ML20118D250
| ML20118D250 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/24/1965 |
| From: | Wilcox R Advisory Committee on Reactor Safeguards |
| To: | Newson H Advisory Committee on Reactor Safeguards |
| Shared Package | |
| ML093631134 | List:
|
| References | |
| ACRS-GENERAL, NUDOCS 9210120036 | |
| Download: ML20118D250 (12) | |
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N. W. Novoos, Dresdam 2 Subcommittee Chairsaa W
t 1.5. W{ned E. H. Wilcox1cas, Assistant to Exe. write Secretary, ACKS Sic FRW t
DRAFT MINUTES OF DR3SDER 2 SURCCWr!Ttt MEE11M REIA CW SEPTEMBER 1,1965 SUBMCT:
Attached for your review are draf t minutes of the subject. e4cting.
Copies are being distribsted to the other ACRS Members de attsaded in the event they vieh to comment and to the remainder of the Committee for information.
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9/24/63 IfERTINO OF
,l DELESDEN t SUBCCHHITTEE September 1,1965 Washington, D. C.
The purpose of this resting vas to review the proposed construction of the Dresden 2 reactor.
Attendeams g
COfPLIA? ICE N. W. Newson L. Kornblith H. Etherington J. E. Hard T. J. Thou9som D. Ctreat CGiHOWEALTH EDISON L. Silvernen
- 1. C. Stratton Murray Joslin R. R. Wileon, staff Jack Bitel
- 0. D. Dutler RfCt71AT105 John H. Hughes Harlan K. Hoyt M. H. Mana L. F. Lischer Arthur C. Gehr REACTUR LICY:!tSI]!Q CENERAL ELEC71 TIC COHPANY R. L. Doaa
- 1. 3. Boyd F. A. Hollenbach
- 9. R. lialler O. H. Greager F. E. Norts.a W. B. Bigge
- 3. Orimes W. I. Collett D. F. Sullivaa J. W. Holt: claw R. L. Waterfield D. McDaniel J. F. 0 %ra SAFRTT STA1mARD8 W. H. Ellis W. D. Gilbert L. 1. Ropp
- 7. A. Elliott W. L. Fiock A. Philip Bray ACRS l
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l Dr. Rooses briefly emaerised the status of the DILL review of the project, u -.laterv 8taff He indicated V Mallar save a chronological rundows of the Staf f's rovf.ew to dste.
that there had been a few more meetings on this project than was usually the care.
and to greater dapth that t
Be felt that IRL had reviewed this plant with greater carft Lots of problems had been cleared up in tha In meetings with the other plants.
applicant.
The big question b
IRL's questtoms had been anewsred generally to its estivfactice.
was se metal-weter reactions, nich the applicant he4 concluded would be 24% by If the hydrogen : ecocabines, the containment could asenming termination at 33000F.In the meeting the previous day, Commonwealth had only withstand a 4% reaction.
agreed to inert tSe containment.
Helting As outstanding problem for DitL was to rationalise why the reaction stops.
It was not clear dether it would through the pressure vessel appeared possible.
reach the ctattattenant shell, although it appeared that there was 5 f t, of conerste Hr. Etheringten pointed out that liquid r-etal doesn't abere the drywell liner.
sit peacefully on concrets, but spatters because of the water of conbination in Dr. Silversuan asked if the metal-veter reaction of the pr-the concrete.
vessel need t,e considered.
The containment wil'1 be tested at 62 poi since both drywell and suppression chaeber will now be designed fee that, h re vill be individual testing of gasket-sealed penetrations.
A ene-loop core spray system vill N provided, with two pucps in parallel, either of Wick will de the job. A core flooding system will be identi:a1 to the cara spr q system. Both take suctis.a aan the suppression pool.
Eachcef two suppression pool cooling systems hna two pur.ps and one heat exchanger.
ThMe vill spray wate into the drywell.
Ds4m of the inner vessel and jet pun,ps te auch that the core can be reflooded The tes a level equal to 2/3 to 3/4 c,f the be.ight. of the cera and not drain out.
applicant claim, and IRL is itwlined to agrea, that subseat. eta boiling vill keep the core coal,
'4r. Kornblith pointed out that the feedwater system is also capet!.e of flooting the core. Dr. (krent tioted that a control rod nosale failure wse14 negate the integrity of the inner vessel and prevent core reflooding although Mr. Boyd thought the feedwater system could overcome such a Isak.
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i Ms esserel red velocity limiter will limit drop-out velocities to 5 f t/eae.
1er. kiler felt that a red drop wea credibles therefore, that it is vitsi that i
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this limiter works.
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'the steam line flee restricter will serve to choks flow in the eveet of a steam l
I line rupture.
The ecatrol red thimble support will catch a brokes thimbla, h support suat be I
reservable for rod drive maintenance.
h cocrol room will be adequately.hleided te keep the dose to an 8 t.our shif t tasa than 503 mram af ter the NCA. Coassouvealth wu14 limit etual dose to its in accominee with 10 CFR 20.
perscamel to 3 res in the course of a severs accident, i
On electrical transmission lines, Dre. **c 5. t about es':a J many lines as any othcr nuclear power plant.
URL's consultant is still verking om seismic design. The Dresden 1 stack design may be a problem. DILL regaria the stack as an engineered safeguard, in that the 4
refueling building exhausts through filters to it af ter an acet&.at.
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New featureo of Dregsden :: ares 1.
Two reseter plants on the same site.
2.
Jet pussps (20 in reactor vesen1).
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100% in-core instrumentation.
DBA questioned GE's assumptim that only 1% of the noble cases and'1/2% of the haloseme are released from the fuel plenums upon c114 perforation, particularly far rod drop accidents, in which the fuel is rapidly heated to or through the melting potat. DEL was still questionius some other GE accident analysir assump-tions as well.
A staae line break in the pipe tunnel would cause a release not through the etack.
Mr. W11er t.hought that the applicant would need a reduction factor of 20
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partition, ste., which he thought could be justified.
Dr. Silverman pointed out i
- he steam that fission product load in the steam could be reduced by a Tech Spech will be line isolation valves for Dresden 2 will close in 3 to 10 seconds, fear stsam lines cr,ws-coess:*ted at the turbine.
Dr. Okreet posed the following questions and got the following answers Would there be way dif ference if fuel e;xposure were 40,000 WD/T instead 1.
of 15,00014fD/TT This had not been thought of Sy Ditt.
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h t about missiles in the dry-wellt h applicant is considertog missile protection; Mr. N11er is not concerned about this and Mr.
Strattaa supported his view.
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ht is the refueling accident with the worst configuratioet t*L felt that GE had picked reasonable assumptions in its analysis of this accident.
4.
Is a preissure vessel failure incredible? Mr. Muller agreed that it was.
N last question evoked considerable discussion. Dr. Okrent sury.ised that DRL seast feet that flaws above a certain size will be detected and that bolts will not fail. If one pressure vessel were to f ail, Mr. Boyd could not say whether all reactore would then be' shut down.
Mr. Strattos cited a recent failure of a screen-vell at a Hartford glectric Light l
Company insta11stice. Dr. Newson renorted three thstances of lids blowing off i
Van de Orc.Jfs.
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l Dr. Okrent reported that a vessel had been shipped in another co* entry and, after the purchaser inspectied the radiographs and asked for a further look, a very large flaw was found. After w a discussion it. vas agreed that this question should be asked of th's applicant.
Mr. Boyd outlined the "TIP systems" problew, namely that a probe could stick in a valve or a single visive might not close, thus violating the containment if the l
tube opens inside the reactor.
Dr. Newson thought the problem could be easily sielved by a shear valve and spring. It was pointed cut that this system would only be used once per month for 5 rinutes duration.
I On the dual reacter question. Dresdena 1 and 2 will share intake and outlet water canals, stack, and operating personnel.
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Dr. Okrent cited some recent personal experience bearing on the credibility of tornades in the Chica$o area.
t - = - alth Edison C.wpeev Mr. Joelin made some introductory remarks. Drendu 1 had scea early problems which were selved. This plant has proven to be depeno<hle and has delivered 4.3 million kw-hrs. to Conanoewealth's customers. N utility has confidence in Dessdes 1 and believeis that Dresden 2 will be competitive and reliable. It be-11 aves that it has a competent crew at Dresden.
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Mr. Elliott described the station layout and electrical systems. He gave the significant data om Unit 2.*
Be listed as new featuras of Dresden 2 1.
Jet pumps 1
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Raflooding capability 3.
Mais senem flow restrictor 4.
Neutron monitoring systems (in-core) 3.
Reactivity excursion safeguarda e
a.
Rod worth minimiser b.
Control rod drop velocity limiter c.
Control rod drive thimble support 4.
Provisions for handling metal-water reaction.
Da the latter point, CE believes that the bear. vay to handle such reactions is to prevent thans through core cooling systems with appropriate flow 2ates and spray patterns.
GE believes it has eliminated excursions which could break the reactor vessel or cause a vessel jump.
Mr. Ellis described the recirculation system which includes 20 jet pumps.
A full-sized Dresdes jet pump is to be tested. A 2-pump installation aill also be tasted, but these wi'.1 be smaller pumps.
The " inner pressure vessel" which assures reflooding capability will be de-signed in accordance with Sectica III of the AS)E Code and will be separately Isak tested.
The stama 1*w flow limiter will be in the form of a venturi. Steam line 1: 21stion valves will operate in 3 to 10 secs, which is faster than on previous 345 plants.
1 The NFER requirenset of the jet pumps is 80 f t of saturated water, so mixing of reactor water with fsed-water is necessary.
Dr. Thompson expressed some concers aboat the interaction with reactivity. The jet pumps will have an "M ratie" of 2.
The two external pumps in this system will have doubts the hersepower of af;a pus:pe in a non-jet pump plant, but there are advantages in loose capital cost, safety, and improved natural circulation.
eFee details of charts used at the meeting, see " Illustrations used in Pre-
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1 he flow limiter is not yet designed, but G3 is thinking in terms of a flow about 150% of normal. L e pressure vessel will withstand such a break and d'
will have close-spaced siilts to support it.
gabcock (m W11cos has been salasted as the pressurs vassai manufseturer.
i Nr. Ersy discussed metal-water reaction problems. Se core spray systess will be designed to provide adequata cooling in the event of loss of coolant. A recirculation line brsak is takaa as the worst essa, and vessel blowdown calculated using Hoody's work on two-phase flow. Gs's model tends to predast quickar blowdown than tests indicate. De core would then heat up, which G3 calcelates using a " bookkeeper" digital computer code. No hast ices cut of L
the enre is assummed.
For core heat-up with core spray operative, only O A to 0.6% of the Zircaloy l
reacts with water.
j C3 has uoed a full scale fuel bundle to do core spray prototype testing.
j Upper and lower bound curves have been obtained for maximum teasperature vs.
tuitial bundle peur. Orderly lata were obtained as a function of flow rate and water temperature.
nere is negligible metal-water reaction below 18000 F, but above that tempera-ture, metal-water reaction controls the rate of heat-up.
After melting, G3 :-
.c assumes the cladding drops and the reaction stops. Lle. Okrant suggested that 2 can also react with meer to make hydrogen, a reaction which G3 had not UO taken into account.
Dr. Okreat asked whether more infomation was needed on two-phase flow, and Mr. Stay agreed that there was on the cooling (heat transfer) aspects. On the ef fect of fuel burnup, G3 is using an infinite irradiation decay heat curve.
Dr. Gcrest aska
- wt.at would happen if the pressure vessel did f ail. Mr. Bray replied that it would depend on the energy rats.
La containment could with-stand a larger break than the NCA, but not e complete break.
Dr. Okreat also saked what assurance there was that it won't fail. Ha postu-lated that a failure occurred in one of several vessels of a similst type and asked where that would leave Comeonnalth. Mr. Joslin referred to a turbine spindle forging explosion which Commonwealth had once experienced. Subsequent investigations resulted in taking some similar machines out of service, scrapping somme, and changing the ingots of future forgings.
Dr. The.apson com-mented that it was difficult, but not impossible, to replace a pressure vessel.
3r. Joelia thought that a vessel failure would call for an investigating board.
Sa possible reaction of authorities to such things as this will influence Casasewealth's directors in deciding on Dresden 3.
Mr. Joslin hopes that AgC wouldn't pania, but vould 30 back and look into fabrication history and radio-graphs. he Dresdam 2 vessel will have a large water annulus and corresponding-ly low ovr...
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Dr. Otreet suggested that a design could be achieved which might periait a pressure vessel failure to exceed Part 100 doses, yet not be a catastrophe.
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Dr. Neveen suggested that keeping the core spray working was a possibility, and Dr. 04rtsat also felt that some method of flooding might be practical.
IE had not thoesht of this.
Dr. Newson exprassed doubt that Dresden 2 was more vulasrable than other reactors and euggested that this be scheduled as a gaaeral issus for ACI.S discussica.
CR measurements of partially flooded fuel rods have showu surprisingly good i
coo 1Las by steam.
t Mr. O' Mare described the physical equipment of the cooling systems ard the design of the pressure euppression containment.
The wet well will be designed for the same 62 psi as the dry well. The containment will be inerted to less than 5% oxygen.
There will be two independant containment spray systest, each : tith adequata dependability and spare p'nsping capacity. The core spray and core flooding sys,tene will each have 1071 of needed capacity, a separate spray header, and the ability to reflood the core.
Dr. Thompson asked what percentags of the total piping was inside the dry well.
The recirculatica piping is entirely inside, whereas other small systems are mostly outside, subject to valving off.
Mr. Joslin understood that 65% of the steam line was inside the dryveit.. The pipe run is 42 ft. free contain-ment to turbine.
The drywell will take the jet forces of the largest pipe break. Dr. Thompson coennented that a quite dif 0 brent design might be better, i.e. this design might not be naas the peak of a curve of maxissun safety vs.
minimma cost.
Ca internal missile protection, GI has previdad for thera.wnsters and parts of the recire. pumps, but not for pipe whipping.
The diesel vill supply adequata power to run one ccotainment cooling system plus one core spray or core flooding system.
Mr. Biggs discussed tha exc.:,rsion analysis made by GE.
G7 ts prepasing a sunenary report which was to be released in two weeks.* 11a discussed the charactaristics of nuclear excursion (see page 13 of the "I11astrations").
Be also gave the following fuel sothalpy scales
_ Calories / gree lhanccuenon 425 sudden rupture threshold i
370 vapor pressure - one atmosphere 220-300 UO2 melting range 180 clad failure threshold Zr-H O reaction begins 110 2
50 average operating fuel 0
680 F ontfah an rmenia'n.Tacteolosb"..by..L.. L..Ahass.ar.,...e t.1
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full Acty - 9/16/65.
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I pr. Okreet suggested that the escursion could be se_ fast that clad woeld not
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fait at the indicated enthalpy and fission gas pressure might build up-to a hight value. Be therefore questions the 425 cal /sm threshold for sudden rupture.
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Be else goesticaed why, above the mettias range, there eculd not be rapid
-Dr. Thompsea pointed out that this could occer l
mistas of fuel and coolmat.
molta. 3 pointed to its rod worth minimiser, eyes af ter shotdown, when the le supports as limiting the possible ascursion.
veleetty limiter, and drive th med programs will be developed and used~ assuming that the minimiser isn't there.
The miniminar will serve as en ist.orleek to prevent withdrawal of improper.
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A 2.5% rod drop will result La
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Rod worths are very configuratica 4 :Dr. Thompson commented that looking at 330 UO2 roda escoeding.170 cals/ga.
the k of the entirs reactor was not appropriate and suggested that local k-This was to be covered in Gs's topical report (" Nuclear j
l needed to be enemined.
Ensursion Technology").
GE wanted i-Dr. Newoont asked why 5 f t/see was selected instead of 0.5 it/sec.
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to set affect the serem too much and to add less than 200 lbs. to the screa l
i forse requirements. GB also wanted no moving parts.
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Af ter lunch, Gs stated that the refueling accident had been analysed for the l
worst possible configuration.
Mr. Collett nest described the neutros monitoring instrumentation, including L
It was suggested that GE source rense, intermediata nues, and power range.
l should analyse the situation with one channel bypassed, as is allowed.
Dr. Thospesa es,sressed concera that chamber failures might prevent sny scree.
Es felt that both safety chassels - should be capable of specting a high flus-Es aise asked for further documentatice of-this.
l peak in any area of the core.
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Mr. Collett described the use of the campbelling approach to instrumentation, which will be used on Desades 2.
This method was reported to discriminate a For reactor faster of 1000 better against samass when esasuring neutrons.
l periods above 200 ases, the linear-type channel used is 'not as good as a j
period channel. _ but for less than 200 meee periode, its response is faster.
We period seren Le therefore propeeed for Dresden 2.
Reiseling of Dresden 2 will be with scattered reloads, 'similar to Dresden-1.
9 Fuel will be orificed to control iIow.
1 Dr..Thompeem postulated en operating condicios in which rods were withdraws i
and voids were present deep into the core. A subsequent pressure transient weald them au lots et reactivity. GE had daalyzed cores with flus skewed GE has analysed pressure transients.: Dr. Thompson both to bottom and top.
- akad abeet such as accident with an atypical pattern and with the turbine He wanted.to know stop valves slamming ebat and nothing else opecing.
vbe Wa* it would rupture the contaimment.
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the core.
situations.
Mr, Digge isdisated that the moderator coef ficients may be positive, but small, teased the end of core life.
Dr. Thoupeem commented that the applicant had started on Dr. Mann's new systas, but had not come to gripe with the bases. He found masch hard to accept on faith and asked for better documsetatien. CE cited the report on excursions sed a document on Campbelling, GE also promised to provide o pies of the charts 4
shout at the useating.
Dr. Thompsea stated a preferenes for in-core as opposed to out-of-core nuclear instrumentation. He was not clear that the GE system was as safe as two sys-tese to scrsss, and asked to see a f4ilure analysis. If two failures could lead to trouble, he was concerned.
j Mr. Gilbett described the engineered safeguards features proposed for Dresden 2.
The containment leak rate is specified as n/2'I/ day.
Penetrations will be testable.
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7.he core can be reflooded within seven minutes af ter blowdown.
The pressure suppression system design was based ou Moss Landing test results.
which are reported in an appendix to the Nine Mile Pt. application.
l If all core cooling should f ail af ter an HCA, the cars cor.sid melt through the l
l reactor vessel. There is 15 f t. of concrete abcmn the liner, however.
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core vaportaation is also possible.
t Executive Session l
There was agreement that more information was needed.
Dr. Okremt felt that a pressure vessel failure was credible.
Mr. Etherington agreed, but thought this should be handled in criteria rather than with this particular applicant. Mr. Strattoa thought that CE had previously presented good information re pressure vessel surveillance. He also suggested that the f
ACES set vessel manufacturers in for a meeting.
Dr. Okrent noted that a flaw over a f t long was present in a vessel shipped from England to Italy.
Dr. vhampson thought more information was needed ce jet pump performance, 1
instrummatation failm philosophy, and small reactor zone reactivity. Dr. Okrent Dr. Silversen wondered if a vessel jump would negate the core spray.
thought that a reactivity excursion might rupture the reactor vessel and the saata 5mmat.
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.s Regulatory Staff Thors was discussion of schedule with Dr. Doaa and Dr. Mann, and then also with Masers. Boyd, ) taller and Crimaa. The staff felt that jet pump stability prob-Lams had been adequ.ately conted in the an. ewers to its question.s.
There was further discussion of the points raised by Dr. Thoepson, including one on how susch total doppist ef fect is really available.
Dr. Does stated that the DEL analysis would be ready 15 days prior to the Ostober usating date.
It was agreed that additional information was desirable.
Dr. Nevson suggested that the project come to the October meetias, but maybe for infonmation caly.
f' m alth Edison Cuerpany Sargset & hmdy ir doing some ccasulting work for G5 ce. piping, and a written answer on pipe whipping problems was promised.
Dr. Newooo stated c. hat there was probably not time for another Subcommittee meeting. Es indicated that ACES would try to schedule Dresden 2 for the Detober meeting, but it would be questionable whether it could write a letter at that time. He noted that there was a lot of information to be digasted and a lot af specific questions to be transmitted by 3CRS to DRL.
Of the probleans in this category, he mentionad 1.
The jet puep system and the consequsaces of dragging bubbles through the core.
2.
Stabilityt large void coefficients.
3.
Instrummattom system; simmaltaneous failures.
4.
Scrams and lack of redundancy @ackup), e.g. the pattern of ion chambers and bypassing provisions.
3.
1.sactivity coefficients and doppler effects.
Be promised that the Subcountittee would try to be in a position to rec-=1 to the full f%=4 ttee that it write a letter.
A question was raised as to whether a turbine rotor failure could destroy the control room. Mr. Joslin had made sure that it couldn't.
Mr. Joelin Ad*4 the Subcoentittee for its time and promised to get the needed material in.
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3 Notes At Dr. Newson's request, Subcoenaittes questions vers developed from the meeting notes by the AC'A staff in cooperation with Dr. Thompson. They wars transmitted promptly to Isi, who passed thema along to the applic4st together with some additional INL questions, fas Subcoummittee questions were noe.18 attached to the 9/3/65 letter freet De to Joslim and answered
>l by the aFyLicant in Amendment No. 4.
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