The Energy Multiplier Module (EM2 or EM squared) is a nuclear fission power reactor under development by General Atomics. It is a modified version of the Gas Turbine Modular Helium Reactor (GT-MHR) and is capable of converting spent nuclear fuel into electricity and industrial process heat, without separative or conventional nuclear reprocessing.[1]
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The EM2 is small modular reactor expected to produce 240 MWe (500 MWth) of power at 850 °C (1,600 °F) and be fully enclosed in an underground containment structure. The EM2 is a gas-cooled fast reactor, which uses helium as a coolant. The reactor uses a composite of silicon carbide as cladding material and beryllium oxide as neutron reflector material. The reactor unit is coupled to a high efficiency helium gas turbine which in turn drives a generator for the production of electricity.
The nuclear core design is based upon a new conversion technique in which an initial “starter” section of the core provides the neutrons required to convert used nuclear fuel or depleted uranium (DU) into burnable fissile fuel.[2] First generation EM2 units use uranium starters (approximately 15 percent U235) to initiate the conversion process.[3] The starter U235 is consumed as the used nuclear fuel/DU is converted to fissile fuel. The core life expectancy is approximately 30 years (using used nuclear fuel and DU) without refueling.
Substantial amounts of valuable fissile material remain in the EM2 core. This material is reused as the starter for a second generation of EM2s, without conventional reprocessing. There is no separation of individual heavy metals required and no enriched uranium needed. Only unusable fission products would be removed and stored.
All EM2 heavy metal discharges could be recycled into new EM2 units, effectively closing the nuclear fuel cycle, which minimizes nuclear proliferation risks and the need for long-term repositories to secure nuclear materials.
The expected cost advantages of EM2 lie in its simplified power conversion system, which operates at high temperatures yielding approximately 50 percent greater efficiency and a corresponding one-third reduction in materials requirements than that of current nuclear reactors.[4]
Unlike light water reactors, the EM2 is gas cooled and does not need to be sited near a water source for cooling.
Each module can be manufactured in either U.S. domestic or foreign facilities using replacement parts manufacturing and supply chain management with large components shipped by commercial truck or rail to a site for final assembly, where it will be fully enclosed in an underground containment structure.
The EM2 utilizes used nuclear fuel, also referred to as “spent fuel” from light water reactors.
Spent fuel rods from conventional nuclear reactors are put into storage and considered to be nuclear waste, by the nuclear industry and the general public.[5] Nuclear waste retains more than 95% of its original energy; the current U.S. inventory is equivalent to nine trillion barrels of oil - four times more than the known reserves. EM2 uses this nuclear waste to produce energy.
By using spent nuclear waste and depleted uranium stockpiles as its fuel source, a large-scale deployment of the EM2 is expected to reduce the long-term need for uranium enrichment and eliminate conventional nuclear reprocessing.[6]
Conventional light water reactors require refueling every 18 months. EM2’s 30-year fuel cycle minimizes the need for fueling handling and can reduce the proliferation concerns associated with refueling.
EM2 technology is designed to be inherently safe and to automatically shut down using the natural laws of physics.
The EM2’s high-operating temperature can provide process heat for petrochemical fuel products and alternative fuels, such as biofuels and hydrogen.[7]