General Atomics has announced a 12-year program to develop a small, commercial nuclear reactor that could run on spent fuel from big reactors. It sounds like a smaller version that is similar to Bill Gates' promotion of the Terra Power Wave (liquid metal fast breeder) Reactor. But unlike Gates' liquid metal (sodium) design, General Atomics' reactor is helium-cooled. The Pebble Bed Modular Reactor (PBMR), which is being developed in China, is also helium cooled. The General Atomics reactors is small enough to be built in factories and hauled on trucks or trains.The General Atomics reactor (EM2 -Energy Multiplier Module), would be about one-quarter the size of a conventional reactor and have unusual features, including the ability to burn used fuel, which still contains more than 90% of its original energy. Such reuse would reduce the volume and toxicity of the waste that remained. The EM2 would operate at temperatures as high as 850 degrees Centigrade, which is about twice as hot as a conventional water-cooled reactor. General Atomics expects the development effort to cost $1.7 billion, and it intends to seek financial assistance from the Energy Department. The reactor design will have to be certified by the Nuclear Regulatory Commission.
General Atomics has built more than five dozen small reactors over the years, mostly for research purposes, including two gas-cooled units. Its Peach Bottom unit, in Pennsylvania, ran from 1967 to 1974, and its unit at Fort St. Vrain in Colorado produced electricity from 1976 to 1989. (WSJ, 2/22/10)
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The General Atomics EM2 is just another re-incarnation of the helium-cooled fast neutron spectrum reactor, referred to as the Gas-Cooled Fast Reactor (GCFR). While this type of reactor has some attractive characteristics, safety is not one of them. To achieve its objectives of high nuclear fuel utilization with relatively compact size, the reactor must operate with very high power density with very little material in the reactor core that can absorb heat during a severe accident. As a result, this type of reactor will undergo a very rapid meltdown during severe accidents, and represents a substantially less safe alternative to modern commercial reactors that use water cooling. Every major nuclear country has rejected this type of reactor concept, in part because of its relatively poor safety characteristics.
The EM2 introduces additional safety and practical engineering challenges beyond the conventional GCFR. The EM2 fuel is an unproven concept and is expected to vent (release) its radioactive fission products while the reactor is operating, which essentially eliminates the fuel as a barrier to radioactivity release and defeats the concept of defense-in-depth to radioactivity release required by the U.S. Nuclear Regulatory Commission. The EM2 proponents also claim the reactor core can last 30 years without requiring refueling. Proving a new nuclear fuel can last this long without significant levels of failure is practically impossible, especially from a nuclear regulatory licensing perspective. Furthermore, this type of fuel cycle represents a significant risk for proliferation of nuclear fissile material, since the EM2 core will contain large quantities of weapons-usable plutonium long before the end of its claimed 30 year fuel cycle. In terms of safety and proliferation risks, the EM2 is an unacceptable nuclear reactor concept, especially for commercial deployment in a post-Fukushima world.
Until recently, General Atomics was the industry champion of the world's safest reactor concept, a modular, helium-cooled thermal neutron spectrum reactor, sometimes referred to as a Modular Helium Reactor (MHR). In contrast to the EM2, this reactor concept has a large quantity of material in the core that absorbs heat and prevents the reactor fuel from reaching meltdown temperatures, even if all of the coolant is permanently lost. Unfortunately, the senior management at General Atomics abandoned the MHR in favor of EM2, and has stuck with this strategy even in the aftermath of the Fukushima accident. The proponents of the EM2 concept have falsely claimed the EM2 has the same inherent safety characteristics as the MHR.
Japan has the high temperature engineering test reactor (HTTR), which is an operational, engineering-scale prototype of the MHR. It has been used to demonstrate the intrinsic safety characteristics of the MHR. Perhaps the events in Japan can lay the foundation for developing, demonstrating, and commercializing a next generation of nuclear power with inherent safety. International collaboration among the U.S., Japan, and other nations on the MHR would provide a relatively quick path for achieving this goal. More information on the HTTR is available at:
http://www.jaea.go.jp/04/o-arai/nhc/index.html
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