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to have gone up and come down. There was no question in any of o minds as to whether there was fuel damage, because I can recall early as Wednesday morning hearing the values that the monito were reading for radiation in the containment, which can only! associated with one thing. That is core damage--in the numbers th. were being recorded. Those values were increasing throughou Wednesday.

I seem to recall I joined Victor at the incident center late in th afternoon, around 4 o'clock, probably. It became apparent that w were going to move several of our staff that had been working in ou offices to the incident center.

Mr. SCOVILLE. Do you mean 4 o'clock Wednesday? Mr. EISENHUT. Wednesday evening. We both became involved, little after 8 o'clock, 8:30, something like that, on Wednesday morning when we happened to have been working on another problem and go the same phone call. We basically worked in two directions.

Mr. Stello went to the incident center where he is a member on th response team. I stayed at the office with a team of people, probably anywhere from 20 to 30 technical people. When Mr. Stello went of the TMI site, I went to the incident center to the response team.. stayed there, I guess, for what~3 weeks, essentially.

Mr. STELLO. Thirty-nine days.

Mr. TERRELL. I am not sure I understand. We had the containment sprays coming on at a certain point in time. I was under the impres. sion that those sprays are actuated upon the occurrence of certain things taking place. Could it have been anything other than the formation of a gas bubble?

Mr. STELLO. Anything that can cause high pressure in the containment would cause the sprays to go off. The pressure was increasing because you were discharging the heated fluid into the quench tank which was raising the pressure inside of the building. That had been coming up, but I do not recall that ever getting to a high enough level to actuate the sprays.

But then, again, I will have to say parenthetically, please reserve me the opportunity to go back and review the record because I am not sure, but I do not recall that the pressure due to the addition of the heated water ever got high enough.

Mr. EISENHUT. I think that is right.

Mr. STELLO. So that would leave you with something like this burn to raise the pressure high enough to actuate the sprays, which is clearly possible.

Mr. ScoVILLE. What you are saying, then, is that there could have been other explanations for the increase in pressure resulting in the turning on of the sprays.

Mr. STELLO. By all means.

Mr. SCOVILLE. So that did not send to you, Mr. Stello, a signal that there had been a hydrogen burn that day! But when you learned about the increase in pressure, the so-called pressure spike

Mr. STELLO. Very narrow, high-right. Very narrow band. It was about 20, 29 psi, the exact number

Mr. EISENHUT. About 28 pounds.

Mr. STELLO. Fairly high and very narrow width. That is indicative

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Mr. SCOVILLE. That sent a very clear signal to you at that point?
Mr. STELLO. Yes.
Mr. EISENHUT. That is the point I was making earlier that we were,

in fact, talking to the site, in fact, specifically seeing how fast the biers in spike was. gh

Mr. TERRELL. But there may have been no correlation between the pressure spike and containment sprays coming on.

Dr. Myers. There was. Mr. TERRELL. I am saying in their minds. I am trying to find out if there was a correlation between the spike and sprays coming on because they came on almost simultaneously.

Mr. STELLO. We did not know about the spike. There could have been other reasons the sprays came on. It could have been caused by others. I remember being preoccupied with how high the containment pressure was getting. My best recollection is I never remember it now getting high enough to actuate the sprays.

Mr. Rers. Just to clarify, when did you know the sprays came on? mohalt

Mr. Mattson. Wait a minute. Reactor building high-pressure isolation signal actuated and isolated the reactor building at 4 minutes until 8 o'clock at 4 psig. That is the only pressure that shows on their chronology. That is when they finally got reactor building isolation, was high pressure, Vic.

Mr. STELLO. Reactor building isolation is listed on this one, and at the same time containment spray went.up. Mr. Mattsox. At what time? Mr. STELLO. 9:49, which is 1,350. Mr. Mattson. This is 7:56 in the morning, 4 hours into the event. Dr. Myers. While we are on this pressure spike, I have one question. Mr. STELLO. Go ahead. Dr. Myers. The fact that it measured 29 pounds on the chart, was that number determined by the response of the instrument, or does anybody know what the actual pressure might have gotten to?

Mr. STELLO. That is, as I recals, a strip-chart recording which would be an instrument recording. How much higher it might have gone and the instrument would pick up depends on the instrument response time. But I would think in the narrow width that that would not likely be significantly different.

Mr. Mattson. It was 6 minutes wide. So the peak should not have been missed by too much. But I do not know the specifics of the instrument. Missed it some, but 6 minutes, not 6 microseconds, as you often think about instrument response times. Mr.SCOVILLE. Could everybody withhold for a minute here? (Pause.] Mr. WEAVER. Mr. Stello, I want to go back to the spike—I may be covering some old territory here, but I would like to hear it. The people in the plant have maintained that their personnel saw the spike at the time it occurred, 1:58 p.m., on Wednesday, and that there were NRC I. & E. people present. Can you just speak generally on that? What do you think happened?

Mr. STELLO. Not having been in the control room at the time the spike occurred or at the time the conversation took place puts me at some disadvantage; so I will have to

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Mr. WEAVER. Let me ask you this, then: Did you discuss this wi thu I. & E. people on the spot, either at the time or afterward?

Mr. STELLO. After I had heard about it, after your visit, I went ovi and asked the person who was in charge of the investigation if the have really concentrated on when did the inspectors truly know th: there was a, quote, "hydrogen burn," a problem in the containment. told him that I thought this was going to be a point of significar interest for people, and I thought he ought to make sure that h. covered it. That was pretty much the first time that I had spoken t anyone about the need

Mr. WEAVER. Who was it you spoke to? Mr. STELLO. Bob Martin. Mr. WEAVER. He was one of the people actually present? Mr. STELLO. No, he is in charge of the investigation that is taking place up there to make sure that he goes back and covers this point in detail.

Mr. WEAVER. Right. Did you ever, on Thursday or whenever, have any discussions with the I. & E. people? Did you communicate with them in any way?

Mr. STELLO. I communicated with them throughout, from the time I had been there. I never discussed this hydrogen burn question with them.

Mr. WEAVER. They never volunteered?

Mr. STELLO. And I never got it from them that I am aware of until Friday. There are probably several possible explanations for that.

Mr. WEAVER. I would like to hypothesize.
Mr. STELLO. One is that it was not known.

Mr. MATTSON. Could I interject for a minute? I had read to me about 3 hours ago over the telephone a memorandum to the Commission from the Office of Inspection and Enforcement which speaks to this question, what the two people from I. & E. in the control room were doing on Wednesday, Thursday, and how they first came to know of the spike. I cannot recite the letter to you, but it was generally that they were in the shift supervisor's office and in the control room with the primary responsibility being to gather information for transmittal to the Bethesda incident center. It goes on to speak about their first awareness and transmittal of the information concerning a spike to Bethesda.

I think rather than any of us conjecturing on what those people knew when, it is probably better to rely upon what those people said.

Mr. WEAVER. I would like to hypothesize. This will enable us to ask better questions, vou see.

Mr. STELLO. OK. The I. & E. people, as Dr. Mattson has indicated, were in the supervisor's office. They were not physically patrolling and independently reading meters meter-by-meter-by-meter, to the best of my knowledge.

Mr. W'EAVER. That is not their job.

Mr. STELLO. That is not their job to be reading the individual meters. In fact, in a situation such as the one we had, I would suspect that you would want to be a little bit removed from there to observe the actions just a bit further back rather than getting physically in the operator's

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Mr.WEATER. Would it therefore this Mr. STELLO. When we asked them for information, a specific ques

tion, they went and obtained the information we were looking for, wenteel and they were focusing on the information we were asking for. mit Mr. ÑEAVER. So you would assume, therefore, that it is the operat

ing personnel's duty to report to the I. & E. person some unusual chart ir ciet reading that has occurred? mifix Mr. STELLO. If the operating crew knew something significant the would have happened and appreciated, understood that signiticance,

Let me finish my hypothetical. When did this become known as a hydrogen burn in the containment is really the issue. Could it have been a spurious indication? A wire that got shorted out and caused it?

Certainly. There was not a discharge of liquid in there, but there were s tac other reasons you could have had the problem. With the accident that point: you had, I do not think anyone would have been able to, while ob

serving the instruments, draw conclusions immediately without some er. bir quiet time to study what they had. ate My suspicion is that some time after the charts were removed

from the control room where the people could look at them, and he ti tried to get the correlation that something had happened, that it na mas some time after the hydrogen burn occurred when it was truly

understood to be a hydrogen burn.

I am not persuaded or convinced yet that the people in the control oferoom knew that they had a hydrogen burn much before Friday. I TV beard nothing while I was up there that suggested to me they knew

they had a hydrogen burn much before we knew it on Friday.

Nr. Weaver. They certainly would have seen the spike. palit Let me ask you this: If something goes wrong in a plant, just Wrong,

and you are right there and you rush into the control room, what are the major gages you are going to look at immediately?

What are the most important ones to see? oft

Mr. STELLO. I do not think you can decide that without having

some additional hypothetical in front of me. Let us use the one we ith it had at Three Mile Island.

Mr. WEAVER. What are the ones you are going to have to look at?
Mr. STELLO. The program meters I was most interested in at Three
Mile Island were the primary system pressure, the temperature of
the hot and cold legs and temperature of the incore thermocouples
with a confirmation that the reactor scrammed and all that stuff, too.
Mr. WEAVER. What is the gage the spike occurred on called?
Mr. STELLO. The gage the spike occurred on is a gage that meas-
ures containment pressure.
Mr. Weaver. That was the first one you mentioned.
Mr. STELLO. No. The primary system pressure.
Mr. WEAVER. Within the pipes, then.
Mr. STELLO. Hot and cold legs of the primary system, incore tem-
perature distribution. As I say a lot of other things you just ought
to confirm. You want to know that you had the scram and you want

peition indications that all the rods went in. You want à reactor building pressure. Was pressure changing with time? Did you see any increase in containment pressure which would be an indicator of a LOCA, as an example.

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We knew we did not have a loss-of-coolant accident in any maj sense because throughout the whole day, once the block valve w closed on the electromatic relief valve, the system was fairly tigl There was no real loss of system of inventory.

So we had, as I described earlier, a situation where you had lot of fission products released in a closed and isolated system.

Mr. WEAVER. Would you call the containment pressure or cha) among the hundred things that you would look at, a minor or maj component.

Mr. STELLO. It is difficult now because you are viewing everythir with the wonderful hindsight.

Mr. WEAVER. Yes, I understand.

Mr. STELLO. Knowing that-I guess I believed you had a high] damaged core. I believed you had metal-water reaction. It is no surprising to me now, nor was it surprising to me then, that yo would have had significant quantities of hydrogen to cause a buri Does not surprise me.

That was after I learned of it, very useful information to hel me decide what I ought to do next, because I already had decide I had a highly damaged core.

Mr. WEAVER. I have no further questions.

Mr. SCOVILLE. You say you had already decided that you had highly damaged core. Was this because you learned about the buri on Friday and other information had added to the information or Wednesday to make you believe the core was highly damaged !

Mr. STELLO. The thing that persuaded me that the core had to be badly damaged was the fact that the exit thermocouple was above saturation temperature. The only way you can get that condition to exist is for the core to have been uncovered, to get superheated steam coming out of the core. Given I had superheated steam coming out of the core, I knew the rods had to be running at significantly higher temperatures to do that. I knew that all of the incore thermocouples were reading question mark, which means they were reading off the range of high scale.

Mr. WEAVER. What was that?
Mr. STELLO. I think that was 700 degrees.
Mr. EISENHUT. Presumably it was 700.

Mr. STELLO. On the computer it was 700. They could have actually been down and did make measurements, and the measurements, as I recall, indicated temperatures were significantly higher.

Mr. WEAVER. They had a board up when we were there the day before yesterday which flashed little red numbers on each thermocouple. And they said that board had been put up after the accidenta Where were the readings for the thermocouples?

Mr. STELLO. On the computer. Mr. W'EAVER. Nothing but the computer? They did not have any of those flashing

Mr. STELLO. Yes, right. All of those real-time recording instruments that you saw were placed in the control room as an addition to monitor transferring the plant from its forced circulating mode to natural circulation. It was preparatory to that step.

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