Two new projects have been recently launched to further develop nuclear technology. One is a prototype modular plant, HTR-PM, intended to demonstrate the commercial potential of the HTR-10 pebble-bed technology. The other is a helium gas-turbine generator system coupled with the original HTR-10 pebble-bed reactor.
Going forward, China is preparing to build a 190-MW demonstration reactor power plant at Rongcheng. If it’s successful, a total of 19 pebble-bed reactors generating 3600 MW will be constructed at that site.
In the U.S., pebble-bed research is ongoing at the Massachusetts Institute of Technology (MIT) and Idaho National Laboratory (INL). MIT partnered with INET on HTR-10 and continues its own programs, described in detail in the April 2007 Nuclear Engineering and Technology (see http://web.mit.edu/pebble-bed/papers1_files/MIT_PBR.pdf).
Written by Andrew C. Kadak, Professor of the Practice of Nuclear Engineering at MIT, the paper notes the differences between the MIT Pebble Bed Reactor (MPBR) and the South African PBMR. Most notably, the MPBR uses an intermediate helium-to-helium heat exchanger that transfers the heat of the helium coolant in the reactor to another helium system to produce either electric power or very high-grade heat to hydrogen-production plants.
Another significant feature of the MPBR is that it is being designed in truckable modules that can be assembled on-site to simplify construction and to minimize differences between facilities. It also differs from the General Atomics design in shifting the orientation of the power-conversion vessels to eliminate the need for expensive magnetic bearings.
INL efforts include the Very-High-Temperature Gas-Cooled Reactor (VHTR), which is aimed at producing hydrogen without consuming fossil fuels or emitting greenhouse gases. The VHTR is part of the Next Generation Nuclear Plant (NGNP) project, which is intended to demonstrate emissions-free nuclear-assisted electricity and hydrogen production by 2017.
The NGNP reference concept will either be a prismatic graphite block reactor, a pebble-bed gas-cooled reactor, or a liquid-salt cooled reactor. One difference with the South African PBMR and the global gas-turbine modular helium reactor (GT-MHR) approaches is that the NGNP is to use a once-through, very high burn-up, low enriched-uranium fuel cycle, rather than recycling the fuel pebbles. The program kicked off in 2004, and operations will begin in 2017.