Atomic Heritage Foundation

In partnership with the National Museum of Nuclear Science & History National Museum of Nuclear Science & History

Meeting Energy Needs

Meeting Energy Needs

The Harvard cyclotron at Los Alamos in 1947

Nuclear Notions

Bell Bend Nuclear Power Plant cooling towers. Photo by Jakec, Wikimedia Commons.

Potential of Nuclear Energy

A bottle of Jack Daniels

Celebrating with Jack Daniels

Wind turbines in Caen, France. Photo courtesy of Olivier Tétard, Wikimedia Commons.

The Future of Energy

The Molten Salt Reactor under construction in 1963. Photo courtesy of DOE.

Molten Salt Reactors

  • Nuclear Notions

    Nuclear Notions

    MIT Professor David Kaiser discusses how the word “nuclear” has become inextricably linked with weapons.

    Narrator: As Professor David Kaiser of MIT explains, the word “nuclear” for some has come to have negative connotations.

    David Kaiser: Words can be very tricky. Nuclear research very rapidly became taken up with and then associated with weapons, nuclear weapons, for quite understandable reasons. That was indeed one of the most early and dramatic demonstrations of our knowledge of nuclear forces and what holds the nuclei together.

    In the very early years after World War II, especially in the United States, all things nuclear were often seen in a very positive light. It was seen that these weapons had a dramatic impact on the course of the war.

    And then when the extent of some of these weapons became clear, or the weapons themselves grew in far greater destructive power, led to things like greater appreciation for radioactive fallout, all kinds of problems with these kinds of devices. Then the word “nuclear” began to have actually quite a negative connotation, understandably.

    The word “nuclear” applies to many types of things. People who were not working on weapons per se have had to contend with the connotations of the word nuclear, again, for good or for ill, for many years. Nuclear power for civilian energy production is still very controversial.

  • Potential of Nuclear Energy

    Potential of Nuclear Energy

    ​​Supporters of nuclear power point to how a small amount of material can produce vast quantities of energy. Oak Ridge National Laboratory (ORNL) nuclear engineers Kevin Clarno and Julie Ezold explain why they believe nuclear power is needed.

    Narrator: Oak Ridge National Laboratory nuclear engineers, Kevin Clarno and Julie Ezold, explain why they believe that nuclear power is important to meeting today’s global energy needs.

    Kevin Clarno: With coal and oil, you’re breaking chemical bonds to release the energy. With nuclear, you’re breaking the atomic bonds. And so, you need hundreds to thousands times more mass to produce the same amount of energy. So, it takes hundreds of train cars of coal or oil to produce the same amount of energy in just a pencil eraser-sized piece of uranium fuel.

    We’d need fields and fields of solar panels or wind turbines to compete with the same amount of energy that’s produced in just this tiny little piece of this uranium. And there’s so many places throughout the world that have a lack of energy, and energy is going to be needed more and more as third-world economies start growing and turning over. So, there’s never going to be a lack of need for more energy. So, it became clear that we needed a very heavy energy density source of electricity. In the long-run, even as new technologies and energy efficiency improve, there was going to be a strong need for nuclear energy, for nuclear fission power.

    Julie Ezold: Nuclear power is what they call an “on-demand.” It’s always going to be on. It doesn’t need the sun. It doesn’t need the wind. It’s always going to be there. And it should be part of the portfolio because it does not give off any of the carbon dioxide. We know how to safely handle them. We’ve been doing this for a long time.

  • Celebrating with Jack Daniels

    Celebrating with Jack Daniels

    When the Second World War ended, Oak Ridge experimented with different reactors to test materials and innovative designs. Nuclear engineer Sam Beall describes experimenting with bent fuel rods and then no fuel rods at all.

    Narrator: In the 1950s, the Materials Test Reactor tested fuel rods that were bent. The fluid test reactor had no fuel rods, just “a pump, a pot, and a pipe.” Nuclear engineer Sam Beall recalls his work on two early nuclear reactors and he remembers how success was sometimes celebrated in traditional, spirited Tennessee fashion

    Sam Beall: At that time, the idea of forming a Material Test Reactor had been funded, and everybody at Oak Ridge at that time was working on the Materials Test Reactor, the MTR, that was eventually built in Idaho.

    I was responsible for what’s called a “hydraulic mockup,” which was really an assembly, just like the reactor, with tanks and a grid inside for control rods and so forth. We were testing the flow of water through the fuel elements. We found that the pressure was so great, the fuel elements, which were flat, would bend like that in this mockup test. Eugene Wigner said, “Well, why don’t we make them bent to begin with? That way, don’t have to worry about them bending.”

    After a year or more, Alvin [Weinberg] asked me to change that mockup into a reactor, because we had fuel elements that had been built in the meantime with those curved plates in it. We had enough so that we could do a critical experiment in this MTR mockup. And we did that, made it critical. Everybody is very nervous when a reactor is made critical, because it could get away. So, we had a wag technician, who right at the time of criticality, blew up a bag and popped it.

    But after six months there, Alvin Weinberg, who always had an idea that was very revolutionary. And that is instead of having a reactor with fuel rods and having to dissolve them back into a solution and separate the critical things, he said, “Well, why don’t we start with a fluid fuel reactor? We’ll use uranium sulfate instead of uranium rods.” So, he asked me to build a reactor that could use a fluid uranium sulfate. So, we did build one in about 18 months’ time that had a tank about this size, surrounded by heavy water, with a pump that circulated the fluid through a heat exchanger, which made steam and could be directed to a turbine, electricity. Eugene Wigner called that “a pump, a pot, and a pipe.”

    Anyway, in 1952, that reactor went critical. And for the celebration, which we always did when a reactor went critical, Alvin was there with a satchel. And he reached in his satchel and pulled out a bottle of Jack Daniels. He said, “Sam, when piles go critical in Chicago, they drink red wine. But when they go critical in Tennessee, we drink Jack Daniels.” So, he passed the bottle around, and everybody took a swig.

  • The Future of Energy

    The Future of Energy

    ​​In a world with finite fossil fuel reserves and ever-growing populations, energy generation is always a key concern. Former ORNL director Thom Mason describes what he sees as the main paths forward.

    Narrator: Former Oak Ridge National Laboratory director, Thom Mason, discusses potential options to meet the world’s energy needs.

    Thom Mason: If you want to be able to supply nine billion people, a much larger fraction of whom have a high standard of living than we see today, if you look 30 years into the future, you’ve got three options. What we call renewables, which in one form or another, generally are solar energy. Wind energy is actually solar energy because it’s driven by the sunlight hitting the earth and driving the weather.

    Hydropower is actually a form of solar energy because it’s the water cycle. The evaporation getting water to higher elevations where you can then capture it as it heads back to sea level. Direct solar energy in the form of photovoltaic. So, all of those share the characteristic that the fuel supply is, for practical purposes, inexhaustible, because the sun’s going to keep going long enough that I’m not too worried about when it’s done. There’s no emissions associated with it. There are technical challenges, because mostly it’s intermittent. So, you got to figure out how to solve that with energy storage and smart grid and so forth. So, promise, but technical challenges.

    Another option is the kind of closed cycle nuclear. Things like the fast breeder reactors, molten salt, so forth. We know we can do that. It’s been demonstrated. It was demonstrated in the ‘50s. The challenges there are how expensive is it going to be and what is the public acceptance? There are potential technological solutions to both those things, and that’s kind of what’s being explored as people look at some of these with renewed interest at some of these old concepts.

    And then, the third option is fusion. Where, again, you don’t have a real constraint in terms of fuel supply. The challenge there is can you actually make it work in a controlled way that you get power from it? We have fusion releasing power in the form of our nuclear weapons, but that’s not very useful in terms of generating electricity. So, that’s why people look at things like tokamaks and so forth. So, you know, all three of those different potential energy sources for the future of humanity are elements of the R&D that goes on in the DOE labs today, including at Oak Ridge.

  • Molten Salt Reactors

    Molten Salt Reactors

    In the years since the Manhattan Project, scientists at Oak Ridge have experimented with many designs for nuclear reactors. As Manhattan Project chemist Dieter Gruen and nuclear engineer David Holcomb discuss, one of the more promising models was the molten salt reactor.

    Narrator: One innovative nuclear reactor used thorium salt rather than solid uranium rods for fuel. While the U.S. government shutdown the Oak Ridge Thorium Molten Salt Reactor in the early 1970s, today that concept is being revived in Britain, China, and elsewhere. Manhattan Project chemist Dieter Gruen remembers the man responsible for this innovative approach, former Oak Ridge National Laboratory director Alvin Weinberg.

    Dieter Gruen: He [Alvin Weinberg] was a very distinguished theoretical physicist, who had a brilliant idea about making a safe nuclear reactor. He developed the concept of a thorium reactor based on the element thorium and uranium-233. It was a molten salt, homogeneous reactor.

    And he used his considerable prestige and power as director of Oak Ridge National Laboratory to start a large program to build such a reactor, and that reactor was built and operated for years at Oak Ridge, and very successfully. And I contributed very considerably to that effort and I used to visit Oak Ridge in those years—this was the ‘50s and ‘60s—very frequently to attend meetings that Alvin Weinberg had periodically to review progress on this thorium reactor.

    Now, what happened to the thorium reactor? There was a political situation that developed in Washington. The reactor was shut down. Alvin Weinberg was fired because he insisted that he wanted to continue the reactor. He remained at Oak Ridge—there was an energy institute which he headed—but he was no longer was director of the laboratory. That whole program on the thorium reactor was shut down and essentially disappeared until fairly recently. And today, the British and the Chinese have active programs reviving the thorium molten salt reactor.

    Narrator: While molten salt reactors enabled operators to reuse nuclear fuel, it was a struggle to get the reactors online. Nuclear engineer David Holcomb explains.

    David Holcomb: The fuel doesn’t actually build up any radiation damage. And so, if you look at what’s going on in the fuel, essentially, you can keep using the fuel. Even in the next reactor, where did you get the fuel from? Well, in the breeder reactors, the concept is that you produce the fuel in the prior generation reactor, and so that largely the waste is the fuel to allow you to create an expanding program. You don’t actually end up with any of the fuel waste until somebody decides the molten salt reactors are no longer an energy source that we’re going to be using for the world.

    There are no molten salt reactors on the grid generating power. I really want that to change.

    We built and ran the MSRE [Molten Salt Reactor Experiment] as a government institution. It worked exceptionally well. It’s the best-run test reactor I’ve ever heard of on its performance characteristics. And yet, it didn’t go out on the market. That says our purely government solution is not the answer. Our answer now is we need to get the private industry into this, building these, making a profit, and selling power to the people.

Quick Fact:
The Oak Ridge Molten Salt Reactor Experiment (MSRE) operated between 1965 and 1969. Today, scientists continue to explore molten salt reactors as an energy source.