ML20114E524
| ML20114E524 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 07/11/1966 |
| From: | Wilcox R Advisory Committee on Reactor Safeguards |
| To: | Etherington H Advisory Committee on Reactor Safeguards |
| Shared Package | |
| ML093631134 | List:
|
| References | |
| ACRS-GENERAL, NUDOCS 9210120200 | |
| Download: ML20114E524 (16) | |
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V'+ Y MIMotANDtM 79 H. Etherington, Dresden Subemanittee Chairman Signed E. H.1711cox From R. R. Wilcos, Assistant to Emes. Secretary ACRS
Subject:
DRAFT MINUTES OF Stf8COMITTEE MEETING ON DRESDEN III IMID ON Jt!LT 7,1966 Attaahad for your renriew are draf t minutes of the subject meeting.
Copies are being distributed in the folders at the 75th Meeting to the other AC15 members who attended in the event they wish to comment, and to the ruinder of the Committee for information.
Attactament:
Draf t Minutes of 7/7/66 Mtna.
CC: Ramsinder of ACRS D. Duffey W. E. Ergea l
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OO b* 4 l MENTItt2 0F DRESDEN T SUBC0tDfITTEE "'., ~ JULY 7, 1966 WASHDCTON. D.C. a The purpose of this meeting was to continue the Stecommittae's review of the proposed construction of Unit 3 at Dresden with particular attention to emer-somey core cooling. i Attendees: { g Consomrealth Edison Company H. Ptherington M. Joslin
- 3. E. Bush.
W. R. Bahnka
- 8. C. Mangelsdorf J. H. Hughes L 0. Nonson 4
i J. H. Ellis R. W. Newson G. L. Redman A. A. O' Kelly. O. (kreat-General Electric Coomany
- 5. J. Palladine C. W. Zabele
- 0. H. Creager R. F. Fraley, Staff * -
E. W. O'Rorks i
- 1. H. Wilcos, Staff a
F. A. Hollenbeek D. McDaniel Remeter Licensina A. P. Bray W. D. Gilbert I. G. Case *
- 1. R. Kobsa j
R. 8. Boyd P. W. Ianni R. L. Tedesee R. J. McWhorter B. Crimes J. F. O'Mara D. F. Knuth W. H. Ellis C. 3. Long Mr. Pennington N. L Woodard W. G. Bisesing Isham. Lincoln & Deale 4 P. E. Noriam N. H. Davison A. C. Gehr
- 3. Invina*
R. E. Ireland
- Compliance R. R. Denton Safety Standarde
- Part time.
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m dwe w -.e.- %.., [ l' I E4EQUTIvg S535105 i Dr. Churent indiaated that the melt-through of the _contairuneet was potentially-s very serious problem. He called attention to recent opeer.hes of Congressmen Rollifield and Aspinall which discussed reactor safety and urged double or eyen triple safety reviews. ~ say. Aspinall mentioned probless of large roastors and g i asked ACRs~to insist on maltiple safeguards. [ i l l Dr. ($ treat pointed out that one set of engineered safeguards (core spray) has i te work in the event of a pipa break or sise the othat safeguards have no value. Dr. ($ treat was now inclined to wonder if power reestors were as safe as pradus-b tism reaators. He urged Committee members not to treat the problem lightly and i net to use what has been approved in the past as the basis for future reviews. i Dr. ($ treat was curious as to how DgL could stand on its previous position on i Dresden 3 and, if it relies on core sprays, why it insists on protection against mets!-water reactions. { Dr. Monson sapressed concern about the steam emplosions which can occur in the 1 presense of both a moltse core and water. Although not well understood, shary j ompioeians have reportedly occurred in other industries.- ~ l Mr. Etherington felt that the potential for core amit-through was recognised loss ago (e.g., by Daniels) and that a small core would-siso melt through. Dr. i Neumoa indicated that this was not discussed in connection with Dresden 1, but l that the increased power level now makes it more apparent. He felt thn? pria viously it has been assumed that the concrete will hold the molten mass. i Mr. Etherington pointed out that water can be poured onto liquid metal without disastrous effests, but that pouring liquid metal on water was more serious. l Dr. Carrent noted that the BML people had indicated only. that. the concrete would sys11. In the past, applicants have not volunteered - that the molten core will j est all the way through. There was some suggestion that the smaller size and steel containment of earlier reestors contributed to laak of concern on molt-through. j, Dr. Manson had calculated that the concrete around the Dresden 3 contaitunent was sunk as to require a 150,000 0F temperature difference to dissipate the heat in-volved. Es felt that Mr. Etherington's analysis was correct,_or that the situa-3 3 tiam sound even be worse. He felt that we must either change our minds about-eore spray or do something about present designs. Br. ($ treat noted that reactors such as the Naval Reactor in Idaho had perhaps all the features that count.- i.e.,_ a good primary system and ~ a core spray that will work. It could therefore be safer uncontained then one which is nominally contataad. l i SURNAME > DATE> N W -818 @.v. W ,,,,,,,,,,,,,,,,y,,,,n,[3 ((,~, ~ ~~ ~ lT
._2 4 ) u. l l 1er. Palladias questioned whether having a pool of water below the vessel was j better or worse. Drs. Okrent and gtherington were both skeptical of the ability j to transfer heat through the reactor vessel and insulation _to the water. - Dr. j O'Estly felt that it would maan real trouble if there is' water bolser the ves-l sel and there is a molt-through. 1 RM31HATQgY STAFE l Mr. Boyd reported that G3 had evaluated its core cooling systems and what hap-l peas if there is no coo 1 Log. Ga has developed a core slug model and has cal-i culated grid plate failure, bottom head failure, vessel movement, reactivity i effects, and the structural response of the coatsiassat building. GE had lodred at a number of additional engineered safeguards and found none feasibia. They had looked at a spectrue of assumptions and a number of paths, j in one of whiah the core melts right through. Mr. Boyd felt that !E had been j working hard on this, had been responsive, and was about finished. The probles is very assusption-sensitive. e f Under questioning Mr. Boyd indicated that DEL was ready to go to a hearing os j Dresden 3. He noted that malt-through was a probles for other reactors as well. I Mr. geherington asked, if core cooling were adequately reliable, whether metal-water reactions need be considered. Hr. Boyd favored an " inconsistent" approach: a. Foe doses, a 1007,asitdous b. For pressure, a 1007,aaltdown and metal-water reaction j s. For the ultimata accident, core flooding protection L Dr. Okreat asked if DEL had looked in detail at core flooding and core spray and j satisfied itself that they'll work. Ha noted that if these dom t work, there is l no more protectica. Since DgL stands on its last month's evaluation, and in view l of the fast that astuation of ccre spray might be deleterious, he vendered if DEL considers it adequata protection. ' Mr. Boyd replied yes-to r.he extent DRL had l laforesties at the construation permit stage. Dr. O'Estly noted that there could be wuter gas-reactions from the liquid metal' ~ ' plus water cashination at high enough temperature. j Mr. Boyd indicated 'that he was driven to being even more inconsistent than re-quiring inerting, e.g., he still believes that Dresden 3 needs more containment spray pasps. Mr. Boyd was not prepared to lead the way toward consistency. Mr. Boyd indiaated that the DgL Staff had not looked at the spectrue of accidente here. Es thought'that the situation was too complea for back-of-the-envelope j salestations. Mr. Palladino suggested that outside consultants might help. Mr. Boyd admitted that it is fatal if the core spray doesn't work.. Nonetheless, he i was willing te accept core spray on the basis of undetailed design. He admitted to feelins unsonfortable and indicated that more informstion at the evastruction t , g t stage was being requrestes on subsequenc projects. .w. Buye M i i.L.a l 4 $URNAME> il DATE> - Form AEC 518 (R.v,9 ) e.. somness sm.mca 1 el 4
4 (. ...-.m. e@ y y a r the regulations inhibit the amount of information which cm be requested at _the [ oomstruction permit review stage. Dr. Okreat noted, however, that the "granda. t father slause" is usually applied at the operating Licasse stage, i.e., reactors _ j j are met stopped from operating despite shortcomings. Mr.' Boyd. stated that he i was met ignoring this>and would like to spend more time looking into probleme l of presently operating reactors. 1 Mr. Boyd did not feel that the Staff'*"let so" of a project af ter the construe-i tima permit was issued, e.g., Jersey Central and Niagara Mohawk have both coma l book and talked with DRL.. Staff and Acts reservations are normally expressed j in hearing testimony (if the applicant is cooperative) or as proposed construe-l tion permit conditions (if he is not). Mr. Boyd indicated that the Staff mise i follous through with Acas reservations on succeeding applications. f [ Mr. Boyd felt that the molt-through problem had appeared between Bodega and Jersey Central. \\< In response to questions from Dr. Zabel,'Mr. Boyd admitted that the DEL Staff Y itself had not really studied the molt-through problem or the adequacy of the l core sprays. The staff hed ;" contemplated" the problem, but felt it was _ too complicated to calculate. -He thoeght, however.. that the core spray could be made to work. Mr. Mangelsdorf. interpreted DEL's position as being that between ; now and the operating 1Leense a satisfactory core spray can be developed, and i j that the plant won't be accepted for operation unless it is. 1 Dr. Okreat noted, however, that DEL's written position on Dresden 3 had no i reservations concerning the vital. question of core sprays. _ He. suggested that l further discussions be held with others from the Department of-Regulation. Mr. Etheriaston wondered if an operable core spray would succeed in getting spray to enter a het core. Mr. Tedesco indicated that GE had apparently tasted this sad was preparing a report on it, j_ Mir. Todeseo also supressed misgivings over what analysis of melt-through could be made. DgL had talked to Cape raaamdy personnel who indicated that concrete. i doesn't stand up to missile firings. Dr. Okrent suggested that, with the pro-l posed Dresden 3 design, either one must accept the_ integrity of core spray or not eacept the design. C(3H38WEALTE EDISON CO.. ET AL Mr. Etherington stated ' that the principal purpose.of the meeting was to dis-eene the molt-through problem in three partei(a) the course of 'the melt-through j~ if more spreyo don't work; (b)~ s' redesign to cope with this probina; (e) how will the eore sooling systems funationt L Mr. Gehr stated Cosmonwealth's appreciation of ACKS cooperation and the attend-l anse at the meeting. -~ He indicated that GE had devoted " man-years" of attention to the probles in the four weeks since the June ACRS meeting. - The studies had omcz> A..... ~$URNAME> 4-DATT b... Wrzta W.418 (R.T. S-68) - - ~ - ~ ~ - -
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M._ w_ M -.. ~.. . ~. r i Q' h } A been given top priority by GE and were thought to be whorough and complete. j / Time had not permitted putting anything in writing, and Mr. Gehr was not sure g i ~/ vbether or not this would be required. He promised, however, a responsive, i. frank and open presentation. ~ j Mr. Bray out11and the presentation Gg would make. The first portion dealt j with trackina of the event and was_given by Mr. Bray. He eng>hasised that GE had attempted to track the probable course rather than to analyse the 'extrans i possibilities, either possimistie or optimistia. He indicated, however, that j i if GE were to design protection against the melt-through as a design basis easident, that protectica'should be provided against practically the complete spostru of the course of events. - i j The comerete at the base gf the drywell is 10 ft. thich in the center and has i a surfaes area of 1600 ft. The integrated core decay heat is 900 million i Btu in ten hours. It takes 400 million Btu to bring the reactor vessel and ~ l tta entire contents up to malting temperature. f { In analysing core heat-up, GE used five axial' nodes, five radis1_ nodes, five j local ncdes, and five fuel rod nodes. The metal-weter reaction and three heat j transfer modes were accounted for. s t l At 2000 seccads after the pipe break, 90% of the core and some residue material will be in the molten state. With an unlimited staan supply, a 24% metal-water reaction ie espected. I GE had carefully analysed to see if the reactor vessel support skirt would fail. If it does, calculations indieste that. the vessel would be ' adequately supported by tna steam lines. i l Mr. Enuth noted that a substantial percentage (perhaps 40%) of the decay heat j would be la noble gases, iodines, etc., which would be in the containment at- - noephere, rather than in the melt. - GE had factored this into its calculations, easept that it had figured only 10-15% of the decay heat would not be in the molten portion. i Mr. Bray figured that the core would begin to melt through the reactor vessel-l besiming at roughly 45 minutes after the pipe break. It would then drop deva onto the concrete drywell floor where it _would eventually become 1700 f t3 of a los viscosity liquid metal (a pool 14 in. deep of 1600 ft2 area). l. Mr. Bray identified the following resultant items of concern: L 1. The molten material r - N out to the structural steel.- GE figures i that within 5 to 8 minutes, it would reach the drywell liner.. Maintaining dry- [ well integrity'is regarded as a measure _of success.- i l 2. Radiation shine to'the walls. This can be handled by the containment oprey, however. OFTICE > t SURNAME > l DATE> INrm AEC.818 (Rev,943)
- s. s. seveneut *einti.e. ems 1s.-enst.e LI
{ t O3 ) } 2 4.,. / h, i j / i j 3. Actuating or not actuating containment spray. It was clear to GE that spraying water on 1700 0F liquid metal maham a 27% metal-water reaction i Look silly. Here is a potential to make 10,000 moles of gas (700 moles are i in the original containeemt volume). Se containment spray water would be at l 130 - 130 #F when it hits the liquid metal. . l l Mare is a cylindrical concrete "sacrifialal" biological shield around the i roastor vessel and extending downward to form the vessel support.. His shield-j would be sitting in the molten material and would be expected to get undercut j j by this material. When this happens, the steam lines would get loaded with 4 1 the vessel weight plus the weight of the shield. This auch load could not be 1 I withstood, se the steen line penetrations of the containment would fail at this point. (na reactor vessel is attached to the shield with anchor bolts designed to vidstand a combined jet remethe plus _ earthquake.) 1 GE estimated the cata at which the molten material would penetrate the base-concrete and figurse five days to melt half way through. Re-bars will melt as the material reaches them. GE envisions a thich molten metal and fused l 003 slu'try at' about 3000 0F, under which is a layer of dehydrated concrete om top of the meia concrete. Above the molten metal is a layer of fused metal, j and above this is a water, steam and metal oxide slurry separated from the fused metal by a thin stems blankat. 4 l Mr. Bray admitted that he didn't know what would prevent the 3000 0F melt j from chewing into the concrete. l A curve of contain==at pressure vs. % metal-water reaction was developed. i h curve was linear and reached 240 psia at 100% reaction. (Twice contain- [ ment design pressure at 50% reaction.) n e pressure was very slightly higher for nitrogen as compared to air in the contaitunant, he time to complete the l met.il-water reaction was 12 hours. l Mr. Bray cited the following as the conclusione to GE's tracking of the event i 1. It has conducted a detailed tracking of the core melt and has l evaluated the core, vessel,- stsup, and containment behavior. l l 2. h tracking revealed many failure modes (hot spots, vessel sas - overpressure, concrete deterioration, drywell-overheat).
- 3.. h containment can only handle part of the accident spectrum.
4. N only reasonable solution is to prevent melting. I ) -A-OmCE > f SURNAME > j l DATr >...... Ph AEC-818 (Rev, H3)
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M [ / l &) ? I i i / l- / Dr. Okrent asked at what reestor power level meltdown and melt-through became probable rather than ingprobable. Mr. Bray indicated that the major points of j j sensera scale well for good design, e.g., lower-power reactors have ses11er ves-0 i sets. In the range of-practical interest, he thought the meltdown was of concorr for t 500 er 1000 MW from that for Dresden 3 (2255 MWt). He agreed with Dr. Okreet that it is a problem from about 300 MW(e) sine up. I I Dr. Okreat asked if a design could be.mede to withstand the hypothetical accident t (therust aspects, gas generation, and stems explosions included). Mr. Bray j thought this could be done if reasonable ecoaumies were not a factor. He sus-l' gested that the contef amant should have tea times the heat transfer area.- He ) l aise felt that rocashiners could be-developed in cooperation with the physical chemists to handle the metal-water reaction.- l So far as steen saplosions are concerned, Mr. Bray had talked to 1.ao Epstein of ? G3 who advised that these would not really affect anything very much. Steen j aaptosions inside the reactor vessel were not expected. I j Even if water is up abore the bottom of the reactor vessel on the outside, Mr. i Brey' indicated that transfer of the heat involved through the vessel well-re-i quires a temperature difference of 5000 0F. (This is based on the decay heat at one hour.) Use of firebrick on the bottom of the drywell in lieu of concrete was analyzed. j G3 concluded that this would provide about en hour's advantage. Dr. Newson noted that open hearths last about two weeks. l It was agreed to defer further discussion of possibis design modifications un-l til after Gs's presentation on the amargency cooling system. i i Mr. Ienai discussed this system, which was designed to limit the metal-water re- [ action te less than 1% for a non-inarted drywell. It is intended to prevent gross j clad and fuel molting, i j vessel lift was studied. The vessel and its internals weigh 2.5 million pounds. j A force of 6.5 willion pounds would be required to lif t all the concrete in the l-drywell. A 9.5 million pound force is needed to break the support skirt, and it j is not until this occurs that the core spray piping is stressed beyond its yield j point. At 26 million pounds force, all pipes that penetrata the reactor shell weeld be sheared. Bacause of seismic design and other factors, the vessel and 1' its internals tend to behave as a unit. 4 Mr. Isani _ indicated that a vessel f ailure due to a reactivity transiest was pre-L tested-against by the velocity limiter. J preneures withia the vessel were calculated using a 5-node analysis. The results have besa superimentally verified to t 10%. Boiling water reactors are inherently slow to depressurise. f OmCE > I .dRNAMZ > ~ For2t AEC.318 (E.v.1Hl3 e. vtaserat esi.rsue.tries 16 4 27614 ,,...~-~.~.-....,~,.n_-._..~-,.......,,.~,...-,,.,-.. .,w
~ + = oO p) i Distribution of core spray watar was deteruined by testing full scale mock-up bundisa, heated electrically. Bare apparently was no tendency to reject the / spray, though GE was not sure vby or how the cooling was effective locally. '/ Some was siso ne spray water tanded to run down the walls of the channels. splashed in against fuel rods where there was considerable mixing with steam flowing upward. Dr. Euah pointed out that diametral expansion of fuel could occur and pose a proklam. (High fissiou gat pressure in the fuel rods plus high temperature.) Mr. Ianal felt that the rods could touch each other without hurting anything, and this was supported by tast results. Mr. Tanat indicated that the operator could wait four minutes before turning on the core spray and not exceed 17, metal-water reaction. 0 Dr. &rst asked about the affect of turning a water spray on a 3000 F sur-face. B is had not been tasted. Dr. Okrent feared that it might be auto-catyltia if het enough. Mr. Bray reported that film coefficients (h) of 3 or 4 were obtained at 1500-1800 0F. Above that, radiation to the channel walls, pra N u tes. It was noted that the inner rods in a 36-rod bundle cannot radiate because they cre surrounded by other rods. Mr. Bray indicated, however, that the peak of 1 the peak haat flux occurs in corner rods which do get cooled by radiating to the I channel wells. Cooling is apparently not by a vetting action directly on the fuel rods. CE's core spray tests did extend into the range of 2000 0F peak temperatures (120 wee delay in actuating core spray). All estimates are that core spray would be actuated in less than 30 sace. I Acts ennbers questioned the lack of test data for spraying onto 3000 0F or so fuel rods. Mr. Bray noted that water sticks to the channel walls ex.:ept that fuel spacars splash it inward. He thought that a coefficient (h) of 4 on the l cha-1 valls was all that was needed, in view of the aforementioned tendency foe the bottast fuel rods to be in the corners. n ormocouple readings in the taats indicate that central fuel rods are not the controlling onas, ne rods ter.ded to stay at about the same temperature. (200 of dif ference at most). The above is based on conservative initial temperature conditions, according to Mr. Bray. Dr. & rent suggested documenting this to enable verification of this point. Mr. Etherington inquired about the effect of smaller size breaks. For breaks in the range of 3 to 50% of feedwater capacity, there is more time to remove decay hast befoes uncovering the core, hence more available time befora the core spray must be started. (All breaks down to 3% of feedvater capacity are calcu-laced to automatieally cause a seras on high drywall pressure.) Mr. Isani agreed that feedisatar or emergency condenser action was also being relied upon for the smaller breaks. Many minutes are available before the e:sargency condenser need be actuated, however, and the core spray is still essantia7to P.eeping ;he cora ~ [ g, ......... ~ M> .. ~.. f%rm AEC-819 (R.v.1H3)
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~ 2, M - m, - -. ~ h h ./ l For a recirculation itne braak, GE calculates that the blowdown will last for 24 / seconds. Core spray is actuated automatically by low low water 1syst and low [ pressurw. ( h pumps etw t on low levell valves open on low pressure.) For the 1 largsst break, 4,t would therefore taka about 30 seconds to start the core spray. 4 l Core rpray pipius inaide the reactor is fastened permanently to the vessel and ... e. to the core abroud. There are two core spray systems, each with independent pipir6 and pixys, but each taking suction from the suppression pool torus. ~ In analysing a small break, GE took credit for feedwater flow to the reactor of __ U the water that was stored in the hot well (two minutes supply). nis is auto. metta (with a===*1 override). hre is a small purs, to transfer additional i l wetar to the hotwell frees the condensate storage tank. ]4 i m design of the internals provides for flooding of the core to the 2/3 levol with a recirculation line break. For a steam linn break, much higher levels would ha rasebed. Feedvatar injection does not help in the case of a recircula-tion line break. (N water runs down the outside of the core shroud and out the broken pipe.) N core spray is relied upon in this instance. The 2/3 flooding of the core was stated by Mr. Kobsa to be adequate for coo 1 Lug and is what is needed to fit in the jet ptsaps. Dr. Newson suggested full flood-ing. Mr. Kobaa admitted that this could be done, although it would require a larger diameter vsesel and would affect the jet pump layout and design. Af ter lunch, Mr. Kobsa described the core spray system design. Duplicate sys-tems are provided for the required capacity. Automatic operation is provided, with = mial backup. Power is supplied to the ptsaps either from the auxiliary transformer or the diesel generator. Tha systems are testable prior to opera-tion and periodically thereafter. Other engineered safeguards (rod velocity limiter, drive housing support) are intended to preclude accidents which impair I the core spray. Tests of the ability of the centrol rod drive collets to perform under impact l were still in progress. Mr. Kobsa indicated, however, that the collet will hold a roi droppina at 15 f t/see, whereas the velocity limitar will keep this below 5 ft/see. The two independent core spray systema are located on opposita sides of the plant. Each vill have three take of f points (only one of which is needed) in the torus 1200 l apart and screens (of either stainless or carbon steel) to filter out debris. N torus water will be treated. The inside of the torus will be coated with an ad-harent plastia material. steps will be takaa to preclude failure of other pipes from failing a cora spray pipe. Encush flexibility is provided within the reactor vassal to acceannodate the differential expansion betvean the vessel and the core shroud. m core spray l nosales will be mada of 304 stainless steel. i Dr. Okrent asked, in view of failure experience at same CE and other reactors, how GE could assure that vibration or relative motion can't Lex to a tauurs nere. l omcE > L..._.. l l l ' SURNAME > t DATE > ltrmaEC 318(Rev.M3)
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t l, , 'Mr. Eabsa indicated that GE had looked into the notion and the hydraulie effects. l ' GE has learned from the SDCf experience. So far, there have been no f ailures of i j / core spray equipcnent. GE feels that the use of a reciprocating pump in the SEIN 11guld poison system contributed to the failure of that spargur. 4 i Durias normal operation, there will be a water les in the core spray lina and as interface in the piping. Dr. Bush expressed concern over possible corrosion attack of 304 stainless piping in auch a bishiy humid area. (This reportedly hed oscurred at Savarneh River.) ~ Design of all reactor internal structures was stated to limit deflections or he within the stress critaria of Section III of the ASME Code during normal opers= tion and maneuvering transients. Rod drives are to be operable as are struckur-i al elements that supp<et core spray sad reflooding capability. Design earth-quake loading plus n. -. operation or MCA is also to be within ASME Code allow- } able strasses. i 1 Mr. Echsa showed the follo.: , to le of preteures: 1l pressure leading, gs,i,i 1 Normal ASME Design Steam Line Severance _ Sparser & internal piping 8 1000 15.5 (107)* l shroud head 8 25 15.5 Upper shroud 8 25** 15.5. Core plate 14 25 42.5 4 Cuida tubes 14 25*** 42.5 Imer shroud 22 50** 57.4 Shroud support 22 100 57.4
- Durin5 operation of spray systems.
- ASME allowable for actual thicknass is 185 psi.
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To this is added the effect of the velocity limitar. ASE allowable for actual thickness is 100 pai. This resulted in some discussion since one of these parts would exceed " allow-i able" stress in a stessa line break. Mr. Kobsa indicated that the identified components were the ones which are vital. GE had lookad at the effect of a 50 pai pressure differsatial across the core plate. There would be no permanent deformation, but there would be 1/2-inch =vi~= combined plastic and elastic j deflection at the center. The = =4= = slope would be at the periphery. The core plata is a plate stiffened by beams. A 50 psi delta P begins to bend the guide tubes for sentrol rods. Dr. Okrent asked how it would be ascertained that auch mponents were in good shape in view of possible oscillation or corrosion during operation. Mr. Kobsa a indicated that there would be visual periodic surveillance. Mr. Casa pointed out that there are cracks in the Dresden 1 grid plate, but he felt that this was a special case. The sparger. internal piping, shroud head and upper shroud in Dresdeh 3 are visibit during refueling. Inspettion of the core plate requires t gftW removal vf,roui guide-tuber MNAME > yqp. DATE >................. Form AEC-818 (Rev.1HLO
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....m.=. i '1 eO y7 i Gross core plate distortion could prevent the control rods fres going in. (At Dr. Monson asked whether least 1-1/2" deflection would be ascessary, however.) [' a failure inside the vessel wouldn't lead to 42.5 pai, and GE was asked to think further about this. Mr. Kobsa noted that this was beyond the design criteria. [ i e Dr. Neweca and Mr. Palladino were concerned about this, in view of the importance of this engiacered safeguard. Mr. Etherington also noted that a supporting analy-sis was required if the yield point is exceeded, and GE wishes to show that inter-forense with other structures is sufficient to prevent gross failure. l GE had analysed the thermal streassa which would occur in accidsats and found thse Lass than allowable in the ahrew4 d piWL An analysis of stresses ce the core support plate was still in progress, and t a numbers could not then be j -eiteds In the design earthquake, a 1/4 ta. dcflection would be espected. Although the Oyster e-eek core spray design analysis is nearly completed, the design is different than for Dresdea. (No jet pumps at Oyster Creek.) i ..a l When asked Mr. Ecbes admitted that the inspection of core spray componenta during fabrication is less than is given pressure vossals. Welds are not radio-graphed, for instance. GE reportsely asercisse more care in reactor internals (Mr. Kobsa felt GE now would predict a thermal design nov t'uan previously. shield vibratica situation lika experienced at Bis Rock Point before it happens.) 7 Mr. Bray indiasted that the core spray pumps only have to work for a few minutas, l after which all that's needed is ~kany equal to the boiioff from decay heat, l unless there is a hole in the bottom of the reactor vessel. u l Se two core sprey sparsers are mounted one above the other. Nosales are Icm cated every five inches around the circumference, offset 2 in. on cha two spar-I
- gers, ne core sprays will be tested before operation to verify flow and operability, j
that noaales are not binekad, and to verify the reflooding rata. During a re-l setor shutdows, system flow can be checked, noaale unblocking assured, and the l system integrity inspected. During reactor operation, there will be periodia checha of the motor valves and other valves as well as the pumps. %ere will be contimuma monitoEing of the differential pressure between the core inlet c and the core spray sparser which should give en indication that thc internal pipias is intact. Torus water level will also be measured continuously. Bare i j will be preoperational tests for vibration as well using special temporary in-l strtsmentation. Mr. Kobsa felt that the effectiveness of the core spray system had been demonstrated, that the system was testable, and that other safeguards preclude damage to it. Mr. Bray spoke for the designers and stated that the design could be beefed up to meet ASHI design requirements. thes 88 tracked the event, the engineers were Iceking for ways to make fixes. Sa-o were lots of concatus, even for the " middle of the road" course of the l accident (as opposed to " worst case"). For a real "fix", Mr. Bray felt that i _.11..- i SURNAME > M> Mm AIJC 818 (R.v.9 43) Y
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) ('} proteccion should be provided for most of the spectrtas. Mr. Bray raxt discussed possible fixas for the various points of concerns Concorg Fix 1bt spots coacrsta arrangement. A 2 f t. barrAer along the perimeter. (Ibis vould just buy time, however.) Yossal sag 'Scamm line holdup. Possible redesi$n of the vessel-concreta joint. Overprecaure Volume (or increase design pressure). Concrete deterioratica Firebrick / refractory (time delay). (A factor of tan on hast transfer area is usaded to freeze the mott, howevar.) Dryvs11 overbset ccatainment spray. Spray walls as well as pool. Mr. Bray fait that the fiz vould have to be a good engineering design which would simultaneously solve all five of these problems. Cooling coils in the concrete were lookad at as a way to inhibit concreta de-tarieratica, but to adequately limit the surface temperature, the coils vould have to be so near the surface that the temperature gradient would destroy the concreta. Dr. & rent suggested a thick steel plate with cooling pipes in it, but 03 fait that the interface would keep molting with the heat flux involved. Allowing the melt to boil would, in GE's opinion, assure the metal-water re-action and containment overpressure. Other suggestions advanced were bare cool pipes on the floor and fins on the floor containina cooling coils. Dr. Monson suggastad, in lieu of containment spray, a larger containment vassal bottom and water coils all around the outside of it. Mr. Bray noted that other toureas of water would still be espable of feeding the matal-water reaction. Mr. Gehr asked why any such system was more reliable than a core cooling system. Mr. ~ Palladino pointed out that the reactor vessel could jtap. Dr. Okrant sug-gested that parhaps both were reliable and adequate protection would than be availabla even if con didn't work. Mr. Falladina askad if the ambient contain:aent atmosphare could be circulated i.lavush the core to keep it cool. Mr. Bray felt that an adequate h was avail-abla, but that the air has poce haat storage capacity, so th.at the melt could not be avoidad. .h. l OFTICE > I I l su= => i our> j
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f i We containment spray was stated to be a second vehicle for taking energy to l' / ,/ thm suppressien pool. On pressure suppression design, Gg still sticks with factors established by PG&g's tests for Bodega. Insoluble gases are carried I / over to the torus. Mr. Bray si-ad up with a nu::bar of " program conclusions". The tracking of J 3 the neltdown spectruse concluded that there was a need for considering core coolias as the basis for protection. All evaluations and efforts were said g to demonstrate the adequacy of the emergency core cooling. GE concluded that I the safeguards approach to the core malt potential must be toward prevention, not postosit contairsment. Dr. okrent pointed out, however, that it could be toward both. Gs's solution, in short, was to " hose it, don't house it". Mr. Bray indicated that steam explosions would have to be coped with for a design basis evaluation, and he added this as a sixth " concern" to his list. Dr. Okrent postulated a maldistribution resulting in some of the, core melting and some not. He suggested that this could lead to a glob of molten 002 falling into water arsi causing a stame explosion in the vessel. Mr Bray agreed to look into this. Mr. Ianni felt that long's experiments ax. red that explosions were poss ale, although not enough to get the vessel. Dr. Monson noted that this was not well understood, howaver. There was further discussion of the possibility for cooling the core using the ambient containment atmosphers. Gg had not thought of this. Mr. palladino asked if enough cooling could be obtained by running the circulating pumps. He cited an example of a case where decay heating had been overestimated. He noted, however, that the heat would have to be removed so:mvbere else. FJtECUTTVR SESSIC81 ~. A lengthy caucus began at this point. Mr. Etherington asked for cocuenta in view of the applicant's position that, in effect, he was not able to fix the melt.through in a reasonable manner. He asked whether ACRS should regard this as incredible or stop Dresden 3 in its tracks. Dr. f.abel did not want to give up on the melt-through problem. He thought there might still be things which could be done. He thought the og calculations were overly pessimistic. Dr. Bush pointed out that the melt-through is a general problem. He vaa pessi. mistic about containing the melt if it vent through the reactor vessel. Dr. Monsoa agreed with Dr. Bush for Dresden 3. He thought that future plants could be designed to contain the melt, however, and he thought on a reasonable econmis basis. He sus 8estad going along with Dresden 3, although some addi-tional steps were possible. l l SURNAME > DATE> -c. n... - i h
j Mwcas _mx. u -yg i L' eo 2 1 Dr. gewoon thought it easier to make a foolproof core cooling sed flooding i system, and he favors " tightening the screws" on these. l Dr. 0'asily felt that Gs's calculations were based as "first pass" numbers, and he could not agree with GE's solution. He suggested a look at the " worst i area" instead of the " probable course" of the accident. He aloe thought the ABS ought not to go along with GE's story om pressure loadings if desiga j improvements were not very much more empensive. l Mr. Falladino felt that Gs could bin more imaginative. It was not clear tc j him that there aren't other solutions. He favored strenshaning the core spray ens a natural circulation system or pumps to ecol the core ustus the ambient l l atmosphere. e Mr. Mangelsdctf indicated that he had not seen a scheme which he would trust for moetaining the melt. He favoes prevention and feels a cooling system to serve the purpose can be devised. I Dr. ($ treat indicated that the Committee could: 1. Approve Drerden 3 as is. l 2. Approve it but with special attention directed to the core spesys. l
- 3. Approve it only af tar a review in detail by DEL and Acts indicatas that the core sprays and internals are acceptable.
l l 4. Ask that the core sprays be adequate and also that there be new methods of con **iaiaa the amit below the resctor vessel. { S. Tura down Dresden 3 because of probless to the health and safety i of the publis. I Dr. (airent noted that the ACES was not here to promote reactors and should l reesumend against them if they ars' economia but unsafe. His 1_ east position l-(most favorable to gplicant) was number 3 above, although he lamaad toward l number 4. Dr. Cairent thought that this could be designed, even with stems explosians. He favors facing the probles on Dresden 3 despite fcrorable ACES comment on Dresden 2 and M111stoms. He noted that even a rural reactor is a problem if the core metta through, from the standpoints of fission product re. j lease and long-term contesination of water. i f ler. gtherington noted that four members felt the esit-through couldn't be i handled, two felt it could be, and two qualified their answers and thought it l eould be handled with design modifications. l l Mr. Etherington then obtained comenents om, assumina that the melt-through can't be handled, whether Dresden 3 could be accepted with everything that could be i done te improve core cooling.- In general, those who thought the esit-through i 1 eas't be handled were in favor of approving Dresden 3, while those who thought - it seuld were against. Dr. (Streat asked that the ACES think of this problem in terms-of all reactors at its July meeting. He reiterated his =ta" position and also su8sested that inspostion; of the core spray man sne yd-=y.y.u .m i: : 2 ef "-- OF71CE
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DAR b Form AEC-818 (Rev.EHL1) .s
[ .m .Amm-l' eD OD Af ter further discussion, Dr. Okrent aise noted that contaitment spray is not j Mr. suf ficient by itaralf to provida protsation if the core sprays don't work. i Etherington thought that a gravity tank might keep the core cool. Cocootwealth Edison. et al / Mr. Etherington asked the applicart, in view of the large ACES attendance at fl i the Subcommittee meeting, to continue on from there before the full Committee.jl i The seriousness of the melt-through led the S4 committee, he noted, to esquestf i fterther consideration of containing the melt-through, e.g., natursi gas circu :, He latten, and also of aestiorating the consequences if a meltdown occurs. asked if hydrogen from the metal-weter reaction could be Mnfmized in some Mr. Etherington a sked that this be looked at even if it -involves plant l way. desism chansee beyond what is proposed for Dresden 3. Mr. Etharington pointed out that great conservatism was needed in the design Weaknesses were identified at thw meeting. He asked 1 of the cooling systems. i the gylicant to identify them and discuss measures to improve thee. Mr. Etherington noted that there is no back-up to core spray to prevent the l l He asked the applicant to look at a way nelt-through for a system rupture. te provide comparable back-up. Different water systems, e.g., a gravity fand j tank,were indicated as possibilities by ACES meabars. has points were read back by Gs. Dr. Newson suggested that even buying time j was worthwhile. W meeting was adjourned at approximately 6:15 P.M. l I i l eee l \\ l l j h t L) t OmCE > SURNAME > '"~*"~' Daft > Form AEC.318 (R.v.1H13) e, s. soeunuset raiana. errics 16-62761-3 !}}