Pioneers in Science and Technology Series: Arthur (Art) Rupp

              
PIONEERS IN SCIENCE AND TECHNOLOGY SERIES


ORAL HISTORY OF ARTHUR RUPP
Interviewed by Clarence Larson
Filmed by Jane Larson
February 1, 1989
Transcribed by Jordan Reed 
MRS. LARSON: Okay, it’s running.
MR. LARSON: All right then it’s okay. Why don’t you just stop it now then?
[Break in video]
MR. LARSON: Okay. Is that, just a second, just a minute. I want to see if our microphones are working all right.
[Microphone feedback]
MR. LARSON: They are. Will you check yours?
[Microphone taping]
MR. LARSON: Good. All right. Fine, we’re all set. They, the focus is all good as far as you’re concerned now. All right. Then, as we’ll say, I’ll just say a few words for identification and then I will say, “Please proceed, Mr. Rupp.” Then you start in with saying the, something about the origins.
MR. RUPP: Origins, radioisotopes and so forth.
MR. LARSON: Yeah. That’s right and then we’ll just take it from there. If you want to stop for a rest, would just hold up your hand like that. And she will stop it and there will be no glitch whatsoever. All right. Well fine. For identification, this is an interview with Mr. Art Rupp and the date is February 1, 1989, and with this Art, would you please proceed?
MR. RUPP: Well, Clarence, we were talking a while ago about the origin of the radioisotope program. I expect that the point that I should make at first is that radioisotope enters didn’t start with the Manhattan Project and reached clear back into the ‘30’s when Irene Curie first made phosphorus-32 using alpha particles. So I always look at that as the beginning of the radioisotope manufacturing, although at the time they didn’t really realize what they were getting into. Then in the period between the early ’30’s and the time the Manhattan Project came along, there was a tremendous amount of work being done in the universities all over the world. Cyclotrons in California, and Karkoff-Walton machines in England and various places making isotopes, radioactive materials that could be used in chemical work, tracing primarily. So the time of the Manhattan Project, the people who were doing chemical work, chemical separations, were primarily for the plutonium process, needed radioactive isotopes, one kind or another to assist in their work. So this was in addition to the fission products, some of the simpler isotopes such as sodium-24 and a few others like that that they wanted to use in chemistry, were used here at the Lab, at Clinton Laboratories and it so happens that when the Graphite Reactor started, one of the first parts of the program was to encase pure chemical target material in aluminum tubes, seal it with a sealer much like one of the can sealers and put them in holes in the graphite stringer, we called it, pure graphite, and this was stuck into the side of the pile and radiated anywhere from a matter of hours. Sometimes we radiated material for months depending on the half-life of the material that we wanted to make. These were then taken out and put into shipping containers which were essentially a lead box with good closures and these were put into heavy wooden boxes and could be sent out to various chemists all around the university group primarily who wanted to use them. So that’s probably the origin of the first radioactivity that was sent out from the Laboratory if you discount the bits of solutions that scientists had around the Lab and they traded with people at universities all around the country. 
MR. LARSON: This was before any real organized plan to extend broadly the uses of radioisotopes, I take it. 
MR. RUPP: That’s correct. That didn’t come along until shortly after the close of World War II and a group of people at Clinton Lab, Waldo Cohn and others wrote an article for Science Magazine which in effect was partially a catalogue of materials that one could get at the Laboratory. 
MR. LARSON: This was in other words late in 1945 then probably. 
MR. RUPP: Probably late in 1945, yes. It actually probably started a little bit before the war ended because the people who were involved and could see what was coming and there was demands for isotopes so it sort of slid right through the end of the war there and they were ready to go.
MR. LARSON: Fine. That was very interesting how this originated and apparently demand was almost automatic for many of these.
MR. RUPP: The demand was quite great and came from universities, as I said primarily, but then all sorts of institutions and then the sister laboratories across the country wanted radioactivity so it picked up quite rapidly. For a long while the only isotopes that we shipped out to speak of, as far as variety is concerned, are those that were irradiated directly in the pile and that included not only chemicals, but it included a great assortment of things, as I recall, from piston rings to teeth to grain to insects, all sorts of things were irradiated in the pile and used either at this Laboratory or at others. The next phase of the radioisotope program is one that, of separation of isotopes in more or less pure form and one remembers that the three that were the most important and still are quite important and I should mention I guess carbon-14, the most important of all the isotopes in some ways and phosphorus-32 were two of those that were worked on to be separated from large amounts of target material and after isolation, worked down into a small solution and suitably packaged and sent out. 
MR. LARSON: Can you give us an example of how you would prepare, for instance, phosphorus, what the target material was and what the nuclear reaction was?
MR. RUPP: In the case of making phosphorus-32, the radiation target was sulfur. So it required quite a large amount of sulfur for a target to make a reasonable amount of P-32 because the Graphite Reactor didn’t have as many neutrons of the right energy because it is a so called NP reaction which requires something other than the slow neutrons which of course operate the reactor.
MR. LARSON: In other words, the slow neutrons didn’t have the energy necessary and so you used only the high energy spectrum of the pile.
MR. RUPP: Right. Of course we made no special effort for screening there. It’s just the yield resulted in whatever we got.
MR. LARSON: Oh yes.
MR. RUPP: So after that the sulfur incidentally was melted into a big aluminum can about so big, like this, which was a big target and had a sort of a built in funnel top and was melted in there, closed up and then lowered down into the pile, radiated probably as I recall a week or so because phosphorus has a half-life of only 14 days anyhow. Usually if you radiate one or two half-life’s that’s quite enough. Then it was taken out and we first separated phosphorus from sulfur by what we called the strong arm method so to speak. It was really, what it amounted to was melting the sulfur again in a big beaker and of course this was done by some rude remote-control apparatus. And then we had a vat of nitric acid, not concentrated nitric acid, but quite strong. I can’t recall it’s concentration and it was poured down through the solution, dribbled down through it and the extraction took place in the nitric acid.
MR. LARSON: Oh yes.
MR. RUPP: So then the nitric acid was drawn off later and by various carrying methods, usually an iron hydroxide, or lanthanum hydroxide, we would pull the phosphate out and then pass it to several other chemical procedures to get the phosphorus free, usually being sent out as very dilute phosphoric acid.
MR. LARSON: Oh yes. And how about the, some sort of equivalent reaction in making carbon then.
MR. RUPP: Carbon is an interesting case because right from the beginning one of the most sophisticated possible methods was used for making carbon-14 although it wasn’t very practical at the time. This is a loop in a reactor containing, the loop contained ammonium nitrate and the nitrate is the target atom, the nitrogen-14 to make the carbon-14.
MR. LARSON: Oh yes.
MR. RUPP: You would have an NP reaction involved. So Art Snell and others in physics put together an apparatus where we had a loop that would go into the side of the reactor and into the neutron zone and back out again. It came out to an apparatus where we could aerate it using nitrogen at that time and would aerate the solution at a somewhat elevated temperature and the bit of carbon that was in there usually appeared as carbon dioxide. Some of it would appear as methane and a tiny bit, as I recall, as carbon monoxide, but these would be swept out of the stream and captured in a column for example and taken out by flushing the columns and working it up finally as barium carbonate.
MR. LARSON: Oh yes.
MR. RUPP: Now barium carbonate was the way it was shipped. The interesting thing about that method compared to the later ones we used was that the specific activity was very high. This was because of the separation practically at the time it was made and if the substances were pure and there was very little carbon in there then it was contaminated with very little. So we got preparations of carbon-14 where over 50 percent of the atoms were of carbon-14 atoms.
MR. LARSON: That’s astonishing.
MR. RUPP: Extraordinarily good. Later on we used calcium nitrate for targets for mass production and the specific activity in that case would run, oh, certainly not over 10 percent and usually around five percent, but this was quite adequate for the work that was being done at that time and they wanted to make organic compounds, labeled with carbon-14 so they would have added a carrier activity anyhow.
MR. LARSON: Oh yes. 
MR. RUPP: The very high specific activity carbon-14 was mostly of interest to the physicists at that time.
MR. LARSON: When was the first shipment of carbon-14 made to, you might say, to outside the project?
MR. RUPP: Well the first shipment, I don’t remember where it was made to, but it was made to the Bernard Free Clinic in St. Louis.
MR. LARSON: Oh yes.
MR. RUPP: It must have been about 1945.
MR. LARSON: Oh very early.
MR. RUPP: Very early, yeah. ’45, ’46, yes. The use of carbon-14 is something that grew very steadily all through the years of the radioisotope program.
MR. LARSON: Oh yes. As a matter of fact I interviewed Martin Kamen who discovered the reaction and I asked him how many research papers use carbon-14 as part of it and he said, “I have no idea, but it’s probably between 50 and 100,000 papers.”
MR. RUPP: At least.
MR. LARSON: He said almost all the work that gets done…
MR. RUPP: I would have guessed a million.
MR. LARSON: …that has been done by virtue of using carbon-14.
MR. RUPP: Well, of course, it’s easy to see how important it would be since the entire system of chemistry is based on carbon, so naturally it’s tremendously useful. Actually, the 5,000 year half-life is not too bad. Some people have said at times that they wish was created with a half-life of a few hundred years, but so that we get more activity for measurement, but the 5,000 years seem to work pretty well.
MR. LARSON: Yes. It’s an interesting thing. Dr. Kamen mentioned as far as the half-life I believe there is some carbon isotope that has a much shorter half-life the cyclotron produced and so they wanted to get another one and they said, “Well, we’ll try carbon-14,” and Oppenheimer said, “Yes, but that would only have a half-life of a few seconds.” So sometimes theory doesn’t work out. 
MR. RUPP: Well it turned out to be really a pretty suitable half-life for many many things. The other important isotope, Clarence, was iodine-131.
MR. LARSON: Oh yes. 
MR. RUPP: We put a great deal of effort into that because it turned out to be a very useful isotope not only for following thyroid studies in medicine, but for tagging things in general. Iodine can be hooked onto compounds having double bonds with the greatest of ease and it was used for everything from tracing oil in pipelines to very sophisticated compounds in medicine that they wanted to tag. We worked it first by making it from tellurium, radiating tellurium, getting a transmutation and then dissolving the tellurium in sulfuric acid and a catalyst, a selenium catalyst probably as I recall, distilling the iodine off and it’s quite volatile, comes off with the steam and then refining through a number of distillations to get it to high purity. In a final shipment a very tiny amount of hydroxide was added to stabilize it for shipment. A great deal of iodine-131 was used through the years and it was the first one where I decided we would have to try to get it from fission products, where you could get a vast quantity of iodine. So it was the incentive we had for the first work on fission product materials and we used slugs out of the Graphite pile and we added tantalum-lined dissolver down in the old C building where we dissolved it in nitric acid and distilled the iodine off and of course we bled off the xenon and the krypton for the atmosphere in those days.
MR. LARSON: Incidentally if I can interrupt for just a second.
MR. RUPP: Surely.
MR. LARSON: What actually, do you remember the approximate date that you started into the radioisotope program?
MR. RUPP: 1946.
MR. LARSON: Right at the start after…
MR. RUPP: It was somewhere toward the end of the year because I was working over in another group with Miles Leverit working on development and then it was decided to farm radioisotope into a semi-business type operation under Logan Emlett. So I transferred and worked with him in Operations Division and we started developing these processes for making all the isotopes and getting them all catalogued and sent out to all the people who might want them. Through the years we also tried to increase the variety and the chemical form that we could send them out in. The fission products have always been a great interest to me and I certainly remember your great interest in helping us along with the fission product project to get large amounts of fission products. That did go through. We finally were, got around to the point with the fission product plant where we not only could, but we did separate literally millions of curies in pure form. As I recall the largest amount we made in pure form was cerium-144 and this was several million curies of pure cerium as the oxide. This was the type of thing where you had to use water cooled tables to keep it on, water cooled tongs to pick it up. It would just glow tremendously in the dark and all of those problems we solved which in retrospect I think were rather tough problems and we solved them very easily as we went along.
MR. LARSON: That’s amazing because you had to work by remote control all the time and the chemistry is not all that simple on some of these things. So you were able to produce these very intense sources. Incidentally what was the requirement at that time for these, cerium as an example?
MR. RUPP: Cerium was one we didn’t really make very much of, but we had to have an Air Force special contract at the time and they were interested in the possibility of using cerium to heat hydrogen for a rear thrust for a rocket.
MR. LARSON: Oh yes.
MR. RUPP: And that would give you a maximum thrust, using the hydrogen gas heated by cerium. That particular project of course never did get to any real big scale but I always have been interested in it.
MR. LARSON: Yes, it’s a very interesting experiment.
MR. RUPP: I remember at the time, you possibly have forgotten, you were very interested in that the cesium we were interested in getting a 30 year gamma emitter that would do the work that cobalt-60 does. It was always offensive to me to have to put material into the reactor to make more radioactivity when we had so much radioactivity that we didn’t know what to do with it. So it seemed to me only a matter of good sense to try to use cesium-137.
MR. LARSON: To have so much yield from a fission reactor.
MR. RUPP: Yes, a big yield and we made those in the form of cesium chloride and cesium fluoride. And we were able to make the pellets in a, using a hydraulic press on the insides of the cells of course and getting little blocks of cesium chloride about so big around, thick, we sealed these in double capsules of stainless steel and they were used in therapy machines most particularly at ORAU [Oak Ridge Associated Universities].
MR. LARSON: Oh yes. 
MR. RUPP: And they are still being used to some extent, much smaller ones for radiography of all kinds, but the other one we were interest in was strontium-90 which is the horror isotope. We made not literally a million curies of that as the oxide and pressed it out into wafers and used it for heat sources. We had one source at the Laboratory which was originally used in Antarctica for generating power for a beacon.
MR. LARSON: Oh yes.
MR. RUPP: I think it is still delivering quite a respectable amount of power, it’s by thermocouples fitted around the source.
MR. LARSON: What is the half-life?
MR. RUPP: It’s about 30 years and even in that late date there was still controversy about whether it was 29, than 30. I haven’t read on the subject in a good many years, for all practical purposes, 30 years. I always thought of cesium or strontium as 30 years.
MR. LARSON: The heat source would have a long life for practical applications. 
MR. RUPP: The ones that we made, and I was interested one time in thinking, and looking at that one is half gone now and this is, people who talk about radioactive waste never think of. This is a waste that disappears by itself if you just wait long enough. I calculated one time that if you had a plant connected with a reactor and it was making the products, the usual fission products and then we separated them in a fission product plant and canned them up and put them away, after about 75 years it would be the equilibrium. The plant would be, the strontium and cesium are particularly items of interest, but it would be just as fast as the plant was making them. 
MR. LARSON: Oh yes. So the world would not increase its radioactivity.
MR. RUPP: I regret that this point is never brought out in articles or discussions on these. They talk about bacteriological waste and that can increase by leaps and bounds and many wastes are at least stable materials- lead, mercury, cadmium- they at least stay the same. Radioactivity disappears by itself if you are patient enough. Though it, we were hopeful that there would be more interest in concentrating fission products using them where you could, storing them where you can’t otherwise, and just taking care of them in other words. This was one interest of mine and I tried to pursue and I don’t think anything ever came of it from the standpoint of making highly concentrated separated materials.
MR. LARSON: Yes. I know you had written several articles on removing some of the fission products, essentially canning those and I believe there were some others in a little bit different category, and this would be a wonderful way to manage the waste.
MR. RUPP: It’s a wonderful way to manage the waste, that is exactly right. That is a very good way to put it. When talking about reactor waste, it’s customary to group radioactivity all together, as if it were equally dangerous and that by large measures is not so, strontium-90 being far more dangerous than the rest of the material. If one just took the strontium-90 out of it, it would practically pull its teeth because the plutonium of course would already have been taken out and the others would decay at a very respectable amount of time. So the consideration of taking out material is always run down by people who did not like those processes by the fact that you couldn’t achieve essentially 100 percent decontamination. It would take a long time to go into that explanation, but that’s essentially a phony argument.
MR. LARSON: Oh yes. This of course, our society is cursed with this 100 percent safety, not only in radioactivity, but almost all the other areas. A new drug has to be 100 percent safe, people are dying because of the unavailability and all the way through the rest of things, but that’s neither here nor there. The radioisotopes have continued to be of such remarkable use throughout the years and the benefits are incalculable.
MR. RUPP: If I could just mention one story having been talking about iodine which is demonstrative of several things. Dr. [Rosalyn] Yalow who did most of the work on radiometric measurements of the enzymes of the body and so forth. We talked together years ago about iodine and iodine now has an eight day activity and this means that one curie of the material has relatively few atoms. I don’t remember now, a few million, not many, but for the purposes that she had in mind which is typical of biochemical work, she wanted to tag the material and then you dilute quite a lot as you go through. If you don’t have enough of the atoms, the tag on there, iodine, radioactive atoms, you come around to a final sample that you can’t measure because of the statistical counting that you have to have in any kind of a counting apparatus. 
MR. LARSON: Oh yes.
MR. RUPP: So it was very important to achieve a highly specific activity which we did by very special handling of target material in a reactor. This case a small amount of uranium-235 in an aluminum matrix, we radiated that and we were able to get a sample of iodine that was as I recall around 80 to 90 percent of the atoms in there were radioactive atoms... 
MR. LARSON: Remarkable.
MR. RUPP: …which is allowed then a tagging of such things as enzymes, hormones, so that one could still make radiometric measurements.
MR. LARSON: She got the Nobel Prize for this work.
MR. RUPP: Yes, she did. 
MR. LARSON: That is a very brilliant application there. 
MR. RUPP: We did a similar thing on that in the assist on the measure with the talon in Columbia, I believe, where we had to make a sample of chlorine-36 which is 100, 200,000 year half-life, I forget at a very pure material. And we attempted to do this in somewhat the same way. 
MR. LARSON: Oh yes.
MR. RUPP: There were special problems of these kinds that came up through the radioisotope program and I think one of the things that we did do and tried to do was to get every special requirement of the scientific community taken care of as well as we could. That is one of the things that I am most proud of. 
MR. LARSON: Well of course every physicist I have talked about pays high tribute to the isotope program because without it, it would not be possible to do that work.
MR. RUPP: We understood very well the work that was going on and we were highly pleased to be a part of it. 
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MR. RUPP: The applications of material to some of the project work was also important. One particularly important isotope which carried the code name ralla [sp?] was actually barium with a lanthanum daughter, barium-140 and that was sent to Los Alamos where by utilizing the intense gamma rays from the hundreds of thousands of curies of lanthanum that was separated from it they could analyze the shockwaves and do other important work there related to the design of the bomb. Similar material was made by us: point sources of strontium-90 which would shoot out a beta particle, high speed electrons which were fixed into rotating wheels which would send pulses through the explosion waves for analysis for example. Those are just two examples of many, many things that physicists did. There is just no end of them where one could use either a gamma ray for measurement or a beta particle for measurement on the actual explosions that they were working on. 
MR. LARSON: Incidentally, what was the half-life of the barium and the lanthanum?
MR. RUPP: It was only around 12 days for the barium. The lanthanum daughter was the equilibrium of that, but I don’t recall that half-life. It was very short. It was just an equilibrium daughter that they used. Many of the other isotope uses were in the field of agriculture and of course medicine. In agriculture there was a very intense period of research in the early years of the radioisotope program where the United States Department of Agriculture and others determined the ways in which phosphorus, nitrogen, carbon, potassium were used in plants and that seemed to me like a period of about four or five years. A very high peak of research activity when they discovered most all the essential things about the movements of atoms in the growing plant. A lot of that work was done at Beltsville, Maryland, the farm station there. 
MR. LARSON: I imagine the phosphorus was very, certainly used tremendously.
MR. RUPP: Yes. Phosphorus is very interesting. It was used also by lecturers by taking leaves and at the beginning of the lecture taking a stem in a solution of phosphoric acid and then after a while they photographed it against a fluorescent screen and you could see all the little veins all through the thing where the phosphorus had been taken up into the leaf. It was a great demonstration. This sort of work was done on a great many plants and as I say it was just a fierce amount of research that was done there over a period of four, five, maybe ten years, I recall now, and they recorded just about everything that they needed to know at least at that time. In the industrial use, it was considerably slower. One of the reasons there I suppose was the nature of industry as compared to biological sciences and medicine and so on, not nearly so adventurous and there even in that early day, radioactivity had a bit of a danger tag on it, so it was slower there. But one of the first uses I remember was the radiation in the pile directly, piston rings, gear parts, sleeves, all the parts where wear occurs and they were running tests on engines and the oil monitored continuously and the wear on the sleeves under different conditions, laundered after taking them out. There was a lot of that kind of work which had to do with the wear of mechanical parts and much of that, I say, was done fairly early in the program. The pipeline usage was another that developed early when oil is shipped through pipelines it has all different kinds of oil in the pipeline. It’s not just one single kind. They will send through a batch of gasoline, kerosene, crude oil and diesel fuel and so forth and they are usually separated by water slugs in between them. There was an early usage there of tagging the water plugs and they had equipment then that you could tell about where everything was in the pipeline and when it was coming through a station. You could make your necessary switch over. Then in refineries themselves on moving catalyst was another where they needed to find out where the catalyst was being worn down, what the movement was, what the turnover in the bed was, and these could all be measured by sophisticated instrumentation that they might have had at that time and much more so now of course, how the cracking process was going along. Any sort of a manufacturing process where there was a need to know where a particular component was a particular time and where it was passing, one could do this. A tank level is another use that has hung on pretty well. Usually cesium sources are used for this. If you put a source on one side of the tank and a detector on the other, by suitably measuring the gamma rays that pass through the tank they are continued by the liquid moving up in the tank and the source is here and the detector here, it will go through varying amounts of liquid. You can tell pretty accurately even down to the number of pounds there in the tank. So there are a lot of uses like that that are very practical. Then another thing in the pipeline industry there is a radiography on the spot of welds that were made and for this iridium was used and I don’t remember the isotope anymore, but it’s a very useful gamma emitter for, it could also be pulled through the pipe. So it could be x-rayed from the inside out, and that was very handy and still is. There are innumerable uses similar to that in the industry, but it didn’t grow to a point as far as I think it should have because of some of the fears of radioactivity. The most notable in that is the use of radioisotope lard sources for sterilization of materials. Most of the bandages and needles that are used now in operating rooms around the country are sterilized by radiation.
MR. LARSON: What radioisotope source is used?
MR. RUPP: They primarily use cobalt-60, but some of them are equipped with cesium-137, but the use for food has never been able to get over the hump very well, primarily sponsored by the Army and Navy in Massachusetts. It was a very good program, it worked quite well. The motivating force there was to have field rations for soldiers that were essentially fresh. I remember tasting some of the bacon and biscuits and so forth that had been irradiated and it was months and months after it had been made and it was quite okay. For a very simple process, for eradicating larva in grain and in spices and things of that kind, they all worked quite well, but it has never been applied in the fashion that it could and I’m not exactly sure why. There is a lot of grain spoilage around the world and certainly something could help with it because a lot of grain is just wasted by spoilage and the radiation of grain in silos has been tried and it’s probably practical if they really worked on it, but that’s another usage that is lying there dormant still to be worked on. We were talking there, what was one of the other suggestions that you were thinking about a moment ago?
MR. LARSON: Well, let’s see, we’ve already gone through the agriculture…
MR. RUPP: Most of the fields of science…
MR. LARSON: Yes. Most of the fields of science use it more or less continually and medicine continues tremendous use of radioisotopes and so, it’s certainly a big thing with regard to a specific isotopes. I suppose at some time or another you’ve almost gone through the entire periodic table for highly specialized scientific uses and targets.
MR. RUPP: There for scientific programs we have made just about any isotope that is possible to make and ship. We made it very often in a form that they needed it in most cases, but I should mention here since we talked about medicine that probably one of the most important uses today is in radiometric procedures. In other words I think you could hardly find procedures in hospitals anymore that are not done by radiometric method. In other words by tagging a special compound, or counting, or either discarding, subtraction is made to get the radiometric measurement. It’s a very important thing that is literally done, I know, in hundreds of thousands and perhaps millions per day, for all I know, for laboratory procedures that are done every day. There are small companies of course, well some of them are not so small, that have grown up to make specialized forms of isotopes that can be used for all these radiometric measurements for everything from the thyroid, the simple things like that to measuring the hormones in the body. Many of these procedures could not be accomplished without using a radiometric procedure. This is probably of course, a lot of people don’t realize the importance of radiometric procedures and modern…
MR. LARSON: They don’t know it’s being used.
MR. RUPP: They quite likely don’t know it’s being used.
MR. LARSON: Yes. Well that’s, this is fascinating the number of different applications. You mentioned something about how some of these applications have gone on broadly and there are many companies in the United States that use radioisotopes for medicine preparations and so forth and actually I guess the, many of these things, the Laboratory pioneered and developing methods for preparation of radioisotopes and then passed them onto an industrial process which created many businesses throughout the whole United States. Would you like to say a little bit about the way some of the businesses developed from the pioneering work which you did.
MR. RUPP: There were quite a lot of them that did develop. One of the earliest that I remember was Trace Lab in Boston and these companies were able to do a lot more service work of course than we were at the Laboratory. They were able to personalize the service and the radioisotope forms that were popular; they could make a lot of them. So there were a number of companies that specialized in carbon-14 compounds. We originally made a few of the carbon-14 compounds. It wasn’t very long before this was a private industry enterprise and there were perhaps a dozen of companies or more that specialized in making carbon-14 and then later those that are also tagged with hydrogen, tritium. Tritium is one of the most highly used isotopes today, 12 year activity, tritium. Many of the fairly large service companies, one that I did consulting work with after I retired, Melloncroft Corporation made a fairly large quantities and shipped it to other smaller outfits who finally turned it out in dose form. So there has not only been one type of company, but a number of types of companies that have spun off from this making radioisotopes available in useable form. Now some of the most usable forms, it sounds like the wheel turning back again, come from very short-lived isotopes made from cyclotrons now.
MR. LARSON: Oh yes.
MR. RUPP: There is a new generation of cyclotrons where they make short lived iodides. These are favored now because lowering the dose of radioactivity that the patient might receive is quite good. For example Melloncroft does have their own cyclotron so that fewer isotopes are made in reactors and more in cyclotrons. I think this is a trend that will probably go ahead slowly. I think there will be more specially designed cyclotrons for making various kinds of radioisotopes.
MR. LARSON: Oh yes.
MR. RUPP: One of the things along this line that you are very familiar with is, that I was interested in, was isotopes by, no matter how one could figure it, one could never get them in extremely high specific activity so we took a page out of the stable isotope method where the calutron, which is a magnetic separation of the atoms by their different mass, wanted to eventually get some specially designed calutrons that could separate some of the highly radioactive materials primarily at that time for scientific purposes, but that never did quite gel. It is quite possible, it is feasible. We did it with plutonium quite easily using radioactivity in the calutron which is used for stable isotope production. We could get a high specific activity materials that could not be gotten in any other way because there were no isotope clocks to get all the ions converted. There is only one case that I can think of where we utilize a similar method, not similar, but a parallel method, a burnout method of material. We took targets of cobalt to irradiate them and we literally irradiated them until we burned out all of the atoms of cobalt-59 in there, converted them into either cobalt-60 or into the decay product, nickel-60. Then processed the cobalt afterwards, taking the nickel out and what we had was a preparation with all of the atoms essentially cobalt-60 atoms.
MR. LARSON: Oh yes.
MR. RUPP: That is another method of achieving extremely high purity, or high specific activity. These are typical of problems that we like to work on, but there is not necessarily the industrial or even scientific incentive in a lot of cases, it’s just things that one would like to do to see if we could do it.
MR. LARSON: Essentially stretch the boundaries of science.
MR. RUPP: Well we did make a lot of materials that were essentially pure. Once I remember making a sample of cesium-137, it was extremely pure and then we allowed it to decay for, oh, I think it was seven or eight years. Then we separated the barium, the stable barium product from it and determined the true half-life of cesium by measuring, by weight on a balance the barium that had been produced. I always loved that little experiment.
MR. LARSON: That is fascinating. So you got a real measurement?
MR. RUPP: That was a genuine measurement using genuine atoms measured on a balance. 
MR. LARSON: Now let’s see, I know also of course in connection with the Oak Ridge Institute of Nuclear Studies [ORINS] they had a program of training people for using radioisotopes and then they would go back to various parts of the United States and then order radioisotopes. So also I was wondering if you had anything to say about the, your orders on the international front. There must have been a lot of aid that you gave on the international science front. 
MR. RUPP: There were quite a number of years that we were the sole supplier of radioactivity for the entire world, essentially, except for a cyclotron here and there, but any fairly large amounts we supplied. We worked with the people in England in establishing, at their radiochemical center which was formerly a place for separating radium compounds and that started the English program. We did a great deal to start that, the design of the equipment, the buildings, the site, and then furnished materials essentially to all of the countries in Europe and a good bit of the rest of the world where there was a scientific interest.
MR. LARSON: So you made available then the science and technology to enable these people to produce it in their own countries then.
MR. RUPP: Yes. There were several ramifications of that where eventually a technique of producing radioisotopes, where one could essentially milk off of an ion exchange column came to be a technique that was used a lot. This was a case where the mother radioisotope with a fairly long half-life and the daughter has a short half-life and you could use this by passing a special solution, an eluding material through the column and draw the daughter off in pure form, sometimes in as short as a few seconds. As long as you had an experiment that you could run that way and that’s another way you are able ship materials around the world. One of the most used right now is the indium column. Marshall Bruster liked to call them cows.
MR. LARSON: Oh yes. 
MR. RUPP: Although I didn’t particularly like that term. I called them generators. The technicium-99 is used for scanning primarily is one of the most used today. A lot of that work was done by the people at Brookhaven National Laboratory and each one of the labs of course did pick out certain projects that they specialized in and the generators were developed to a great extent by a group there at Brookhaven. We did make them and ship them, but there are new ones that have been made also that one can use. Another thing that we developed was the use of stable isotope targets. 
MR. LARSON: Oh yes. 
MR. RUPP: In order to get a highly concentrated target, a highly pure material because there was no side reaction, if the atom that one wanted to bombard with neutrons was a nearly pure atom of your target material. 
MR. LARSON: Without complicating isotopes.
MR. RUPP: Without complicating isotopes. We introduced the use of stable isotope targets. We were by that time a part of the same group. We worked together on it and made all kinds of targets and in addition made them into forms that were sent out in the form of cyclotron targets which are very often copper plates, material plated on in various ways for use in cyclotrons. There were a lot of services like that that were developed through the years. Many of those things have been taken over now by private groups around the country and the policy of the government and that was to, if it was shown that service could be given the material produced by an outside outfit then generally speaking we withdrew from the production.
MR. LARSON: Incidentally however, I’ve sort of lost contact with this, but are there, how big is the program in Oak Ridge now in other words. 
MR. RUPP: I’m not too familiar with the details now, but it’s primarily down to irradiating large amounts of material, for example cobalt for cobalt-60. A special very new isotopes for heart studies. I have forgotten now what that is. There is specialized materials in general that either can’t be made by other places or the interest or the commercial and economic interest isn’t high enough for outside groups to do, but I think they do several million dollars’ worth of business a year yet. 
MR. LARSON: Oh yes. For mostly these specialized applications? 
MR. RUPP: Yes. Either very large amounts of something like cobalt, or something that is not made very easily at other places.
MR. LARSON: Well this has been a fascinating exposition of the origin and course of the use and application of radioisotopes. Before closing though I wanted to see if there are any other miscellaneous remarks in this program that you may have forgotten. 
MR. RUPP: Well, over a period of time, we realized that we were in a group, as far as production was concerned, we were going to work ourselves out of business so to speak. And this was never to be an enterprise that was growing in actual size, it was measured by dollar input. There were facets of it that were developed and financed by the government that were along the lines of information collection and putting out a magazine which we did for a number of years, The Science and Technology Magazine in which we reviewed all the current work that was being done. These are still around in libraries and archives of the work that is being done. I think that in the later years it was important to get out information on what had been done and this is one of the things that we tried to do. 
MR. LARSON: Well fine. Essentially you established the business, you established the technology, got the technology out into widely separated parts of the United States in the commercial world and it’s still going on full force in the United States and the world in general. So essentially you accomplished your mission.
MR. RUPP: I feel very lucky.
MR. LARSON: The world is still benefitting from all of those activities.
MR. RUPP: I hope that it will still develop. One never knows when an interesting item is going to crop up in research.
MR. LARSON: Well, thank you very much, Mr. Rupp, for this very illuminating discussion and I’m sure that this tape may be of interest to many people who are interest in knowing about the history of the field.
MR. RUPP: Well. Thank you very much.
[End of Interview]