My recent posts have been about breeder reactors which generate more fissile material than they consume. There is renewed global interest in breeder reactors for the production of nuclear fuel and the destruction of nuclear waste. I have been covering the history of United States breeder reactor research and development in the past several posts. My previous post told about how the U.S. lost interest in breeder reactors in the 1980s. Today, I am going to deal with efforts to sustain and revive research into breeder reactors up to the present day.
Although the liquid metal fast breeder reactors (LMFBR) were the main focus of the U.S. breeder program, other designs for breeder reactors were explored. One design utilized helium gas to cool the reactor. Other designs relied on moderated or thermal neutrons and used either ordinary water or a molten salt as a coolant. These thermal neutron reactors were intended to breed U-233 from thorium. In the molten salt design, the fuel was mixed with the molten salt. The solution was circulated through the core of the reactor and then through a heat exchanger. The molten salt reactor was considered as a possible power plant for a nuclear aircraft carrier. Several of these molten salt reactors were built and tested at Oak Ridge in the 1950 and 1960s. Plans were drawn up for a demonstration reactor called the Molten Salt Breeder Experiment but the LMFBR reactors were the main focus of the AEC and consumed the majority of the funding available. The molten salt breeder reactors were not as efficient as the LMFBR reactors. The molten salt research programs were shut down in the early 1970s as was research into the other alternate breeder reactor designs.
Since the mid 1980 when the breeder reactors programs were cancelled, Argonne National Laboratory (ANL) and the Nuclear Energy program in the U.S. Department of Energy (NEDOE) have worked to reignite interest in breeder reactors. One design that was heavily promoted is called the Integral Fast Reactor (IFR). This facility would include a fast breeder plutonium reactor and a spent fuel reprocessing section that would utilize pyroprocessing and electro-refining to separate the plutonium and other transuranics from the spent fuel so they can be used as fuel again. The goals of the ANL and NEDOE were to come up with a breeder reactor facility that would be environmentally safe, produce power economically and would not contribute to the proliferation of nuclear weapons. Unfortunately for that last one, it would actually be fairly easy for a country with such a facility to separate pure plutonium for nuclear weapons from the output of the reprocessing.
ANL and NEDOE managed to get some funding to pursue the IFR concept though the 1980 and into the 1990 but the program was finally cancelled by President Clinton and Congress in 1994. NEDOE managed to keep the IFR alive to reprocess the left over nuclear fuel and sodium mixtures from earlier LMFBR experiments. About one third of the waste was reprocessed and in 2006, the DOE came up with an estimate of the cost of reprocessing the remaining two thirds for two hundred and thirty four million dollars. Tomorrow I will discuss current U.S. research on breeder reactors and participation in international organizations dedicated to the development of advanced reactor designs including fast breeders.
Diagram of Molten Salt Reactor Experiment:
MSRE plant diagram: (1) Reactor vessel, (2) Heat exchanger, (3) Fuel pump, (4) Freeze flange, (5) Thermal shield, (6) Coolant pump, (7) Radiator, (8) Coolant drain tank, (9) Fans, (10) Fuel drain tanks, (11) Flush tank, (12) Containment vessel, (13) Freeze valve. Also note Control area in upper left and Chimney upper right.