A Primer on Nuclear Safety: 1.2.1 Heat, Water and Reactors

1.2 Heat and water
1.2.1 A history

The period of 1944-1945 was a period of intense ferment among the reactor designers at the University of Chicago "Metallurgy Lab". The great World War II reactor projects had passed the design phase. A couple of interesting minor reactor design projects were underway. One at Chalk River in Canada, and from this project was eventually emerge the Canadian CANDU reactor concept. The other project was was a most interesting one. Both Eugene Wigner and Enrico Fermi were interested in cooling a reactor with a water which contained a mud like uranium fuel in suspention. Thus the amazingly simple core of the only contained water and Uranium fuel in a mud or soup like suspention. The reactor was called the "Aqueous Homogeneous Reactor." It turned out to be one of the safest reactors ever designed, but it also turned out to have some problems that inhibited its development beyond the experimental stage.

Fermi built an Aqueous Homogeneous Reactor called the LOPO (for low power) at Los Alamos during World War II. By that time enriched uranium was beginning to flow from Oak Ridge, and the LOPO appears to have been the first reactor to run with enriched uranium fuel.

We have seen that the first two attempts to build water cooled reactors were not entirely successful. THe Hanford reactors had recognizable safety issues, which precluded the use of the design for civilian power plants in the West, but not the Soviet Union. The Uranium slurry fuel of the Aqueous Homogeneous Reactor proved to be less than successful. But Wigner and his group of very bright young men had thought of another approach to water cooling reactors.  The idea as to build a reactor that was structurally similar to the graphite pile reactors, but without the graphite bricks.  Instead water would be used as both a moderator and a coolant.   The designed was quite feasible, with the exception of one technical problem.  

Alvin Weinberg was to be assigned the patent for the Light Water Reactor.  At Oak Ridge Wigner with Weinberg's assistance design of a water cooled and moderated reactor that was to be used for Materials testing.   The development went lead to the creation of a small prototype, the Materials Testing Reactor mock-up to test controls and hydraulic system.  The Mock-up had the capacity to go critical. 

In 1946, as thinking about water cooled reactors was beginning to evolved in Oak Ridge, a maverick Naval officer, Hyman Rickover appeared on the scene. Eugene Wigner had decided to creat in Oak Ridge a sort of informal graduate school for training in the new nuclear technology, and Rickover was selected by the Navy to receive reactor technology. Rickover quickly made himself the man to go to about reactor issues in the Navy, and in 1947 he assigned by the Bureau of Ships with the task of exploring the use of reactors for ship propulsion. In 1949 Rickover was givena second assignment within Division of Reactor Development, U.S. Atomic Energy Commission and then assumed control of the Navy's effort as Director of the Naval Reactors Branch in the Bureau of Ships. These dual assignments gave Rickover great power.

Rickover saw early on the potential of the water cooled reactor for ship propulsion. By the late 1940's the U.S. Navy had been using steam powered ships for over 100 years. The Navy prided itself on its technologically advanced boiler technology, a technology which gave U.S. Navy ships unusual cruising range without refueling. A range that helped it to defeat the Japanese Navy and eventually to destroy the Japanese empire. The reactor held the potential for Rickover and the Navy of extending the Navy's reach, at a time when the cold war was heating up.

Rickover needed to convert the water cooled reactor into a generator of steam. Working with Alvin Weinberg and the scientist and engineers of Oak Ridge a design for a pressurized water reactor was developed, and passed on to the Navy's reactor engineering labs, the Knolls Atomic Power Laboratory founded in 1946, and the Bettis Lab, founded in 1948. Together these Labs produced the actual designs of the reactors that were to power US Atomic submarines, and were to play a major role in the development of the civilian power reactors.

The first civilian power reactor in the United States was a naval reactor that had been designed for aircraft carrier use, but which the Navy intended to keep on land for research purposes. Rickover arranged to hooked up a generator to the reactor, which was dubbed the Shippingport reactor, and donated it to President Eisenhower's "Atoms for Peace" program. The Navy continued to conduct research with the Shippingport reactor until it was decommissioned in 1982.

Most subsequent civilian power reactors were scaled up and modified versions of the Shippingport reactor. The safety problems of civilian power reactors are inherited from their Naval predecessors, and have to be understood in that context.

There is little doubt that Rickover's influence played a pivotal role in the choice to concentrate reactor research on two reactor designs, the Light Water Reactor, and The Liquid Metal Fast Breeder Reactor. Both reactor concepts have safety flaws. But Rickover was more introduced in producing quick results, than in building the safest possible reactors.

A. Stanley Thompson worked for North American Aviation during the 1940s and spent time in Oak Ridge during the Aircraft Nuclear Propulsion days. Thompson had a chance to observe Rickover in action during a conflict between Rickover and two officials of North American Aviation. Rickover traveled to the North American headquarters to meet with company officials on a Saturday in 1949. Officials were called in for the meeting, and everyone arrived with the exception of physicist Mark Mills, who was out on a tennis court. When Mills finally arrived, Rickover started chewing him out about a report Mills had written about the potential for chemical explosions in reactors. Rickover launched into a tyrade, and eventually Mills tired of the abuse,

"Sir, I resent your treatment of me. I will no longer stand for it. I'm leaving!" Mills said, and started to walk out.

Rickover also stood smilling, and said, "Mark, I think we now understand one another. You can get back to your tennis game."

After Mills walked our, Rickover commented to us, "Mills is now conditioned on reactor safety."

After the meeting, North American's Chauncey Starr complained to the AEC about Rickover's abuse of Mills.

Thompson continued:

"The next time I saw Rickover was in Oak Ridge, Tennessee, at a conference on the nuclear propulsion of aircraft hosted by Alvin Weinberg, Director of the Oak Ridge National Laboratory. Rickover was there in his self-appointed capacity of keeping himself informed on everything in the nuclear business. Chauncey Starr gave a talk, for which he had been coached by aircraft engineers at North American, on the importance of Mach number, aircraft lift to drag ratio, and engine thrust to weight ratio for the design of an airplane and its nuclear power plant."

"In the evening we were invited to a friendly and welcoming dinner at the home of Marge and Alvin Weinberg with several of the senior members of Weinberg's staff and their wives. After dinner we were seated in a circle in the Weinbergs' living room. For a while, Rickover was directing at Starr on the opposite side of the circle a series of stinging remarks against which Starr was doing what he could to defend himself. The rest of the party had lapsed into a stunned silence. Finally one of the wives remarked, "You know, there's something going on here that I don't understand." Rickover addressed her, "I'll tell you what's going on. This man [pointing to Starr] has been knifing me in the back, and I don't like it." Word must have got back to Rickover that Starr had talked to people at the Atomic Energy Commission about Rickover's visit to North American. On the way down the hill from the Weinbergs' party, I saw Starr and Rickover walking arm-in-arm, and talking in a confidential manner. I assumed that Starr had now been "reconditioned" on interference with Rickover. I was impressed with Rickover's ability to turn on alternating charm and ferocious attacks, as suited his purpose at the moment."