Milton Levenson

Lab-to-Lab: US-Russian Lab-to-Lab Collaboration Story [Archived]

Milton Levenson | Cheryl Rofer

Exchange of non-weapons data | A Different Chernobyl

Milton Levenson has 73 years of nuclear experience, starting at The Oak Ridge National Laboratory in 1944. He retired from The Argonne National Laboratory in 1973 as Associate Director for Energy and the Environment to become the first Director of Nuclear Power at The Electric Power Research Institute (EPRI).

Image of a document with the photo of a man and a stamp on it.

Milton Levenson, foreign member of the Soviet Nuclear Society.

He is a member of the National Academy of Science, Engineering, and Medicine, a Past President of the American Nuclear Society, and received the Robert E. Wilson award of the American Institute of Chemical Engineering for contributions to nuclear chemical engineering.

Most of his career has been in nuclear reactor safety and fuel processing but currently he is a Senior Technical Advisor to the weapons safety program of NNSA.

Dr. Levenson shared some unique memories about his encounters with the Soviet and Russian nuclear energy issues and people. He wrote them up specially for this web site. They give a rare perspective on events that are now history of an expert whose knowledge of the nuclear safety has been sought by peers and political leaders.

Men in suits around a table

Milton Levenson at a briefing to Italian Prime Minister Andreotti on Chernobyl, 1988

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Exchange between American and Soviet/Russian nuclear scientists of non-weapons data

Milton Levenson

The major role played by scientists in avoiding nuclear based disasters is outlined in the two volumes of Doomed to Cooperate edited by Sig Hecker.

The dawn of the nuclear age had produced a whole new set of secrets. The very existence of the Manhattan Project was a secret – even from the US vice president. There were secret cities of Oak Ridge, Hanford, and Los Alamos. There were three basic technical classes of secrets—the weapon designs, the barrier material of the diffusion plant for Uranium enrichment, and the details of how to produce weapons-grade Plutonium. The first was a physics matter and largely the responsibility of the weapons labs. The other two were basically chemical engineering matters. The applicability of any of these to peace-time uses such as the generation of electricity was not originally considered.

In the early 1950s, the Eisenhower Atoms for Peace program changed all the guidelines of secrets. By the time of the first Geneva Conference on the Peaceful Uses of Atomic Energy (1955), medical and industrial uses of radioactive isotopes were widespread. The generation of electricity by fission reactors had been demonstrated in 1951 by Experimental Breeder Reactor I (EBR I). The question was what should be declassified for Geneva. The answer was for weapons design – nothing, for Diffusion barrier – nothing, for Plutonium – maybe, for reactor technology – yes. A classified paper covering solvent extraction for Pu recovery was prepared by S. Lawroski and M. Levenson. Steve Lawroski was director of the chemical engineering division at Argonne. He went to Geneva with authority to declassify the paper and present it if the Soviets were prepared to present their Pu work. A.M. Petrosyants, who at that time was Chairman of the USSR State Committee on the Use of Atomic Energy, agreed; and information exchange began on chemical processing and reactor technology.

Petrosyants believed that long-term fast reactors would be required so that Uranium 238 and Thorium could be used to supply fissionable material for future centuries. Fermi and Walter Zinn had come to the same opinion independently and that was one of the reasons that the first power reactor was a fast neutron reactor; so, fast reactors were the basis of exchanges. Another reason was that the technology for a fast reactor already existed while the technology for the high-pressure vessels required for Light Water Reactors was marginal.

A few years after that first Geneva meeting, Steve Lawroski visited the Soviet Pu facilities. In the 1960s, I hosted a Soviet Delegation at Argonne Illinois and at Argonne Idaho for a tour of EBR II.

The delegation included about a dozen Soviets, most of whom were technical people rather than policy people – the Soviets were interested in getting as much information as possible. A self-imposed restriction by the Soviets meant they did no sight-seeing in the Chicago area and there was a long discussion before they accepted an invitation to brunch at the home of Dick Adams, Argonne Illinois Director’s aid.

In 1974 I was a member of a US delegation that visited a number of Soviet Union reactor sites including Fort Shevchenko (BN 350) and Sverdlovsk (BN 600 under construction). These two sites had quite different security rules. At the BN 350 site, cameras had to be checked and left at the airport and the curtains on the airplane windows had to be closed on approach so no aerial photos could be taken. At the Ural mountains site (BN 600) the director would not meet with us until we got our cameras and told us to take pictures of anything – with one ABSOLUTE EXCEPTION. On the site was a 1/10 version of what was to become the RBMK (Chernobyl). The exception was the control room of this prototype. When we got there, it was obvious why – no security issue but a major safety issue. The power level control system used an ancient galvanometer—a mirror on a fiber. A camera flash could either scram the reactor or make it surge in power.

When we asked about the difference in camera policies the answer was: I’m proud of what we do here and those people in Moscow who call themselves Russians can’t tell me what to do.

Over the years, I encountered a number of similar cases of plant managers (who often were also the local mayor) that took initiative deviating from Kremlin guidance, including a Siberian one who traded coal that was supposed to go to Moscow to China for fresh fruit and other food and an RBMK site manager who used city garbage to raise chickens in the plant courtyard so that his operators could each have a chicken a week.

If we fast-forward to the Kyoto environmental meeting, we hear the Chinese say they have to build coal plants to save lives because of the shortage of electricity. They announce the order of a number of additional nuclear plants and say the coal plants will be shut down as soon as nukes meet the demand. They also announce a joint fast reactor program with the Russians.

It appears that after that meeting they had concerns about the world’s opinion of a nuclear partnership between two Communist countries. An American law firm became involved in an attempt to make it a worldwide project. One US utility pledged some millions of dollars if they could have the carbon credits. Because of my personal contacts, I was asked to go to France and see if they would join and to Moscow to see Russian Minister of Atomic Energy Evgeny Adamov (he was minister from March 1998 to 2001) about conditions for US participation. In France they said yes if the request came from the Russians, no if the request came from China. The Adamov meeting became complicated when he was accused of graft. The issue of a Chinese man leaking Los Alamos weapons data to China meant no more contact with China for people with clearance. As far as I know, the Russian/China program continues. A change has been made in that BN 800 will not be built in Siberia across the border from China, but is now under construction at the BN 600 site. My contacts say they think the primary reason for the change is that the Russians do not have the resources for two fast reactor sites.

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A Different Chernobyl

Milton Levenson

This may be a little different from other Chernobyl stories you have read but my starting point is probably unique.

Background to the story: In 1974 I was a member of an American delegation that visited the Soviet Union as part of our reactor technology exchange. While the subject of the visit was Fast Reactors, I did get to see one of the RBMK prototypes at the Ural mountain site. I understood that two different versions had been built, one a boiling water version and one a superheating version which turned out to be too complex, so Chernobyl became a boiling water reactor. A couple of years later the UK, as part of an assessment of reactor types to select one for the UK to adapt, had their Nuclear Power Company Limited do a review, with Soviet assistance, of the RBMK. Although the report was proprietary, the relation of EPRI and the UK was such that I was allowed to see the report. The conclusion was that while a pressure tube reactor did have some advantages, the Soviet approach to safety was so different than that of the UK that the RBMK would not be considered for UK use. That report was released to the public after the Chernobyl accident. I was also personally involved in the post-accident activities of the EBR-1, SL-1, and TMI-2 core melt down accidents.

I was in South Korea at the time of the Chernobyl accident—no internet then, so no information was available. On the way home from Korea I stopped in Japan for R&R. I was surprised to see pictures of the Chernobyl site that had been taken by Soviet helicopters on Japanese TV. One picture was of the roof of a building adjacent to the reactor where a graphite stringer ejected from the reactor (fig.1) had started a fire – one of 20 fires. The intact nature of the stringer meant that the official version of the accident was probably not correct. Figure 2 shows the official version, a criticality explosion. The time required for the 1000 + ton top cover to travel far enough so that an intact airborne stringer would not impact on the cover was too long for an intact stringer to escape. The top cover was made of steel and concrete, was ten feet thick and weighed over a thousand tons.

When I returned home, I found I was to be a member of the US delegation to the IAEA meeting in Vienna at which the Soviets were to discuss the accident. Shortly before the meeting I was told that so many Federal employees wanted to attend that I was no longer a member. The American Nuclear Society was accredited to the IAEA so I contacted Hans Blix, the IAEA Director General, about being able to attend as an ANS representative – and he said yes. That turned out to be very useful. Academician Valery Legasov, the Soviet delegation leader, was under strict orders not to speak with anyone from any government delegation or anyone from the media. I was neither so he agreed to talk to me. When I told him my observation he invited me to come to Moscow. I was later told that the Soviet technical people had ten versions of what might have happened but they were told that under no conditions were they to admit they were not sure what happened.

While the basic design had been known to me, a number of details were learned on my Moscow trip. Significant ones included the following:

  1. The connection between the Zirconium pressure tubes and the Stainless steel pipes was a diffusion bond that was very brittle and sensitive to thermal shock (fig. 3). Due to the order of the power dispatcher to stop at ½ power, the status of the reactor (Xenon poison distribution) was one the operators had never seen. In taking unscheduled actions to assure core cooling they had almost certainly thermally shocked the pipe joints.
  2. Each of the 1600 pressure tubes had its own flow control valve. The valve designer knew many times what I knew about valve mechanical design but when I asked about vapor blocking he said the hydraulics was done in another institute. It appears that no one had considered this phenomenon. (foot note: under varying conditions of high temperature liquids, it is possible for a valve to vapor lock—shut off flow almost like closing the valve).
  3. The RBMK does not use a containment building like a PWR does but rather uses Pressure Suppression like other boiling water reactors do. While the Soviet system was designed for major postulated accidents like double ended pipe breaks, pump or valve failures etc., it was not designed for multiple pressure tube failures. Since each pressure tube was enclosed in graphite they assumed a domino effect due to one failure propagating could not happen and they designed the vent from the core to the Pressure System for one failure only. They never considered a common mode failure that could affect a number of tubes.
  4. They were aware of the Wigner effect and the Windscale accident caused by a graphite anneal that got out of hand. As a result, the RBMK was designed so that the graphite always operated well above the anneal temperature. The result was that unlike other reactors where the irradiated fuel is the heat source and everything else is a heat sink, in the RBMK the graphite is the hottest thing and almost an unlimited heat source. Extensive cooling is required even for new fuel channels that have no fission product heating.
  5. Soviet calculations showed that no combination of control rod movements could have caused the accident.

On returning home, I came to the conclusion that the first event was a multiple pressure tube failure that blew off the lid. (footnote: one PSI will levitate concrete one foot thick, so only 10+ psi is needed to levitate a 10-foot-thick cover. Steam pressure in the tubes is about 1000 PSI so only a few tube failures would cause destruction.) The RBMK physics has a positive void coefficient; so, as the water was expelled from the broken pipes, the reactor went critical (fig. 4) and ejected the stringers.

Now it was not just an observation but an explanation I did not know what to do with it—it was still Cold War days. I contacted Dick Kennedy who was in the State Department with rank of Ambassador. He suggested I outline my scenario and send it to the US delegate to the IAEA. His guess was that the Soviets would know it within a day but I would not be responsible.

Shortly thereafter I received an invitation to attend a conference on Sicily titled “International Seminar on Nuclear War”. Among the attendees was E. P. Velikhov, the vice president of the Soviet Academy of Science, and therefore a science advisor to Gorbachev. Velikhov told me they were having trouble getting technical help with the accident analysis because the only US contacts they had were with the State Department and DOE, neither of which had experts in reactor safety details. I suggested two things to him. One was to have a non-political technical review and the other was that the Soviets form a technical society like the American Nuclear Society that could then hold meetings with similar groups in other countries. He accepted both ideas. The technical review was held in Sochi with the Soviets funding all in-country costs. Attendance was 15 Soviets selected by Velikhov, 15 Americans selected by me, and 15 Europeans we jointly selected. The meeting included a visit to Chernobyl, a visit to Leningrad to talk to people at the Radium Institute who had done most of the sample analysis, and a week in Sochi for discussion.

The Soviets also formed the Soviet Nuclear Society and for the next decade I served as an ex-officio member including twice arranging for a Nuclear Regulatory Commissioner to be a speaker at their annual meeting.

While the official cause of the accident remains the same, the plant changes made to RBMKs included increasing the size of the vent between the core vessel and the Pressure Suppression System so that a larger number of tube failures would not duplicate the Chernobyl accident.

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