The Perpetual Promise of Breeder Reactors
In the early days of nuclear energy, enthusiasts talked about “breeder reactors” that could produce more fuel than they consumed, thereby offering mankind a virtually limitless supply of energy.
Breeders have been tried numerous times in the Western nations but have now been more or less put on indefinite postponement. The developing world is still giving it a try and may succeed in leapfrogging over the West in the development of the technology. Either way, it is still a long road ahead and it may be decades before they become common. The theoretical possibilities haven’t gone away but they still have a futuristic quality.
Tom Blees is the major exponent of fast reactors in this country. A 6-foot, eight-inch 63-year-old who spends his time touring the world in favor of the technology, his book Prescription for the Planet is the Bible for breeder enthusiasts. “Several countries are planning to build fast reactors,” he says. “The question is who will do it first. There’s a high likelihood Britain will do it using GE’s PRISM design. America still has the best technology but we’ve been reluctant to share it. It could be an immense benefit to the world.”
Basically, there are two types of breeders, those that start with uranium and those that start with thorium. A conventional light water reactor breeds a little bit of plutonium and that can be extracted and used to fabricate a “mixed oxide” fuel (MOX), as the French are doing. But a breeder surrounds the reactor core with a “blanket” of non-fissionable that can be transformed into large quantities of plutonium. That’s where the “breeding” comes in.
The thorium cycle is somewhat different. Once it is “ignited,” the thorium absorbs a neutron and is transformed into Uranium-233, which is also fissionable. This can also be wrapped in a blanket of the more common U-238 and again produces a plutonium fuel. The best breeders have a “breeding rate” of 1.5, meaning they produce about 50 percent more fuel than when they started. This leads fast breeding enthusiasts to talk about “unlimited amounts of energy.”
In the early days it was believed that natural uranium supplies were limited and breeder reactors would be needed to sustain the nuclear electric program. But as more uranium supplies were discovered, the concern about handling plutonium began to overshadow the effort. Oak Ridge National Laboratory in Tennessee started building a breeder reactor at Clinch River in the 1970s but the effort was ended by the Carter Administration.
Interest in “fast” reactors began to grow in the 1980s. In a conventional uranium reactor the neutrons must actually be slowed down in order to be captured by other uranium atoms. Any small atom – carbon, lithium, helium – can do this and in a light water reactor the water both moderates the neutrons and cools the reactor.
But it was discovered that unmoderated “fast” neutrons can also sustain a chain reaction if the fissionable material is dense enough. Moreover, “fast” reactors have the advantage in that they can use any radioactive material for fuel. Therefore they can burn spent fuel, the so-called “nuclear waste.”
“We have enough spent fuel and depleted uranium in this country right now to provide all our electricity for several centuries if we burned it in integral fast reactors,” says Blees. This is where the promise of unlimited energy comes in. An experimental integral fast reactor was built at the Idaho Experimental Laboratory in 1964 and ran successfully for 30 years but was shut down by the Clinton Administration in an effort to end all nuclear research.
Since then the ball has been carried by other countries. France’s Superphenix operated for 13 years until it was shut down in 1998, also for political reasons. India has built a fast reactor using uranium but may eventually switch to thorium, which they have in abundance. Russia now leads the world in construction, having operated its Bn-600 and BN-800 since 1980 and 2014 respectively. It recently sold two BN models to China, which is going to push ahead with the technology. This week Blees was in South Africa speaking to university students on behalf of fast reactors as that country undertakes a nuclear program to cut its reliance on coal.
“The GE-Hitachi PRISM integral fast reactor is probably the best reactor that’s never been built,” says Blees. “GE just doesn’t have a spare billion dollars to get it through licensing at the Nuclear Regulatory Commission. But the British are looking for a reactor to burn up the huge amounts of plutonium they have stockpiled over the years at Sellafield from their light reactors. They may be the first ones to build a PRISM.”
So Americans continue to lead the world in nuclear knowledge and research but remain reluctant to put any of it into practice. It’s an odd situation. Many countries are holding back, hoping America will take the lead. But Russia, China and India are not being shy and odds are within a decade they may have moved ahead without us.