressure steam discharge transient. Each SRVDL at
$ Limerick has 2-5 spring hangers, all of which are located in the drywell. ), The dynamic load effects on the piping and supports of the 7 test facility due to the wat er di scharge events (the al ternate i shutdowe Lunlang mode) were found to be significantly lower than ), corresconding loads resulting from the high pressure steam
% discharge event. As stated in NEDE-24983-P, this finding is c
considered generic to all BWR 's s ince the test facility was ff.. des igned to be prototypical of the features pertinent to this Ml issue. Furthermore, assessment of a typical L ime rick SRVOL @ c cn fi gu r a t i on has confirmed the app l icabil i ty of the generic ) statement to Limerick.
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( During the water discharge transient there will be ) significantly Icwer dynamic loads acting on the snubbers and 3' rigid supports than during the steam di scha rge tr ans ient. This will more than offset the small increase in the dead load on )' these supports due to the weight of the water dJr ing the alternate shutdown cooling mode of oper at ion. Therefore, design x adequacy of the snubbers and rigid supports is assured as they l- are designed for the larger steam discharge trans ient loads. )'
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_ x ; < $ r .w-- - -. . . . . . u . a r, e m m . . t. u 4 m . . _.. ~_ _ ._ I-This question addresses the design adequacy of the spring hangers with respect to the increased uead load due to the weight
) of the' water during the l iqui d discharge trans ient. As was discussed with respect to snubber s and r igid supports, the dynamic loads result ing f rom i nquid discharge during the dlternate shutdoon cooling mode of oper ation are s ignif icantl y 2 lower than those from the high pressure steam discharge. The A spring hangers have been reviewed f or the deflections resulting
.- from the steam discharge dynamic event and f ou nd to be accep tabl e. In addit ion, the spr ing hangers have been evaluated
. for the increased dead load due to a water filled condition.
[ Both the spring hangers and piping stresses were acceptable. P Furthermore, the effect of the water dead weight load does not I affect the ability of SRVs to open to establish the alternate shutdown cooling path since the l oads occur in the SRVOL onl y ..d after valve opening. hl c 2' u et v. ir p-. T C r
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V b NPC QUE STION 3
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The purpose of the test program was to determine valve e performance uncer conditions anticipated to be encountered in the
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." plants. Describe the events and anticipated conditions at
- s. . Limerick for which the valves' are requi red to operate and compare V these plant _ conditions to the conditions in the test' program.
13 ' - Describe the plant f eatures assumed in the event evaluations used
][ to scope the test program and compare them to pl ant features at
- Limerick. For example, descr i be high level trips to prevent c water from entering the stean lines under high pressure operating 73 .. conditions as assumed in the test event and compare them to trips ys used at Limerick.
1% e h-fro RESPONSE TO NRC QUE STION 3 y bN , i# fd hi The purpose of t he S/ RV test program was to demonstrate that the Saf ety Pel ief Valve (S/RV) will o pe n and reclose under all r% expected flo. conditions. The expected valve operating kt conditions were ueterraned through the use of analyses of [$ acc idents and anticipated operational occurrences referenced in yi Regul ator y Guide 1.70, Revision 2. Single failures were applied fl to these analyses so that t he dynamic forces on the safety and
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f;. relief valves would be maximized. Test pressures were the
;f highest predicted by conventional safety analysis procedures. $j The BWR Owners Group, in thei r encl osure to the September 17, pp 1980 letter from D. B. Waters to R. H. Vollmer, identified 13 Q: events which may result in liquid or two-phase S/RV inl e t flow bf that would max imize the dynamic forces on the safety and relief valve. These events were identif ied by evaluating the initial ;fl events described in Regul atory Guide 1.70, Rev is ion 2. with and y"R without the addit ional conservatism of a single active component -
E- failure or operator error postulated in the event sequenc e. It
'A was concluded f rGm this evaluation that the alternate shutdown ih cooling mode.is the onl y expected event which will resul t in 'i . liquid at the valve inlet. C onsequ en tl y , this was the event cg s i mul ated in the S/RV tes t pr ogram. Thi s conclus ion and the test resul ts appl icabl e to Limerick are discussed below.
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W . The BWR Owners Group iden ti f i ed 13 events by evaluating the initiating events described i n Regul ato r y Guid e 1. 70, Revision 2e l with the additional conservat ism of a single active component failure or operator error postulated in the events sequence. These events and the pl ant-speci f ic features that mitigate these j events, are summarized in Tabl e 1. Of these 13 events, L onl y nine (, dre applicable to the Limerick plant because of its design and W speci f ic pl ant conf igurat ion. Four events, na mel y 5, 6, 10 and
, 13 are not applicable to the Limerick plant for the reasons i listed below:
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)[' , (a) Events 5 and 10 are not applicable because Limerick does g not have a High Pressure Core Spray system.
y l i: (b) Event 6 is not applicable because Limerick does not have ('[ RCIC head sprays.
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14.- (c) Event 13 is not appl icable because large~ breaks will not [{ De isolated at Limerick. Uf, For the nine remaining events, the Limerick specific features, such as trip logic, power-supplies, instrument line ((i^ configuration, alarms and operator actions, have been compared to the base case anal ysi s presen ted in the BWR Owners Group lj [L submi tt al of September 17, 1990. The comparison has demonstrated
;. that in each case, the base c ase analysi s is appl icable to L Limerick because the base case anal y s i s does not include any plant features which are not already present in the Limerick design. For these events, Ta bl e 1 demonstrates that the Limerick I.9, specific features are included in the case case anal ysis 77 presented in the BnR Owners Group submi ttal of September 17, ok 1980. It is seen f rom Table 1, that al l pl ant features assumed
') F in the event evaluat ion are al so ex isting features in the 3y Limerick plant. All features included in this base case anal ys i s ik are similar to plant features i n the Li mer ick design.
)# Fur thermo re. the time available f or operator action is expected
- $- to be l one 1 in the Limerick plant than in the base case analysis for each case where operator action is required due to the if' y
c on se r v at ive nature of the base casa analysis. 4 Event 7, the al te rnate shutdown c ool ing mode of operation, is 63 the onl y expected event which will re su l t in liquid or two-phase c fluid at'the S/RV inlet. C ons equen tl y, this event was simulated Q1 in the BWR S/RV test program. I'n Limerick, this event involves If; flow of subcooled water ( appr ox i matel y 31 0F subcooled) at a
, pressure of approximately 156 psig.. The S/RV inlet fluid y? conditions tested in the BWR Owners Group S/RV test program, as ); 4 documented i n - N EDE-2 49 3 8-P, are 150 to 508 subcooled liquid at 20 i
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). . I psag to 250 psig. These flui d conditions envelope the conditions expec ted to occur at Limerick in the al ternate shutdown cooling mode' of operation. As discussed above, the BWR Owners Group evaluated transients ) including single active f ailures that would maximize the dynamic forces on the safety rel i ef. v al ves. As a result.of this if evaluation, the alternate shutdown cool ing mode is the onl y I3 expected event ' involv ing liqu id or two-phase flow. Consequentl y k[ this event was tested in the BWR S/RV test program. The fluid conditions and fl ow conditions tested in the-BWR Owners Group test program conservatively envelope the Limerick plant-specific I(( {4r fluid conditions expected f or the alternate shutdown cooling mode of operation. { y+ !x ti W .e f. a i u I-tL
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) l N PC QUESTION 4 ) ) L, Descr ibe how the values of valve Cv 's in report NEDE-24988-P ).1 will be used at Limer ick. Show that the methodology used in the ,y. test program t o d ete r mi ne ttxt . v al ve C v w i l l be consistent with the application at Limerick. I v RESPONSF TO NRC QUESTION 4 k it , d 7 Y
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f j G-The flow coefficient, C v, for the Target Rock 2-Stage safety relief valve (SRV) u t il iz ed in Limerick was determined in the g generic SRV test program (N ED E-2498 8-P) . The average flow );j coefficient calculated from the test results for the Target Rock Valve is reported in Tabl e 5. 2-1 of NEDE-24988-P. This test 4 , value has been used by Philadelphia Electric Company to confirm ), that the liquid discharge flow capacity of the Limerick SRV's will De sufficient to remove core decay heat when injecting into the reactor pressure vessel (RPV) in the alternate shutdown )', cooling mode. The Cv value deter mined in the SRV test
^ demonstrates that the Lir.ner ick SRV's are capable of returning sufficient flow to the supp re ss ion pool to accomodate i njection Q
il by the RHR or CS' pump.
! If it were necessary for the operator to place the Limerick )5 plant in the alternate shutdown cooling node, he would assure (t that adequate core cool ing was being pr ovided by monitoring the
.E4 following parameters: RHR or CS Flow rate, reactor vessel
); pressure and reactor vessel temperature.
s The flow coefficient for the Target Rock valve reported in j' NEDE-2498d-P was determined f rom the SRV flow rate when the valve inlet was pressur ized to appr ox imatel y .250 psig. The valve flow rate was measured wi th the su pply l ine flow venturi upstream of 14 the steam chest. The CV for the valve was calculated using the nominal measured pressure differential between the valve inlet (steam chest) and 3' downstream ofFur the valve and the th e rmo r e , the test IN corresponding measured fl ow rate. I t
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- conditions and test configu ration. were representative of Limerick plant c ondi t ions for the al te rnate shutdown' cool ing enode, e.g.
pressure upstream of the valve, fluid temperature, friction losses and liquid flowrate. Theret ore, the reported Cv: values are appropr iate f or. appl icati on to the L irmer ick pl ant. e , e
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RCIC L8 Trip Failure g z x x * * #5 Transient HPCS, 5 HPCS L8 Trip Failure g x -
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#8 MSL Brk OSC C rip Failure
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* * * * #11 SBA, HPCI, HPCI L8 Trip Failure
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