A young Scientist's Meetings with Wigner in America



Richard Wilson



Wigner Symposium

Hungarian Academy of Sciences,

Budapest

November 8th 2002



It is indeed an honor and a pleasure to talk about Eugene Wigner although a pleasure somewhat less .than discussing the contents with Wigner himself. All students of physics, in whatever sub discipline learn about the work of Eugene Wigner sooner or later. This will therefore not be a detailed account of his professional work which is far better understood by reading the seven volumes of his collected papers. It is a personal account of how I interacted with Wigner. I began to learn about his work as an undergraduate about 1944. I learnt more as a graduate student, working experimentally on the nucleon interaction when I came across Wigner's 1935 paper on neutron-proton scattering, and his work with Gregory Breit, also from eastern Europe. Valentine Telegdi reminded me that he and I first met at a nuclear physics conference in Oxford in 1948 and we both met Eugene there. I was probably introduced by my Hungarian friend Nicholas Kurti.



I looked for Eugene in Princeton when I first visited in August 1950, but he was away, probably at Oak Ridge National Laboratory where he spent many summers, and it was not until about 1957, when I was 31 and Eugene was already 55, that I gave a colloquium at Princeton on my experiments on proton-proton and proton-nucleus scattering and really remember meeting Eugene. I had been warned about one facet of Eugene's formidable reputation. This mild looking man would sit in the front row and in the question time after the lecture would, in a gentle voice, ask the most penetrating, and shattering, questions showing the weaknesses in the lecturer's arguments. Valentine tells me that he was much less gentle in Hungarian and had learnt the gentle courteous behavior believing that was the way Englishmen were supposed to behave. Whether or not it was originally a pose I do not know. Suffice to say that for physicists at least the pose had become the man by the time I knew him. But the, most physicists do not speak Hungarian.



I realized later that Eugene was indeed very troubled by fuzzy thinking and even more by pretension. Although I have my share of both of these, I am fortunate that his wrath was never turned on me. I saw it in action for the first time some 17 years later, in 1994, at a summer school/conference in Boulder, Colorado. A lecturer was explaining his speculations about possible ways of using solar energy to produce hydrogen. Eugene was quiet until the end. Then came the bombshell. "Dr X, will you please return to your second slide?" "Dr X please look at the fourth chemical reaction on the list". "Everyone" (meaning only Eugene) "knows that this reaction does not go."



As happened on almost every one of my visits to Princeton over the following 20 years, Eugene was willing to spend time discussing experiments with me. He was delighted that I plotted some of my data against a theoretical calculation (phase shift analysis) by his friend Gregory Breit, and that I had found and explained a small discrepancy in the Coulomb interference region which Gregory had ignored. But it was not until a 3 week summer school and conference on energy futures for the world in Boulder, Colorado that I talked extensively with him. He was there with his friend Edward Teller, his sister Manci and his brother -in-law Paul Dirac. Eugene's interplay with Teller was fascinating. Eugene gave several lectures about nuclear energy. He would make some point about which it was just possible to argue. Edward Teller would say "I disagree". Eugene would stop and stand still, somewhat like a reproved naughty boy, but with a huge smile on his face as Edward made his disagreement clear. It was usually trivial, and often for the sake of disagreeing, but they clearly both enjoyed this little game, which I saw repeated on other occasions.



I am not sure how and when I became aware of Eugene's huge contributions to understanding and using nuclear fission. It was probably about 1947 - before I had ever met him. There was a cold winter in England and coal trains could not get to the power plants. Electricity was rationed. We all talked about the energy crisis and the future of nuclear energy. My graduate work had just begun, with Dr Hans (von) Halban who, with Joliot and Kowarski, had measured (in 1939) the number of neutrons in fission for the first time. Somewhat later, in 1950, I used the thermal neutron flux from the British Experimental Pile (BEPO) to try to measure neutron capture gamma rays. This was a graphite reactor, and physicists there talked about the "graphite disease" alternatively called the "Wigner effect" and described by Wigner as early as 1943. It is the fact that, in a low temperature graphite reactor, fast neutrons will knock a carbon atom off its lattice and that atom could not get back. This would then store energy. As Seitz and Wigner stated in a semi-popular article in Scientific American in 1956, "the amount of sword-of-Damocles energy stored in this way can reach up to hundreds of calories per mole. Obviously a sudden release of it could lead to unpleasant complications". As a result of this calculation, Wigner stated (earlier) that "it would be unscientific to claim a useful life (for the reactor) of more than 100 days." Fortunately the lattice is able to readily recover its original form by a controlled temperature rise and annealing. This was regularly done and graphite reactors last much more than 100 days Radiation damage studies of all sorts are now common. Sometimes they provide information on the lattice. Seitz and Wigner ended their brief article by saying "it is gratifying that a phenomenon which originated as a pure nuisance promises to provide us useful information about the solid state in general." But also radiation damage studies are done to be sure that the material in question can survive intensive radiation bombardment.



It was in 1950 also, that I learned of Eugene's huge contribution to the design and construction of the Hanford reactors - an engineering achievement of considerable magnitude, which involved the scaling from Fermi's zero energy reactor to a 250 Mwt water cooled reactor. Such a large jump in size usually takes many years and many intermediate steps. The actual time is on record and was about 100 days. But I remember Eugene's description to me 30 years after the achievement: "I told General Groves: give me 100 scientists and engineers and I will have that reactor for you in 3 months. I was wrong. It took 4 months and when it was finished there were 10,000 people on site. The second reactor took 6 months and the third took 8 months" (presumably because Eugene was not watching by that time). This comment, from memory, of Eugene's was in the context of the length of time to build an electricity producing power reactor - in 1974 it was 4 years, and now often much more. As Eugene himself wrote sometime later: "However this is not the full story: present reactors are expected to perform definite functions for extended periods in addition to performing a chain reaction."

The initial design of the Hanford reactors was Eugene Wigner's although DuPont Corporation was in charge of construction. It was Wigner who persuaded everyone that a graphite reactor cooled with helium gas (now a type favored by several designers) was less appropriate than a reactor with water cooling channels. The design is fully discussed in a report of summer 1942 (top secret at the time) "On a Plant with Water Cooling" with authors Weinberg, Young, Christy, Plass, Wigner and Williams. Although he was the first named author, Alvin Weinberg always maintains that he did not design the Hanford reactor but "I sat beside the man who did". The detail in that paper is extraordinary and is shown in the many tables. "Oxygen and Hydrogen Content of Circulating Water." "Heat Exchanger Design" (including numbers in "engineering units", such as BTU/ft2 deg 0F, that physicists use at home but hate to use in the laboratory) and many more including a detailed materials list. I am told that several of the engineering drawings (such as those in the report) were made by him personally and that he would pore over suppliers catalogs and personally determine delivery times..



Wigner was certainly well aware that there was a positive void coefficient in a water cooled reactor - boiling of water in a channel would increase the reactivity - and the report has a whole paragraph showing how the water reduced the reactivity constant from 1.10 to 1.07. Inversely, a sudden removal of the water would increase it by 0.03 which is more than the fraction of delayed neutrons which allow control of the reactor. But as laconically noted by Alvin Weinberg later "no one dared to think of the consequences of a complete failure of the cooling". At least the Russians did not, even though the water in the channels of the RBMK reactors was normally boiling under pressure. Not taking proper account of the positive void coefficient was one of the several Russian mistakes that, taken together, led to the Chernobyl accident. But Wigner's natural uranium reactors at Hanford (which as noted above he had only expected to last 100 days) were replaced after 20 years to avoid this problem. In 1986 when the Chernobyl accident took place many scientists and engineers, myself included, thought at once of the Wigner disease, and of the 1956 Windscale accident where, according to statements at the time, there had been inadequate attention to the problem. But the temperature of the graphite at Chernobyl was high enough to anneal the graphite continuously and avoid that particular problem.



Wigner in his memoirs describes his relationship with DuPont. Dupont engineers were more conservative than he would have been. But in Alvin Weinberg's words, Dupont "saved his bacon." When the Hanford reactor first went to high power, it shut itself down after an hour or so. Eugene and other physicists were not aware that one of the xenon fission products had a high cross section for thermal neutrons. Fortunately Dupont had allowed more space in the reactor vessel than Eugene's design and when this was filled with fuel rods to compensate the "xenon poisoning", the reactor worked well.

The 3 week long school and conference in Colorado in 1974 was particularly interesting. Data were presented by someone about the 50 odd power reactors then operating. I was able to add my recent conversations with William Webster, President of the New England Electric System, about the costs of electricity generated by nuclear fission. At that time the (small) Yankee Rowe was producing electricity at a busbar cost of 0.9 cents per kilowatt hour, and Connecticut Yankee at 0.55 cents per kwh (including some contribution to paying off the mortgage). I clearly remember Eugene's pleasure, and indeed surprise that nuclear electricity had at last become cheaper than electricity from fossil fuels. He had always said very succinctly "if nuclear power is not economic, it makes little difference whether it is only slightly economic; it will not be built if other sources of energy are cheaper". I am sure that he would have been as chagrined as many of us at the recent great increase in cost, beyond inflation, to 1.9 cents per kwh (in year 2000) plus a much larger sum for paying interest on the costs of construction. Some of the increase is due to inflation, some to increased staff in response to regulation, some to an increase in interest rates and some due to a general increase in construction costs above normal inflation. But my estimates of these effects do not add up to the actual cost increase. Eugene would be better than I have been at understanding and explaining the difference.

Eugene rejected the projections, which were common in the early 1970s, that US energy use would continue to double every 10 years as it had in the recent past. He stated his view that energy use would reach a plateau very soon. He put this in writing 2 years later after a nuclear energy symposium in Louisiana. Eugene was right By 1974 energy use in the USA had already reached that plateau at 10 kW per person. Energy intensity, in energy per unit of GNP has since fallen in approximately the same amount as GNP has risen, thus reverting to a long term trend rather than the 1950 - 1970 period. Eugene expressed in his view in a typical worldly manner. "It is wrong" he said at a large breakfast "for a single individual to consume too much of the world's goods." Another philosophical remark he often made was "the promise of future science is to furnish a unifying goal to mankind rather than merely the means to an easy life; to provide some of what the human soul needs in addition to bread alone."



I had some trepidation in going to this conference. I was invited to give some lectures on energy and the environment based upon my work - then just beginning - of comparing risks of energy systems. I had feared that there might be some huge mistakes and that I would be mercilessly criticized. Fortunately I was wrong. Eugene said afterwards "You seem to know your numbers. It is very important to really know and not merely believe." It was there that we formulated a simple concept that when there is a lot of easily available stored energy, such as easily burnable fuel, (or indeed carbon atoms knocked off the lattice by fast neutrons) in one place and a lot of people in a nearby location there is potential for disaster. Of course this concept was not new; the good citizens of London used such a principle in 1848 when they forbad the shipment of petroleum fuels up the Thames closer than 30 miles from London Bridge (at Canvey Island) but Eugene thought it a useful guiding principle. With encouragement from Eugene and others I continued and expanded my work on risks and gave a copy of my most recent book "Risk-Benefit Analysis " to Eugene's daughter Martha and to the Hungarian Academy of Sciences.



Many scientists think only about their work and their contributions. But Eugene put his work into the context of other people's work and was generous in crediting the work of others. This was clear in conversation, and as I read his memoirs in preparing this talk, I realize it was true of his writings. In his memoirs, for example, he spontaneously praised Seaborg and pointed out that he had completed the plutonium chemical separation plant ahead of schedule - a schedule many leading chemists thought was not possible. In his memoirs about the early days of nuclear fission research that he referred to the French group under Hans von Halban and Frederic Joliot - a reference that many Americans omit. For me this interest in other peoples work was a great pleasure.



I keep running into articles written by Wigner in unexpected places. Early on in my work on nucleon-nucleon scattering I read (in translation) Wigner's paper of 1933 on neutron-proton scattering. Of course I also knew about the work on resonances with another eastern European - Gregory Breit. When Alex Green and I were planning a conference on the nucleon-nucleon interaction in 1967, we invited both Gregory and Eugene but I was surprised when both of these great men came. Eugene explained to me his reasons: firstly to be again with his old friend Gregory, but also to catch up on the developments in a field in which he had an interest very early.



Eugene could and would write detailed papers as well as smaller papers. When I started thinking about nuclear reactor safety in 1973, I was surprised to find a small paper with K. Way, written in 1948, about the rate of decay of fission products. Eugene explained that there is a proportionality between the disintegration constant and the fifth power of the disintegration energy. As a result, the total radioactivity from the products of nuclear fission falls as the inverse 1.2th power of time. The paper shows that this is experimentally confirmed. This "trivial" fact is easy to remember and therefore easy to use -and I use it frequently when I think about nuclear safety.



Although I read Eugene's book with Al Weinberg "The physical theory of nuclear chain reactors" when it came out in 1958, I only recently became aware of his many papers and his 37 patents on nuclear reactors. These were mostly written at the tail end of the second world war, in 1945, and the years following (1946 and 1947). He studied many designs. The materials testing reactor at Oak Ridge was one of his designs. After a lull of some 15 years, he reverted to a review of new ideas on nuclear reactors in 1969. During the present (1990-2002+) lull in activity in building of nuclear reactors, more and more scientists are asking, as Wigner did in 1947, what are the useful combinations of fuel, moderator and coolant? Those involved in the "Generation IV" program of new nuclear reactor types could well examine carefully Wigner's memoranda of spring 1945 and his 37 detailed patents.



I do not always agree with scientists who are far brighter than myself. So it was with Eugene Wigner. He had a deep distrust of Russians and it seemed that he was in favor of fighting any war in which Russia was even remotely involved. Thus, he and Edward Teller, fully supported the Vietnamese war till the end. I did not; nor it turned out did his sister, Manci or his brother-in-law Paul Dirac. This led to an embarrassing discussion at breakfast at the Colorado meeting. Ma nci started to talk to my wife (nee Andree Desiree Dumond) and myself. "How well do you know Eugene?" I explained that Eugene and I had discussed physics for over 20 years. "You must talk to him" continued Manci. "You must persuade him that we (the USA) have to get out of this wicked war". We both chickened out and said, somewhat weakly but truthfully, that we did not know him that well. At that time Eugene was deeply troubled and believed that the Soviet Union had built many air raid shelters for the important elements of their population. This would enable them to survive a nuclear war whereas the United States could not. He spent much time advocating air raid shelters and even spent a year on engineering designs - surely a waste of his talents! Eugene was not alone in this. The Nobel Prize winning chemist, and a former AEC commissioner, Bill Libby, also made his own air raid shelter, but less thoroughly. The mind boggles a little at the single mindedness of this determined man - committing himself to tasks far below his skills in a cause he believed in, because no one else would do so. But if I ever have to be in an air raid shelter again I would rather it be in one designed by Eugene than one designed by Bill.



I found myself disagreeing again when Eugene organized a small conference funded by the Rev. Moon. He invited many distinguished people including several of my colleagues. We disliked the "Moonies" and did not want to go to any meeting sponsored by Rev. Moon. My colleagues who had not developed a personal relationship with Eugene just ignored the invitation. But my friendship with Eugene was enough that I could not ignore his gracious invitation and painstakingly explained to Eugene why I would not go. As with all such discussions with Eugene I learned a lot: I had to explain in an exchange of letters my reasons for not going. Eugene insisted that Rev. Moon was funding the conference but not influencing him in any way. Of course we all receive funds from organizations that we do not always like. Nonetheless I and others felt that the very existence of the conference would be used to advertize what we believed to be an organization that was perverting many Americans. I found out later that one of my "liberal" friends went to this meeting - Dr Fadhel Jamali, who some 40 years before had signed the UN charter on behalf of Iraq, and was thrown out of office, narrowly escaping death, in the revolution of 1958. But our circumstances were different. Fadhel was over eighty, in poor circumstances in Tunis and when someone would pay his fare to the US he could ignore a domestic American problem.



At this meeting we honor Eugene Wigner and remember our friend. We honor him best not by agreeing with him all the time but taking his work, his ideas and his principles and subjecting each and every one of them to the scrutiny he wanted and he would give to the work of others.