ML20129J517
| ML20129J517 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 02/04/1980 |
| From: | Udall M HOUSE OF REP., INTERIOR & INSULAR AFFAIRS |
| To: | Ahearne J NRC COMMISSION (OCM) |
| Shared Package | |
| ML20127A105 | List:
|
| References | |
| FOIA-84-311 NUDOCS 8507230106 | |
| Download: ML20129J517 (74) | |
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RAFfte.0VM D PAT U.gbaJA.s.E. ,t C.e.La. ff. The Honorable John Ahearne Chairman, Nuclear Regulatory Commission Washington, D. C. 20555
Dear Mr. Chairman:
y The following questions relate to those contained in my letter of January 21 concerning the fact that on March 28, 1979. Federal officials were not given important information indicative of conditions at Three Mile Island.
- 1. What inference is to be drawn from the [:
disparity of recollections concerning the i significance of the incore thermocouple measurements made prior to 9:30 a.m. on March 28, 1979; e.g. Messers Bennett - (I&E Tape
#311, p. 18-19), Wright (I&E Tape #310, p. 18),
and IMB (I&E Tape #315, p. 18) recall informing ,
.d.
Mr. Porter that they believed the temperature 1. data to be indicative of the core being [
. uncovered.wh ile Mr. Porter has made inconsistent statements sometimes implying that he did not believe the readings and other times suggesting that, "I guess I was afraid it was real." (I&E Tape #237, p. 20.)
Does the preponderance of evidence support the recollections of Messers Bennett, Wright and IMB, that it was generally a-agreed by them that the incore data was valid and indicative of the core being uncovered or does the preponderance of 1: evidence support the recollections of Mr. Porter to the effect that he at the time concluded the data was probably invalid?
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The Honorable John Ahearne February 4, 1980 1
- 2. What specific statements did Mr. Porter i- '
make leading to the statement on page 30 of the report of the Special Inquiry Group that, ..
'2 concerning the incore thermocouple readings,
" Porter shrugs . . . off /the readings / and returns upstairs to brief Miller. He tells Miller of the readings, but says he does not believe the high ones are accurate . . .?
- 3. If Mr. Porter concluded that the incore thermocouple data was unreliable, what did he believe to be the source of this unreliability?
Was Mr. Porter's explanation of the malfunctions of the thermocouples consistent with the fact that the thermocouple data was recalled from the computer several times on March 28 and the following days apparently (according to John Flint) because this data was indicative of what was happening to the core; e.g. if the thermocouples had become unreliable by 9:00 a.m. on March 28, what would have happened to increase ._ their reliability thereafter? If the thermocouples were unreliable because of their having been overheated, what temperatures would they have had to experience in order that multiple junctions be formed? What
. would have been the significance of these temperatures? Was a cause of formation of multiple junctions discussed with Mr. Gary i
Miller and if so, what was the outcome of such discussion? I
- 4. On page 138 of Volume II, Part 3 of the report of the Special Inquiry Group it is stated that,,"It is not clear that any of the actual /incore temperature / readings were communicated to the NRC on March 28, despite requests for such information, although the general range of readings may have been .
transmitted." Why is it not clear that the readings were communicated to'the NRC? What is meant by the statement that the general range of readings may have been transmitted? Which of the incore data obtained by the instrument technicians was transmitted to the NRC?
- s. Q The Honorable John Ahearne February 4, 1980
- 5. Which of the TMI supervisors or reactor operators recall informing or discussing with Mr. Gary Miller during the afternoon or evening of March 28 that the containment sprays had automatically initiated at approximately 1:50 p.m. and were turned off -
shortly thereafter? If Mr. Miller was not informed what reasons have the supervisors given for not having informed him? Where in the control room or adjacent offices was
'Mr. Miller located from approximately 1:50 p.m.
to 2:00 p.m. on March 28?
- 6. Does Mr. Mehler recall having discussed with any of the other TMI supervisors or reactor operators (as he recalled discussing with an NRC inspector) his reasons for believing t.
that the pressure pulse record at 1:50 p.m. on March 28 reflected a real pressure increase in the containment building? Were the TMI supervisors who dismissed the pressure pulse ._.. and actuation of containment sprays as having 0. resulted from spurious electrical signals aware of the circuit logic (as were Messers Chwastyk and Mehler) requiring at least two of three pressure sensing circuits to detect electrical signals equivalent to a pressure of at least 28 pounds per square inch in order for the containment sprays , I to be triggered? What was the rise time of the pressure pulse on the recorder? f What was the decay time? Did this pressure - pulse have the characteristics of a spurious electrical signal? ,
- 7. What were the circumstances leading to ,
review of the reactor building pressure on Thursday, March 29? Which officials of Metropolitan Edison and General Public , Utilities were involved in this review? Who ordered the review? Was the pressure , data reviewed as part of a general ef fort {' to review all data, or was the review undertaken as the result of TMI personnel remembering that the pressure pulse had . occurred? If the latter, which TMI personnel recalled the pressure pulse? At what time and to whom was the pressure pulse information given to NRC staff?
E . 1 s .s . q-The Honorable John Ahearne February 4, 1980 ;
- 8. At what time did TMI supervisors recognize that there were non-condensable gases in the system? Did the pressure and temperature data available at any time on March 28 clearly indicate the presence of non-condensable gases? If so, and this was not recognized on March 28, what were the reasons for the failure?
- 9. Did any of the persons,at Three Mile Island on March 28 seek to infer from the containment radiation levels, as had been done by Mr. Floyd in Lynchburg, an estimate of the number of fuel rods that had cracked or ruptured? What did TMI staff diagnose as the source of such radiation? Who at TMI had made such estimates or diagnoses on March 28? If such estimates or diagnoses were not made, what was the reason for not .a doing so? ;
E_
- 10. At what hour did it become apparent to Messers Miller and Herbein that attempts to depressurize the system had been unsuccessful? Was the fact that the depressurization e# fort did not appear to be succeeding reported to Lt. Governor Scranton?
Who made the decision to repressurize the , system? At what hour was this decision made? , Who participated in the discussions leading to the repressurization decision? ,
- 11. In a'May 9, 1979 mailgram to me, Mr. Herman Dieckamp, President of General Public Utilities Corporation, stated:
"There is no evidence that anyone interpreted the ' pressure spike' and the spray initiation e in terms of reactor core damage at the time of the spike nor that anyone withheld any .
information." Prior to sending me this t mailgram, what steps had Mr. Dieckamp taken to determine whether any of the TMI supervisors had interpreted the pressure spike and spray initiation in terms of reactor core damage? Is Mr. Dieckamp's statement quoted above consistent with the recollections of Mr. Chwastyk that he (Chwastyk) had recognized that the pressure pulse was real, that it I
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~ iiifff. s The' Honorable Jdhn Ah'earne February 5, 1980 was probably a manifestation of a hydrogen [.?.T explosion, and that this was an indication g,:
of severe core damage? o Thank you'for your assistance. Sincerely,. - { . . . . Wo . s
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- Early Indications of Core Damace at TMI-2 >
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-Introduction At approximately 6:00 a.m... on March 28, the water level in the TMI-2 reactor pressure vesser fell below the top of ,
'the heat producing hrbon of the fuel rods. During the next .
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'. hours a substantial . rtion of the reactot core was cooled
_ iram=ittently by steam produced in Iwater boiling within .'the , pressure - u.. . . e.. ~ . - . ves s el . - The steam was a significantly less efficient coolant than water, and for part of this period' radioactive decay of fission products generated more heat within the fuel than I was ' removed by steam flowing past the fuel cladding. Therefore, cooling was inadequate; portions of the zirconium
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cladding reached temperatures at which it reacted with steam, p:: od.ucing circonium oxide , hydrogen and an additional significant cuantity of heat that needed to be removed from the pressure vessel.
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Prior to the zirconium reaching temperatures at which rapid oxidation occurred, increased pressure from gases inside thc. fuel rods and loss of strength due to the higher temperatures caused the zirconium cladding to bulge and split. Kemeny Commission staff concluded that all or nearly all 36,000 rods balloned and ruptured, releasing the radioactive gases contained therein. (Kemeny, Core Damage, p. 4.) Kameny Commission staff also concluded that during the period of core uncovery fuel temperatures in the upper 40%
. to 50% of the core exceeded 1500 degrees F., and temperatures in 30% to 40% of the core exceeded 4000 degrees F. ('.io rma l fuel terperat-Ses during cperation a e about 650 degees F. IZ regulaticas a n a r- i n t w <- ,e " = r .' c u c c.m c .cr be d .:. c i o n e d n. . t.-- -w: ;
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? s. 5- zirconium cledding tcmperatures shall not exceed 2200 dngrees F.
5 in the'evsnt of'a'ccidenfs which m'ust be taken into account ~
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in the reactor design.) Kemeny staf f estimated that ultimately
. between 44% and 63% of the core's 20 tons of' zirconium cladding were oxidized, producing thereby some 1000 - 1300
*.. pounds of hydrogen and' causing some 60% to 70% of cladding to
. . . - m m. .-- .m'1 L.: i.a . ; . become so.' embrittled that it lost its structural integrity. R.. . . - .: .. .: s ...,,..c - g, (Ibid. , ,;p'. ' l) . _ The NRC's Special Inquiry Group estimates
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less claddihg oxidization; i.e. 31%-35% leading to production of 720-820 pounds of hydrogen. [SIG, Vol II, Part 2, p. 283.) (NRC regulations required that reactors be designed so that no , more yhan 1% of the zirconium exidizes in the event of accidents of a kind that must be taken into account in the reactor design.) Ecmeny et al. concluded that as a result of oxidation and emb5ittlement of the fuel rod cladding, several feet of the upper part of 'he t core fell into the gaps between the fuel rods, causing partial blocking of the flow of steam or water 9 that removed heat from the damaged fuel. . During the course of the accident, the TMI reacter pressures, temperatures and core geometry evolved into such an unusual state that the operators were unable to achieve a relatively, stable cooling condition until late in the day of . March 28. By 9:00 a.m. information available in the control room indicated that the core was severely damaged. High radiation levels in the reactor building indicated that a large percentage of the fuel rods had been damaged to the
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. point where they lost radioactive gases contained t.herein;
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showed that the reactor pressure vessel and
.a asso'iate c piping contained steam rather than water; and *
' numerous temperature readings indicated that the core had been.
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4 55 . c.. uncover'edJand the zirconium cladding of the fuel had been
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C; oxidized with the concrxnitant production of hydrogen.
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.. The NRC's Spe.cial Incuiry Group concluded that the foregoing and other manifestations of damage would have warranted the following actions at 9:00 a.m. Monday, March 28:
Actices 7hich Appear 7arranted '.. ..
- s. . .
- 1. Advise or order plant that. core appears t o hav e' been .
uncovered and thereby damaged. ."ari:us SPI ficv should be j crovided to recover the core, -cpen PoRV block valve for l
=axisue relie f flow. .
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- r. 2. 1.dvis e Sta t e officials that the core has been badly da. aged and has released a subst antial acount of radicactivity. The plant is nov in a condition not pre viously anelyzed for eccling syste: perfor:ance. Presucing that full EPI flow is
_, turned on, advise the State that if the cooling systens do not functico adecuately, portions of th e cor.e could begin :o - melt which could le~ad to significant offsite releases in a ,
.fev hours. If the cooling syste:s are successful, evidence
- cf that success should be a vailable in a f ew hours.
Fece::end to state officials that they begin a precautionary
' evacuation of the firs: fev ciles around the :laE. vi:.h a n '
al+:t for a larger radius (10 siles) e vac ua tien which :.ay f oll ow. Evaccecs from the innor zc=e of f.e v mil es ' . ra d:.us should be :oved to locatiens at least 20 miles dis ~ tant. 1 I ( SIG, Vol. II, Part 3, p. 268) i
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. . tly .' a.,t. ..this very hour when the SIG concluded that a partial. evacuation w'ould have been warranted, Pennsylvania 1
Lieutentant Governor Scranton called the TMI-2 control E room and was briefed on the situation by Station Manager =e . ae. ,. . .:... . .
.sw . .. . .
While the exact nature of the informatidn
"" " " Gary Miller: -
can'veyed to the Lieutenant Governor is unclear, it must have been ,
- far different from the picture that culd have been readily inferred from knowledge of events that took place since 4:00 a.m. because it led Mr. Scranton to announce at a press conference at 10:55 a.m. that:
... he had been advised that everything was
_, under control anc that there was no danger to the public healt.k and safety." (SIG, Vol. II, part 3, p. 382.) While most of the core damage had been done by 9:00 a.m. .. 4 ~ the situation remained precaricus until approximately 8:00 p.m.. The control room supervisors struggled for most of the day to reach a stable cooling configuration. Uncertain at 11:30 a.m. as to whether cooling water was reaching the . entire core, a. decision was r.ade to depressurize the system to the point where a low presssure cooling system could be used. Eut the depressurization effort was unsuccessful and at apprcximately 3:10 p.m. it was abandoned, apparently
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in fd$r of a repressurination strategy. The new objective was to make sure the reac:cr pressure vessel a:.d associated piping was filled with water so th:: the main reactor ceclan-
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...5-pumps could ba used'to circulat'e water between the reactor pressuref, vessel' dnd',the steam generators'from which heat would be removed in accordance with dstablished procedures.
A t 'a pp r o x ima..tely.1: : .:. . . . . .... -. .. . . ..-.. .30
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. . . ..while
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.. . .depressurization t
effort was still under way, a large pressure surge was
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_.. observed 1n the . reactor building. The surge resu'lted from y .. .. . 2_ . u ., 7 .~.i~ .;.'. . . a J1ydrocjen_ .
'explosion+. or fire .(subsequently referred to as a
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__."d eflag ration ") , that occurred when hydrogen produced as a
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byproduct of,, oxidation of the zirconium was released in the reactor building where it reacted chemically with hydrogen.*
. Meanwhile, federal and State of ficials remained une, ware that there.had been (or continued to be) a real danger of a meltdown. On Thursday, March 28, NRC Chairman Hendrie
. briefed the Energy and the Environment Subcommittee, leaving
*All references to hydrogen explosions or_ fires in this discussion concern the hydrogen detonation outside the pressure vessel in the containment building that occurred at 1:50 p.m.
on March 28, the first day of the accident. This is not the potential explosion that directly concerned the NRC in the period March 30 - April 1, when the Commission believed there was a possibility of a detonation or fire within the pressure vessel resulting from generation of oxygen which might react with the hydrogen bubble that was believed to occupy a substantial volume at the top of the pressure vessel. Subsecuent analyses appear to indicate that there was no mechanism under conditions then prevailing within the pressure vessel that could lea. to net production of oxygen, and therefore there need not have been serious concern about an explosion within the pressur~e vessel. While there may have been no danger in this period from an explosion within the pressure vessel, other dangers haf not passed and a further deterioration of reactor systems might have lead to a major radiological release.
- .~.
+
the impression that while the accident had been the most severe in the history of the nation's nuclear power program,
-there was and=had been little.. dancer of a core meltdown.
Chairman Hendrie stated: .
"The result /of the equipment malfunctions 7 has been' '
apparently some overheating ir the primary system _ ... that caused the venting. There apparently has been, 50 . judging'by-the radiation levels, some core damage ' in the sense that fuel rods have' leaked. gaseous _ radioactivity, I-rather doubt there is melting. . There does not seem to be anv indication of that.*h (Transcript, p. 23) It was not until the following day, Friday, March 30 thau the Commission came to realize the full implication's of the accident. Based cc in'c: ration indicating the occcrence of the F2_rch 28 hydrogen explosion in the reactor building and the exceedingly
'high radioactivity lev,els .in the reacter cooling water, the Commission concluded that damage had been severe and there was still danger of a major radiclogical release, resulting
., ;g either from another hydrogen explosion cr'from failures of equipment which was then performing under conditions for which it had not been designed. Kemenv staf f concluded that some of the uranium cxide
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e el nav have becone licuid at the temperatures which exceec,ed
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k000 decrees, even though the temperatures were less than.the
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temoeratures of 5200. Tne reascn he u~aium' oxide meltine
'uel licuifving at temperatures less than the uranium ox;cr ice
- - -tem'oerature is that it was in contact with zirconium ,
mel*'2$ce and mel' tine ocint of the zirconium / uranium oxioe mixture was lower than'the melting poin of the uranium xide standing in isolation. e d
1: . u - During the period March 30 thrcugh April 1,, serious consideration was gi.ven to .the need for evacuation of persons living ..w..i.th..i.n.. 5. .m. i.l. e. s - o. f... Three Mil.e . Island . .Had. officials known the status of the reactor on March 28, 'it is likely . (as suggested in the excerpt from the SIG quoted above) m that a precautionary evacuation would have been called
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on the first day of the accident.
, Because Federal and state
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officials w'ere not provided inforr.ation necessary for _ them to a ss e s's tn'e danger, they were prevented from fulfilling their responsibilities with regard to protection of the public health and safety. '
'To date, three major TMI inquiries have been completed; none have adequately addressed the reasons for failure of TMI management to provide significant information to officials of the NRC an' d State of Pennsylvania, information that the latter officials needed to ccmprehend the nature zu of the situation confronting them. The first such TM inc.uir.v r tha t conducted by the NRC's Of5 ice of Inspection and Enforcement and reported upon in NUREG 0600, virtually
, ignored the question. While the TMI inquiry conducted by the President's Commission on Chree Mile Island (the .Kemeny Commission) did not pursue the quesrion in detail, Commissicn member Governcr Bruce Babbitt states in a supplementary e
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view incorporated in the Commission report:
"It now appears that there is evidence to indicate
- that MIT Ed technicians understood, within a few hours of the accident, that the nuclear core had been~ubcovered an(~th'a't'th'is' specific information was transmitted to supervisory personnel at the '
plant early Wednesday. There seems to be little.
- question that the technicians who took the -
temperature readings that morning understood what they found. The real cuestion is what happened to this information and whether it
. was transmitted to the appropriate management personnel. It certainly did not get transmitted to responsible public officials, including Lieutenant Governor Scranton during a meeting with Met Ed that afternoon."
The third major TMI inquiry was that conducted by the NRC's 5pecial Inquiry Group. The SIG concluded variously
~
~
that ... the evidence failed to establish that Met Ed management or other personnel willfully withheld information from the NRC," and, "The f act that SRC and S&W did no better than Met Ed/GPU in reporting critical information up the managment chain and acting upon it tends to support our conclusion that there is no evidence to show willful withholding --, of information by Met Ed from NRC." [SIG, Vol. I, p. 15 9-16 0. ) In reporting the SIG results) *
- 5hto the N RC , Group Director Mitchell Rogovin stated with regard to the question of withholding information:
. .. There was a mind set or a ' group psychology
, that apparently tended not to believe that the
.. cora was uncovered. They didn ' t even think of the possibility of the core being uncovered.
People went along in that f ashion. " . (Rogevin/i;RC Transcript, p. 57.)
9-SIG. Deputy Director George Frampton stated to the Commission O that:
"Our conclusions are less important than the. - . -
'evidends itself. "The' evidence will all be
" made or has been-made public this aftern'oon '
and I think on the question of coverup, -
,- there is conflicting evidence. There is '
definitely conflicting testimony. There - - are things that don't make coherent sense pGi .
. . to us. We made a judgment about the weight .
'. of the-evidence. b'e found tha t, while -
there is some evidence to suggest that there . is an' intentional withholding of information, that the weight of the evidence doesn't support that, others could come to a different conclusion based on the evidence that we developed." (Ibid, p. 60)
- The following discussion addresses circumstances relevant to-resolution of the question as to whether TMI management withheld from state and federal officials information that should have been provided these officials.
Emergency Command Team , In considering the kinds of data that were available, it is useful to keep in mind the emergency management organization and procedures established by Station Manager Gary Miller. Upon his arrival at the TMI control room shcrtly after 7:00 a.m., he organized a group for the purpose of analyzing informaticn and determining what actions should be taken. In a statement dated May 7, 1979 and presented to the E&E subcommittee on May 24, Miller described this , command structure:
. . :- 4 ;, 5:. : .. : . : : a :: : . :.:- 3 c :.. :. i ... i. .: n : :: - - :.
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The first concern I had as ! arriv;d in the C:r.t 31 kes at a:pr:mirately 7:Cf. =as
- tectre fully c:gni: ant cf .Se sitaaticn as it esistec an cece ! fully gree-stood
' tre :! ant c:-ci:*:rs ae.c t*e rasia: ten e ergency. I 1. e:ia:ely *::t caa ;e :f .;e
. ::ntr:1 R:: . and a:;:lete geeter :e::le to tire:: ?e ne: essa y evc16:te-s in :ne vital areas to assure ina* tre :.:1tc was tr e::ee. . .. .
tha: :Se reietse was a:nt:orec. tr.at ccesr.icatiens were oc: ering anc :N: the :iant as t r:egr.: in s:e:s :: a sta 1e ccacitten. The ecmano set v:. which I just ces:rtzec ret frecuestiy in-osgn:w: . tre cay. The g-:v: prese .tet unit c nct:tces. statss cf [. ergen:7 Flan actions, shares c:inices, discusste te:*$tcal esta, a.-t ra:e e::=er.ca:icts. isc.ssicas were and O heic with .*.tnage,ent, anc/or 8atcock & Wilcoz. Lync?.sve;. the 5:ste. ,the NR* a . following these evaluations. I cace a:crecritte ee isions and se directed tae, i::l e .4r.ta ti:#.1: tu *:r.trt,1 Room and infereed c ners %:n insite anc ov:sice tne .* plan as necessary. East: ally. I set v: this !.mer;escy ccer.anc tea.s in the early newes as I arrivec at t*e :lant and the ractatiet eme ge cy mas in :-:;*tss. :y esse *.ially fc .tr.g y sester pec:le ' .to a ne:-ces it s.:ervtse. c n: set te e t ;t" a- re::r: :: re r.fie Ortating the ;1ert :: a safe tencr ier.. e Ress .as : it. cha r;e :" De*at'. .s tc cire:* ;$e Sr.ift $6:t-viser. .*.? C.:sei .as 6: tr. cr.a rge c' acia:1cr. c: ce-ns. inciscing ractatien surveys, cesite -lf fsite tea s. a:::. :st'I' y caeck, esse :iy I cf see:ie. ge tting tr. :: eta c: =t:* the [me ;eecy *:a:*:* 1:atter !!:1l p etc.. =r. SeeMege* was in eve-all ctarie cf L'nt * . **e I e te-tv 0:* - .1:a t t er . s '.41: i ,
- 0:rtr:1 f.:n ar.c tt ass.;te P.a all f ace ts cf U.e e e itrey pian we e f:.c.e:.
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wa r:vice me assurance tr.4 ali at:ttes .e e :eteg te se arc :c te sgre :Se ec:'f'. ca*tCt calls we's Pa ce . ** : r.ttageNS: .as *.:*' fie . att all c:r" ricJ!iC*s were
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- lace. Mr. let s:$e-s was re veste: ic ;-c.*:e te*-*.tcal agsts:ancg ;',yg lif..y;
" wi 9 P.is Mc.St c##tte as %e c:dc. *r. As*ct' als * *
- a*;e cf te: tical sv :cP anC c cT.P i c
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Tha following" discussion accresses une various xincs or information available to plant management which should have
~
indicated,that the reactor core had been severely damaged. Temperature Data . By observing the temperature at various locations gg;
- in - the reactor cooling system, reactor operators should be able to determine the adeguacy of core cooling and whether there could be i steam .waces in the reactor sf , / vessel' or 'in the hot-leg pipes leading from the pressure vessel to th'e steam generators. Such temperature measurements enable operators to know, in the event the system contains steam, whether the steam space has *
. expanded to the point where it encompasses a significant portion of the reactor core.
~
'~ Temperature data,can be interpreted approximately as follows:
-- If temperatures at the top of the core are less than the temperature at which water boils for;the prevailing
... pressure of the reactor cooling system, the fuel rods are cooled primafily by water and cooling is adecuate. This is called a "sub-cooled" condition. If tCMtures at the top of the core ecual the temperature at which water boils for the prevailing pressure, the fuel rods are being cooled either by water or a steam-water mixture; cocling is probably adecuate. This - is called a " saturated" condition, a$d can be converted
'to a "sub-cooled" condition by increasing the system' pressure at vhich point the steam in the mixture condenses to water.
i l l'
-- If temperatures at the top of the core are greater than the temperature at which water boils for the prevailing pressure, some portion of the fuel' rods is being cooled by steam; cooling may be inadequate rM ' .
and the temperature of some of the cladding is higher than the steam temperature. Steam at any temperature above the saturation temperature is called "superheated" and is indicative of inadequate cooling. Such conditions are, at least, a warning _ sign that insufficient cooling water or steam-water mixture may be making contact with the fuel fuel rods, and thatArod surface temperatures may be on the verge of rising to levels' where the zirconium cladding will react chemically with steam, producing irconium oxide and hydrogen.
-- Temperatures at the top of the co're in excess of 2000 degrees are indicative of inadequate core cooling and of a cladding steam chemical reaction.
A typical B&W reactor normally operates at a pressure of 2185 pounds per square inch (psi) and a het leg piping temperature of about 604 degrees T. This means that the hottest water temperature is approximately 45 degrees below the boiling point. In order for the water to boil at this temperature, the pressure would have to drop frcm 2155 psi to about 1600 psi.
r.
. Hot-lag .
. A princip'al indicator of sy tem conditions at TMI was the temperature of fluid (water or steam) in the hot leg pipe,*
which'is"ths"pipc~that'dhrries*: hot *watsr'from th'e reactor to the steam generator. Hot-leg temperature data at TMI , was normally presented on a computer printout and on a s, trip D*' ,
. - chart recorder mounted in the reactor con. trol room. The computer
. was progra=ned to record data between 520 degrees F. and 620 degrees F.; when, temperatures were outside this range, the computer printed question marks. The strip chart was capable of recording temperatures up to SOO degrees F.
~
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- 14 Apparently owing to the computer being incapable of indicating temperatures in excess of 620' F. , Station Manager Gary Miller, .soo.n . af.ter. h. e.. arriv. ed a.t, about 7 : 0 5 a.m. , directed that a meter able to indicate the full range of hot-leg temperature .
be set up in the control room: Sh When I turned to focus on plant conditions, an initial concern was that the hot-leg indication was off-scale. , I asked that an extended scale readout device be connected to the hot leg RTD (resistance temperr.ture laeasuring device) . (E&E, TMI-2, part 2, p. 297.) s,
)
Miller stated that:
" the' extended hot leg temperature readout device indicated 720*F." (Daid.)
exceeding . Any temperature A 660*F at the.then prevailing pressures (which ranged up to 2200 psi) clearly indicated the presence of superheated steam ; i.e. that the core had been uncovered. The readings from the hot leg instrument are also referred to by Ivan porter, TMI-2 Instrument ar.d Control
- engineer, and by John Flint, an engineer e.h. ployed by Eabcock and Wilcox who was stationed at TMI, porter had been responsible for setting up the instrument, and he told NRC investigators that after intially cuestioning the validity
- s of the readings he had checked some of the temperature 1
readings taken from instruments within the core (see 6 below) and that: to me it confirmed that,what I was seeing en the
'RTD. That we had temperatures greater than 700 degrees in the plant, since 700* degrees was full scale on the computer and I was reading greater than 700 on uhe hot les RTD." (I&E, Tape 227, p. 15.)
l , l .This is in reference to the in-ccre therr.ccouples discussed bele The computer could indiccte the in-core temperatures up to 700* if whereas it could indicate the hot-leg tem.eratures : en_y tc 020'.
, v .
John Flint recalled that at this time (sometime after 9:00 a.m.)
~
... Ivan Porter showed me a special setup with a RTD, that was approximately 724 degrees." (I&E, Tape 323, p.
34.) Flint also noted that he himself had nenitored the strip chrt recorder in the back of the roonstich was recording the data Flint refers to in'the preceeding quote, biis chart sh:7~ed hot-leg te peratres indicating su:erheatef es,
. conditions in the pri:rary system shich in turn indicated sections of the core has been uncovered for a significant portion of the period m
between 5:40-a.m'. and 7:50 p.m.*, the latter being the time at whic' a relatively stable cooling arrangement was established. The strip chart shews that the hot leg temperatures rose rapidly from'the temperature at which water boiled for the prevailing pressure (i.e. saturation temperature) to superheated temperatures following shutdown of the main reactor coolant pump at approximately'5:40 a.m. Virginia Notes taken by E&W staff in Lynchburg4cn 14 arch 28 indicate that personnel at TMI were not using the hot-leg temperature ! data as indicative of whether the core was.ccvered. The notes state the pressurizer temperature was being used as the basis for inferring core output te. paratu e since the flow of water was from the reactor pressure vessel, into the pressuri::er, and cut the top of the pressurizer. The hot-leg temperature the sensor was measuringAtemperature at the top of the hot leg where steam and/or non-condensible gases were blocking flow through the steam generator. Therefore, the temperature at the top of the hot leg was more indicative of temperatures
*see rigure II.
l
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[ . , that had existed' earlier (when the core was uncovered e.g. l at 7:00 a.m.) rather than later in the morning ( e,. g . 11:00 a.m.) r L when,it was. believed tha't.the core was probably being cooled .
- via high pressure injection flow through the core and'out the '
pressurizer.
~
In-core Thermocouples .
. "Other sources of temperature data were the 52 thermocouples l
installed inside the reactor pressure vessel above the fuel asserblies. These thermocouples sensed water (or steam) temp,eratures at particular points across the top of the core. Ea t. thermocouple provided an indicatien of the temperature above conditiens A a particular fuel asser51y while the hot-leg L terprature sensing 6evice,s (discussed above) norally indicated the r 1 ! average romperature of water (or steam) leaving the reactor pressure vessel. There were, in fact, large differences between average temperatures as measu:ed in the hot-legs and the , peak tcaperatures measured by the incividual in-core thermo-in-ccre couples. It was these peak temperatures that confirmed not only 4 l 4 i e r
,6 (1
' - 1? -
that the coro was uncovered, but that the zirconium cla.dding was reacting with steam, producing hydrogen and zirconium oxide. Credibility of in-core thermocouole data. The TMI personnel showed an early and continuing'inte' rest 3 in the in-core temperatures. They instructed the computer toprintthesetemperaturesatabout8:3da.m., 8:47 a.m. 11:10 a.m., 12:40 p.m., 4:11 p.m., 6:30 p.m., 7:59
. p.m.,
8:56 p.m., and 9:56 p.m. Bedr:en .6:00 a.m. and 6:00 p.m. the temperature data for at least 40% of the thermocouples (EhRI, Fig. cl-ll) wee printed as cuestionmarks, indicatine
. either that the thermocouples had failed or that the temperatures were in excess of 700* F. Eccause some of the thermocouples alternated between indicating cuestion marks and temperatures less than 700 degrees, it was more plausible that the readings were indicative of temperatures in excess of 700 degrees indicativo of thang, instrument malfuncticn.* Moreever, if many had been damaged while others continued to function, this in -
itself would have been a reasonable indication that something major had happened in the core resulting in disabling of the thermocouples. The folicwing excerpts from interviews conducted by TMI investigators indicate that TM personnel did in fact believe the in-core thermoccuples vere providing useful inicrmation.
'By approximately 12:45 a.m. en March 29 the thermoccuples were mostly indicating temperatures less than 700 degrees and cre cf were apparently used thereafter as a crime indicator ccnditiens. '
l l i l
l
-.18 -
John Flint, Babcock and Wilcox engineer stationed at TMI told Gen. era.l Publi.c. .Ut.il.i.t.ies. . investigators .in an interview held on April'20: .
... shortly after I came in we also started calling up on the computer the incere thermocouples Ed attempting to establish what had happened in ths core. Many of,them were indicating cuestionmarks which indicated that they were greater than their 700F range. Only one or ' two seemed to indicate that thev were in f act bad. These, temperatures were monitoried for the rest of the day to follow what was happening to the core."
Flint also told NRC I&E Inspectors that:
"When we first started dumping them cut (i.e. calling up the incere thermocouple data from the computer) many of them had cuestion marks, which indicated they were above their normal scale of 700 degrees not printing out " bad" which would indicate that they had failed. Over the nex few hcurs these thermo-couples gradually came back en scale [:) we recovered l more and more of them and towards late afternoon I believe we had most of them indicating 'on scale. "
(I&E, Tape 58-59, p. 8.) - Ivan Porter told NRC investigatcrs: l
... I believe shcr:ly after 7, he (station manager, .
Gary Miller) asked me about the readings on the in-core l temperature detectors, and I punched out several of them (i.e. asked for computer printcuts)..." (I&E Tape 237,
- p. 16) -
Porter said he reported the results (i.e. temperatures in . excess of 700' F.) to Miller who asked Pciter whether there was any way of measuring the thermoccuple voltages in order to determine how much in excess cf 700 degrees the to peratures l f 1 l l
t. t c . might be. Porter told Miller that he thought he could get l the information by connecting a digital voltmeter directly
. 1 l
l ' to the wires leading from the reactor core and measuring . f and therefore the' temperatures) l ' .:n thereby the voltagesfbeing fed into the computer. -At this L_ . point there are varying recollections as to exactly who it was that' Porter told to make the measurements. In_any event, l' l four technicians in addition to Porter either participated in making the measurements, or observed as they were being ! made. One technician who the NRC investigators have , l designated Instrument Man 3 (IV3) in deference to his wish for anonymity, stated that:
... T o of the thermocouples, the first few we had measured, were around 700 to 800 degrees, specific temperatures I can't cuote you, I don' t know. We had taken one off and we had measured 2600 degrees in and abeti that vicinity, it was very close to that. At that time neither one of us believed that this was,a true reading because after seeing two, three that were 700, 800 degrees,
- 2600 was hard to believe so we decided to take a few more off. ... I believe in the course of testing . ;
thermocouples, we had at least 10 or 12 we had disconnected t? total. He had seen temperatures ranging anywhere from I i know there was a botton of about 690 degrees to uppers of 3700 to 4000 degrees. (I.E. Tape 315, p. 11) , While cladding temperatures probably did exceed 3500', there is disagreement as to whether temperatures as high as 4000 degrees were actually measured since it is unclear that the thernceouples 7 would function at such temperatures. There is general agreement, hcwever, that at least five people (Porter, !bintents:a Foremen Bennet and Gilbert, Instrument Man Thomas Wright, and Instrunent l Man 3) were directly aware of the it.str. men: readings indicating l.. r t L.
'. _ 20 _
temperatures in excess of 2000 degrees; i.e. temperatures at
.Sould*be~'
which thereA . significan't production of hydrogen. Porter , questioned the validity of the measurements and he tol'd the technicians to repeat them usiag another meter. The technicians M4 ~ did so and this time they took measurements of 51'of the 52 thermocouples. Nine of the 51 were in excess of 2000 degrees. Where there was' overlap, the second set of measurements, taken
~
shortly a.fter the first, confirred the first set." IM3 told the MC investigatcrs "Now the second set of readings d".6 in fact correle.te the original set of readings that was ta'icn Qith'the thermocouple reader. The general feeling at least
. amongst Jim (Fright) and myself was that the readings we had were true and accurate. All five of us that were present there did in fact visually see the actual
~
readings we had taken both off the thermocouple reader and millivet reader. All five cf us did in fact verify that the millivolt reading through the conversien table war, correct. Sc I am sure we didn't read the wrong table or the wrong ene er something of that nature. (I . E . Tape 315, p. 16) Sennet, Gilbert, Wright and IM3 have stated with varying degrees of certitude their conclusion that the data indicated the core was uncovered. IMB told the investigatcrs:
"... it was the general consensus amongst the instrument people there that the core was definitelv un cvered, we . -
kind of found it hard te believe that this many high temperatures that we had seen that all those inceres would have been bad and the only way that they could have went bad that radically would be an uncovering of the core, and super overheating. (Ibid. , p. 17) ! Bennet: h*e had pessibly uncevered the core was the only way we could see that ycu cculd have chtained temperatures of tha magnitude." ( .I. Tape 111, p. 1E) l
S Wright:
'"I feel then that there was a definite sign then.that the core had definitely been uncovered to the point, where it suffered damage. But it, I still.say that, -
.you know,'I'm there to take the data. - I'm not there:to analyze it. So I gave them my personal opinion as in the, yeah, I do believe we did~ suffer some damage there.
'" . (I . E. Tape 310, p. 14). , Ivan Porter was responsible for reporting the thermoccuple
- measurements to Gary Miller. In his statements to the NRC-investigat6rs Porter is ambtguous with regard to what he believed the significance of the in-core measurements to be. When asked whether he believed a reading of 230b degrees to be ancmalous, he stated:
"I don't know. I guess I was afraid it was real."
(I.E. Tape 237, p. 20) But Porter also suggested that the measurements were not believeable. He said that in reporting to, Gary Miller that Miller had asked him what he (Porter) thought the thermocouple measu,rements had meant. Porter told the NRC investigators that he was not sure of what his repense to Miller had been, I but that: ,
"...my personal evaluation was that they (the thermocouples) had been destroyed." (Ibid. , p. 19)
IM3 told the investigatcrs, however, that he had told Porter (IMB that heAcel)ieved the temperatures reading's indicated that the core was uncovered e
- ... I cersenallv told him that and he'was physically there to read the readings. He saw the actual temperatur.es we ha.d.,',This is why the first time he didn't believe it.". (I.E. Tape 315, p. 18)
IMS also said: .
"I believe Ivan (Porter) didn't really want to believe what was really taking place. I don't know whether it was an attitude of " hey, your measurements are wrong, you guys don't know what the heck your doing or
'. whatnot." I think the general consensus throughout L.- the whole first day was number one nobody really knew.
what was actually happening, number two, some that had an inkling ~of what was happening didn't really want to believe what was going on. ONce you start seeing a temperature of 3000 to 4000 degrees in a core, well ... the first thing that starts coming to mind, you've got a meltdown coming. The core is uncovered." (Ibid., p. 18-19) Whatever it was that Porter actually reported to statio.k Miller told manager Gary Miller,4NRC investigators: : So you know, the bottom 'ine l here was that they (the in-cores) are hot, they were hot enough that they scared
~
you, as far as what you're looking for. It told me the l reason the computer was off scale at 700 degrees... The in-cores were reading anywhere from 2500 or so,.and I picked 2500. It could have been higher than that. But that you know, I was looking for a gross indicator f" and I had it. ... I know that we were superheated and all that sort of thing, I don' t think we tumbled to that l kind of lodge (sic, logic?) but we just know we didn't l have a control, we were out of centrol. We knew the situatic.. was one we hadn't anticipated too many times here." l (I.E. Tape 159, p. 51-52) None of the TMI investigators' interviews has indicated whether Gary Miller (who,as indicated above,had been informed of l l the first set of measurements) saw the data obtained from the second set of readings. This data when plotted on a map cf the core t f i showed hot regions within the core and col'd regions on the ' t. periphery.* Instrument Man Themas Wright who was invclved in recording the data said tha: the data was supposed te ha.'e bEen turnef ,
- See Tigure !!!.
9
l
- 22 a -
FIGURE III l
. l
-~ ;
. .i I
'8 10 11 12 13 14 15 l 4 '6 ' 7,' '9'
,.f. ';, ',
1 2 3 5 A A ..., .' *.-
.' . .q:
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' 4 'r 469 957 325 C ;....:~'4 >
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1196
.. '. I !
326 E ! 599 1926 25S0 E . 1 i 323 555 F F SO 2366 2375 1805 1875 234 G , G 375 2272 1774 1295 217e 1852 H H 250 2452 K 1811 632 1760 K 296 1774 L L 373 1566 3S2 252 M M 325 2171 2327 346
'N N 413 578 2167 1135 308 O O 356 462 P
P 291 . R 352 475 F.
'0 11 12 13 14 15 1 2 3 4 5 6 7 8 9 .
Figure Cl 12. f.'.ap cf Core Exit Temperature ('F) 2LD-330 min. g
. . .23 -
.~.. ..
y over to Ivan Porter. He' stated to the NRC (I.E.-Tape"310, p. 18-19) that Porter was. aware of the data. Wright recalls also that
~
Porter had remarked that it appeared to him that it'"... looked like w ame,youknoO,that 'oked.like o they'a been damaged." It is not clear from this whether Porter was saying that the core or'the thermocouples had been damaged. It is also unclear .mi whether Porter actually received sheets on which the data-was written, and Wich mt unnoticed,. it 'seems, from :
- March 28 until May 7. .
Mike Ross, a TMI-I superintendant, who was a member of the group making decisions en March'28 engaged in the following dialogue with NRC investigators. Hunter (NRC investigator):
"Okay'. Do you rech11 in the discussion, think tank discussions, that the thermoconcle '~
temperatures were, in fact, brought up in the discussion's?" i Ross: .
" Thermocouple temperatures were brought up to .
Gary Miller, and I guess the bottom line they got out of that, was that they were not conclusive. It showed the core was het, basically. I was going to say his range varied, very scattered. . He had like ... He was saying he had various temperatures scattered throughout. So, well, Gary and he discussed it,-and basically I think the botten line was yeah, the ccre is hot, or it
, is at least hot." .e (I&E TMI Tape #226) 8 9
- That the in-core thermocouples had indicated ter::peratures
. ib._y. cess of 2000 degrees . (iglying probable hydrogen production) was t, .
apparently not reported to the NRC during the first few days
.. . NRC 75~ of the accident. Victor Stello (thenf6 Director of Operating Harold Reactors under4Denton) said he had not knowh6f such measureme'nts
- until the week of April 1 . Roger Mattson (Director of Systems Safety under Harold Denton) stated to the E&E Task Force on May 9 that this was the first he had heard of.such temperatures.
s
-m G O 9
0 s O e
- 24n -
Stello, however, had been concerned on, March 28 about data
~
indicating superheated conditions in the hot legs. He requested comcute.r. .or..into.u.ts. .of..t.he .i.n ,cor.e . thermocouple data. There emsued ths following dialogue between Three Mile Island and the NRC's -
- Incident Response Center in Bethesda:
Voice: . First of all, I can't get the in-core temperatures. Ok,ay? . Voice: You cannot get them? Voice: ' They print out questionmarks. Voice: They print out questionmarks? Voice: Yes. - Voice: Okay, what's that mean? Voice: That means that either the ecmputer point is messed up -- okay? Voice: Yes. Voice: or that the line -- you know, the -- where you sense it, that line's broken or something's messed up with that line. Okay? They were printing earlier. Yeah,
.the computer just won't -- the computer won't spit out a good number for them. They're trying all of them to see if we can get any of them to print. Okay?
(-01-033-CH 2/20-MEM-10.) Based on the foregoing discussion, SRC It.I investiga:crs wrote: - ~ (At approximately 4:10 p.m. on March 2E) " Reported in-rnta te"mer?.t re: unavaila':'.:. 7tporvisor (at T.'4I ) repor's t :c SRC the. . (in-ccres) are all printing
~
questiens marks .thich means.sither the' computer point
. cr the senscr is malfuncti:r (sic). (NURIG'060~, IA-101)
.4b -
Yet practically coincident with the conversation in which the NRC was told'that the computer was printing out question-marks, the computer was in f act displayins not onlycuestionmarks but also two on-scale readings, one indicating that thermocouple
.r .
. 9-H was showing a temperature of 596.9 F., and the other showing thermocoucle 6-L indicating a temperature of 562.1 F. Both r d..
' temperatures were indicative of superheated conditions in the.
core and'of the likelihood that the reason for the questionmakrs was high temperature rather than a malfunction of the instuments. A reproduction of the compu er printout follows:
- T_ .s6. 9. i_ .:, 1.*., J . J _1.T.. R . }
C s'.i . l . J f "ils . 7 f 5 'i . L 5u :" . 's ". .' . 0. ". , 6 . '., ",.*.- . .
.0 -. > . . _ _ I .c e. . s , 2.. .e. . c. .9'.5 e
ls'iG.0 1..".,.6 - m..
-,n.>
.. a . ". . '. i . l. .
. :. . . " . . > .ur .
"'16 : 1'. : 32 DATA 0493 IN INCORE T/C 3-H TE;iP -???.?
. 16 : 11: h l.... DATA 0k94...lM !NCORE T/C 9-H TE:.1P
, , .r.. ':; . 9 ,
. m., ,. .o
.. . 1 ,r. o. D,\~,~A U40.2' l .' ' l i .".'n.Ps. 'i / r. 0. - C> 'i . i.2 ?. ". *. . S.
-???.7.._.
__16 : 11: 5.7_ DATA . 04 96. _ I N I NCORE T/ C . . E .: . T E! *P IC:12:05 DATA Ok97 IN li: CORE T/C 9-E TEMP -?.??.? .
,g .
3 e .. , 4, _,,.. __G n"0" 5 '.n' _# f ") i OPERATOR GROUP C . 02'!3 Ol, .' .', , ", . '.m. 10-2 0 "~'S 0:,0. 0... 0 3. ". O,' 5.', . r.", 'i .) .
.' n. 16 . .12 . . .1 1.". 2 .. ':. ' 21. . "a '
."...'a 4'iG.k 455 0 ';" '
In' ". 3 s"o u . .; .' .". . . ' . 16: 13: 4h DAT;\ Ok": li4 INCORE..T/C 7-P TE:!P . ......???.?.._ 16:13:53 DATA 0499 IM INCCRE T/C 7-E TO;P -??".? " 15:'L: 03 OATA t.'500 ' lN INCCRE T/C G TI;;P -???. - O _ 3,..
. e.. . . .._4 t
,. 4 -- 0 c .,1 . .m.. . :- , c. .. .I . . n. .. nm :. i /r .e3 - 6. : cn. . :-. , --.,:::?. :
2 b. .: .t.i : t G n,0. .P n.e. .i.. J . L. '. OPERATO t GRO:.'P c 1032 03:0 0390 03S9 0':53 0393._0972 okt; :M? s-20 ,5:02 3 .c. ,.> . e _3 s :;...i :s.i.0 u. si,.9 i;5.2 i r.j s. .... <.ns . 5 2 , -,s . - .n.... . s. O 16: 15 : 54_.. DATA 0502 .. IM !! CORE T/C 5- H. TEli? .. ..... ... -???.?._. 15: 16:03 DATA 0503 IM !!jCORE T/C 5-R TEil? -???.? I . I n. o. r. c _ / ,.v . e , . i tr 3
- w : co : .v._ DA,m. . n. r.0.,: .. ._____,.b... . . 1.. _
O 10: 1G : 22 GROUP TREND .
,' 00.: Pst.T..a. ._GROU.S. C._ _.
103'i 03SG 03*90 03S9 0437. 0 3 " .'. O'i ?.? 03 0.t. 0400
-, r,- 15 3 i e p ._,._3.es.1. .e .i .n n. . r., s=. ; . ;. 4 7 :. . ?~ .1n.~. s :. Su.. a . 4..0. 3 : es u . *, .e . .. . .o y' ~ . . .
16:17: ._ . 54 _ OATA 0505 IN !!.' CORE T/C 7-M TE;;P -???.?
- n. ..:,
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' Althongh 'tihe 'iri-5cid 'thdf:hodouple data was printed at least 9 times between 8:00 a.m. and 10:00 p.m. on .v. arch 28 there appears to be no record of any set of such data ,
having been transmitted to the NRC's Incident Response Center in Bethesda. . 6 m e
~
Neutron Detectors TMI-2 instrumentation inclnded neutron detectors mounted outside . the reactor pressure vessel and 52 strings of detectofs n.ounted inside. Both in-core and ex-core detectors are installed for the, purpose of providing operational data; during nbrmal operations, the in-core neutron debx: tors indicate-power production at various locations within the core. During the TMI accident both in-core and ex-core detectors provicec cata incicating the core was uncovered. ) The ex-core instruments indicated increased neutron levels. These were interpreted initially as indicating that the reactor was,near the critical point where a self-sustaining chain reaction might be occurring. The operators believed that this might happen as a result of insufficient bcron concentration in the primary system coolant. In actuality the apparent increase in neutron activity resulted from t'ne . fact that neutrons -- normally produced in small cuantities in a reactor core even when the reactor is nct running - .were, as a result of voids in the core, less likely tc be absorbed prior to their escaping the pressure vessel and were therefore 4 reaching the en-core instruments in greater numbers. In short, the increased number of neutrons were due ,tc the pressure vessel having lost its water and not to a restart of the chain reaction. O
-_____-___________._-_-_________-_---________.--___-___a
The in-core' neutron detectors also yielded data indicating that the core was uncovered and the 6epth of the uncovering. Once the water level wen't below the neutron detector and the . temperature of its surroundings rose, the detectors responded to the higher temperatures and became, in effect, tempefature y
. sensitive devices which provided indirect indication of -
water level in the core. (See Figure IV'.) The record'is unclear as the extent to which the TMI supervisors used the neutron detector data as an indication been that the core had Auncovered. The record shows that increc:zd counting rates were initially interpreted as an indicator of the reactor becoming critical. As a result, additional
, boron was injected into the primary cooling system. During the morning of March 28, S&W engineer John Flint looked at the neutron detector data and concluded that in all probability a '
the increased counting rates were due togchange in the leakage path, i.e.. as a result cf voids in the reactor coolant-fewer. neutrons were absorbed by water before reaching the neutron detector. Flint told the I&E Inspectors:
" Indications for the source and intermediate range (neutron detectors) appeared to be normal, for this period of time following a shutdown condition. I did notice, however, that there were several blips on the recorder for source / intermediate range and in conversatien with Ed Fredericks he informed me that they thought at the time that they were going critical and that they had added additional boron to the system. At this time, I informed them that in all probability this was not the case, that there had been a change in leakage flux path from the reacter core to the detectors and it was not in fac: the
. case the reactor going critical again."
ILE Tape 55, 59, p. 4.)
- 26a -
t FIGURE IV Reactor Vessel Sl
- p ,
Plenum
-y ,'
assembly . t>v'
+ '
+ +
Y
, p in-core & .
7 / thermocovoles * -{ j y . (above 52 fuel assemblies) j g i. 3 Downcemer k Fuel assembhes
\ - (177 total) g -
1 Source Core - range ex ccre neutren 3s _ detect 0r (2) Seti powered
,/ neu:ron detectors .
U (in 52 fue: assemDhes a -
~
for total of 364) . r1 e j Q
+ i Lev.er grid assemoly i y------_.----.-_-- - ,
% / ',
m s#
^ -
Tc caris so eacing room
? a S:C TG E CtOr C Ofi9 C*EtiOn ECC in5*.rument lccations.
27 - High Radiation Levels in Containment At 6:35 a.m. a radiation monitor mounted at.the top of the co.nta.inment building.in.dicated radiation levels of about 0.1 Roentgen (R) p'er hour. By 7:30 a.m. this , monitor was indicating levels in excess of 10,000 R per ho'ur. v;
. . - (Accroximately 50% of persons exposed to this dose rate '
would receive a lethal dose in about 4 minutes.) 'These radiatio'n levels implied that radioactive fission product gases had been released frem a significant fraction of the fuel rods; the cnly way such a release could have occurred would have'been through development of cracks or perforations in the cladding. Based on this reading alcne, James Floyd, a TMI
' supervisor inferred that approximately 1/8 of the fuel rods had failed. On the day of the accident, Floyd was in Lynchburg, Virginia for training on the 3&W reactor simulater.
.. Having been told of the accident by a colleague, . Floyd called the centrol rocn at around
-7:30 a.m. and was given information on radiation levels frc= , which he inferred that the cuantity of. radioactive gas in the containment building was approximately ecuivalent to 1/8 of that that had been contained in the fuel rods; this led to his inference that 1/E cf the fuel had been damaged.
Floyd told the Kemeny Cc=mi-ssion that the inference he mace in ,yncyburg u . coua..c nave alsc been made by persons in-he TX:' control recr on the day of the accident. (Kemany e
. ., I Hearing, May 31, 1979,qp. 186-188.) Kemeny Commission member Ted Tay. lor asked:
"Well, to whom did you give this information (i.e.
Floyd'stinference ' . ~ . . that it looked like at least an eighth of the cladding had failed') during,. - the course of the day on Wednesday, outside the
= people you are immediately involved with at Lynchburg?"
,'u~;a '
- - Floyd responded:
"No'one."
Taylor:
"No one. Were you assuming that people at the plant knew this?"
Floyd:
"Yes sir." (Ibid., p. 188-189)
Floyd later indicated that it was not until he sat in on th$ Kemeny hearings in lat May that he realized that the supervisors and management at TMI had said that en March 28 they were unaware of a substantial amount of core damage.
. .; . (Ibid., p. 194) .
4 9 1 4, 4 e
.,n- y --,,y
._ Hydrocan Combustion During the morning and early afternoon on March 28, a significant portion of the hydrogen produced in the zirconium
~
steam reaction was released f, rom the reactor coo 1ing system into the containment building via the pressurizer relief , valve. At approximately 1:50 p.m. the hydrogen ignited.Ib What is pr5bably.more accurately described as a fire than an 2:
. explosion caused several effects including a.28 pound per square inch (psi) cressure pulse in the containment building,*
This pulse was recorded on the strip chart that recorded
-containment building pressure. It was also recorded on a series of other pressure measuring devices which used the containment pressure as a reference. The fire raised temperatures in the containment from about 125 degrees to "175 degreesF,an increase of 50 degrees dissimilar to any other ,
te.wature changes cbserved that day; these texperatre data were recorded on strip charts in the control rocm. The incr, eased temperatures
~
triggered several alarms. The containment pressure pulse also actuated vari.ous emergency systems, most notably the equipment that caused water and sodium hydroxide to be sprayed into the containment building. TMI supervisors and operators have given two explanations for not.having reported the hydrogen fire to either Federal cr state officials:
"F gure V .;
Figure V-3
" . Figure V-C pr
'See f.r. p. 5, regarding this nc: being the perential 3
4 fire and/cr explosion feared or :: arch 20 and subsecuen: days. f
29a - FIGURE V-A
.~
~
v _ N
~
o
=
P
- O o
"Ei c C e, 2 C C
~
X .c h e G 4 o - co ac m a o s e 2 o e "O ~c m
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' 2 -2 s 3 O
- D ~2' u
< .O e o e
C c O P t e i I. l
- N t
I l i s l I l l i ' i ! I N e o n co N N o e N c:: e o y N - - l (6! sc) a>nsse;d Su:.pnns ;c:czag . r I i. l l
- I i
Y .*
. - 29b -
FIGU.E W-B
.. 270 '
-5
.g 0 n o OTSG "A" ,
265 -
- OTSG~B" -
0 t
- S 26 -
5 e O O O I C 255 - c 10 0 2e $ 2n o o 1 S c S _ p 250 -
! e -
15 < c ! c / e c o n l ./ m O l O 245 - c _ 20 l I '
. Ic 2e.0 -
25 235 - - 30 l I i i i s 13:50:20 13:50:30 13:50:40 13:50:50 13:51:00 13:51:10 13:51:20 Time . Effect of H 2 ig.,ition on measured stearn pressures. AO S
29c -
. FIGURE .V-C l
8 e E-- vp, - I ei onnOO E,,O e O a N, . N. . v aaoa EC c S.c c C_9 ._9. ._9
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c0 u C ccc _o _o o c
- tO O O -O _o
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C c C.
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w
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O _v c cC C C - e ~ c* t' C 3- u o E cS c =- e ca B C C *- N e w w ~, 0 GS - C O U I ~5 j =;: :- g x y x .9 m .9 .g - O/- C
= 3 .
EEEEGG
- 8o
- aC o C C -
to LO < C < < ccN C3 O l l l l ! ! ! ! C O O O O C O C C O O OO c,
- .o s c
Q v O N C C' C tw , 4 0 e e a
- ~ . .
. . . e
- 1. The exolosion manifestations were caused by spurious electrical. signals. .. . . . .
- 2. Because the pressure did not remain'at a high level, .
the cause of the pulse was not important, and the e. yui - operators were too engrossed with establishing a stable cooling configuration to pay attention to it. Neith'e r of these exclanations is plausible.
- The first is cuestionable because of plant design considerations and the simultaneous occurrance of pressure and temperature-effects indicative of a red. pressere pulse. Given their basic training in reactor engineering it is i= plausible that the TMI supervisors would consider the pressure pulse to be insi nificant in li ht of the multiple indications ch core uncovery and hydrogen production.
The record contains conflicting testimony. Excerpts . _ ,_ follow. The first concerns whether the electrical malfunctions could have caused the pressure pulse. TMI-2 Reactor Operators encacec in the rol.lowinc clalocue with Ed Frederick and Craig'Fiust the E&E TSI Task' Force: Myers: What could have had two of those three sensing devices sense high pressure and lead them to think the pressure was high, other than hich scressure, real high pressure, actual high pressure? - Is thcre anything that c.ecices tne c.ressure is coinc to. t.na: coulc. . nave led those sensors to think the pressure was high? Frederick: A test sicnal. - . Myers: Would a test signal go to two of them at the same time? Faus:: No. In fact, you wou'd have to hook it up. Frederick: It wculd have to be a lengthy manual a :icn to
.. ge: it to de it, other than actual bui ld ing pressure.
.. o . -
31 - Myers: Is there anythine that vcu can think of other than excess building pressure that could have simultaneously led the meter to read 28 pounds per square inch and to turn on the spray tan:ss or turn on the containment spray? Frederick: No; it had to be high level pressure. Faust: There had to be a pressure surge in the building
,g i r it to happen. (E&E TMI Part 1, p. 147)
At a later date (on September 11) Frederick told interviewers from the NRC's Special Inquiry Group that he did not believe the pressure spike to have reflected a real increase in pressure because his training had not informed him as to the eossibility of such a spike. Frederick stated that ncne of the percens present thought it plausible that the pressure in a 2 million cubic foot building could rise and fall so rapidly. Frederi'ck stated:
"That's why none of us considered it plausible. It's imposcible to do that." .
SIG interviewer Ron Haynes responded:
"I wouldn't say it was irpossible. I thought it actually occurred."
7:ederick then stated:
" Eased on our training, it was impossible. It was completely foreign. If you look back through everybody's training and the FASR and safety analysis and the building construction, you will not see a paragraph that projects that type of transient. Nor will you see it in anybody's
. - a.4..4..c. c o ." a . ac -- ' ' = ' -
. --'e c-
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a 4-.0, r. c. . . . .- - - g.. C-. , , - . 9 i
4 Instrument Engineer Ivan Porter was asked by NRC
- investigators whether Porter-thought the pressure spike could be explained by any form of instrument malfunction. Porter responded: -
"I would think not. 'It did look like a real spike, pw- to me. That was when I was specifically asked if it could:be real." (I&E Tape 237, p.. 35)
With regard to whether he saw the pressure pulsa on March 28, Porter said: ,
"But somehow I_have a feeling, I didn' t look at those charts until.the next day. I'm nou specifically sure that I was aware of it that day. I know that I very specifically remember a discussion where we icoked at the chart, was asked if it could possibly be real, and I also look at the . wide ranged pressure chart and saw that [the pulss] showed up as a decrease in pressure on the wide range reacter coolant system pressure, but I sincerely believe that.that was the next day that I looked through,the stuff." (Ibid., p. 34)
It is not clear why they would be waiting until the next. day to look at the data, or if it were the next day, what it was th'at led them to do it then. In addition 'to the spike appearing to be real to Porter, he found a'similar negative spike, in the reactor coclant system pressure history. This would be expected since reactor coolant system pressure was measured using the containment building pressure as a reference; when the containment pressure went up, the reacter coolant system pressure would appear to go down. As noted above, a similar negative pressure pulse das observed in other pressure histories.
"Eee .rigure V- E .
e
. e3-Shift Supervisor William Zewe said that he had observed the pressure spike to occur at the mcment the pressurizer relief valve was cycled, but that he did not associate the spike with a hydrogen explosion. He said that he had not been aware of temperatures in the core of sufficient -
magnitude for the cladding-steam chemical reaction to have 6E occurred. Zewe was apparently unaware of the in-core thermocouple measurements that implied production of hydrogen. Zewe said, not knowine. what the seike could have that been,Athey ascribed it to an electical malfunction associated with the operation of the valve. hnile Zewe may have considered have been the pressure pulse togan electrical anomoly, others seemed concerned that it was real. TMI Supervisor Joseph Chwastyk said:
~
"... I actually saw the recorder, the pressure recorder on tn.e ullc. .ing, so. r:ec towarc.
2 cien,: now what caused it but the fact that the spray valves started indicated to me that we actually had some kind of pressure spike, either on the sensors or:in the building itself. I was not sure. The spike of course started all the buildinc. s.trav eumes, decav. heat nume.s, etc. The pressura spiked up and it was on1v. t.o . briefly, as a mctter of fact, a couple of heart beats. I know because I missed those heart beats. It came back down again." (I&E Tape 232/233, p. 9)
.Chwastyk (who arrived in the control room between 11:00 a.m. and 12 noen, and who was apparently not aware of the direct measurements of the in-core temperatures) also re:errec to an explosion in describing ..ow u .
it was :.na: he came to realize that the reacter core Might have been significant.ly camagec:
"It was like I said, everybefy was pretty busy and I didn't want c step anybody frcm wha: they were doing so I just tried to get a feel for what was
,, happening by lec:.ing around and asking the cperators a :he panel what thev were dcine. "- --#1 time er sometimi F. ter t.Ce expics1Cr anC. 1: Cawnec
.. .'he .
cr me what it waS, I didn't : T. c *.- h e '.- ~7. 0 0.'~ damCge ws h!.f . (Ibid., c. l!' N-6 rl;..
L-
. 'Also, TMI shift Supervisor Erian Mehler has told investigators that he. believed the instruments to have indicated
. . . . . ~ .. . . .
. occurrance of a'real pr6ssure pulse and not.to have been a
~
~
' manifestation-of spurious electrical signals. Mehler referred
. . . . to the pr' essure pulse as having originated with a chemical ?.x . . reaction; he stated that he did not recall t.hinking that
~
a hydrogen detonation might have occurred. O. 'Okay, I think in your I&E interview you said that you thought initially tha- the pressure spike in the containmer when you saw it, was probably due to scmebody fooling around
. with the transmitter.
A. Yes, I said that. But then I also said it couldn't
-- have been possible becauss building spray pumps started.
Q. Which meant that there had been acressure' sicnal that ~ 1 i . . . went through anc. startec t.ne sullc..ing spray pumps? A. Right. Q. Now, after looking at it in that initial dismissal,- did you later realize that there had been pressure in the containment that caused that spike on the instrument? A. Yes. O. Do you have any idea what cculd cause that kind.of a rapid pressure spike? . A. I know Joe and I talked abou; it later on that day, about what cculd have caused is and I don't think hydroge.- S entered into it. We though maybe some kind of chemical reacticn or sene:hing happened because it was up and down so CuiCh. . E
. 1 O e Q. That is Joe Chwastyk?
A. Yes. s Q. So you really didn't have a good diagnosis? l A. I personally'didn't think hydrogen could form that,
~ '
quick in the building to that concentration to ca'use it in that period of time. (SIG, Mehler, p. 13-15, 10/11/79)
- s. 1 e~=
Mehler also recalled in his conversstions with investigators that on March 28 he had been told not to turn on oil pumps in the containment, apparently out of concern'that electrical sparks might be produced which could cause detonation of hydrogen in the containment structure. On October 11, Mehler told SIG investigators that: a I do know scmetime after the pressure spike happened we were told-not to start equipment because they assumed tha it [the pressure spike) could happen again and they probably put it that there was hydrogen in there, but that was sometire ..a after 1:50. Now how far past that, I don't know. And I do not, I said -- well, to Gary Miller I said -- he said don't start any more cil pumps and I said we don't have to, I already tested them all, because they were concerned -- but how far into the afterncon at that time, I don't know whether it was 4:00, 2:00 or what, but it was sometime after,
< . u_
i . , .p . _. u. . . . This recollection is similar te cne reported in the New York Times wherein Mehler was said to have "O 9 L
r - P . i *
. . f.
. L -
responded to his superviscr's warning not to turn on the L. , pumps by saying'that he had already done so. -According to the" Times article someone then allegedly said: .
- "Well, that means we don't have any more hydrogen
$*C in there'." .
? l Mr. Mehler was interviewed acain on Octover 30 and at this l t time he was less certain that the above noted instruction i not to start th'e pumps had been given on March 28. The
'folicwing exchange took place during the October 30 interview L
i where.the questions' are being asked by Mr. Frampton of i the SIG and the answers are Mr. Mehler's: O. Since the inter. view tha our group did with you
~
f on October 11, as indicated by Mehler Exhibit Sc. 2, you have become less certain that this instruction and the l j conversation you had with Mr. Miller.was on Wednescay, t . .a . , March 28th. - t . L l A. That is correct. . l O. What is it that has caused you to doubt the l recollection that you had before? l l A. I've talked to some other people that were there i E on the 28th, and also thinking back upon it, you know, I i i l cannot be certain that it did harten.en the 28th. O. In talking with other .:eeple -- well, let me ask you who ycu have talked te about it? l A. I've talked :c Gary Miller, Mike F. css, Joe Chwast; l ! ,, Eill 2ews, and ncne Of the rec 11ect that ins::ue:icn being given en the 2Eth.
37 - O. Do any of them recollect such an instruction being given on the 29th? A. I don't think they would say specifically that it happened on the 29th either, but I do believe some of . them recollect it being given. y O. Do you remember which ones? A. I think Joe does. 1 Q. Any of the other people? A. I don't know. Q. In your conversations with them, what is it that they have said that's made you think that your reccliection is probably wrong that it was the 28th? A. Well, they would have been in the room the same time I was to h. ear the instructions, and it seems funny,
.. . 2woulc. be the on1.v one that remencerec it har..oenine.
1: on the 28th when there were other people in the room that don't remember it. . w: O. So this is in part conversatiens with other people that you have had and in part sort of a general reconstruction of events that's made you think that ycu're wrong in thinking it was the 28th; is that fair to say,? A. That's fair to say, and also, you know, cuite a bit happened the 28th. A:.d I did come back the 29th. It could have very well been the 29':h, and I wouldn't ever say fcr certain it was the 29th right now. O. It's ccnceivable i: cculd have been the 20th? A. I wouldn't want tc get definite and sa. it was -- .
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. Q. .
Would' it be fair to say that your own recollection, l faulty-or not, standing alone, has been that it was the 28th, but that in talking to other people, you think that your L recollection is most likely to be somewhat faulty and l it was more likelv that it was the 29th? -- A. That's correct. (SIG, Mehler, P. 15-17, 10/30/79) %s * - i . Chw'astyk also recalls being told, "
... not to restart any equipmen.t in the reactor building. And someone at the time had just finished starting a piece of equipment."
i Chwastyk said he thought the equipment referred to was the DC oil pumps en the reactor coolant pumps, presumably the same pumps referred to by Mehler. Chwastyk said that he l thought the instruction had not been issued en Wednesday, i March 28, because he reme.$bered receiving it in the supervisor's office,-and "... I don't think on Wednesday I wcs in the shift supervisor's office at all." (SIG, Chwastyk, p. 16, 10/30/79) I This recollecticn of Chwastyk is referred to in the SI'G report (Volume II, part 3, p. 0147) and is part of the basis for the SIG conclusion that Mehler was probablv incorrect when'he remembered the discussion, about not turning on the oil pumps, as having occurred in the shift supervisor's of fice on Wednesday, March 28. On the other hand,, TMI supervisor Mike Chwastvh Ross did recalig beihg in the Shift Supervisor's office on , i i March 25:
"At time Joe (Chwastyk) would ccme into the think l
tank, (i.e. the shift superviser's office where { i l '
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supervisory personnel convened during the day for
. t. . ,
the purpose of assessing events and de,ciding upon 4 . D-; actions to.bo taken) where we were at, and he would
<.cF:3
'N W enter discussions.
, (SIG, Ross, p. 15, 10/30/79) 7_ .,
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- 2. .
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- .
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- tn. Jh - - conflicted with Chwastyk's recal"J ine tha't he didn't :think
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. Sc . ~ .;si=:iT he had3eeni.in =
this offico .on; Wednesday, March 28.~ The5SIG
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. _ _ -:Hepg.
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'M
*'ikE :7r'"W558repiirt'moties .but does not comment upon a-further. discrepancy
.. m o r: . . -- 2-7~.m re = = .in}the-testimon.y of Rehler an'd Miller: Mahler. testified M.:.KMO L
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~ * - :..~" that it was Niller.who gave the instruction not: to start __
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?~ef.%c.'._ the pumps even though the date was uncertain; i.e. Mehler's
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.. '. _ .=_ES: .own z.ecollection was that the instruction had been issued .
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' $_.On.the 28th', but after talking to other people, he .s aid J
.r cr.J.... .that ;his recollection was most likely f aulty and.it was. -~ ~
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.y. ;3:'.T.r== control = room on the 29th -fat -the -hour which wns Mehler's.== '
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" 2 OJ: W-+ - new. recollection. of the time at'-which the instruction had' q ' __f r- .~ ;.
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. . . - q: - ~ been Si ven. . (SIG,.Vol.: 7I,.Part.3, p. 147-148.;):-% J zT : -- .
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i . Theodore A reactor operator,/Illjes, who arrived in the control room after the detonation, told NRC investigators that he , had been briefed on.the.. reactor.b.uilding pressure pulse: :"
"I was told they had a spike on both indications of the ,
reactor building pressure recorder. There was some discussion as to what it was. A hydrogen explosion was discussed. This was later in the evening." (IEE, . g Tape 261, p. 6) . When asked again as to whether the dis'cussion of a possible hydrogen burn had taken place on the first evening (March 28) Illjes said:
'"As far as I know that pcssibility was discussed that evening." (Ibid., p. 10)
At about 2:30 p.m., some 40 minutes after the hydrogen. detonation, Station Manager Gary Miller left the site for the purpose of briefing Lieutenant Governor Scranton. (E&E, TMI Part II, p . 2 7 3 ,) Miller has written that while in the centrol room en :: arch 28:
"I heard a noi.re at apprcximately 1: 50 p.m. , however, I did not asscciate it with the burning of hydrogen l< .
-~ ~
or the actuation of the safeguards system at that , time. I was first aware of the reccrded pressure. pulse and associated actuatien of the safeguards system on Friday morning, March 30, 1979." , (Ibid., p. 298) Others who were present say that Miller was aware of the pressure pulse at about the time it occurred. When Reactor Operator Frederick was asked whether others in.the centrcl rocm had reacted to the pressure spike, Frederick stated:
"I think ':r . '?arshall tried te figure i cut, and Gary ' aller was partirularly interested in it."
( _; u. r , 2. 2 1 ,. ..: )
e 41 - Zewe stated in a deposition for the Special Inquiry Group that Mr. Miller was in the control room when the
. pressure pulse occurred (SIG, Zewe et al., 9/11/79, p. 257) ,
Zewe also stated that:
~
"I focnd it hard to believe that anyone who was in
== . the control room observing anything would have missed. that (the spike) or turning off the pumps or any of the discussions at all." Mike Ross, who was TMI-I Operations Supervisor, but acting as se'cond in command tc Miller at TF.I-2 cn March 28 stated when asked whether he was present when the pressure spike occurred: .
"Yes. I was near the~censole at that time and if we are talking about the same time was around 2:00, sometime in the area. And at that time we get an IS signal and some of the components restarted, decay heat, what have you. He got building isolation again and we took care of that and we icoked back and the control room operator said "Jeese the spray pumps are running." and ue locked back at the charts at that time. We saw a fairly large spike en the chart and the exact pressure at this time I don't know, ... it was arcund 30 pounds. My thought at the time and Miller was cut there with us and he
~
cuestioned he said, ";eese you know I thougn: I heard something, too." He are moving dcun the road there 100 miles an hour and we locked at it and we said "Jeese the spike was so sher it must have been an instrument." That was our reasening at the time. We reached ever and we said you can shut the spray pumps cff new because the pressure came right back to 0, ... almost very, very rapid return and we shut the spray pumps of f. I new know that surav cumes were on abcut five minutes when
~
icoking back. b'ecause I did look back on that particular
~
cne. I personally didn't associate it at the m ment with
m 42 - any kind of explosion in the builcing. I associated
'it with'an' instrument ~ problem perhaps anc u t a t u.s so did Miller at tne time because we gust went on.:o somethane. e. l s e It wasn't until the next dav. that we thought about anv.th,ing'like that and started lookinc.
back. (IEE Tape #226, p. 4-5) [ Underline added.) .
're
, Shift sucervisor Chawstv.k who had observed the pressure spike but did not hear the noise referrec to by Gary Mille'r told the NRC investigators of a suggestien made to Miller on the basis of the spike having occurred upon operation of the pressurizer relief valve:
.Chwastyk: No, I did not hear the noise. But that was the
. . ... y point at w. .nicn I hac. assumec t.nat we cic .. ave some kind of explosien in the building. And that is when I suggested to Gary Miller we no longer cycle the electro-magnetic ..
relief valve because. it had ... . the explosion ... or racic :: sinc cressure. n :ne reactor culacine corresponcec to o.ren nc. tn.e electremac.netic re.r 11e-. valve. (IEE Tape , v232/233, p. 16.) Chwastyk stated in subsequent interviews with the SIG that he recalled informing Garv. Miller of his concern that an explosion had occurred. On October 11 he said that en March 2E he had been concerned even prior to the explosion that water should be pumped into the primary a: a ".igher rate and that:
"It was right after the hydrogen explosion and I
. mentioned that I correlated the cpening of the valve with the detonation paried that I again went to Gary Miller and explained what I thcught had happenef'as far as the hydregen de:cna:icn and the simultanecus c..e...'.. c'. .'.c. vc.
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I i On October 30, Chwastyk was asked again whether he thcught-he had mentioned :the possibility of a' hydrogen explosion to Gary Miller in so many words, or discussed what that would - had mean'or what happened.to the system. Chwastyk replied: o ,
"My best' recollection of that is th,at I did relate
~
to Gary that we had~some sort of an explosion. Whether I said it was hydrogen or not, I'm not sure. But I remember distinctly putting.together the operation of the valve and the spike, and I think I relayed these
' thoughts to Gary." (SIG, Chwastyk, p. 17, 10/30/79.)
When told that. Gary-Miller did not recall learning of the explosion until two days later on March 30, Chwastyk stated: i . "Well that could ver.v well be true. Again, I can't I absolutely -- if Gary said -- I may not have told him what I thought at the time, because I really wasn't L. certain. (Ibid., =. . 19'-20.) . Chwastyk was then asked again for his best recollection and the following dialogue ensued: ' l Q. I understand. Let me ask you this: Was there any -- strike that. Let me start it a different way: When ycu saw (put) this and then it together what you thought had happened, that must have been sc=ething that gave ycu some cause fer l
- concern?
l l J. , Yes. :t scared the hC__ cuc cf s. I I _ - - . _ , --- __ , c _ . - ~ .-m_.m_ , _ . . _ - _ , , _ . _ , , . - . _ , _ _ _ , _ _ , _ . . _ . . .. ._. . . _ . _ . - , . - . _ . .m,
, Q. Did you think,that this was something that better ought not to be generally broadcast around the control room and outside? Was there.any reason to keep this fairly'close among the people who were there in light of the fact that -
it was fairiy alarming? .a , A. I'll say this: I didn't go out in the control; room ar broadcast it, no. It did scare me, therefore, I'm sure I didn't just make it general knowledge to everybody in that control room. I'm sure I did pick out specific individuals that, my counterpart types of people, and talked'to them about _ O. You said you think that you probably discussed it wi:2 3rian Mehler, and,your-htptreccliectionit that you discussed it with Gary Miller. Do you have a ,-pretty specific recollectic:
) of who else,veu may have actually discussed it with on the 25:'r
'l
/
. A. I ha /e sc=e reccliecticn of talking to seceene frer the NRC about it. At the time, I did not have the time to m.
f discuss possibilities,w'ith hit, and I'think I-related that I think.there d.ay have been seme e kind of explosion in the
;/--
building, but I didn't know whst. (Ibid., p. 20-21.) At the end of the Octcbor 3( interview Mr. Chwastyk was a@ain asked by the Metropolitap. Edison- attorney participating
.s in the deposition, about whethe_r he had told' Gary Miller on
, d
' March 28 that he had correlated the pressure spike with a p,cssible explosion:
* - r N
W Y D
, ' o.$ .
Mr. Diaz: I don't want to put words in your mouth. You recall makinc the inference o but you don't recall whether you conveyed that inference to Gary' Miller; is that correct or incorrect? . The Witness: .My best recollection is that I did related (Ei i i I43 ~that information to Gary. That's the,best I can remember. i . i f
. . How much of that information though, what information I gave him, I definitely don't renember. I do know that I gave (sic) him the information of the bank y the valve o.oeninc. simultaneous; with the pressure spike.
Kow, if I related that or if I put that together and told him that I thought it was a hydrogen explosion, if I thought it was an explosion at all, I don't remember. (Ibid., p. 28-25 ! In sum, on May 21, E979, Chwastyk told I&E investigators that he believed on March 25 that an explosion had occurred, and that he had told Station Manager Gary Miller that they should no longer cycle the electromagnetic relief valve t cecause the cressure c.u,se .af corresconded te co.en nc. o: this valve. On October 11, Chwastvk said after the hydrocen explosion, he went to Gary Miller and explained what he,
" thought had happened as far as the hydrogen detonation and .
the simultaneous cpening of the valve." (SIG, Chwastyk, !- October 11, p. 18.) In another interview on October 30, Chwastyk repeated that p he had told Miller what he thought, that he did tell Miller l his thcughts on the . .. spark due to the valve opera:icn [ w . n e-a
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*4 actually did tell Mil 1er that he thought there'had been ~
~
[ an explosion, Chwastyk (for the first time, on October 30) , 1 4 p'. ".. '
. . said that he could not be sure, although.he thought he did~.
i It is not clear from the record what was the basis ~ for'Chwastyk's changing his mind exc.ept;that his. recollection differed from ~ Miller who had said he D' iller) did not recall learning on ! March 28 that there had been an exolosion. L l I-Mr. Herman Dieckamp, President of General Public Utilities, stated in a May 9, 1979, $ailgram to Chairman Udall:
"There is no' evidence that anycne interpreted the-
' pressure spike' and the spray initiatien in terms of reactor core damage at the time cf the spike nor that anyone withheld any information."
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J 4 6 -- Loc Entries Two loc.s containinc. a listine. of sienificant events - Ethat occurred on March 28 indicate that a pressure pulse
, - l q- occurred at~approximately 1:50 p.m. One, log lists the !
= pressure spike-as having been 4 pounds per scuare inch
,um3 and acconcanied b.v actuation of reactor buidline scravs; h'
the'other, log-lists the pulse as having been approximately 5 pounds per square' inch, and does net mentien the containment-1 spray.s . None of.the investigation reports addressed the c. cuestion as o why the pressure pulse was indicated to have been 4 or 5 psi when in reality is was approximately 28 psi. In fact,-the only reference in the SIG report to the logs
-indicatine. that the .=ressure sn.ike was 4 e.si is a crv tic ..
.one:apparently in support of the SIG conclusien that, contrary
,, , , ; to the perception of Chwastyk and ::ehler, the spike was T. m, ~ disr.issed as beine. insienificant; 1.e.
- SIG states:
"Furthermore, an entry in the control roer operator loc book for the afternoon of March 2E nctes that at 1:50 p.m.
an engineered sa,.eguarc.s initiation signa 3_ was received, the reactor .cu _,cing sprays came on, anc t.ne reactor .cul.,cing pressure spiked up to 4 psi." (SIG, Volur:e II, part I,
. . ,0 . 144.)
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Presence of Hydrogen in the Primary Cooling System Rydrogen produced as a byproduct of the oxidation of zirconium cladding collected at high points in the reactor-cooling system; e.g. at the tcp of the reactor pressure vessel, pressurizer, and upper (candy cane portion) of the-
. hot legs ( See Figure I-A, I-3; pages 13a,13b.) hnile.the hydrogen in'the pressurizer could be released'from the system via the pressurizer relief valve, there was no such valve in the other locations; h.ydroc.en could be eliminated from these areas onlv .
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_# _1- . _- . than'either allowing it to escape from the water in the pressuriner wherefrom it could be let into the containment or extracting it from water removed v a the letdown system. A cane maxture o_,.nvcroc.en anc sucerneatec steam . n t.ne cant had for most of the day obstrue:ed fillinc. the c.rimar.v svstem with water, thereby preventing an ef f ective use of the steam c.enerators for removal of heat c.roduced in the fuel bv radioac.tive decav.
~Qata available in the control room had, in fact, indicated -
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~(most likelv hv droc. en ) in the system appears not to have been reported either to the NF.C c: officials of the State of Pennsylvania. .
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' -Perceived adecuacy 'of' procedures to assure adecuate core cooling.
Statements made during' interviews conducted by accident investigators indicate that during the day of March'28 there were periods when.TMI personnel appeared uncertain asLto core conditions and whether the procedures being
-followed'and actions being taken were adequate to lead .
.c to stabilized conditions. TMI Station Manager Gary Miller - told General Public
-Utilities invest'igators on April 12:
. . . We o being_me and Lee Rocers, called Lynchburg prettv. earlv. r and we sat in the reem and everv.
hour tried to figure out how to keep pumping
~
water into it. But all we were deine._was cumoinc. . . that BWST / Borated Water Storage Tank / through the electromatic to the floor. Nothing was changing, so you know we pumped 12' cr 13' out of BWST and mv fear :was . cum inc. 50 feet out and the
.ccre still hot and no' water in the SWST.
So our goal was to semehow get some circulation going, either natural circulations from steam cenerators or reacter coolant pump, usine, HP injection the whcie time. My memory is that we
.cumoec ac.a nst the electrematic at rair y high pressures like 1800 or 2200 psi. We could nave.n.ume.ec acainst ~
t.ne coces, . cut we.assessec that what we'd do is.get the same flow through the cafes' without being able to see pressure. . We pumped through there until'arcund 11 in the . morning, at which time we decided te take a shot at getting on core flood. And the reason we took a shot at core flood -- now remember Lynchburg was on the phone with a lo of good advice, but it was clear that it was my decision -- ue assessec that 1 ., we cou.,c get ccwn anc activate core flood-tanks and we saw them dump on the
-core we could get assurance that the core had
'some water on. We cculdn't tell ths.L; we were scarec :na wasa,t hancenine. Rac..iation was all ever the place, everything was cff scale.
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_ao._ . Mike Ross gave the,following rationale for reducing system pressure in order that cooling might be achieved from what was thoughito have been a better method than the one they were then using which depended upon keeping - the system pressure high and using the high pressure injection pumps:
... One, we were running out of water in BNST'and we hadn't gained an inch. I mean we hadn't gained any headway in where we were trying to go our goal being one to establish some mode of cooling a reliable mode of cooling to the core. Two, we, at least I wasn't sure that we purposely or we in fact had the core covered and all high pressure injection was going to the core. I was not totally convinced.
I didn' t have anything to tell me. Hey, high pressure injection is in fact going through the core. So based on that, we discussed going down with the goal being one, to let the core flood tanks come in and verify that yeah, the reacter was in fact covered, two, give it a drink of water. That is a little coarse I know, but give it a drink of water if it wasn'.t getting it, and maybe go on decay heat removal wnich is a forced mode of cooling. That is what we were trying to do at that time." (IEE TMI Tape # 226, p. 26) Perceptions concerning core uncovery The record contains few specifics with regard to perceptions of these present at TMI as to whether the core was or had been uncovered. It appears that TMI personnel concluded that, after 9:00'a.n., the core was probably cov'ered. The apparent basis for this conclusion was tha: the pressurizer water
- er.perature was at less than saturaticn level, and since the pressuriner temperature-was E.- indicator Of C0re output
F . N ? -..'. l .?.:. { temperakure, pressurizer temperature:was assumed to indicate j that the core was probably covered. There is little in the recordtoindic'atetheinte'rhreta'tionofthehighin-core thermocouple temperature measurements , which in f act 'showed local boiling and a badly damaged core. . n'i . L While it was generally assumed the core was covered a',fter . 9:00 a.m., there is little discussion in the record to suggest what.the~ thinking might have been with regard to core: uncovery between 6 : 00 a.=. and 9:00 a.m. As the foregoing discussion suggests, there was censiderable temperature data to indicate that the core had in fact been uncovered during-this period. The most extensive statement on the record is an interview conducted by Kemeny staff with 3&W engineer John Flint. Flint was apparently unaware of the extended period during which water had leaked frcm the system through the stuck open pressurizer relief valve, and he was also apparently unaware c:P the in-ccre thermocouple measurements . " indicating' temperatures in excess of 2000 degrees. On
- the basis of temperature and neutren data, Flint didhencludg however, at 10:30 a.m. or thereabouts that the core had been _ .
uncovered earlier, even though it appeared to him that by
-10:30 a.m. it was again covered.- Flint _ engaged in the following dialogue-wirh Kemeny interviewe,rs. The answers are Flinds:
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Q. When you reached the conclusion that the' core had been uncovered approximately an hour to an hour and a half after you arrived, which would be something in the order of 10:00 to 10:30, did you tell anyone? A. Yes, I did. I believe I mentioned it to Lee Rogers at the time. 51 '
. Q. What was his reaction? .
A. 'I believe he.went to discuss it with' Gary Miller and George Kunder. Q. Were you present during that discussion? A. No, I was not. Q. Did he report back to you? A. I don't remember him addressing that specific cuestion, nc. Q. Did you ever find out what discussion he had with Kunder and Miller with respect to core uncovery? A. Not that I~can remember, no. Q. Did you tell anyone else that you had reached the conclusion that the core had uncovered? . A. Eill Zewe, Ed Fredericks. O. What was their reaction? A. I would cay surprised. . Q. . It was news to them? A. Yes. Q. It was news to Rogers too when you told him? A. That is correct, sc far as I know. _3ine a t o p . _, ,, , cine a.. [ .s..emey , _. int, p.aa, 6
Percept' ions held on Maich~28'as t~o extent of core damage. The foregoing indicates the existence on March 28 of. . manifold indications of core damage. Based on partial ' 'i ' information'available to him (i. e. he did not know of the 20'00 degree' core thermocouple measurements or the manifestations of an explosion),. Victor Stello,-then Director of the NRC's Division of Operating Reactors, told the E&E Subcommittee TMI Task Forcs on May 9 that he suspected oxidation of the cladding (and presumably hydrogen production) on March 28. Mr. Stello engaged in the following dialogue: Mr. Stello: My initial reaction was that considerable failure of the fuel had occurred, with large numbers of failed fuel rods._ And that the pctential for oxidation, metal-water reaction, was clearlv there. The periods of time involved were, even if 'the heat-up were not significant, at lower tenperatures, with the top of the core unccvered for extended periods cf
. time, metal-water reaction was clearly possible.
The rates -- how high the temperature got I would not even-indicate -- I cculd have cuessed at. Sut oxidation of'the cladding was something I clearly expected; failures of the cladcing were clearly evident. Mr. Terrell: When did you suspect this? On Wed.desday you are talking about that you expected this fuel damage? Mr. Stello: Yes, I think just from knowing what was . happening to the core, you had to expect that there was cuite a bit of damage tc the fu'e1. (E&I, TM: part 1, p. 4-5)
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Another indicatios of there being suspicion on March 28 of hydrogen production can'be inferred from a statement made by TMI supervisor James Floyd. As noted above, Floyd was at the B&W facility in Lynchburg, Virginia on March 28 , and had inferred from limited information that about one eighth'of the claddine. had failed. On Mav. 31, Flo.vd s. told the Kemeny Commission of his suspicions.about hydrogen
; production when he engaged in the following dialogue with Commission merber Ted Taylor:
Taylor: Had you sometime Wednesday made the connection in your mind between the high temperatures in the
. core, cladding failure and hydrogen?
Floyd: Yes, sir. The March 29 New York Times described a press briefing pr[sented by Jack Herbein en March 20 which gave a different picture of the situation: Jack Herbein., a vice president of the utility that operates the plant, told a news conference held en a bluff.over-
~
., looking the plant that "a valve failed in a shut position" in a feed pump that scuirted water around the reacter. .
Mr. Herbein spent almost an hour de' scribing the accident , and emphasized that the main safety systems in the almest
. -brand-new plant had worked to prevent a very serious accident, or indeed a catastrophe.
Using bland terms, he described the series of events
.in the plant as "not the normal evclutien" in stating
, that there was "some miner fuel failure."
This translates to the fact that seme of the pellets of enriched uranium fuel became so heated because of loss of coclant that the pellets nel:ed through the zirconium clad tubes that hold the pellets. Uni: '.; c . 2 has 177 fuel assemblies, each containing 208 reds, each cf which Ocn iin 2 0 uranium pellets.
"On;y a few cf'the. rel:ed through,' :*r. Herbine said.
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-4 On March 28, NRC issued a Preliminary Notification of. Event or Unusual-Occurence which.gave little indication of the actual
. severity of damage: ,
Facility: Three Mile Island Unit 2 Middletown, Pennsvlvania - . .4 ~. (Docket No. 50-320)
Subject:
REACTOR SCRAM FOLLOWED BY A' SAFETY INJECTION AT THREE MILE ISLAND - UNIT 2
+*
The licensee notified Region I at approximately 7:45 a.m. of an incident at Three-Mile Island Unit 2 (TMI-2) which occurred at approximately 4:00 a.m. at 93% powar when the secondary feed pumps tripped due to a feedwater polishing system problem This resulted in a turbine trip and subsec,uen reactor trip on Eigh Reactor Coolant Pressure. A cctbination of Feed pump Operation and Pressurizer Relief - Steam Generator relief valve
.operati on caused a Reacter Coclant System (RCS) cooldewn. At 1600 psig, Emergency Safeguards Actuation occurred. All ECCS ccaponents' started and operated properly. Mater level increased in the Pressurizer and Safety Injection was secured manually
.apprcximately 5 minutes after actuation. It was subsecuently resumed. The Reactor Ccciant Pumps were secured when low net positive suction head limits were ap,: roached.
At 10:45 a.m. the Reacter Coolant System Pressure was being held at 1950 psig with temperature a- 220'? in the cold lec. Bv 10 : ,, : a . m . , r a c. .iation levels o,_ s m:/.nr nat reen detectec.- a 500 yards offsite. ( PNO- 7 9- 6 7 ) 9 9 4 8
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o.** . .* . . The March 28 Rashington Star quotes Lieutenant Governor Scranton:
"Everything is under control. There is and was no
', danger to the public health and safety."
^ - Officials of Metropolitan Edison / General Public -
Utilities have said subsequently that on March 28 they did. net Li'
, reach conclusions such as those of Stello and Floyd referred to Mrve about the possibility of cladding oxidation.
. 1 In answer to a written question as to what at 11:00 p.m.
on March 28 was his estinate as to the amount of cladding that had been oxidized during the period when the core was uncovered, Herman Diechamp, President of General Public Utilities, responded: I interpreted damage to mean cladding failure. I
~ did not think in terms of cere uncevering, high temperatures, or Er-5 2 0 reactions. (E&E, TMI Part 11,
- p. 2 8 3,')
In resc.ense to the forec. cine. c.uestien, Metropolitan Edison Vice President Jchn Herbein stated: . I didn't consider a stear clad interacticn produc_,ng hydrogen until it was discussed on March 30th. (Ibid.,
- c. 290) .
In response to the questien as to what was his estinate on March 28 as to cladding oxidation, Statio.n Manager Gary Miller stated:
. . . I did not conclude there was an,cn-going steam-claddinc interaction and theref ore, had nc estinat'e cf the accent of cladding fai ure by 11:00 p.m. en .
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A Whatever the indications of hydrogen production p . available to the NRC on March 28.and early March 29, little idea of these was convey'ed to the E&E Subcommittee on March 29 when, as-noted above, Chairman Hendrie stated: . ..w " - "The magnitude (of release of radioactive gases) suggests that perhaps one percent of the core might i .
. have been involved in the cladding cracks." (Tran script', . p. 60.)
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