One of the leaders of the MSRP effort was Paul Haubenreich, who was the co-author along with Dick Engel of the journal article “Experience with the Molten-Salt Reactor Experiment” in February 1970. Mr. Haubenreich is a WWII veteran and graduated from the University of Tennessee and the Oak Ridge School of Reactor Technology (ORSORT). Mr. Haubenreich worked on the earlier Homogeneous Reactor Experiment-2 (an aqueous homogenous reactor) and then went on to supervise the construction and operation of the Molten-Salt Reactor Experiment (MSRE).

First part of the interview (AMR, 470KB, 5:00)

Sorensen: Please tell me what you just said, about shutting down the Molten Salt Reactor Experiment:

Haubenreich: OK, my recollection is that we had been told that we would have to shut the reactor down in 1969, by the end of 1969, and by the way, the reason that we heard was from an old classmate of mine, Milton Shaw, who was head of reactor development in Washington. He was an enthusiast for the fast breeder reactor. The way I got the story … he called up Alvin Weinberg and says “stop that reactor experiment…MSRE…fire everybody, just tell them to clear out their desks and go home, and send me the money!” Weinberg says “Milt, if we do what you say, you’re going to have to send us more money because we have contracts to pay everybody off, the termination allowances are not in this year’s budget”. And so anyway, the bottom line was that we had to shut down around the end of 1969. We had been together for five years, the crew had, operations, analysis, and maintenance sections. The reactor had first gone critical in June of 1965 and from that time…sometime earlier in ‘65 to late in ‘69 we had kept it hot, salt molten, with around the clock coverage, three shift coverage, 24 hours a day. As the end approached, and the curtain had to come down, it occurred to some of us it might be a nice thing to do to let everybody go home for Christmas. Up to that time we had kept people operating Thanksgiving, Christmas, every Easter weekend and everything else. So, that sounded like a good idea and I said “we have to get this place secured before we can close the door and take the day off”. So everybody agreed to that, we put the salt in the storage tanks and by Christmas day we said “everybody go home, have a good holiday, come back, we’ll see if there’s anything else we need to do”. And that’s what happened, that is my recollection of it, and I guess that’s pretty accurate. We didn’t mean for it to end that way. We had a facility there that we could strip the uranium out of the salt, and had done so with the first charge in which partially enriched U-235 was our fuel for the first… what? 4 years? no, 3 years. And then we loaded in U-233. U-233 had never been used, it had been discovered by Ray Stoughton and Glenn Seaborg –yeah, the chairman of the Atomic Energy Commission at that time, Glenn Seaborg out in California. We stripped the U-235 and U-238 out and put the U-233. The volatility process did not remove plutonium, so we had a smacking of plutonium in the salt at the time, at the last period of operation. This is all very interesting from the dynamics reactor

Second part of the interview (AMR, 470KB, 5:00)

Paul Haubenreich: Anyway, if you don’t register you can take notes. Anyway, there were 40 of us at Oak Ridge who constituted the student body of the Oak Ridge School of Reactor Technology [ORSORT] and we were enrolled in a program to last twelve months. I don’t know why that’s interesting but — oh yeah, twenty of the forty were new graduates like me, twenty were from the Navy and Milt Shaw had been working for [Admiral Hyman] Rickover and the Navy, we had people from the Electric Boat Company that were overseeing the Nautilus reactor submarine, and from General Electric, Westinghouse, all these people. Twenty of them and twenty recent graduates. Shaw and I were among the forty students in the Reactor Technology. He was a little older and had had the experience with the Navy and I was first-out-of-school and the twenty who were new graduates had the option at the end of their year of ORSORT…they were free agents. Because of the jobs situation and all, each of us got several offers and I was the only one of the twenty that opted to stay at ORNL [Oak Ridge National Laboratory] and a couple of others straggled back later but Shaw went back to Washington and I stayed at ORNL on the Aqueous Homogeneous Reactor Experiment and then with…in 1964 they organized a department at ORNL to do the operations and analysis of the Molten Salt Reactor Experiment [MSRE]. We trained and practiced for the better part of a year and the criticality was achieved during June the first of ‘65. And I guess… when was it? oh!, part of the reason why I was tapped to be the manager of that department was that I had meanwhile turned into a nuclear engineer. I had that year of ORSORT and when the ORNL wanted its engineers to do the Tennessee Professional Engineering Exams, get the PE after their name, I was grandfathered for the Basic Engineering, didn’t have to take that. They said “what branch of engineering do you want to take the test in? You’ve got a bachelors and masters in mechanical engineering” and I said “yeah, but I have the ORSORT stuff so I believe I’ll take it in nuclear engineering”. Well, in the lull between aqueous homogeneous and molten salt UT [University of Tennessee] Knoxville said “we want a Nuclear Engineering department”. My advisor on my Masters in mechanical was Pete Pasqua. He said “I don’t know anything about Nuclear Engineering” they named him to be the head of the department…

Sorensen in the background: was he whom the Pasqua building is named after?

Haubenreich: Yeah.

Sorensen: Ok, yeah

Haubenreich: Pete Pasqua. He jumped down to UT from Purdue, just a few years before being my advisor on my Masters thesis. But he came to me and said “can you come up with a curriculum for graduate students in Nuclear Engineering?”, well, yeah, I guess I could, so I had all of my textbooks from ORSORT and knew the people at Oak Ridge and was working out there, so I came up with a one year course in Basic Nuclear Engineering using Glasstone and Edlund

Third part of the interview (AMR, 910KB, 9:42)

Haubenreich: When I took the [professional engineering] exam at Knoxville, the written exam, I didn’t have much trouble, because I had taught that graduate course in nuclear engineering. And when I went down to Nashville for the oral, they said “Mr. Haubenreich, we have a question: did you see these questions before you took the exam?”

Sorensen laughs hard on the background

Haubenreich: I said “well, in a sense yes”. They said “yes!?” I said “well I taught this course and every one of these questions on your exam are what I gave my students. [Sorensen laughs again] I would’ve been disgraced if I didn’t ace this exam”, which they said “you did!”, I had a perfect score. So anyway that helped to get me the job of managing the Molten Salt Reactor Experiment. But I had some very able people. And I will tell you another little sideline: the operation of the MSRE was not too difficult…wasn’t too burdened with problems…but there’s some. And the people that I had working for me, that was in the 1960s, had grown up, most of them, in East Tennessee, and one of the things they all had besides hound dogs under the porch were old cars out in the yard that didn’t run very well. And every one of these country boys had to learn how to raise the hood and get…uh…fix things. And when 10 or 15 years later they were assigned to the Molten Salt Reactor, if anything came up… we cut the rope on the windlass one time, I’ll tell you about that if you wanna hear it [Sorensen agrees] for sampling and feeding fuel in and… and I said “Oh my goodness, we’re out of business” and they said “we can fix that!” and I said “how are you going to do it” and they said “I don’t know but we will fix it!”, and they did! Several things happened like the time the skunk went to sleep in the trash can and they got him out without having to fumigate the place…a lot of fun things happened. We had a good…well organized… we had a fun time. I went deer hunting a couple of years with my technicians who operated the facility in… so we were almost family, I think. So, it grieved me when at the end of the operation we had to tell some of the people: “we don’t have a job for you anymore”. But that was the way it was.

Sorensen: Can you tell me a little more about Milt Shaw and why it was he instructed them to shut down the experiment?.

Haubenreich: Milton Shaw was sold on the sodium-cooled fast reactor…breeder reactors. And I am not familiar with his… why that was. At the time he was working for Rickover, the Navy was still pursuing the sodium-cooled reactor which went in the Seawolf submarine [SSN 575, not the modern SSN 21] and the pressurized-water reactor that went into the Nautilus. And so, by the late 60s Milt Shaw still had it in his mind that the sodium-cooled reactor which was the type of reactor EBR-I (Experimental Breeder Reactor I) out at Idaho was still viable. But it needed more money to develop it, and so he said “well we can get some money from shutting the Molten Salt Program down”, and as far as I know, that was his idea. But that was a true story I said that Shaw told Weinberg “you gonna have to shut the Molten Salt down and give me some more money for fast breeders”. And the fast breeder persisted for quite a while, as you know…

Sorensen: The money that they were spending on the MSRE, I’ve seen the budget, what they spent on the sodium versus what they spent on molten salt, and the molten salt was a little tiny fraction…

Haubenreich: Oh, yeah, yeah, we were minor-league, money-wise compared to some of the other programs. So we realized that. And I won’t say that the penny-pinching affected our operation any, but it did, we wanted to strip the uranium out and put it back in the hot cell over the next in(?) and do something about the salt where the fission products remained, and they said “well, here’s what you do: Everybody go home, but once a year go by you can heat the salt up and let the [ Sorensen interjects: “fluorine recombine?” ] radiation damage to the frozen salt heal itself. And next year we’re going to have a permanent waste facility in New Mexico”…that was before Yucca Mountain was conceived [the waste disposal proposal to bury at Yucca Mountain long term decaying radioactive waste]. and they said: “We will just take that salt out there to New Mexico and bury it in the salt, in a sodium chloride salt dome and that’ll be a good enough place for it,” that was in ‘69, and we don’t have it yet!. So anyways, the upshot was that “chemical transuranics, you’re redundant, we don’t need you, we’re not going to strip the fission products, we are not going to strip the uranium out of the salt and ship the salt with the fission products to a storage facility” and that’s the way it went. So we were, you might say, forced back into the dugout, shutdown, the game was over, Christmas ‘69.

Sorensen: So, the program continued for a few more years after that.

Haubenreich: Yes it did, and Rosenthal was the director of the Molten Salt Reactor…they gave me a post as assistant director or something like that and I did a lot of spare time work on nuclear safety journal, and the environmental impact statement for Duke’s Oconee plant but three years, in the spring of ‘73, the fusion program needed somebody and so Weinberg told me “you have your pick, you can stay in the fission reactor with Paul Kasten on the gas-cooled reactor, or you can go to fusion”. I thought about it, prayed about it, Mary and I did, and we said I am going to stay with something I know something about…in the fission [program]. A few days after that, Floyd Cutler, who was the associate lab director came in and said “I need to talk to you in private”, and I said “come in Floyd” and he said: “I know we told you you had a choice, but you made the wrong the choice!” [Sorensen laughs] “and I am here to tell you why fusion is better”, he convinced me and I went to fusion. Of course that was a good move. I spent the rest of my… how many years? ‘73 to ‘91 in fusion. But they said “you know how to work with people” and I said “I don’t know anything about…”

Fourth part of the interview (AMR, 2566KB, 27:21)

Haubenreich: His secretary answered the phone, “Mr. Weinberg’s office”. He was not “stuck up”, we would say in East Tennessee. But he was top notch, he was a good friend of Eugene Wigner. Wigner was another down-to-earth genius and that I had some contact with. He was an advisor on the Molten Salt program. MacPherson was another top-notch person. He didn’t have the recognition that Weinberg and Wigner did. Ask me a question about Weinberg!

Sorensen: Weinberg in his memoir said that he was told he needed to leave Nuclear Energy in the fall of 1972, and in January 1st 1973 he took an extended leave of absence from the lab but he knew… he says in his memoir, that he knew basically…he was being canned. You know? and it was on orders from Chet Holifield [member of the JCAE or Joint Commission on Atomic Energy] and Milt Shaw [Haubenreich says “yeah!”] and what I’m wondering about is how’d you feel and the team feel when you found out that Weinberg was leaving the team?

Haubenreich: That was… I felt let down, I had to say. But I was aware that times had changed. Weinberg was not a convenient but an inconvenient originator of ideas and during the 1950s and 60s his ideas… the climate was such… the timing was such that the AEC [Atomic Energy Commission] gave him a couple of million dollars and said “see what you can do about with that idea” and that was a lot of fun. And Weinberg ran with that ball and thought of another one or two while that was happening and by the early 70s there wasn’t any place for a person with his stature and even though he was extremely well qualified to guide nuclear programs, the AEC, Washington, felt like they had plenty of people up there who could guide the programs “and we want people somewhere down in the laboratories that knew what we want done and not to bother us with all these ideas”. I guess MacPherson was one of the prime advocates of “let’s dig some of this shale that’s underlying East Tennessee and get the thorium out of it! and make U-233 out of it in a reactor!” He said “we’ve got worlds of fuel material, shale has enough thorium in it to make recovery feasible.” Weinberg was… had the… he said… “fluid-fuel reactors are nothing but a pot, a pipe, and a pump” And pumping that kind of stuff around and of course that ignores a lot of reality. The Aqueous Homogeneous Reactor was summarized by one utility executive to come to visit one time, he said: “you’re pumping uranyl sulfate solution at 257 centigrade or a little higher around” and we made enough steam, we’ve got a steam whistle out of a Southern Railroad steam locomotive put one in on the end of our building. We made steam with the Homogeneous Reactor Experiment and piped it up. Everybody had to turn on our last day before everybody had to go home we got to pull the cord, blow that whistle. We got a phone call from over in security the next day “what’s goin’ on over there? We heard that whistle blowing”, [Sorensen laughs] We were just having fun. But anyway, I got sidetracked with the whistle, let’s go back to your chart.

Sorensen: What I was thinking is that you drive a good point here that Weinberg had inconvenient ideas versus the way the Atomic Energy Commission…

Haubenreich: Yeah, I don’t… I wasn’t privy to his latest ideas… by that time “I had my nose in a different book” and so I had the impression that there wasn’t any statement made that… for the staff at ORNL that really gave a good clue as to why he was being… his status was being changed. The impression was that he was doing it under pressure because he was still enthusiastic when he would come to our meetings and gave every impression of thinking we really ought to do something about this…

Sorensen: About? you say “about this”

Haubenreich: Well about the thorium-U233 cycle and the potential of molten salt for being used in that cycle. They were not identical but they were… they had some connection.

Sorensen: So Weinberg was very enthusiastic about thorium and the Molten Salt Reactor?

Haubenreich: I did not detect any diminishing, diminution of his enthusiasm. So, I would feel safe in saying he was still enthusiastic. You would have to ask someone else, Murray Rosenthal about Weinberg’s enthusiasm, but his enthusiasm and his position were not sufficient to get the kind of money that we, Rosenthal, and MacPherson felt like we needed to keep the program going. So when I left in 1973 I was too preoccupied, Herman Posma was a division director at that time, and later became the lab director [in 1974], and Posma kept looking over my shoulder and when I said “I don’t understand this fusion business, I don’t understand how magnetic fields interact with plasma, and how everybody around here seemed pleased when they get a burst of a few seconds in length”, and I said “I’m used to running… we were in the Molten Salt reactor, I think, hot one time–for 10,000 hours, that’s more than a year!–without shutting down and freezing. So, I was… I had a totally different frame of reference”, so for the first couple of years in fusion I would be bothering the physicists, “can you explain to me what’s going on in there, how that works? I don’t get it” –they said “well, you’re too dumb”, [snickering] “well, that may be but until you get some more dumb people on board, you ain’t gonna have a program”, so they had to do that.

Sorensen mutters “tape recorder”, a female voice asks “what is that instrument?”, Sorensen replies “it’s a phone, it’s a phone but it will record your voice and I went and saw Murray Rosenthal and had a great conversation this good with him and I didn’t record it. And I was just kicking myself afterwards”.

Haubenreich: “Yeah”.

Sorensen: “whoa! and I did have a recorder, so I thought if Paul would let me, I’m definitely wanna record it because these reminiscings are precious to have”.

Haubenreich: “Yeah, retrospect is good, I kick myself a couple of days ago. We had a big noise in the night during the wind storm. I looked up and there was a tree sticking down through the roof and the ceiling of the car porch [female voice says: “just missed the car”] and it was a six inch diameter trunk. It’s patched now, they fixed it. But there was this big trunk, came down and stopped this short of the car. And staring back it looked as if there was a tree coming out of the roof, because that treetop would blow out of next door, came down butt-first and rammed through the roof. And the big branches, some of them bigger than my arms held it up and I should have gone out and shot a photograph of that, but I didn’t.”

Sorensen: I really appreciate your time and I don’t want to take too much of it, but there is a question I’d really like to ask: Here we are in 2012 and it’s been a long, long time since you all shut down the MSRE and you’ve had a lot of experiences with fusion, you’ve seen what our country has and has not done with nuclear energy. You’ve seen what we’re doing now burning gas and coal. Looking back on all that, on thorium and MSR, what are your thoughts now looking back, was it a good a idea?, was it a bad idea?, should we have done it? where do we make the right move? [Haubenreich, forcefully: “Molten Salt Reactors!”] …just a big picture, kinda if you could talk to the President and give him some advice, you know, what would you say?

Haubenreich: I think this is a concept whose attractive features are very high temperature source of energy… well maybe I shouldn’t say “very” because there are higher sources, but high temperature and low pressure! [Sorensen: “Yeah!”] Just the opposite of the aqueous homogeneous where we had to have 2000 psi of pressure to keep the stuff from boiling at 300 centigrade. So anyway, I said it has these attractive features. The Atomic Energy Commission through ORNL designed and operated a facility, a device, that was appropriately called a reactor experiment, and its purpose, first principal purpose was to see “can you operate this thing and when it breaks down, can you fix it? can you operate it reliably enough and when it breaks down, can you fix it?” there’s lots of subsidiary questions to that. That reactor experiment operated at high temperature, low pressure from 1965 through 1969 and the answers were positive. I have a notebook down there near my computer. I got congratulations on the successful operations of the MSRE.

So it got some recognition, and the answers were mostly very positive. The materials which had been an Achilles’ heels of the aqueous-homogeneous reactor… …Oh yes! this utility executive who came out and said “if you gave me a stream of hot sulfuric acid and said make steam, make electricity, I would say, I would laugh at you. I would turn it down”. Because we depended on an oxide film on the container material to protect it, to keep it from having catastrophic corrosion.

The Molten Salt Reactor had a container material –let me think–INOR-8, yeah we called it that, Hastelloy-N later, and we had graphite, and we had molten-salt, salt. And the components of each of those three materials in my mind I said “they like to be where they are and they don’t try to attack their neighbors”. So the materials compatibility was a thing that we demonstrated. We pulled out graphite after tens of thousands of hours, I don’t remember, 20 or 30 thousand hours and it looked just like it did when it went in.

There was some sticky points in the operations, the design. The pump worked fine. And the pipes, and we pumped the salt through a radiator, just like on your car. But we didn’t have any anti-freeze and the air was 800 degrees below the freezing point of the fluid, and you were here when the air is 10 degrees below the freezing point of your automobile coolant.

So, anyway, the pipes and everything were red hot, makes nice photographs [Sorensen: “yes, I’ve seen that photograph”] but how do you design a valve to shut off the fuel from the storage site? and the only answer we came up with, before the reactor was built, the experiment was built, was freeze-valves. One of the freeze valves led to a crack in a pipe that released probably a thimble-full of salt into the reactor cell. We detected it immediately. But it was because the freeze-valve was not manufactured to the design, you have a section of the pipe with the salt in it that is flattened and there is a shroud surrounding that section, and you blow air in. And you had baffles to keep the air on the section of the pipe you want. Those baffles are mounted in a sleeve that does not contact the red-hot pipe, and the baffles are thin metal that are not fastened to the pipe, hot pipe, except for a welder that evidently said “look at here, this piece of metal is not welded to the pipe!” and he welded it to the pipe. So, every time you froze and thawed that valve that baffle tried to work the pipe and eventually it cracked. Not bad, but it cracked. And that happened very late in the game. In fact, during the final shutdown period. And we didn’t mess things up. Anyway that’s what happened.

Reminds me the story when they built the gaseous diffusion plant, acres and acres of it, the drawings were not perfect and the craftsmen got tired of interpreting and making them go to the right place and they put compressed air onto the urinals. When you got to do with your business, flushed the urinals and compressed air blew out everything in the urinal out in your face. That’s a true story, I’m told. So that little baffle in the freeze valve was another place where the craftsman thought he knew better than the designer. But the other thing that had us stop for a couple of weeks or more, but less than a month, but a couple of weeks, was the arrangement for putting concentrated fuel salt into the molten salt and dipping samples out for chemical analysis to figure out what’s going on. We had a lot of chemists who wanted to see if it was corroding, and they wanted to take samples periodically. The arrangement was that we had a windlass up here and a can, air-tight can, and we had a flexible steel cable that passes on to the capsule, and I can show you the capsule. And to get it into the business, the reactor, we went through a gate valve, big valve that you’d turn, actually it had a motor that turned it. And the escape valve comes in. One time the cable got tangled up and I said “is it in that gate valve?” –and they said “we don’t know” the driver up here says “it’s far enough down in there it could be on the gate valve, we think we’ve got to hoist it up” and I said “can you put a crank on there instead of that motor and ease that gate valve then and if you run into the cable, could you feel it?” –and they said “we don’t know” it’s got a pretty good mechanical advantage on that drive but after a few days I said “try it and you won’t be fired if things don’t go the way you think”, so they did and they came in “we have bad news, here is the end of that cable” [Sorensen laughs]. Cut off [Sorensen: “oh-oh”] “the sample capsule is down in the pump, it’s on a cage and here is the raw end of the cable up here”.

So I said “what are we going to do?” and there’s the good old boys for you, they said “we’re go in there and fish that thing out, with the cable, and we’ll make another one, put it in there and not get it tangled up next time” I said “you’re kidding, what does it look like down in there?”, they said “we don’t know”. I said “is there such a thing as fiber optics?” “fiber optics? I’ve heard of that” and at that time the only manufacturer of fiber optics only made lengths like 50, 60 ft. long. but we made up a viewing device, that would be put down in there, and there’s the capsule. “Can we make up something to hang on to cable, that would grab that cable, on the capsule, and let us pull it out?”, they said “let us think about that” and they thought about it and came up with something, and they fished that capsule out and we were back in business after a while.

But that was a little sore point … so, the freeze valve, sampling and fuel addition are such thorny problems, though not surprising, that at the end of the experiment we got problems with them.

So, back to the question, what would I tell the President? I would say that we worked for several years on an experiment that in our estimation proved what it went out to prove, that you can handle this molten salt reliably and when things go wrong, the things that went wrong with us, anyway, we were able to fix. And that the dynamics, the chemistry, the materials situation was better than anybody, well except enthusiasts might have dreamed that it might be that good, but everybody else was sure to have their fingers crossed. Anyway, it turned out wonderful materials-wise. The freezing, we had a radiator that blew air across the red-hot tubes with the salt on them and the air went up a big stack. And in the wintertime, when it was bitter cold, all the birds in Anderson County perched at the top of that stack to get warm, meanwhile down there it was red hot, but up there it was just nice. But that worked for years, it never froze up. The radiator never froze. So, that was one that was more of a challenge than the freeze valves, but the freeze valves had a glitch and the radiator didn’t. At one time we had to scram, we had doors that dropped down on either side of the radiator, salt still going through, to stop the air flow. And the big doors made by Joy Blower Company had a hub that was about this big of cast aluminum, big veins that went around and I was down at scout camp and they didn’t bother to tell me that hub blew up! [Sorensen: “I’ve heard that story, yeah”], it cracked and pieces went everywhere. So the doors dropped down like they were supposed to, we got the salt down in tanks, cooled it down, went in and inspected it, there weren’t any crumbs of the blower hub on the hot tubes, the tubes that would be red-hot. We thought that might be a problem, but that ended up alright after a while. Joy had made a lot of these same blowers for NASA, and they were fine.

Anyway, my word to the President would be, in my opinion, the potential, the advantages outweigh the difficulties and the concept is ultimately going to be a practical application, so that’s my bottom line. [Sorensen: well, good!, good… I’m getting stuff on that, thank you, thank you!]

Sorensen Note: Many thanks to Eduardo Madrid for the transcription of the interview.