ML19262A512
| ML19262A512 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 09/05/1979 |
| From: | Yuspeh A SHAW, PITTMAN, POTTS & TROWBRIDGE |
| To: | Frampton G NRC - NRC THREE MILE ISLAND TASK FORCE |
| References | |
| TASK-TF, TASK-TMR NUDOCS 7911090316 | |
| Download: ML19262A512 (10) | |
Text
C m
s S HAW, PITTM AN, PoTTs & TROWB RIDG E 18 0 0 M S T R E cT, N W-WASHINGTON, o C. 2OO36 e A M S A, o. e.o,,3 StavrN L Mattare trots 33-4 00 Sit uent t ev e se AN DE AN O AWLIC m G,E.o.m O.E FNo. mow J O,.".N E 'e G.C L t
S.. A. o C M A.o,,n e e DO C S. N, M. M,.
M.o.r,L.c.
M N o,5, w
. N vcLcCo
.c-
- "#rta ",rANM" C A?.".,^g"ALg4A MY ".
's o *>
- a o a = A * * * *-' r a o GEORGEM nOGC4% Je meCMAmb g JOMN P MMcNC L ANQg e ROWERT m noggeNS SmuCE w CMumCM*LL L AW" A # FAmeAND TELER ILL eCTomte J pg aN 89-2893 ISM AwgAw wSMI MARTIN O. en
%'.".^."&'6"J! ""
'? "" ".!",i'," '"-
cA=Le SMA ~ ~-
m Am e Am A M. noS SOf?'
GEO"GED CaOwktv.JR OEORGE V ALLE N. J A.
MsCMAE L D. MAT S
"."c ! "',; ". "' ' " ' *
'"a%'o"JJ.*S o",", "
' """*"'"o" FpCDcmASNgm STEvCN M LUCAS CC* ARD S CROSLAND N ATMAmitt p e n t g o, J a.
R AND L ALLEN M.A R EN. S.U G E.N G L.O.C R AL, AN, AMJ W CI.S S.A.R D A
COUNSEL c LA
.J wu A
Cant.groN E JcNES ALAN &TuSetM ToeosAS A SAsTre Joegas L Caen. Jn J Au t S M. SURG g g pesetep A Magy gv SM E LOOM J, WE s S EL.M
- .A v L. #.IC.M ac A N...o r Jou A.M.CuiLOo v-ovM M.
J. D AY4tC A MIC M ( v CHARLE S W. SW4 ASE T e JAMES TNOM AS LENMART September 5, 1979
.M,m....
George Frampton, Esquire NRC/TMI Special Inquiry Group Nuclear Regulatory Commission Washington, D. C.
20555
Dear George:
In response to your request for documents following the deposition of John Ililbish on September 5,1979, I enclose a copy of the Development of Understanding analysis.
It is my understanding that this analysis is the document which Mr. Hilbish referred to during his deposition as the " growth of knowledge" memorandum.
I am informed that there are no surveillance records for the TMI-2 Fuel llandling Building Air Cleanup System Charcoal Analysis Procedure 2311-14 which relates to TMI Unit 2 Technical Specifications Section 4.9.12c because the procedure only is applicable "whenever there is irradiated fuel in the storage pool".
To date, no irradiated fuel has been placed into the Unit 2 storage pool.
Sincerely, I
t Alan R. Yuspeh ARY:ry Enclosure
}
,,i~,
,v
N':,( $
.-s
.G L,fy ;*
. :' s;
[$/c?/ G - N S~
,r' 9
c.;n DEVELO? terr 071RTDERSTA'TDINO
/)
inns
,e, 1 J /J The object of this task is to re-create, as best as possible, the chronology and an on-going status understanding of the TLE-2 accident as it developed.
It is obvious frem the sequence of events and the response actions taken by the operators that perception and understanding of the transient were changing, especially in the early hours.
Levels of complication in assessing this devaloping undarstanding are introduced by the various communication interfaces which were established about the data source. These interfaces provided data (as wall as on-going assess =2nt) to' an increasingly growin3 number of people (h
who inturn contributed to what may be regarded as a common understanding of the accident.
As time wore on the number of co=nunication interfaces grew
~
a geometrically;and became so intertuined as to give rise to an apparent co= mon pool of understanding. Consequently the task of unraveling the growth of understanding becones increasingly more difficult as more co=nunication interfaces were established (later in time following the accident).
Necessarily then, the subject assessment must be attacked starting with the TMI-2 operator's understanding and procede through that of the site management, Met-Ed management, CPU management, the GPU response team, and the industry advisory group. Further the peripharical O
1920 086 e
~
2-
~
branches of BG1 and NRC understanding could also be examined. Figure 1 attempts to illustrate the challenge and the scope of the above.
]h}{f hC41 I, An analysis of the parceptLon ofsignificant problems and growth of knowledge during the event can be divided into three areas:
A) Efforts to maintain control of the plant 'during the first four hours, B) Assessmant of the radiation emergency,'aad C) Perception of the non-condensable gas bubble in the reactor vessel.
A.
Efforts to Maintain control of the Plant
.During the First Four Hours of the Event, the main concern of the oparators was to bring the primary and secondary systems to a stoble condition.
Several key factors should be discussed to focus on the basis for operator actions. Detatis used to formulate each of these key factors were derived from interviews with the shif t suparvisor, shif t foreman and two control room operators.
1.
Pressurizer Level Indication - From very early into the transient, operations personnel were very concerned with precsurizer level indication.
Within five seconds after the reactor trip the operator had started a second make-up pe=p in aaticipstion of the exp2cted rapid dacrease in
~
- r. ' l 1evel never occurred, and within six minutes the pressurizer icvel was off scale high. The operators felt they had caugh; the expected leval decrease with increased high pressure injection. The major concern of the operators at this point was to not take the R.C. system solid.
Based on high level indication and concern of taking the system solid, the oparator bypassed Safety Injection, stopped trJPIC, and throttled 0
1920 087 e
e a
9 Iciteh4q E VerY, bt Tuskon(edahiM.
A h
ow
@ebs A> g.g se SWmAcel A
1 A
E 2
Agedes J>
~
S 0
mi Skhht
&qSe d""W*#
Nf" c
NRC.
A A
3 g
7 7
o rgs 5
A Nef-Ed.
g 7
ream Hanupted
-y p
wa
, Haegemed dua mM Ae 324pumf oL Lc'eseunaj g
G 1920 088 m.m,e~~
---mem--
e
.-me
+- sw w
,....eem nn m.o.-
~.-
a.-eo..m~.w
-- ~
~
.. _ At this point RC pressure was still decreasing, arid the MU-V16's.
based on either past judgments were made primarily on pressurizer level i
training, or experience during feedvater transients or reactor tr ps, procedural guidance.
Close -
2.l Failure of the pressurizer Electronatic Relief Valve to due to the During the initial reactor coolant system pressure increase urizar opaned, turbine trip, the ciectror.atic relief valve on the press After the reactor trip, the valve failed as designed, at 2255 psi.
i lthough the oparator to : lose as pressure decreased through 2205 ps, a lve.
did verify that the valve indication _ did not signal an open va two This valve renain:d open for the first two hours and twenty-Thus, the control room operators had fatled to etinutes of the event.
relief valve for h
recogni::e a coastant loss of coolant through t e opan On at least three different occasions, the operators
}
that p2riod.
bands on the relief
-f l
checked the computer output for the thermocoup e h
l e had properly valve discharge piping to determine whether t e va vi interpreted scated as indicated; however, the co:puter data was m s d twenty-two minutes.
and the block valve was not shut for two hours an 30 -230. The 0
Readings from the thermocouple were in the range of 2d to press op2rator judged these valves to be quite low compare concluded that the 3
f temperature (approximately 603 ) and there ore The oparator did not realize that the electro =atic must be closed.
trapped to the outside l
temparature indication was from a ther:ocoup e sdin 3s in the range of the discharge pipa and based on heat losses, rea vere an indication of art open relief valve.
of 250 O
1920 089
, on pam
<-m e-m mm,,
e
-m qm ww m.
' m meno mw
- = =
m W w Ms
l5"l2 w.-- -
_4 During the tira that this valve was open,.dany other indications of a loss of coolant accident were present in the Control Room, such as rapidly falling RC pressure, rapidly increasing RC drain tank pressure and teaparature, increasing RB sc=p level while both serp Althoqgh pu=ps running, increasing RB te=perature and pressure.
na n t.
~ hese indications of a.LOCA exist' d, the op2rators did not associate e
t The operators continued to then with the stuck open relief valve.
t (loss of feedwater) and atte=pted to
{
focus on the initiatLng event
~. -.. - -... -.
deal with the consequences of that event on the condensate system and the turbine heat sink.
3.
Reactor Co31 ant Pu=7 Operation - At one hour and thirteen two Reactor Coolan.t pu=ps were tripped due to minutes into the event, observed "flov fluctuations" and allowabic NPSH requirements of opar-
/
Approxicately thirty minutes later the remaining ating four RCP's.
two Reactor Coolant pumps were trippad based on similar concerns.
1 Approximately two minutes after the Reactor Coolant pumps ware i
tripp2d, the oparator began to raise stema generator level from thirty percent on the start-up range to fif ty p2rcent on the Within the operating range to further induce natural circulation.
next thirty minutes RC hot leg temperatures ware increasing to of f It was realized that natural circulation 0
scale (greater than 620 ).
was not occurring probably due to a steam bubble forcation in the Attempts vare made to again start A loop (the B loop was isolated).
a RC pump to force circulation through the core; however, attempts (The 23 RC pump ware aborted due to pe=p motor low running current.
was run for a period of about 19 minutes some 75 minutes after the
'The LA Reactor Coalant pump va ; started 3
last pa=p was tripped.).
I920 090
L.
t e
5-approxir.ately fourteen hours after all pumps had been stopped.
It appears that the actions of securing the Reactor Coolant pa=ps were taken based on minimizing equipment da= age (i.e.
to d
prevent pump cavitation and protection of p =p seals) and not base on an un'derstanding of what was occurring in the primary system.
Assessment of the Radiation E=argency_ - The grotrch of B.
knowledge in this area developed rapidly approxt=stely two hour!.
and forty-five minutes into the event, as the first radiation
~'
~
L the plant. ~~This know - -
monitoring alaras vero received throughout ledge was accumulated quickly, and used efEcetively to determine Although action icvels accordin3 to the radiation emergency plan.
he event, the extent of fuel failure was not realized this early in t the perception of the significance of the radiation tonitoring system readings was accurate.
in the Reactot Percention of the Non-Condensable Gas Eubble C.
vessel _ - Early in the evening of March 29th, a group of Two of these engineers engineers met to discuss present plant status.
By approxi-reported to the control roam to back up the oparating staff.
this group that a non condenssble bubble mately 210], it was apparent to Prior to 2300, a for=ula was existed in the reactor coolant syste=,
Gas derived to calculate the size of the gas space in the systen.
bubbic volu=es vara routinely calculated throughout the 30th of March and calculated volumes began to decrease late in the evening of the Based on analysis of the 3/28 reactor building pressure spike 30th.
and contaiament air'sarple analysis which began at approximately 0400 on 3/31, it was determined that the gas bubble in tha reactor coolant G
1920 091 e
m,
- .=
- ==.=
ewwmn
- w e.e,,
- p-,we.,eeww
,-e w-.
w m e, %.
,pu n,
=
e=-
^
y systes was primarily hydrogen. Volume of the gas space decreased steadily through April 2.
This was confirmed as the increase in hydrogen concentration of contalnment at=osphere leveled off as the bubble in the reactor coolant system diffused.
wbes The first management co=aunications concerning the TMI-2 accident ware drafted in a telephone conversation between Mf. Herbein and Mr. Fabian At this tima, they mutually approximtely 7:15 a.m. Wednesday, March 28.
drafted a statement for response to press inquiras that related that the TMI-2 reactor was shutdova due to i malfunction in a feedwater systen.
The entire unit systemtically shutdova and was expected to be out of service for about a week whlic equipment is checked and repairs were 920.092 made.
At approximately 9:30 '4cdnesday corr.ng, Gary Miller called Mr. Troffer to relate his conversations with Lt Governor Scranton concerning the During these conversations, Gary indicated that there unit status.
was some fuel pin leakage, however, he noted that he didn't have any, indication of fuel mit. The prepared statement to the press was updated by noon, March 20. This statecent revealed radiation icvels were belag monitored in and around the plant and that there had been no recordings of any significant icvels of radiat on and none vare expected outside i
No avacuation of the local population was indicated at that the plant.
tim and that the reactor was being cooled according to design by the reactor coolant system and should be cooled dova by the end of the day, March 28.
It added there has no danger of a melt down.
Durin3 the Met-Ed press conference in Hershey, on Msrch 29, Mr. Herbein said it was too early to tell the extent of the fuel damage at THI-2.
g However, he noted that fuel failure had been experienced irring the He related this fuel failure to the point of turning off accident.
the reactor coolant p ups during the transient. He updated the plant
=- -
=ao
- -.o
--we,,a
. m
,.m wom
i-
_7 status to say that a reactor coolant pu=p was running and cooldova was proceeding and that he expected to be on the decay heat system in approximately 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. In responsa to questions from the press, Mr. Herbein related perhaps one half. to one. percent of the rc>ds may have experienced some melting and that the fuel had primarily failed due to the reactor coolant system depressurization and the need to shutdown the reactor coolant ptcps. He noted that it was possible for sone steasing in the upp2r core region at that time that lead to the fuel failure.
Early in the evening of Thursday, March 29, Mr. William Love, Mr. J. P. Moore had gone to the Unit 2 Control Room to assist the operating staff. Based on obsarved indications this group assessed that there was a non-condensable gas bubble above the core. Later that evening, calculations began to determine the volt.: of the gas bubble.
G During the press conference given on March 30, Mr. Herbein revealed the evidence of the gas bubble above the core. However, he noted that it appeared that the fuel assemblies were covered at that time and that decay heat removal was progressing. He suggested at this time that the fuel failure was caused by a comentary uncovering of the fuel during the transient.
During the press conference on March 31, M*. Herbein revealed that efforts were underway to reduce the size of the bubbic over the top of the fuel. Initial indications indicated that the venting process was successful and that the bubble had reduced in size.
He did mention at this tio2, however, a concern that the venting process has lead to a build up of hydrogen in the reactor building. During the evening a 0
1920 093
s.
d that sa~ple of the reactor building atmosphere has been taken an in the at this time there was no danger of an explosive mixture reactor building.
d on The first results.of the reactor coolant cnalysis were receive Based on these results, Mr. Herbein noted in the March 30::h.
d March 31 press conference that the core was indeed severely dassge f fuel and that there was a possibility that a very large percentage o This March 31 press 4.
assemblics vare in the dam ged condition.
After that tims, cornaications confe:ence was the last held by Met-Ed.
concerning the plant status were han.dted by the NRC.
G P
f920 094 O
d wee n e.ww._.
+. -..
.-p,
,--w.e--
4-
-e.em..-