ML19289G324
| ML19289G324 | |
| Person / Time | |
|---|---|
| Site: | 05000514, 05000515, Crane  |
| Issue date: | 11/07/1977 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19289G307 | List: |
| References | |
| NUDOCS 7908220514 | |
| Download: ML19289G324 (13) | |
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'g UNITED STATES y4
.-r,- 3 g NUCLEAR REGULATORY COMMISSION
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' ADVISORY COMMITTEE ON REACTOR SAFEGUARDS
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wasaincron. o. c. :osss November 7, 1977 Carl Stahle LPM Pebble Springs Nuclear Plant
SUBJECT:
ACRS QUESTI0;iS RE PEBBLE SPRIflGS REVIEW Attached are questions raised by an ACRS member, to which the Pebble Springs Subcomittee wculd like written responses prior to ACRS full Comittee review of that project.
At this moment it is not planned to schedule another Subcomittee meeting prior to full Comittee review, therefore it is requested that responses be provided as early as possible.
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'Ragnwald Muller Senior Staff Engineer ATTACHMEitT Questions raised by ACRS Member cc:
R. Boyd L. Crocker S. Varga T.H. Cox (2 copies)
J.C. McKinley M.W. Libarkin J.C. Ebersole S.H. Bush M.S. Plesset H.S. Isbin O. Okrent 2043 IM 7908220 6\\
'ICPICS ON PESSI2 SPRINGS (related to BSAR-205)
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1.
Provide the intrepretation used in design, of GDC 19 and Reg. Guide 1.75 (IEEE 334).
Tne less conservative interpretation of GDC 19 coes not allow comon damage in control room.
R31.75 permits convergence of total plant snutdown capability down to spacing measured in inches (wita
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some form of panel or plate type of carrier) to a few feet of cpen space.
More conservative interpretaticn of GDC 19 would re-quire (as IAEA does) that safe shutiv, n can be accom-plish) if the control room (and presumacly any otner given safety " space") is sucject to cocmon damage within that space.
Use of the less conservative interpretation of enese criteria results as a " soft" design witn extre.mly heavy requirements on "ach:inistrative control".
If ths design is "sof t" descrire the correspondingly "hard" ac=inistrative cont:ois.
2.
Clarify the rationale used for locatien of straight secticns of main steam and feedwater lines in respect to potential damage to safety equipent. Is it assum d that sucn pipe sec.icns are infallible?
2041 127
3.
Does the design accoanudate potential for inacvertent flooding frcxn vessel and piping failures witnin
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" safety" structures or in sucn areas where safe-shutdown equiprent is locateo?
4.
htat is stress-level and raxima local deferration in steam-generator tubes and tutb sheet as result of Post-I.CCA flooding of tube-side of superheat section of steam-generators? Would some tube failures at tnis point in time seriously affect core cooling?
h~nat is the :raximum secencary system pressure developed after turoine tiip with first sucsequent rancem f ailure ceing loss of rain feecwater ficw centrol leading to flooding of superneat section of steam generators.
Assu: e turoine trip witncut ' ypass (1 css of cen-c censer vacuum).
6.
Does applicant knew enat ti:m-dependent levels will occur in pressurizer, steam generator anc reactor vessel after a relatively stall pritrary coolant creak wnicn causes coolant to approaca cr even partly un-cover fuel pins? What does cperator do in respect to interpreting level in pressuri er?
2043 128
During primary system refil.L frem high pressure in-jection pu::ps there is scc:e period when neitner condensation not natural convection is present to How is effect heat transport to secondary side.
transitica to natural convection without assistance from crimary coolant _ pumes obtained.
Wnat is the particular design of the start-up piping 7.
Oces it in-and pumping system for Pecbie Springs?
volve operating witn a liquid-solid secondary system?
Bas the Staff perferred a safety analysis of this system?
Can the plant cctain access to tne icw-pressure isHR 8.
system f rom the high-cressure condition usino culv safety crace equiprent?
Defend tne rationale of having eniy tw " active" 9.
service systems wnich perform continuing or icng-term safety functions. The first " accident" is the failure of one train thus destrcying "ncr al" redundancy.
Dependence en a single system in terns of consequence of failure of that remaining system is essential to understanding intrinsic risks of such designs.
2043 129
Descril:e each such system anc consequence of total failure of services provided oy that system as a function of time. Only " active" f ailures ceyond first failure need be considered.
Possiele examples of such systems are:
1.
Battery (DC power system) (consider parasitic loads)
On-site AC power system - assuming prior loss 2.
of off-site AC system 3.
Service water system 4.
Ccreponent cooling system
- 5.,F.nvironmental control (hvAC) systems
" Redundancy" may oe expressed in terns of ti::e to restore service by any means wnatever cefore uncue cam. age ensues.
Knat are off-site dose levels resulting from Steam-10.
Generator tube failure, associated witn loss of off-site Wnat AC power due to upset from turoine generator trip?
is procacility of sucn a gric failure following turoine trip?
Are any special precautions taken for storage and 11.
handling of nydrazine?
2043 130 6
Miat is status of investigation of merits of a pricary 12.
vessel coolant level indication system for use in post LOCA cooling for scall breaks?
The fire protection system may be characterized as a 13.
"hard" or " soft" system in respect to independence or depen:ience on fire detection and extinguishing systems.
In a local sense, in what particular locations is this plant dependent en administrative protection and early detecting-extinguishing tecnniques to protect vital shutdown system frem fire damage? Is complete 'urnout c
assureA for lecal plant space or area sucn as one
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spreading room?
As a general principle way is tne design neavily 14.
cependent en tne ccc=cnent cooling system for safe snutdown rather than using tne presuraoly more reliaole service water system? Botn concepts are used in ene indust _7 As an exa.:ple of equipmnt separaticn wnica may 15.
ce overlocked, cescrihe the separation of the ccm-presscrs for safety grade air cooling systers.
2043 131
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- 16. Describe the inlet-air protection system for tne main control room.
ishat dose level would be imposed on operators after a I4CA with " realistic" releases (Not TID) to containment but with a single failure being that of electrical olow-out of an intecediate si::e penetration (say 10" dia.)?
- 17. Descrite electrical protecticn for pcwer-carrying pene-trations subject to in-contaircent faulting during LOCA. Include penetration for main coolant pt=ps.
Descrite protecticn in context of botn overcurrent trip ara grcund f ault (arcing) protecticn to prevent electrical curnout and rnus loss of mecnanical integrity of the pene-traticn.
Incluce penetratiens nancling non-safety grade pcwer circuits.
- 18. Pa:e 9.9 descrices what is apparencly an electrical cool-ing system for Auxiliary Feecwater Pt=p rooms. Diversir/
was the casis for requiring engine criven Aux. feedsater pt=ps, yet apparently electrically pcwereo rocm ccoling is necessary to assure the engine-driven function.
Please clarify.
2043 132
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In respect to the volcanic asa proolem:
19.
Are tne diesel-engine air filters designec to prevent disaoling uptake of ash to tne a.
engine during tnis situati,cn?
l ted vihat other air uptakes have been eva ua to insure continued safe operation to shut-o.
down during this condition sucn as:
Centrol room ventilation and cooling Diesel generator air cooling Aux feedwater engine air cooling Service water trotor cooling Any otner critical air cooling system.
For a rain steam line failure inside containment 20.
folicwed by the first randem failure teing tnat of l
to close, the opposite main steam line isolaticn va ve descrite hcw excess ficw is preventee througn "ncn-qualified" valve f ailures suca as turoine cy-cass valves.
in In this ccnnection, clarify the raticnale whicn, i ident sc.e designs, assu es tnat the large LOCA is "co nc assuming no LOCA, tne
(!)" with an eartnquake but, failure cf cther kinds of "cassive" elements (suen l
c-as main steam lines in centair.~ent) cannot ce to failure since sucsequent application of tne sin:le randem criterien wculd destrcy critical active services.
2043 133
-g-Are the main feecwater isolation valves cesignec to 21.
provide the closing function in a bi-directional flow sense? Is. instrumentation diversifiec to assure main feedsater ficw interruption when required? Does enis include separate d-c or inverter powered systems?
What prevents scurious closure of main feedwater systems in the lignt of the critical need to step suca ficw when necessary? What is tne esticated frequency of sucn closures as tne original accicent?
Tne SER indicates that certain cacles will ce tested 22.
fer wSter resistance by su::cergence.
Jicw often'will tnis te done and wnat is tne procacle frequency of exposure to tnis conditica curing opera-ticn?
Is rhis sert cf testing program pecposed for tne electrical wiring and genetraticns witnin contairant.
If not, why not?
In ence-througn stea.Menerator designs, tne auxiliary 23.
feedsater system must respcnd veri pre.ctli after rain feedsater is tripped. Furtherrore, tne rain feedsater system is presu acly assured to trip curing any signi-ficant seismic event.
2043 134 6
6
Against these conditions it appears to ce poor practice not to seismically qualify the condensate storage tank as the viable " passive" source of critical feedwater fol-
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lowing a post-earthquake trip and shutdown. The present design coes not require this but, instead, depends on ene electrically driven (stopped and restarted on ciesel pcwer) service water systen to provide suction to the Auxiliary Feecwater pug s.
For this particular condition, the advantage of the diverse engine driven Aux feecwater pumps is lost since suction must i:e provided cy ne electrically pcwered service water pumps.
Wny has tne' design evolved in tnis canner?
24.
Frem the standpoint of finding tne worst credicle situation in the centext of tne maxis:cm rate and cegree of succcoling of the uncrcken primary coolant system, it appears tnat rain steam line failure witnin containment (wnica cis-acles pressurizer heaters and provides ECCS trip signals) coupled with failure of rain feedwater trip, is preca:1y tne worst configuraticn (It is also presurably intoleracle, if persistent, frcm tne standpoint of contain.ent pres-suri:ation).
2043 135
,a l.
Discuss the consequences of tnis event in respect to:
Degree and rapidity of return of fission power a.
after rod insertion.
b.
Thermal gradients in cost severely affected parts of reactor vessel and steam generators and sucsequent sudden rise of primarf coolant pressure to safety valve setpoints after enilling the interior face of the vessel.
Maxima containcent' pressure as function of time c.
of continued run-on of main and/or auxiliary feedsater flow to the failed steam generator.
- 25. ' In the startup of newer design B&d systems, using cccparatively large pumps and piping and using a water-solid seconcary system, i
s, the tengerature of the water in ene seconcary system is o
raised to 400-500 and sucsequently tne secondary is drained J
I until normal level is octained. Has the staff exaau.ned tne safety aspects of :nis system?
- 26. Considering such matters as (1) off-site pcwer failure, (2) concenser vacuum f ailure, (3) spurious main feedsater valve closure (see item 21 preceding) and recent incicents j
of failures in auxiliary feecsater systems it appears tnat, single failure criteria notwitnstanding, at least sncet i
term failures of the auxiliarf feedwater system must ce considered to estimate the neeced reliacility of sucn system.
1 for instance, would 'e One peax pri.ary system pres-c
- Wnat, sure, consequences to primary coolant system safety and relief valves and rate of pri.carf coolant icss icilcwing f ailure of the Auxiliarf feecwater pumps wr.en needed?
2043 136 2
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Cuestion 10a; Consecuences of SG tube ructure and loss of offsite oower
'le generally do not analyze this accident in detail at the CP stage;
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however it is an event that is considered in every case (SRP 15.6.3 describes review procedures). At the OL stage we will review appli-cant's analyses in detail to confinn that consequences are acceptable.
This event typically governs technical sp~ecification limits for pri-mary coolant activity; the STS values can be lowered if the calcu-lated consequences are excessive.
I 1
The applicant's analyses indicate that consequences are acceptable. Some values are less conservative than used by the staff (50t meteorology, l.
i SG iodine decontamination factor of 10), and some are more conservative
( a spiking factor ca top of a coincident spike).
On bal,ance, the results look reasonable, although we have not performed an independent
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calculation.
Ouestion 11
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The applicant has identified the special provisions for personnel safety.
In addition to these provisions, the properties of hydrazine are con-sidered from the fire protection standpoint and from the standpoint of control rocm habitability.
Questien 16
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The ACRS has previously asked several questions of this type on a generic basis. The generic topic is scheduled for consideration by the ACRS at this meeting..However, the applicant has given a fairly concise and complete answer to the specific question en Pebble Sprir.gs, one in
..hich we are in general agreement.
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