Frequently asked questions
ThorCon is a hybrid thorium/uranium liquid fuel fission power plant. It is a molten salt reactor.
Yes. Small Modular Reactor is a term usually applied to solid fuel, light water reactors generating up to 300 MW of power. Each ThorCon power module can generate 250 MW of electric power.
ThorCon International will form consortia with investors and national businesses to build fission power plants to sell electricity in developing nations seeking ample, reliable electric power, cheaper than coal.
ThorCon fuel is a combination of 80% thorium and 20% uranium. The uranium is enriched to 19.75% U-235 (LEU20). The fuel will be delivered to the plant as fluoride salts.
Liquid fuel was first conceived by Oak Ridge National Laboratory as an alternative to the water-cooled, zirconium-clad uranium oxide solid fuel rods used in light water reactors. Thorium and uranium fluorides are dissolved in molten salt. ThorCon molten salt is a mix of fluorides of beryllium and sodium heated to 560-700°C. The fuel flows through the reactor vessel (the Pot) where it fissions and gets hotter, then through a pump and heat exchanger to cool it and deliver the thermal energy, then recirculates.
Liquid fluoride salts enjoy several advantages over zirconium-clad solid oxide fuel. Liquid fuel tolerates much higher temperatures without damage. It can be rapidly reconfigured by draining the fuel away from the moderator ensuring fission stops, into a configuration which readily loses decay heat. The liquid fuel is at low pressure; it’s not near any pressurized water that might push fission products into the environment. It chemically binds up the two most difficult fission products strontium and cesium so they will not volatilize. The liquid fuel easily maintains homogeneity because the circulation mixes the fuel to burn evenly. No excess reactivity is needed and no burnable neutron absorbing poisons are used, efficiently using valuable neutrons.Liquid fuel makes allows removal of the fission product xenon which otherwise absorbs neutrons and complicates reactor control.
Fluorine gas is very reactive, combining with almost any other element. Once combined as a fluoride, the resultant salt is very stable. Sodium fluoride is in toothpaste. After 4 years of operation at Oak Ridge, the molten fluoride salts did corrode the prototype metal reactor vessel (Pot) to a depth of 0.1 mm. In ThorCon corrosion is controlled by managing the redox potential and by changing out the Pot after 4 years of use.
Yes, for solid-fuel rods. No, for liquid fuels. Solid fuels rods contain solid uranium oxide pellets that are stacked inside zirconium metal pipes to protect from the corrosive effects of the cooling water heated to 315°C and pressurized to 153 atmospheres. The interior of the fuel pellet can reach 1400°C, so there are large temperature gradients, stresses and strains that much be carefully engineered for and tested. In ThorCon the uranium fission takes place in the heat absorbing liquid fuel salt. Oak Ridge demonstrated this in two prototype molten salt reactors.
Yes, the graphite moderator logs in ThorCon shrink and swell during years of neutron irradiation. The graphite is not structural. The graphite restraint system accommodates these changes and also temperature changes. Based on Oak Ridge testing, the graphite lifetime exceeds four years; the ThorCon Pot with the graphite is only used for 4 years before being swapped out.
The parts of the power plant that are subjected to neutron irradiation are within the Can. The Can is used for 4 years, idled in the plant for 4 years, then transferred by CanShip to a Can Recycling Facility for inspection and refurbishment. The rest of the power plant can be maintained with standard industrial practices.
ThorCon is built with steel-concrete-steel sandwich walls of thickness 25-1000-25 mm. The outer steel layer is in contact with groundwater or seawater. The steel is coated and also protected from galvanic corrosion using impressed current cathodic protection and other techniques common in the marine industry.
Three years will be required to complete the detailed design, build the pre-fission version and conduct temperature and pressure testing. Thereafter a year will be required to build and install the prototype power plant. Initial testing will take place for one year, before delivering some power to the grid. Stress testing will continue for another year. After this step by step commissioning process we expect to obtain a license to build more commercial power plants.
Two years from receipt of a firm order; transmission lines, permitting, siting, cooling are local limiting issues.
A 500 MW ThorCon operating at 91% capacity generates 4,000 GW-hours per year, with fuel derived from 73 tons of natural uranium. ThorCon uses about half the uranium of a light water reactor, due to ThorCon’s high thermal efficiency, removal of Xe-135, and the production of fissile U-233 from thorium.
The World Nuclear Association reckons current uranium reserves are 5.9 million tons at $130 per kg uranium. If 3 million tons were available to ThorCon then we have 21,000 GW-years of uranium. If we start turning out 100 one GW ThorCon power plants per year, then we are into a 100+200+300+400+… = 100*n*(n+1)/2 series. At year 20, we will have used up our 3 million tons. At this point, 2100 GW of ThorCons will be producing about half the world’s electricity while generating no SO2, no NOx, no ash, and nil CO2. ThorCon will have been spectacularly successful.
This ThorCon fleet will then be eating into the remaining reserves at the rate of 300,000 tons per year. Re-enriching the used fuel back to 20% would cut this burn rate by a third. If reserves were static, we’d run out of uranium in another 20 years, about 50 years from now. But the reserves will not be static. Demand will push up the real price of uranium and new reserves will be developed. Known low grade sources such as phosphate deposits, enrichment tailings, and coal ash will be exploited. Advances in extraction technology always seem to outpace the predictions. For example, the sea contains about 4.6 billion tons of uranium. River flows add about 32,000 tons of uranium to the ocean each year. Even using expensive, $600/kg uranium extracted from seawater adds only 1 cent/kWh to ThorCon power costs.
No. ThorCon fission power plants must be located so they can be serviced by ocean-going ships that replace Cans and fuel salt casks. Presently 50% of the world’s population lives within 100 km of the sea. Three quarters of the world’s cities are near the sea. ThorCon CanShips can service plants on major rivers. The CanShip is 168 m long, 23 m beam, 14 m air draft, with a river draft of 2.5 m.
High voltage direct current (HVDC) long distance transmission lines operate near 1 million volts potential. Compared to AC transmission lines they lose less energy because of lessened dielectric losses. HVDC transmission lines as long as 2300 km operate in South America, and a 3300 km line operates in China. Nearly all inland cities are within the reach of an HVDC transmission line from a waterway navigable by ThorCon and a servicing CanShip.
Thanks to high temperature, ThorCon uses the same, competitively sourced, high efficiency, supercritical steam turbine-generator as a modern coal plant. Thanks to low pressure, ThoCon avoids reinforced concrete and 9-inch-thick forgings. Thanks to liquid fuel, ThorCon can move fuel around with a pump. No exacting fuel pin fabrication nor complex reshuffling refueling systems are required. Coal plants are more massive because the energy density of coal fuel is so low compared to uranium. A one-GW coal plant must pulverize 10,000 tons/day of coal and dispose of over 1000 tons/day of ash.
In addition to ThorCon’s low capital costs, ThorCon uranium fuel costs are a fifth of coal fuel costs. ThorCon liquid fuel uranium costs less than LWR solid uranium oxide fuel rods that require precision manufacturing. Thorium costs will be relatively trivial. Staffing costs will be modest because the passive safety systems prevent any operator actions from creating a dangerous situation.
No. Shipyards building ThorCon fission power plants need no special licenses or skills to handle radioactive materials. After a ThorCon is installed and pre-tested, uranium and thorium fuel will be supplied to the plant in fuel transport casks transported by ship.
ThorCon is a molten salt reactor. Oak Ridge National Laboratory built two molten salt reactors in the 1970s; the second operated for 4 years. The ThorCon team analyzed the experiences and furthered the design. All this research was well documented and is posted publicly. The design team draws heavily on this information.
Today’s fast computers and powerful software simulate fuel fission, heat transfer, fluid flows, and materials properties. There is no new technology in the ThorCon design; it is an assemblage of well-understood technologies. Certainly this new fission reactor will require cautious testing, just as new airplanes must be tested before the FAA licenses them for commercial use.
It’s too expensive and time consuming. In 2015 our team did visit the Nuclear Regulatory Commission and the Department of Energy to discuss building the first ThorCon in Washington state at the Hanford Reservation, the site of nuclear reactors used to produce plutonium for weapons. The Pacific Northwest National Laboratory is there. The GAO has estimated that it would cost a billion dollars and take a decade or more before the NRC would decide to grant a license to build ThorCon. In August 2016 former NRC chair Allison Macfarlane confirmed this to MIT Technology Review.
Instead of licensing based on theoretical risk analyses and extensive computer modeling with prescribed document submissions and approvals, we advocate step by step commissioning. We plan to work closely with the national regulator during construction and cautious testing of the ThorCon fission power plant. When testing is completed and the regulator becomes familiar with the new design, the regulator can establish rules to license new such power plants for commercial service.
Yes. ThorCon can change generated power at 5% per minute. Reducing the molten salt pump motor speeds reduces the heat moved to the steam turbine that turns the electric generator. With less heat removed, the fuel salt temperature rises slightly and the fission slows, solely due to the physical properties of the salt, moderating graphite, and Pot. The process is reversed to increase power.
In an ordinary LWR nuclear reactor, the fission product xenon-135 is produced within the fuel rods. It builds up, with a half-life of 9 hours. It strongly absorbs neutrons, requiring compensating increases in fission rates. When power generation is reduced, less Xe is created, but as the prior level of Xe decays, fewer neutrons are absorbed, and reactivity perversely increases. Managing this requires skilled operators during power changes.
In ThorCon, most of the fission-produced Xe-135 is removed from the liquid fuel by the off-gas recovery system, so that neutrons are not absorbed by Xe in the Pot where fission takes place. This removes the xenon instability and also makes ThorCon more fuel-efficient than an LWR.
No, but US laws limit the transfer of nuclear materials and technology. There are fewer restrictions for transfers to countries that have signed the Nonproliferation Treaty and also signed bilateral 123 agreements with the US. ThorCon intellectual property is guarded as trade secret information, requiring non-disclosure agreements. The US DOE National Nuclear Security Administration affirms that export of ThorCon information to Indonesia is correctly registered under 10 CFR Part 810.
The large, reinforced concrete containment dome over an ordinary LWR is to contain the volume of steam that might be released if the high-temperature cooling water, pressurized to 150 atmospheres, were to breach its piping. That steam might contain radioactive contaminants. In ThorCon, the radioactive fuel salt flowing through the primary loop (Pot, pump, primary heat exchanger) is at garden-hose pressure. In a breach there is little propulsive force. The primary loop is contained within the Can. The Can is contained within the silo. The silo is contained within the power module within the hull. There are at least three containment barriers retaining radioactive material in any casualty.
ThorCon will send one cask of used fuel salt to storage every four years. Each 3 m diameter cask results from 2 GW-years of electric power generation. At 5 m spacing 800 GW-years of casks would occupy one hectare. This can be reduced by re-enriching the valuable remaining uranium.
Ships at sea are designed to operate in storms with wind and waves that can generate accelerations up to 1.0 g. The similar design of the ThorCon power plant is adequate for 0.8 pga (peak ground acceleration). Restraint systems within the Can protect the Pot and piping against earthquake acceleration. The Can itself rests on elastomeric bearings. The strong hull sitting on a sandy seabed is little moved by earthquake waves.
Should a tsunami engulf the ThorCon power plant, the fission plant proper is sealed from the waves with heavy hatches on a deck made of a steel-concrete-steel sandwich. ThorCon is sufficiently ballasted down to remain in place during flooding.
In normal operation Cans are normally swapped out on a 4 year cycle and transported by the CanShip. To decommission the plant the Cans are simply removed after their normal four-year waiting period and returned to the Can Recycling Facility. Radioactive fuel salt will be returned to the Fuel Processing Facility in fuel casks. The ThorCon hull can be refloated and removed, reused, or deconstructed.
A large shipyard could build 20 ThorCon fission power plants per year. After prototype demonstration and commercial licensing, the planned elapsed time from firm order to delivering electric power is two years, dependent on timely licensing, site preparation, and transmission line construction. ThorCon block construction technology is compatible with existing shipyard construction facilities and practices. A ThorCon power plant is much smaller than a tanker ship. There is global shipyard capacity to produce 100 GW of ThorCon power plants per year.
Each GW of ThorCon power plants saves 8 million tonnes of annual CO2 emissions from avoided new coal power plants.
Keys to prosperity for developing nations include transportation, clean water, education, property rights, good government, and electric power. Each 1 kWh of electricity correlates with $4 of gross domestic product. Electrification is necessary (but not sufficient) for prosperity. Each 1 GW ThorCon plant enables $32 billion of added GDP.