Mr. WEAVER. Let me ask you this, then: Did you discuss this with the 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 over and asked the person who was in charge of the investigation if they have really concentrated on when did the inspectors truly know that there was a, quote, "hydrogen burn," a problem in the containment. I told him that I thought this was going to be a point of significant interest for people, and I thought he ought to make sure that he covered it. That was pretty much the first time that I had spoken to 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, you 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. WEAVER. 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

C

Mr. WEAVER. Would it therefore

Mr. STELLO. When we asked them for information, a specific question, they went and obtained the information we were looking for, and they were focusing on the information we were asking for.

Mr. WEAVER. So you would assume, therefore, that it is the operating personnel's duty to report to the I. & E. person some unusual chart reading that has occurred?

Mr. STELLO. If the operating crew knew something significant would have happened and appreciated, understood that significance,

yes.

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 other reasons you could have had the problem. With the accident that you had, I do not think anyone would have been able to, while observing the instruments, draw conclusions immediately without some quiet time to study what they had.

My suspicion is that some time after the charts were removed from the control room where the people could look at them, and tried to get the correlation that something had happened, that it was 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 room knew that they had a hydrogen burn much before Friday. I heard nothing while I was up there that suggested to me they knew they had a hydrogen burn much before we knew it on Friday.

Mr. WEAVER. They certainly would have seen the spike.

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?

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 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 measures 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 temperature 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 position indications that all the rods went in. You want a reactor building pressure. Was pressure changing with time? Did you see any increase in containment pressure which would be an indicator

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

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

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

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

Mr. WEAVER. Yes, I understand.

Mr. STELLO. Knowing that-I guess I believed you had a highly damaged core. I believed you had metal-water reaction. It is not surprising to me now, nor was it surprising to me then, that you would have had significant quantities of hydrogen to cause a burn. Does not surprise me.

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

Mr. WEAVER. I have no further questions.

Mr. ScoVILLE. You say you had already decided that you had a highly damaged core. Was this because you learned about the burn on Friday and other information had added to the information on 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 accident. Where were the readings for the thermocouples?

Mr. STELLO. On the computer.

Mr. WEAVER. 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.

Mr. WEAVER. The computer was turning out dollar signs so all you knew it was over 700.

Mr. STELLO. There are three ways in which it could have been printing out the dollar signs. It was off-scale low. You immediately say that is not possible. It was off-scale high, or it was possible that they had somehow become disabled, broken, which to me would. mean they were ranged high and they were broken, because if they were broken you would expect the temperatures to have gone well in excess of the 700. The best guess I had is they were still functional but they were ranged off their scale, and the computer, because of the electronics, would not take those above 700.

Mr. WEAVER. When did you find out the readings, the dollar signs! Wednesday?

Mr. STELLO. Clearly Wednesday. The hour on Wednesday I am not sure. I think it was Wednesday morning.

Mr. WEAVER. Wednesday morning?

Mr. STELLO. Yes.

Mr. WEAVER. Knowing what I know now, it is evident to me that that was a real tip-off, as it seemed to be to you. Why do you think that was not a tip-off to other people?

Mr. STELLO. I have no reason to believe I thought I had persuaded people that we had a damaged core on Wednesday. I did not know of anyone who believed to the contrary

Dr. MYERS. On Wednesday, we had people that told us the damage was perhaps a half percent. Then on Thursday they thought it might be up to 1 percent.

Mr. MATTSON. Half a percent or 1 percent of what?

Dr. MYERS. I guess half percent

Mr. MATTSON. Of the fuel was failed?

Dr. MYERS. The number was given without ever saying exactly what was meant, half percent.

Mr. STELLO. No. I do not know why anybody would be guessing at percent of failed fuel.

Mr. MATTSON. Is part of the problem here the Mattson transcript which says we could not convince B. & W. until late Thursday night we had a badly damaged core? Is that the problem?

Dr. MYERS. No. What we are trying to do is reconcile in part our own recollection of trying to follow it at the time with what your recollection is. Also just trying to understand what it is that people knew when all this was going on.

Mr. MATTSON. The only point I would make is there is damage; there is badly damaged and there is badly damaged. There was some nuance of it got worse as we understood more. Knowing about the hydrogen explosion, knowing about the primary coolant sample activty, knowing that the temperatures came down slowly and monotonically but took a long time to come down, all those things put together ultimately led to the picture we have today of what the core looks like. That is generally worse, I think, than what was earlier thought. But significant damage was realized early on.

Dr. MYERS. Did anyone, say, on Wednesday actually seek to measure directly the voltage of the thermocouples? You say there was a com

puter that was programed to cut off at 700, and if they were measur directly, that would have gone up higher.

Mr. MATTSON. My recollection, we asked them for that on Thursd: afternoon. Because they were running around doing a lot of oth things, we did not get it until Friday some time. They were able go behind and recalibrate all the thermocouples eventually when the had the time to do it.

Vic, do you remember whether they did any on Wednesday? W asked on Thursday and it was not until Friday we got an answer th: I recall.

Mr. STELLO. The first recollection that I have, I think, was the fo lowing week, that I had heard that one of the technicians went dow during the transient and put an amplifier directly on the instrumen and I think it indicated temperature ranges on the order of 2,000 That is the only recollection

Mr. WEAVER. What was this, sir?

Mr. STELLO. It was during the transient. It would probably hav to have been Wednesday.

Mr. MATTSON. Had to have been Wednesday.

Mr. WEAVER. I see.

Mr. EISENHUT. Let me try to glue these two pieces together. There was also, while these discussions were going on some time Thursday. understanding what was being printed out and what was meant. We were mapping in the core the actual thermocouple readings as they are coming back on the scale. As Dr. Mattson said, later on Thursday and Friday we were asking the utility that when they had somebody available to go in and actually take a reading, to calibrate those numbers, to do that, too.

So we were asking them. Both of these things were happening. We were trying to not only get a handle on what the numbers were pretty precisely; we wanted them to go in and find out exactly what it was. Mr. WEAVER. You mentioned a reading some place of 2,000°.

Mr. STELLO. My memory is that some time later after the transient, I heard that one of the instrument technicians went in and placed an a amplifier during the transient on the thermocouple wires themselves and had gotten a reading that indicated a reading on the order of 2,000°.

Mr. WEAVER. Those thermocouples can read any temperature. How high do they go, the actual thermocouple itself, as opposed to what it reads out?

Mr. STELLO. The instrument technicians tell me that you will continue to get readings so long as the wires are intact.

Mr. MATTSON. About 2,300°. I think they said 2,300°.

Mr. EISENHUT. Certainly about 2,000°.

Dr. MYERS. But was the 2,000° ever reported to Bethesda? When did you hear that in Bethesda ?

Mr. MATTSON. I had never heard it before in my life.

Mr. STELLO. I had never seen any discussion or analysis. But again, I do not attach too much to it. If you had any metal-water reaction started of any proportion, which we clearly believed we had, temperatures of the order of 2,000° are not the least surprising.

Mr. MATTSON. The postaccident analysis says there were temperatures in excess of 2,000° over a significant portion of the core. The