Lightbridge has until recently been focused on nuclear plant fuels that are a mix of Thorium and uranium. They now are developing fuels that appear to be similar to the annular fuel work at MIT, which is also being commercially developed in South Korea.
Nuclear plant uprates are cheaper (2-5 times cheaper per kilowatt) and can be done faster (12-24 months) than building a new nuclear plant (4-6 years in Asia and 6-12 years in the USA).
Lightbridge signed up a new advisory board including executives from Exelon and Duke Energy and Dominion, two other leading nuclear generators, in a sign of their interest in the new fuel. Lightbridge only has about a $39 million stock market valuation, so they will need to partner closely with the larger utilities to bring this technology to market.
Full scale tests of the fuel are scheduled for 2014-2017. The first uprates using the fuel could be in the 2019-2025 timeframe. An aggressive push by the US DOE could enable and expediting approvals from the Nuclear Regulatory agency would enable the uprates to start in 2017 and incentives for a faster deployment through 2025 would have all of the nuclear plants that are in condition to be uprated to have their power increased. This would add about 150 TWh of non-polluting energy.
Uranium Seed and Blanket Fuel
The all-uranium seed-blanket fuel assembly (U-SBU) is designed to provide up to a 17% power increase in existing PWRs operating on 18 month fuel cycles, including Westinghouse-type 4-Loop plants. A smaller power uprate can accommodate longer fuel cycle lengths, for example the U-SBU is capable of increasing power output by 10% and operating on 24 month cycles, saving one fuel outage every six years.
The design of the U-SBU allows drop-in replacement of the fuel assembly with conventional UO2 assemblies. No changes to reactor internals are required to use Lightbridge’s U-SBU (some changes to plant systems may be required depending on the desired level of uprate). The U-SBU design utilizes Lightbridge’s metallic fuel in the central region of the assembly and a peripheral row of standard, pelletized UO2 fuel rods. The design is fully compatible with existing UO2 assemblies to facilitate insertion of lead test assemblies and batch reloads.
All Metal Fuel
Lightbridge’s all metal fuel (AMF) assembly is comprised entirely of metallic fuel rods and is capable of providing up to 30% increase in new build PWRs operating on 18-month fuel cycles. Due to certain constraints associated with the size of equipment that can fit in the containment structures of existing PWRs, there are limits as to the maximum power uprate level existing PWRs can accommodate without changing their existing containment structure. However, a new build unit can be constructed with a larger containment to allow for higher capacity equipment with relatively small capital cost increase.
General Overview of Lightbridge’s Metallic Fuel Technology
Lightbridge’s metal fuel differs from the alloy fuel that has been historically evaluated for fast reactor applications. Previous investigations into metal nuclear fuels focused on low alloy compositions such as U-10Zr wherein the concentration of uranium is significantly higher than the alloy constituent. The Lightbridge Zr-U alloy is a high-alloy fuel comprised of U-50Zr. One of the primary differences, with respect to irradiation characteristics, of Lightbridge’s metal fuel compared to U-10Zr is a significant reduction in irradiation-induced swelling. The U-10Zr fuels exhibit high radiation-induced swelling (typically, ~30 volume percent within 2 atom percent burnup) while swelling in the Lightbridge metal fuel is expected to be around 1 volume percent per atom percent burnup.
Lightbridge’s metal fuel technology came out of the research and development work for our thorium-based seed-and-blanket fuel assembly. The metallic seed rods used in our seed-and-blanket design are capable of operating safely at increased power density compared to standard uranium oxide fuel. Lightbridge determined that a fuel assembly comprised of only metallic fuel rods could provide significant benefits to a nuclear power plant
Power Uprates with Lightbridge’s Metallic Fuel Technology
Power uprates are a common practice in the commercial nuclear power industry and represent an efficient use of capital as the cost per kilowatt-hour of an uprate is several times lower than that of building a new plant. Lightbridge’s metallic fuel is capable of safely providing up to 30% more power in pressurized water reactors. It is anticipated that similar benefits will be attainable in other light water reactors, including boiling water reactors as well as small modular reactors.
The flexibility of Lightbridge’s metal fuel technology allows the utility to determine the level of power uprate most effective for their facility. Depending on the level of uprate desired, various power plant system upgrades will be required. Lightbridge’s initial analyses suggest that uprates above ~20% will likely only be achievable for new build reactor units where the nuclear power plant owner would pay a small incremental capital cost for the necessary reactor equipment upgrades rather than paying the replacement and disposal costs of upgrading components in an existing plant.
Lightbridge’s metal fuel technology can provide up to 30% power generation increase in pressurized water reactors. As a result, the initial capital cost per megawatt and the annual operations and maintenance costs per kilowatt-hour, which typically account for over four-fifths of the total cost of nuclear power generation, are expected to be reduced.