ML19345F865

Forwards Excerpt of Rogovin Rept Re Hydrogen Problem During Accident,In Response to .Nrc Did Not Keep Record of Individual Contributions to Resolution of Problem

ML19345F865
Person / Time
Site:	Crane
Issue date:	12/30/1980
From:	Harold Denton Office of Nuclear Reactor Regulation
To:	Everett J AFFILIATION NOT ASSIGNED
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NUDOCS 8102190445
Download: ML19345F865 (11)

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UNITED STATES

[ y,.,,, f j NUCLEAR REGULATORY COMMISSION

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Mr. James A. Eve rett, President Everett, Brandt & Bernauer, Inc.

314 West 24 Highway independence, Missouri 64050

Dear Mr. Everett:

Vith regard to your letter of November IS,1980, a detailed account of the hydrogen problem during the accident at Three Mil'e Island is contained in the enclosed section on " Hydrogen Production, Removal, and Hazard" from Vol. II, Part 2, of a Report on Three Mile Island to the Commissioners and to the Public by a Special Inquiry Group of the Nuclear Regulatory Commission.

Unfortunately, we did not keep a record of the individuals who contributed to the resolution of this problem and thus do not have the information to respond directly to your request.

You may wish to contact the Metropolitan Edison Co.,

the operator of the Three Mile Island station to see if they have any speci fic information concerning Mr. Billings' role.

Sincerely, g

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Ha old R. Dento, Di rector 0 fice of Nuclear Reactor Regulation

Enclosure:

As stated l

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J A REPORT TO THE COMMISSIONERS E XC ER 9 T AND TO THE PUBLIC MITCHELL ROGOVIN director GEORGE T. FRA.".1PTON, JR.

deputy director flUCLEAR REGULATORY COMMISSION S?2C:AL C;CUIRY GROUP 51 Oh i BD a-y

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• m inese resutts. one can cautcusty ccnctuce 1-nYCTC;en Df00:0D0~

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nat ::erween 40% and 60% of :ne core inventory of 2 nycrogen a::Ountn;-

re ease groups 1-01 was re' eased to the coo! ant; tnat

3. calcutaten cf Outore s::e.

Onty a sma!1 fracten cf group IV was releasec: and

4. removal of the nycrc:s, ture!e. and

na: only m:nute amounts Of :ne rema:ning groues 5 *ne na a'd fr0m !P9 P:C'0?en 0'00

• v.ere released. Tne amount of refra:: cry :sc:cces teeased is cens: stent w:tn leacn:ng (see Appenc:x Hycrogen Precuct0n gg),

These ca!a tend to confirm cther analyses of Two pess.bte sources of hycrogen are con-

re camage. The ca:a on racicactivity re; eased secered. meta!-water rea:t ns and rac:clys:s. Oth-are too scarse anc vana0!e for a prec:se conciusten er conceiva::;e sources :n::cce exicanon cf UO.

to ce mace on the amcunt of Ore camage; howev-whicn nas net teen eves:. gated. The crec.:t n 5 er. :ne follow:ng cone:usiens a::cear to De suc00rt-hy: regen from metai-wa:e* rea:nens.s e:wn :

ec.

nave een ta ge. :nerefere any ny::: gen f*:m ::ner meenarusms s expe::e::o te sms m ecmeanson.

1. About 50% cf tne reacter core was camaced suf-Rac:chs:s is not ex ected to accu e Wge fic:ently to release the mest velatile fission pro-ameums cf hycrogen. n s mvest;;:e :e:ause tne cuets.

i

2. The low fractions of te!! unum. ruthenium, and pessdaty cf cxygen preceton was conseered at the time of the a :: cent. If oxygen had been strontium indicate that no sign:f; cant cuantty of fuel reachec the meitng pc:nt of UO (5200*F).

reteased. the hycrogen tnat was tran::ed in the 2

reacter cocMt system could have be::Ome fiamm-

3. The amount of refractory isotopes in the reactor aW.

coolant is censistent with leaching.

Metal-Water Resaticn

d. Hydrogen Production, Removal, and Hazard Many metals are oxid.ized by water. The reacten I

is very s!cw at icw temperatures for most metais.

'mroducten Both steel and zirconium are oxidized at an increas-One of the surpnses of TMI-2 was the fermation ing rate as the temperature nses. The oxidaton cf of large amounts of hycrogen from the reacti0n of z:recruum the major consttuent of tne c:a::$ng. oc-i TABLE 1157. Total volatile isotopes released from core i

Reteased Isotope (fraction of core inventory)

To Xe

'3'l "Cs

'33 Cs Environment 0.01' 2

3 RB Atmosonere 0.46 RB Water 0.22' O.48' O.34' RC Water O.14' O.12' O.08' Aux. B!dg. Tanks 0.03 0.03 0.C2 Totals O.46 0.39 0.63 0.44 I

'See Ref.199 20asnes incicate low vanes (generally less tnan 1*.)

3Sest estimate from cata in Ret.197.

Average of ocservations.

1 6

527

+

i

c _ s r:2 0'.,

as the temperature a: Orca:nes the wnen the tem: e aire n:vesses trem 2:22 F to m

.:.n! Tre rea:t:n is a220 F the re; t;9

9-::: nea'. C 2 ! m taster.

Zr - CH,0 - ZrO, - 2H2 Because of the very large enercy re' ease 10* -

cation. the cladc;ng heats up taste'r than the steam ta0.1 mote of steam produces prec:sely 1 mo!e of hy0r0;en. so that no enange occurs in the volume can e!!minate heat. (At hign !emperatures the reac-tion power can exceed the cecay power) Because it the zircentum is in the form of a f.ine powcer, cf the sceed with wn:ch exicat0n proceecs. Once ;t 1'e reacton takes place very rapicly because the has started. m:ncr errcrs or uncertamt:es :n !ne rate water vapor has instant access to meta:he arconium w'in. at most, a very thin'shiefd ef arconium oxide.

the water level in the reactor vessel. If the water Mcwever, the cladding is solid metal and the water level is low enouch for a long enough time to exrd::e has a::ess on:y to the extencr. Any water vapor accut 10% of the th;ckness, the rema:ncer can be on the insice of the clacding is rapidly exnausted cx:cized in a shcrt time. Oxicatien a: e! erat:en is anc can eniy oxic:re a minute cuantity of metal.

also possible due to fractunng er transfermat:cn cf ire in: tat ext::aticn of the extener is very rac:d.

tne fermed oxide, layer at h:gn temoeratures. How-

- v.ever, the termat:on of an oxice layer sn:etcs the ever, tnese mechanisms are not expectec t0 be unreacted metal trom access to tne steam. Th:s coerative until the runaway exidatien has begun, formaten causes the reacton to proceed slower as and they would not change tne resu'ts apprec:ab;y.

tne oxice layer becomes thicker. The shielding is e eh M M ZmW W NN n0t per'ect, however, and some oxidation still oc-tion of clad melting. As scon as the methng tem-cuts even with a relatively thick oxide layer. Experi-erature of the clad (or of the mixture of metal and ments have shown that, when the temperature of tne arconium is constant the thickness of oxid the rod-like candle wax and refreeze in a !cwer, can be approximately represented by the equation cocier zone. This procedure takes the unreacted h' = Kt metal away from the runaway oxidation reacton, so where h is the thickness of oxide procuced up to that exidation can be at least partially limited by the time t. The cuantity K can be reasonably well melting. The molten metal-oxide mixture readily represented by d:ssolves UO. and the rate of oxidation of the 2

resultng mixture is not well known. Therefore, once K = Aexp (-E/RT) licuefaction has occurred, there is great uncerta:nty where A and E are expenmentally derived con-about the extent of cxidation that follows. This un-stants, R is the gas constant, and T is the absolute certainty, coupled with the lack of precise temperature. Most investgators now use the knowledge of water level, means that rather wice Cathcart-Pawel rate constants in which A bounds must be placed on our ability to calculate

=

2 0.00349 in /s and E/R = 32 512*R.

the amount of hydrogen produced.

in a reactor accident the temperature of the clad-Hycrogen also can be produced by the reaction cing is not constant. Each kilogram of zirconium of water with steel. However, the amount procuced exidized releases about 6% MW. The release of appears to have been small in the TMI-2 accicent.

this energy raises the temperature of the cladding.

Calculations of the steel-water reaction have been The table beicw shows how the oxidation rate in-performed. The uncertaintes are even greater than creases with increasing temperature.

those involved in the Zirconium-water reacticn. Be-cause of the low production of hycrogen by th:s 2

Temperature aF K in /s reaction, the overall uncerta.nty is nct greatly affect-43 ed.

1000 1.9 X 10 1500 1.0 X 10 A check on the calculation of hydrogen produc-90 2000 4.4 X 10-9 tien cccurs. The summed partial pressures of 2500 5.3 X 10 steam and hydrogen must ecual the system pres-

-8 3000 3.1 X 10 sure. The partial pressure of the steam is only ap-

-7 3500 1.2 X 10-6 proximately known; therefore an exact check is not 4000 3.2 X 10~8 possible. However, the partial pressure of hydrogen at any time must certainly be fess than system For a grven oxidized thickness, the speed of the pressure; this fact can help to reduce the uncertain-reaction is prcportional to the quantty K, so that ty in the calculation.

528

supp essed Uncer boen; cenc. tens an a ::s!

Rr c.a 3 stoichiometnc mixture cf mc'e:u!ar hic Oce : ac R s: On acs: ce in water causes :t to c.s:n-cxygen coutd form in tne vaccr space Tne Orcca:-

e:ra:s '.!: its cea.stituents-hycrogen and oxygen.

tion is always slowed because scme re cmo:naten Many Oc~:::iex reactens are involved, but the net exists before the molecular procucts are removec

S# 'S This recombination is particulany important wnen H 0 - radiation - H - OH the boiling rate is low, which was typicat et conci-tions in the TMI-2 accident. An excess of nycrogen a ~"

will recuce the effective yie:cs of hycrogen and cxy.

H-H-H 2

gen even wnen boiling is taking stace, a:tncugn :ne OH-OH-H O reducuan is not as impressive as in tne noncoil:ng 2 2 regime.

The hycrogen percxice finally cecomposes into ox-Honekamp, et al. have calcuiated that the contri-y;en and water. Reverse reactons, or recombna-bution of radiolysis dunng boiling could nave raised ten. are the oxygen concentration in the bucc:e only to H., - OH - H,,0 - H Cchen calculated a maximum oxygen H, C., - H - H[O - OH cencentration of about 1*6 from a!! sourcesM lodine and other ha:0 gens a!so promote decom-and pos: tion, but by another process. Halide ions act as H - OH - H O 2

racical scavengers, and thus inhibit rec 0mbination.

If tre radiaten is in the form of heavy alpha parti-Expenments have been conducted with dilute hahde c!es, inere are high local concentrations of the radi-solutions, and marked scavenging of radicals has been observed.201 However, it would be difficult to ca:s H and OH, and the procucton of H and H 02 2

2 is fav0 red. On the other hand. if the radiation is cuantify the extent to which the trace concentra-sparse:y a0scrbed, as with gamma rays or slow tions of iodine in the TMI-2 accident might have neutrons, the radicais are dispersed so widely that scavenged radicals.

producten of hycrogen and oxygen is not favored.

Schwartz has calculated the effect of reactive im-In addition to the ionization density, the water purities.2m He shows that the amount of impunties enemistry influences whether decomposition or present is more than 2 factors of 10 too low to recomb: nation governs. The most important chemi-prevent recombination.

cal regulators are dissolved hydrogen and oxy-During much of the TMI-2 accident, a targe gen.20c.2c1 If only hydrogen is in the water (above a volume of mixed vapor and gas existed in the reac-icw threshold concentration), recombination is much tor coolant system (RCS). Water vapor can also be more racid tnan cecomposition, and no net hydro-decomposed by radiation. However, the molecular gen or cxygen is produced. If both are present with yield is extremely low, and the only effect is usua!!y g

and the production of H and OH radicals. These radi-l hydrogen precominatng, the production of H2 H.0 nses to a peak and then quickly deciines cals recombine to water in the presence of radia-2 essentally to zero. If hydrogen and oxygen are tion. Impunties might increase the decomposition, both present in about equal concentrations, both will but no major hydrogen or oxygen production from centnue to be produced as long as the radiation is radiolysis of water vapor would be expected in the aescr::ed.

TMI-2 accident.

Pressunzed water reactors are operated with The net result of all these factors is that probably c:ssolved hydrogen to promote recombination.

little hydrogen or oxygen was produced by ra-Even if this were not so, the metal-water reactions diolysis within the reactor coolant system. Some produce hydrogen, thus increasing the hydrogen oxygen might have been produced dunng periods of concentration in water. Furthermore, before clad boiling. The amount so produced cannot be pre-ructure, the radiation was mostly gamma rays, cisely calculated.

which co not favor decomposition; after clad rupture Some decompcsition might be possible in the some fissien products were released, but very ex-water that flowed out of the PORV into the reactor tensive prior hydrogen production would have inhi-sump. This water was exposed to high linear ener-i l

b!ed dscomposition.

gy transfer (LET) radiation from entrained fission l

These cond;tions are not necessarily true if boil-products and actinides and was exposed to the ing occurs. The rising steam bubbles scavenge the containment atmosphere. The containment afways molecu:ar

products, and recombination is had mere oxygen than hydrogen. Oxygen is also 529 l

l

'*:4 s : e inan nyOrCgen E:~ fa:!:f s C T*

IC 250 kg IPe I: Asf e II~a* # Y ~9 = 5 CI

~e: ! *are tre sumD water Oxf;e" nCn. wn. n COmm:sst:0 tecnnica; staM W W: na 9 2 Min 2:: '

Wa P.a. e ennance3 ra0:0iy*.

ce:Omocs;ti:1 350 89 in COnta!nment anC. nence. at u' 120 kg "

r-Wever. tne corcentraten et rac.:nuclices was tre RCS. The maximum crocucten a:::rc:n: ic

!Ow. an: c:sscNed n:trogen and NaCH inh et tne President's Comm:ssicn tecnnicai sta't. wn::n :s ce:Omcos:t:cn: tnerefore radiclyt:0 hycrogen was Cons;cerec less likely, wculd grve an RCS content cf 0 : a:y not a ma;0r acd: ten :: the very large 270 kg.

ameu t te eased from metai-water reactens.

These estmates assume tnat We r>:r:;en was Tne raciclyt reactons are far frcm simpte.

procuced dunng later cepressunraten Ints prem-Yie!:s are ccmclicated functens of tne LET cnarac-ise is believed I;ke!y. Even if some cf :ne cere was tenstes of the radiatort and recomcination is a uncovered aga:n, the rocs exposed a!reacy wout3 ccm :: ate: functon cf water chem:stry and state.

have teen at least partia!!y oxic::ed, and furtner ex-Estimates of hycrogen and oxygen formaton in the idation would have teen slow.

TM -2 ace: cent cou!c be inaccurate and incens: stent The estimate: 'mest liKety' amount remain:ng in un.ess case: on excenmems concu tec uncer very tne RCS 100 kg. m:!uces tre amount n s:!uten sr.nar concincns. Esumates of tne maximum and taDeut 26 kg at 1000 :si and 2E0?s as we:I as trat m:n: mum reasonable yiencs can be mace, but :t in a butble (aceut 74 kg). At a pressure cf 1000

- snould be uncerstocd that these are only estimates.

ps;a and 2807 (typical cf cend: tens cunn; tre several cays fc!!cwmg tne accident) tnis measu e 3

would be 645 ft. If about 1.6 pcunc moles of fiss:en Hycrogen Accounting gases and 3.2 peund moles of he:ium are accec to A numoet of estmates of the amount of hydro-this, the total of all noncendensib!e gases in the 3

3 gen produced by the metal-water reaction have bubble is 684 ft at 1000 psia and 2S07 (29000 ft been made. For example, Picklesimer made an ear-at 273 kg and 1 atm pressure [STPR ly estmate of 220 to 260 kg of hydrogen in tne first The largest amount 00nsidered for the RCS,270 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.20s Cole estmated 350 kg in the same kg. would give 244 kg in tne bute:e, for a tota' 3

tme frame.20s A !ater estmate by Cole was based volume of 2166 ft at 1000 psia and 2S07 (92000 on more realiste calcu!ations and indicated that 450 ft3 at STP).

kg at 6 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> probably was produced.207 This Bubble size calculatiens extrapolated back to 16 3

calculation includes less than 10 kg from oxidation of hcurs give a volume of 1470 ft at 1 COO psia. If the starn!ess steel. Tne President's Commission techni-mest likely* hydrogen estimate is correct, tnis ca! statf estimated that from 434 to 620 kg prcb-vc!ume would be accut 44*6 bycregen; the ably was produced 20s. A calculation made for this remaincer could be any other gas, mostly steam.

3 study (Secton !!.C.2.b) produced 330 to 410 kg in For example, a 786-ft bubble of steam in a ' hot the first few hours; this is consistent with a total sect

• within the damaged core would be possib!e.

production of 450.

The maximum estimate of 270 kg is impossible if The calculation of Cole also includes the parti-ine bubble size calcu!ations in the next section are tioning of hycrogen between the RCS and contain-correct. This estimate lends credence to the belief ment.207 This parttioning is important in accountng that the smaller quantity is more reasonable.

for the removal of hydrogen. Because Cole's esti-Based on the "mest likely* Quantties, the hydro-mate is within the bounds of Picklesimer's 20s it will gen accounting is then as fo!!ows:

be used as a starting point for the analysis.

Cole estmated that at 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />,250 kg of hy-Produced 450 kg drogen was in the RCS and 200 kg was in the con-Released to containment 350 kg tainment. In later depressunzation, between 7.5 and Burned 270 kg 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />. abcut an additonal 100 kg is believed to Remaining in containment SO kg have been added to the containment. At the tme of Remaining in RCS at 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> 100 kg hycrogen burn,150 kg might have been in the RCS In solution at 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> 26 kg and 300 kg in the centainment. The calcu!ated in bubble at 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> 74 kg amount bumed, based on the peak overpressure, was 267 kg.205 Cc!e estimated inat 330 to 360 kg existed at the time cf burn. 07 Measurement cf the hycrogen concentration en March 31 indicated The bubbfe size was calculated dunng the course about 80 kg at that time: therefere the amcunt con-of coc!down and bubbie removal by Ystrep::itan sumed ac Ording to Cc!e's estimate would be 250 Edson and Sab :ck & W!ccx. The same physica!

E20 o

y

nrc Owme cemet:ance cf a licuid containing a the ccmcress:b:!. y and thermal excans.cn of water gas ::u::::e--was used cy eacn crgan::at:cn. After and me sc!cc.!ay Of nycr gen. Tnese simO.6 cat.cns 3

me ac:: cert. Sanc:a carried out an incecencent in-lead to a ecnsistent 3C0 ft cvercrec:ction of tne ves::;a::On at :he recuest of the TMl Special In-bubble stre at 375 Osi.

207 l

cuiry Grcuo. The results of the latter study, as grven The B&W formuta2co inciuces these effects but in Figures 3-33 and !!-34, shew that the bubble was negfects changes in vacer mass in the pressun:er abcut 1470 ft at 2.00 p.m. en March 28 and was and the effect of the hemiscnencal !cwer head of 3

cmc:s:e:y ;cne ::y 6.00 p.m. cn Apnl 1 the ::ressunzer and cces not cens:cer the :: art:al A.t cugn eacn organtraten has used the same pressure of water vaccr. The net res:it is generally casic cnnc:cie. the equations a; pear different be-accut 5% under::redic :en of butble s::e.

2C7 cause :htferent s:mDlifying assumctions have been The Sancia formula inctudes all of these terms used.

but negiects the ef*ect of 'easage cunng bucc!e size The Met Ed fcrmu!a is the simplest. It neglects ex;enments line ecmciiance of the steel vessef and 20s ISO e

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183 e l

i i*

140 PRESENT WOR K ($AN DI A)

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129 s

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TC3 ii ik 5

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9 3

n i. *)

e g

62

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-\\ *uv e

• 3k I... ?.

• p.s.

a

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e

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t 50 100 150 200 258 W

HOURS AFTER 003.3'21/71 i

FIGURE II.33. Total Hydrogen in RCS 531

~

,-, - -.,, - - - ~. ~ -. -

.n,_-.-,.,..,,,,,,.__.--,_.,.,,n,

.-n.,.

-.e

".2" e Cf cens:!y because Cf temDerature Cnange pressure fer two reas:"!: be 3use Of:

~.-*CL '-

r.;: exOeriments). The et*ect et tne tast two terms et the gas and De:ause m:re of :ne gas :+5 : =

"as Deen e.aMated and is known to De small. Ihe sClution at tne h2;ner ::ressure Tne la"e* e"s:t tea. age eMe:t has not yet been evafuated but ts was neglected by Met E0.

a:so expectec to be small Even if an accurate formu!a is used that in:!uces Ea n bubole experiment was performed by sub-all the physical effects, tne inherent inaccuracy cf fe:tng the RCS to a known enange in pressure and the measunng system would make an a::uratt CE a :n; tne ass 00:ated change in vetume. From prec t:en d.fiice !.

One nee:s :: meast e sm:

Inis enange tne compliance of the Inquid gas system cnanges in voiume that corresp:nc :: smi!

was calculated, and hence the size of the bubcle.

changes in pressure in a very large system by us:n; The s::e of the bubble decreases w:th increased instruments that are not cf labcratory cuality.

1.8 e

1.4 s

n I

t i

1.2 g

i s

\\

\\

\\

g a

PRESENT WO R K (SAN DI A) g IJ i

g i

n g

~

g e

2 i

uw n

=

s i i g

g g s t g s J

g i j

s s s es s A

es gsi i si ee t%gt g%

2 i se e i iii t

O esp * # e si e

2 f

f I

f f

f I

t I

f f

f a

so too tso

cs 15e 3::

HOURS AFTER e4Co. 3."8/79 FIGURE II.34. Bubble Volume at 875 psia 532 I'..

-m

,,-., _. __ _ _ ~....

....,.--m..

.r

~

.__._y

._-_y

Erec' A-ris s taken to ce the intercect wtn :ne hor::enta ax:s --

An er cr analys:s of tne Sancta forme:a has been c:sanoearec between 3:00 and 9.03 om en A::rc 1 camec cut. Tne errors in bubc!e s::e are depen-The removal of hycrogen was accomchsnec Detn cent en ne cond:tions of the excenment and on tne W

UU*"

• i s::e of :ne buobie. Cond: tons for mcst of the bub-possde b esmate accumey N am ree l

e e s:e excenments were accrcximately as follows:

by each. However, from the fact that tne hycroga" in tre containment a!mesenere increase:: cy en, a RC5 oressure 1000 psi mocest amount dunng ventng, it can De assumec j

RCS temoerature 280*F that ventng was not tne pnnc: cal removal mechan-1 Fress.;ri:er level 250in ism.

j Maeco tanx level 45 in The removal rate by letdown is

' taseco tank temperature 81*F 3

t RCS c essare 12.2 tt / psi error 3,,

1.58 ft, F error

--H = p

-H p - w (N R, N, A" 3

=

~

ROS tem:eratare Fre:sur;:et sevei 97.3 f tNin error 3

r,taseup tann level 181.4 f t /in error 3

Sc!cbility 4.43 ft / percent error wnere an/ct is the molar letdown rate, moles per m:nute; M is molecular weignt; and cm/ct is the mass ietdown rate.

I Errors in eacn of the measured cuantities could N is the mole fraction of hycrogen in solution, be as great as 2% of full range.2m However, data A

and the subsenets H and w refer to hydrogen and are normally more accurate than this, and 2% of water and R and Af refer to RCS and makeup tank eacn reading is consicered more likely. An error of conditions. The mole fraction in soluton is, by 1C% in sclueility is consicered reasonable. Then the Henry's law.

pcssib!e total errors are:

N, = P,/K 3

Error due to RCS pressure error

= 244 ft is the partial pressure of hycrogen in the 3

A 9ft 9s dK.is the Henry's law constant. For RCS Error cue to RCS remperature error

=

3 Error due to pressurizer level

= 486 ft conditions K = 9.3 x 1 and for makeup tank 3

8 Error due to makeuo tank level

= 163 ft conditions K = 11 X 10.

These values are for 3

44 ft 3C07 and 757, the nearest tabulated points to Error oue to solubility

=

2S07 and 80*F. The partial pressure of water vapor All errors would probably not occur simultane-is taken to be equal to the saturation pressure at cus!y and would not normally all have the same the indicated temperature. This condition is not s:gn. Note, however, that the largest error-that strictly accurate but is within a few percent. The due to pressuriser level error-is nearly as large as partial pressures of hydrogen are 933 psia and 39.6 the bubble, and several of the errors are large frac-psia at total pressures of 1000 psia and 40 psia for tions of the bubble size. This clearly explains the the RCS and makeuo tank. With these values, let-great vanability in bubble size estimates.

down removes 9.64X10" mcles of hydrogen per mole water. Note that Dalton's law must held for a i

e gases. N a sepade We e Removal of the Hydrogen Bubble tains pure steam. Dalton's law cannot be applied to i

=xcept for changes in dissolved hydrogen due to the total.

changes in RCS pressure and temperatures, de-The letdown rate as grven in postaccident notes gassing at a constant rate of letdown would give a was about 30 gallons per minute, except for times l

constant rate of bubble snrinkage. Figure 11-33 when the letdown cooler was plugged. An a'.erage j

shcws the results of bubble calcu!ation with the rate might have been about 25 gallons per minute.

j Sandia fctmula. along with a least scuares fit for re-This rate is a mole rate of 10.64 pound moles of wa-mcva! rate. Also shown in Figure 11-33 is a removal ter per minute or 0.0103 pound me!es of hycrogen rate ca'cu:ated by B&W and a one standard devia-per minute, referred to RCS conditens. for the 94 t:en errer band about the Sandia fit. Figure 11-34 hours of bubble removal that would have removed shows the same data. except that the ordinate is to-52.6 kg.

tal hycrc;en in the RCS--in the bubb!e and dis-Leakage is estimated to be 5 to 6 gallons per

(

se!ved in the cociant. The time of removal can be minute. It is assumed that a!! leakage is due to reac-533 l

i

-r r.

-,,,. ~ _,,

. ~,, -,. -. _.

_,.,-~r-

: : : : n:: tens. esrere :ne Da'tal cressure cf tne :ntermat:n was n:* ::.:st'e to a cress /cc:

ry:-:;e, is so icw tnat :t wcu:3 oe censicerec water reae:cr anc cena.n. ::: ne act.) :0 :ne s -

neg:;:;e <n companson witn RCS conc: tons. The tuation at TMI-2 in v.n::n tne ceciant nac a :ar;e 4

mecr remcval rate is then 0.001 moles hycregen amount of hycrc;en in s:luti:n. Some scient.sn per me e water, and 5 ga: tens per minute (aga'n re-wno were cuestened were unacle to g:ve cef:n,twe terrec to RCS conditions) will remove 10.5 kg in 94 answers promotiy.

n urs %.cn of the leakage actua;ty eventua!y g:es N tes taken at tre t:me at the NRC eme*;s :3

:ne :ete:wn system. Tne efference !n nycre;in cemer, in::u:m;.ese ey ?.T:sen co no: n: : ate scaven;:ng rates is negiig:bfe.

that anyone c:sagreed w;m tne Ocss:beitty cf a The amount remaining (74-52.6-10.5), or 10.9 kg, hycrogen-oxygen exples;cn. Among these cueried l

C0uic r: ave teen removec ey venting of tne cressur-cn the effe :s anc prctac:! sty of ex0 lesion was cer. Tn:s ventng wou!d cause only a 0.2% increase 83W. The only note found to incicate mdd csa;'ee-in ecmainment nycrogen content, wnren eclains ment is the re:Ord Of a c:nversaton w:th B&W te v.5y a marse: increase in hycrogen centent doe to the effect that 35W ' fee:S *nat H; reccme:nat.:n :s sentn; was n:t ccserved. Leakage sncu:a nave tamng place uncer gamma flux? Notes in :02tn; caused an acc:tenal 0.2% increase in centa:nment inat ciner ex: ens ::ascaty a;teec m:n :ne es:-

hycro;en centent.

mates of oxygen crecucten exist. On Apn! 1. tre The amcunts removed by using the "mest hkely*

werd from S&W <<as tnat S&W ctt:c:a!!y 'tninxs not eng.nal amount are:

fiammable."

The ccinion was aimest universal that the bucc:e Letdown 52.6 kg (71%)

would be expicsive, eitner very soon cr in a matter Leakage 10.5 h (14%)

of some days.

Venting 10.9 kg (15%)

Late in the day of March 31. and especia!!y en April 1, other data began to be received that cen-tals 74 kg (100%)

tradicted the belief that the bubble contained oxy-eo gen. In the meantime, however, other scientists had No excuc cr imcrobable mechanisms need to be in-been asked about the pcssibility of an exp!csion, veked to explain the postulated cisappearance.

and stil others were delivenng cpmions on the damaging effects of exclosions. It was difficult to sort out the facts in the confusing me!ange of d.ffer.

The Hazard of the Hydrogen Bubble ing opinions.

In view of the disa;teement by the expens, the The instal concern expressec en March 29 was foi!cwing summary was prepared on April 1.

that the bubble was growing because cf radiofysis of the water in the reacter to produce hydrogen.

5% O in pure H; j

Later interest focused ucen the like!! hood of oxygen Flammability limit 2

formation and the hazard of an explosion within the 0, procuction rate 1% per cay i

reacter.

Current O concentration 5%

2 Detonation limit 12% 0;in pure H2 l

Cxygen Ccntent Emergency center notes fcr Acni 1 show that in-Assurance had been given as early as March 29 formation was increasingfy being received stating by a B&W scientist that no oxygen prcblem existed.

that no oxygen was being produced. On April 2 vir-This information was given to T. Novak but ap-tually all incoming information stated that no oxygen parently did not reach the NRC officials to inform existed.

the public until much later.

A wide cress section of experts was involved On March 30 and 31. Roger Mattsen re :uested NRC staff, National !aboratones, NRC contractors.

both the Office of Research and the Division cf Sys-De; artment of Energy laboratories the academic tems Safety of NRR to determine the pcssibility and community, and reactor manufacturers.2'3 At some consecuences of a hycrogen explosien in the reac-time on Acn! 1, the weight of ccinicn was that oxy-ter. The rescenses are summarized in Refs. 211 and gen was probably not present. Even then, hcwever, 212. Tne earty information given to Mattson was exp!csion and structural experts, who had not yet i

base: on excenences from a boiring water reactor been advised cf the fatest findings, continued to g've and fr0m the acvanced test reactor (ATR); hence, cpinions en the nazard cf explosions.

l I

l l

l 534 l

l i

c:una moies on March 2B c c n:t c1maae me ::>

Eces,e -a: arc in Rea:::t Vessel A numcer cf ccmDutations were mace of the ef- * * " * "

fe t that a hycrogen cetonat.cn would nave en :ne age me conmm reacter vessel assummg that an ex0losive mixture erstec te:On was hqnly impretabiel. These calcu-Fmc;n;s lat : s :t e mese cf Pef. 214 are typ; cal. gen-The most likety estimate fer hycrc:en crc:,.:t:-

era.ty sncwed mat malcr camage to tne reacter is 450 kg. ecuivaient to oxidat;cn ot accrexr. ate,

vessei was urheiy, a!! hough some showed that tne 50% of the cladding. It is possible tnat tne amount strengm cf me ucper head might be margmat Gen-produced could have been, as great as 520 kg. A era 9y. scerans!s n explosive damage would be un-20<e te Ore:::t me effects en tne basis of such cal-

tal gas volume of 1470 ft was precacly present en at 83 pm on M 28. De kamn O, culations.vecut expenments. Less soonistacated nycrogen in this bubble or buccfes c0c!d have Desa.

of wh;ch nad assumed a ara'yses-ma y s cien meme uture-gave nse to excessive fears e by Wown, lesage, am vems m asd CE#" # 3 for the safety of me reactor vessel Of ectal mterest is whether fragments of the anus W m M Whesd b amm reacter vessei could have been prCDefied with suffi-f#rD'tbt*'**0**Ln esma es cf We se cm c:ent velec:ty to breach the containment. Specialists ent mmocs of em=tatm mat wem e ma new genera 3y are agreed that this is so e. probableused W Meret aganMons and hm me 6 that it can ce virtua!!y ruled out, especia!!y because herent inaccuracy in the method of measurement.

any expics:ve fracture would De highly unlikety.

Secause no possibility existed of an explosive The bubble disappeared about 6.00 p.m. on AprJ t was pmsd n m We ad mixture ceing formed. the whcle question is e

om acacemic, and it can be concluced that no explosivea very low probabi!ity of explosion existed. The in-percephm of an exWesion ha:ad stemed m

hazard was present.

ammg sosec egens. Es Ccnsidenng the !ack of unanimity on March 31 na ttle cecisien to consider whether the bubbfe was perception was known or should have been known eWNWedWt potentia!!y explosive was correct. In the face of con-A flammable mixture in containment due to tradictory opinions it is proper to give consideration release of all the hydrogen would have been possi-to the wcrst case.

ble but very unlikely. Even if it had cecurred, me Exclosive Ha:ard in Containment A mere realistic hazard was the possibility of

e. How Close to a Meltdown?

sucden cepressunzabon, with release of the hydro-gen from me RCS to the containment. This depres-The extent of damage to the reactor core at 3 sun:atio.. was unlikely but possible. If the entire in-and 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after the start of the accident was es-ventcry of hycrogen had been added to the contain-timated and discussed in Section ILC.2.b. The es-ment, an exp!csrve mixture mignt have been formed.

timated damage at 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> consisted of embnttled Analysis of the containment atmosphere on Zirca!oy fuel cladding down to about 8 feet from the March 31 showed 1.7% H,15.7% O, and 82.6% N bottom of me core, with a 'debns bed" above cen-2 2

2 for one sample,and 17% H 16.5% O,,and 818% N sisting of fuel pellet fragments, Zircaloy oxide she!!s, 2

for another. At a temperature of SOT and pressure fractured Zircaloy cladding with an exide layer on of 14.3 csia. the fatter would be 86.1 pound moles the outer surface, and frozen masses of liquefied H.,. 835.9 pound moles 0, and 4144 pound moles dissolved in the Zircaloy metaLZrcaloy 2

fuel (UO Nh The addition of a!! the hycrogen in the RCS-dicxide eutectic licuid).

2 1CO kg or 110 pound me!es-would raise the hydro-The damage produced later, shortly before 4 gen concentration to 3.8% This elevation is stilhours, lowered the deem of embntifement and me However, if the entire cebris bed, and may have produced adet:enal be!ow the flammable limit.

bucc!e was hycrogen, an addition of 185 pound amounts of liquefied fuel in the debns bed. whien metes wculd occur. This addition would give a hy-then ran down the subchannels between neighbor-crogen concentration of 5.2%, which ceuid be ing rods to reach depths of abcut 1 fcct from the

!'.ammab!e. However, the burning of about 290 535