Low cost, walk away safe molten salt reactor design that will lead to thorium reactors

There is a new design for simple, low cost molten salt reactor that will eventually lead to a low cost thorium nuclear power cycle.

ThorCon requires no new technology. ThorCon is a straightforward scale-up of the successful Molten Salt Reactor Experiment (MSRE). The MSRE is ThorCon’s pilot plant. There is no technical reason why a full-scale 250 MWe prototype cannot be operating within four years.

ThorCon is a simple molten salt reactor. Unlike all current reactors, the fuel is in liquid form. If the reactor overheats for whatever reason, ThorCon will automatically shut itself down, drain the fuel from the primary loop, and passively handle the decay heat. There is no need for any operator intervention. In fact there is nothing the operators can do to prevent the drain and cooling. ThorCon is walkaway safe.

The ThorCon reactor is 30 meters underground. ThorCon has four gas tight barriers between the fuelsalt and the atmosphere. Three of these barriers are more than 25 meters underground. Unlike nearly all current reactors, ThorCon operates at near-ambient pressure. In the event of a primary loop rupture, there is no dispersal energy and no phase change. The spilled fuel merely flows to a drain tank where it is cooled. The most troublesome fission products, including strontium-90 and cesium-137, are chemically bound to the salt. They will end up in the drain tank as well.

The ThorCon nuclear island requires one-sixth as much steel and one-fourth as much concrete as the portion of the coal plant upstream from the turbine. A 1 GWe ThorCon nuclear island requires less than 400 tons of superalloys and other exotic materials. ThorCon operating at near ambient pressure has a 2:1 advantage in steel and a 5:1 advantage in concrete over its nuclear competitors on the nuclear side. Much more importantly, very little of ThorCon’s concrete is reinforced. Reinforced concrete is impossible to automate, drives the critical path, is not amenable to block construction, and entombs the critical portion of the plant in a mausoleum making repair and replacement extremely difficult. In contrast, ThorCon can be produced entirely in bargable blocks at shipyard assembly line productivity.

Based on resource and labor requirements and allowing for stringent inspection and testing, the ThorCon nuclear island should cost less than $500 per kW on an overnight basis. ThorCon uses the same steam and electrical side as a standard 500 MWe supercritical coal plant. But gone are the massive coal handling systems, the 100 m high boiler, the flue gas treatment system, and the ash handling and storage system. A generous estimate of the overnight cost of the ThorCon steam side, everything but the nuclear island, is $700/kW. This is a well established number.

Uranium and thorium fuel will be dissolved in molten salt. Production is expected to start by 2020.

Rapidly Deployable

The entire ThorCon plant including the building is manufactured in blocks on a shipyard-like assembly line. These 150 to 500 ton, fully outfitted, pre-tested blocks are barged to the site. A 1 GWe ThorCon will require less than 200 blocks. Site work is limited to excavation and erecting the blocks. This produces order of magnitude improvements in productivity, quality control, and build time. ThorCon is much more than a power plant; it is a system for building power plants. A single large reactor yard can turn out one hundred 1 GWe ThorCons per year.

Fixable

No complex repairs are attempted on site. Everything in the nuclear island except the building itself is replaceable with little or no interruption in power output. Rather than attempt to build components that last 40 or more years in an extremely harsh environment with nil maintenance, ThorCon is designed to have all key parts regularly replaced. Every four years the entire primary loop is changed out, returned to a centralized recycling facility, decontaminated, disassembled, inspected, and refurbished. Incipient problems are caught before they can turn into casualties. Major upgrades can be introduced without significantly disrupting power generation. Such renewable plants can operate indefinitely; but, if a ThorCon is decommissioned, the process is little more than pulling out but not replacing all the replacable parts.

Cheaper than Coal

ThorCon requires less resources than a coal plant. Assuming efficient, evidence based regulation, ThorCon can produce reliable, carbon free, electricity at between 3 and 5 cents per kWh depending on scale.

SOURCE – Thorcon

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