ML19224D171

Forwards Comments Re Proposed Meeting W/B&W to Discuss Stable Cooling Mode.Present Pressurized Cooling Mode Should Be Maintained as Long as Possible

ML19224D171
Person / Time
Site:	Crane
Issue date:	04/04/1979
From:	Tedesco R Office of Nuclear Reactor Regulation
To:	Case E Office of Nuclear Reactor Regulation
References
NUDOCS 7907110022
Download: ML19224D171 (14)

Text

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Office of Nuclear Reactor Regulaticn FROM: Rcbert L. Tedesco, Assistant Direc:cr for Reactor Safety, CSS ~ SU3 JECT: PROPOSAL SY S&W TO MET ED TO ADDRESS STABLE CCCLING MCDE: T?tI-2 A review was made of a pr posed plan to cve frc the present :cce of Operation (i.e., pressurized to 10C0 psi) to a stable icng term acde of core cooling. This review was performed by: Charles Graves Ron Frahm Norman Wagrer Can 5:erncerg (IE) Syren Siegel Frank Orr Jim Watt Zoltan Ros:::c:y Ma-k Rubin Gary Holahan The ?r :csed pian basically calls for placing the system in

.n e natural circulation cooling mcce. The RHR systa: i: not to be used because of the hign activi:.v level in the react:r ::alant.

On,the basis of cur review,the folicwing rectmmendations ape made: (1) Maintain as icng as p:ssible, current 50de of cooling; i.e., RCP and pressurized at 1000 psi with degassing taking place. A 260 075 7907110cvRA '

t 4 Edson Case 2- ~ Even if level indication was icst, we woulc rec mmenc continuing in this mode with the folicwing suggestions: (a) continue to monitor core thermal instruments - iniet and cutlet tem:erature readings; (b) keep reactor cooling pump in coeration until cut-off pres ure is reached; (c) measure system cressure (go solid but keep pressure below 2000 psi); (d) maintain heat balance - input - makeu: - beat removal; (e) establish controlled depressurizatien of the system to a pressure level abcut at=cs:neric. ~ In the event RCp failure a:peared imminer.:, try to restar : other pum:s to maintain this preferred c0 cling made for as long as ~ possible to allow decay heat level to decrease daily (-4 5% re-duction per day). 1 (2) In the event that preferred mode cannot be maintained, then the rec:= mended made of natural circulation will become necessary. There are some aspects here that need to be considered. If the ccre exit thermaccu' les are c:rrect then it is apparent that very little ficw is going through the Ore. This could be the resui: f wide s: read fi:w bicckage (90% :: 93% ' all assem: lies), c()(, diU e%

i Edson Case - .s as it could be the result of reduced core inlet ficw, caused by stuck opened vent valves, plus less ex ensive blockage in the = core (-90% blockage in 20% of the assemblies and little or no S_ blockage in the remaining 80% of che assemblies). In either case core cooling will be difficult at the reduced ficw rates available from natural circul a tion or frc= the RHR pumps. On the basis of results from natural circulation tests at Cconee, =- it acpears that 1% to 2% of full ficw would be available frca natural circulation if the vent valves were closed and no core

== bicckage were present. The test results and S&W calculations in- "~ dicate a relatienship of 4% to 10% ficw for eacn 1% of power in 4. this power range. Since this ficw rate is comparacle to the flow rate frcm the RHR pumps, there does not appear to be an advantage to choosing RHR Over natural circulation. It must be noted that there could be di fficulty in initiating natural circulation because of pessible core blockage and/cr opened vent valv'es. / It is not clear hcw effective natural circulation would be when the current heat level is icw. In the limit, there could be no fl ew. m Thus the core would sit in a pool of water and boil which would help to re=cve the decay heat. Cepending upon when this cde z.d

r Etsen Case 4-of cooling starts the presence of he spot: would de armine whether we would expect further core damage - again, the longer we maintain present cooling, the better will be the core situa-ti on. Ancther code here would be : 90 water-solid in the secondary system to i=crove natural circulatien. Ficw would go to the ho well and be recirculated. C nsideration would be needed for bracing the steam lines, particularly the steam lines inside the c:ntair. ment building. (3) Cepressurizaticn effects have been censidered in our review. Scme non-condensible gases remain in the primary sys tem. We estinc:= a ra a of production of approximately 30-35 ft"/ day of H. and 02 (lCC0 psia) due to radicivsis in the core. We c are :Old by ex;erts at rapL that the pc:ential for rec:mainatica is good pr:vided there is no boiling. Thus it seems preferable to delay depressurizatten of the system a that gasr.s in the coolant would not be released and boiling would act occur. However, while we still have the instrumenta-tien, it would be helpful to depressurize sicwly to obtain in-for ation on the a cunts of hydrocen gas that would be released. S

1 Edson Case '~ This information would be helpful for later decisions and actions; e.g., in the event depressurization neecs to take place, then .. _.. 1 degassing would be necessary. In this regard, members of the ACRS suggested that we attemp to assess the effect of depres-surizatien by de:ressurizing TMI-2 by about 200 psi and measure the off-gas via the level technique previously used. I have discussed this with Roger Mattson at the plant. While he agreed with the consideration, he indicated concern abcut in reducing any pertur- ]~l baticns to the plant at this time. Mcwever, he would discuss this aspect further and get back to us. In summary, we believe wa should make every effort to maintain the present pressurized cooling moce for as long as possible. In the event that we ~ Icse this, then go cnto natural circulation again pressurized. We should cnlydepressuri:e wnen absolutely necessary. We therefore are in agrescent with the proposed plan except th'a we no: new go ento natural circulation. (ficte : Mark Rubih questions RCp mode without level indication. I believe we have addressed this above.) 4 Robert L. Tedesco 6 [$ [ - g g) ( ",/ 8

/. u . +.. _.. / 9 /_/ Okay Occtor, I am recording new. Okay, you are recording now, let me talk for a c:ucle of minutes and then iets s:Op, turn it off and Okay. What I have in front of me is a ~ piece of paper received yesterday or this morning about 5:15 which is a cooy of a cc=munication frem Babcock and Wilcox :: Me:recolican 5dison concerning the craft plan for mcving fr:m the present mcce of cperati:n := a stable icng tem mece of c:re c:ci1ng. .nts is to be discussed this evening with -he managemen: cf G;U, Mr. Heman CeCamp and i-is '.ikely at that time he will pre;cse this plan or something very similar to it as their current preferred method for ciacement of cthe core in a icng term stable c: cling mcce. I want to read it over the onene int the recercer and we will transmit it in writing as seen as we ge: the ecui; ment ut. I: 4D g n =.4

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._.. c S and W Preliminary Preposal te Metr:;olitan hisen for :utting a plan in place for deliberately =cving frca the current :: cling : de : warc the ultimate cooling made of the core in its presen; state. I need that information to be available to Case and Levine as early as Ocssible and .. g.- will be transmitting the wri::en fem as scen as we ge: the ecui;: ent hc0ked up. e h e ea M 'E \\[D 30 i

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Cecas the Reac:ce l. This must be d:ne wnile we still have react:r c clan: pumas. Oc inis by increasing pressurizer level to a: Teast 200k anc maintain the small bleed en the co of the pressuri:er ::en to ::ntinue the =- = -. degassing. Aisc, c:ntinue : degas tnreuen the makeuo tank. 1 ,:..nen sample sink is avaliable verity : ta. gas in reactor cociant i 4. system by normal analysis. 3. The reactor should at all times be in a c ndition Oc g immedi ately c natural circulaticn assumir.g failure of ne A-1.teactor c: clan: ~ ~

umo and then inabili,.v :: start an.v other react:r :001 ant cumo.

Tnis means : / a. Steam genera:Or water level in A and 5 genera: Ors must be at 9.2% of Operate range. ~ b. Auxiliary feed nc el on ecde cenera crs must b. ca:able of being fed. O L) UO-

X.- ~ _ 2 c. Sufficient auxiliary '.ed water must be available via the emergency steam nozels to raise steam generator sec:ncary water to within 10 feet of the bot:m of the u;per tube shee

o pr::::e natural circulatica start.

II. Grcunc Rules for Final Conditien of Three Mile Island to :eactor v\\ 1. Because of nigh activity levels in the reac::r c:01 ant the decay lj H heat system must not re: eat must not b2 used in the recirculati:n -t mode. .i 9

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k ro ". c. a.. a..a. d i. #. ^..*. w n '.... = s m. '. *. 4..."... -.d.. a 3. On mecnanical ecuipment and instrurentaticn:inside the reacto. i s w^ "e -'. '. 9 "3 .u '. 'i c i. n.c.. "o e -=..= s ~ n #. - ". ..h i s i s....=. ".= ". '. 2 - 4. ^v.. _' a-a_ a i 0 reac Or ::clant pum:s anc instrumentaticn wnict -2.y ul timately make them in0perable. The final c ncition cf :he reac r mus / be capable of being sustained for hundreds of days while reac:ce building cleanup proceeds with the objective of ultimately gaining access of the reactor c clant system. O. The ultimate c:ndition of the reactor must be achieveable frc its a present ::ndition thr ugh an Orderly and deliberate series Of '.=s..--.'.i-'.=".(=".'.'s""= --esi'la _,..,,,/ o.,. s 4.../ e. a. i=. .v-i-v.i .4 .~ f%.g m e _ [) (g UOJ r 5 e

2 4 '~.... III. Ultimate Cenditien of Reactor Ground Rules (( '= i. Reactor cociant pum:s assumed inoperable. 2. All reacter building instrumentation assumed inc:erative througn progressive failures to radiation degredation. 3. Makeup to reactor c:clant system via a. syntrif.g:1 pump cacable Of about 5C0 PSI head through continucus coeration to maintain pressure On the system via existing makeu of cther lines. Th's may be a F.ew pumo with backup installed for this purpose. a. Reacter pressure read or inferred from discharge :ressure of the acove described pump. ~ 5. Rate of makeuc dete. mined by ficw meter in dAscharge of acove pum dowrr: ream of a recirc line. Recirc line needed to alicw dead head

e rr.tions. Steam generaters are solid with continucus recirculatien

~ fr m auxiliary feed system frem coldest source of acceotable waters ~ cn the site. Put ice in c:ncensate tank? d 6

1 - _ _ ~. 4, s 5. Temperatures in steam generators determined by cverficw water in ~ = ' " - secondary system. 7. Core temperature acnitored by present in-core detect:rs which are assumed to survive. 8. H?I. pumos assumed avai".able to take water frem SWST and c001 reactor thr ugn electromagnetic release valve in c:re tem eratures increased to acceptable levels. 9.

is assumed uncer tne above c:nditions that natural circula:icn is taking place.

4 IV. Ultimate Buildine Cleanuo to Sairn Access 0 0eacter for.ecoverv 1. This is assum ng tha: natural circulating as described in ultimate i / c:ndition of reactor above. 2. Modification will be made to the recirculating line in the reacter building sumo : extract in a controlled manner the 253,000 gallens It is of highly c ntaminated water new in the reactor building. assumed that portable materirls will have to be brought to the site 4 00 pr0 cess this higniy contaminated water and shi it for 5 Orage

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2 7 3. The reactor building spray system shculd te c:nsidered for water washing the building to further decrease decantaminatien er the =' activity described in No. 2 above for processing water is going cn. "se existing piping, make modifications as necessary :: extract water fr:m the react:r c:Olant system f r dis:: sal of purification to reduce c: lant activity and building radiati:n levels. 5. Further actions as they are found to be r.ecessary. e W = e e e A r) {^)s nbd (

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