Hitachi begins joint research with MIT, U Michigan and UC Berkeley on next-gen nuclear reactors that use radioactive waste as fuel
28 August 2014
Hitachi, Ltd. has begun joint research with MIT, the University of Michigan, and the University of California, Berkeley aimed at using Transuranium Elements (TRUs) as fuel, and the development of Resource-renewable Boiling Water Reactors (RBWRs) to use that fuel. TRUs are contained in the radioactive waste materials discharged by nuclear power plants that have atomic numbers greater than that of uranium (92), and which require a long period of time to decay.
|Start-up Transatomic Power is developing an advanced molten salt reactor that would consume spent nuclear fuel cleanly and completely.|
|The reactor can be powered by nuclear waste because it uses radically different technology from conventional plants; instead of using solid fuel pins, Transatomic dissolves the nuclear waste into a molten salt.|
|Conventional nuclear reactors can utilize only about 3% - 5% of the potential fission energy in a given amount of uranium before it has to be removed from the reactor. Transatomic says that its design captures 96% of this remaining energy.|
|The main differences between Transatomic Power’s molten salt reactor and previous molten salt reactors are its metal hydride moderator and LiF-(Heavy metal)F4 fuel salt. These allow the the reactor to be more compact and generate electricity at lower cost than other designs. The reactor can operate using fresh fuel enriched to a minimum of 1.8% U-235, or light water reactor waste.|
Through this joint research, Hitachi plans to evaluate the performance and safety of RBWRs, which is being developed by Hitachi and Hitachi GE Nuclear Energy Ltd., and to study plans for testing with a view toward practical applications with each university.
The uranium fuel used in nuclear power plants contains TRUs, which are harmful to humans, and it is estimated that it takes about 100,000 years for the radioactive properties of these materials to decay to the level of uranium ore in its natural state.
If TRUs could be effectively removed from these spent fuels, then the period of decay for the remaining radioactive waste materials could be reduced to just a few hundred years, Hitachi notes. For this reason, research and development is being conducted throughout the world targeting nuclear reactors that can achieve nuclear fission in transuranic waste.
As one solution to this challenge, Hitachi has undertaken the development of RBWRs based on Boiling Water Reactor technologies, which already have an extensive track record of applications in commercial nuclear reactors.
RBWRs could potentially use TRUs separated and refined from spent fuel as fuel along with uranium. Although RBWRs use new core fuel concepts to burn TRUs, they use the same non-core components as current Boiling Water Reactors (BWRs), including safety systems and turbines. As such, RBWRs are unique in that extensive experience accumulated through the application of BWRs can be leveraged to achieve efficient nuclear fission in TRUs, Hitachi says.
Hitachi conducted joint research targeting RBWRs with MIT, U-M, and UCB from 2007 to 2011, evaluating safety and performance in the burning of TRUs, as described above. In this next stage of joint research, utilizing the knowledge and insights acquired through the previous stage, and applying the more accurate analysis methods developed by MIT, U-M, and UCB, Hitachi will continue to evaluate the safety and performance of the new reactors, and will study plans for tests with a view toward practical applications.
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