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Nuclear Power Turns To Salt

This article is more than 9 years old.

Today, it was announced that the Department of Energy’s Oak Ridge National Laboratory  (ORNL) in Tennessee is partnering with Canadian nuclear company Terrestrial Energy Inc. (TEI) to assist with TEI’s new Integral Molten Salt Reactor (IMSR). The engineering blueprint stage for this GenIV reactor should be reached in two years. The reactor should come online in less than ten.

Think of it: a nuclear reactor that

- is cheaper than coal

- creates much less waste and few long-lived radioactive elements

- uses almost all of the fuel which lasts 7 years between replacement, and can be recycled easily

- is modular, from 80 MWt to 600 MWt, able to be combined and adapted to individual needs for both on and off-grid heat and power

- is small enough to allow fast and easy construction, and trucking to the site

- operates at normal pressures, removing those safety issues, and at higher temperatures making it more energetically efficient

- has the type of passive safety systems that make it walk-away safe

- does not need external water for cooling

- can load-follow rapidly to buffer the intermittency of renewables

- cannot be repurposed for military use and has strong proliferation resistance

- can last for many decades

- uses a liquid fuel

Now that is different!

Nuclear power has been biding its time, waiting for the new round of reactors to bring the industry into the 21st Century so we can address our numerous environmental and energy challenges. This announcement is a good step in that direction.

Many innovative designs for advanced GenIV nuclear reactors have developed logically from our 60 years of nuclear experience. The hundreds of millions of hours that the traditional GenII and GenIII reactors have been safely operating, and the lessons learned from the only three nuclear power accidents over that time, have shown us what the next generation of nuclear needs to be (see Nuclear News for a broad description of reactor types).

Several of these designs are expected to become reality, each with various advantages. Improvements in fundamental safety and operational designs increase efficiencies and lifespan, dramatically reduce the amount of waste generated and the time that it’s radioactive, and reduce the possibility of core meltdowns to almost zero.

But the hurdle is getting these new reactors commercialized. Lacking policy leadership, the general industrial world has not until recently seen the incentive to commit to the specialized nuclear facilities required for the precise testing of components, development of specific material needs, and other work necessary to complete the design and construction of these new reactors.

This may be changing and Terrestrial Energy’s access to Department of Energy facilities like those at ORNL illustrates this. ORNL’s partnering with TEI is ideal since ORNL built and demonstrated the first molten salt reactor back in the late 1960s. Former ORNL scientists who played central roles in molten salt reactor development will be working on the project.

Then there’s the issue of getting any new reactor design licensed by the U.S. Nuclear Regulatory Commission (NRC). A new design takes longer to understand and evaluate since there’s no precedent and staff are unfamiliar with new designs.

This is where the ORNL connection is key. They built a molten salt reactor that worked and NRC has access to all that data and experience, and the licensing should not take much longer than normal.

The IMSR’s fundamental advantage lies in its most novel feature - the fuel is a liquid. At first glance, that might seem odd. But molten salt, with the uranium dissolved in it, can operate at low-pressure and absent are chemical or mechanical driving forces which can cause so many problems with traditional solid fuel reactors.

With multiple layers of secure containment, there are definite safety, operational and cost advantages, and with these advantages come licensing advantages. The liquid fuel allows natural circulation to transport decay heat, and being liquid eliminates the need for costly solid fuel fabrication.

Transuranic elements, in particular plutonium, can be recycled from the liquid fuel without the problems and costs of reprocessing solid fuels, making the nuclear waste virtually free of troublesome long-lived radionuclides. Uranium fuel requirements per kWh become about one-sixth that of a traditional light-water reactor. The IMSR uses normal low-enriched uranium but can also be use thorium and other actinide elements as fuel.

The IMSR can be maintained and operated with relative simplicity, important for an industrial reactor. The reactor is in a permanently sealed modular core-unit, that includes multiple redundant heat exchangers and pumps. This whole unit is replaced periodically on a seven-year cycle resulting in little reactor down time.

Removal of decay heat by passive means is a distinct advantage of any molten salt design, but the Terrestrial Energy reactor uses the natural convection of the molten salt to remove the heat to the vessel walls passively. Here its containment silo simply adsorbs the heat decay and conducts it away – this is passive cooling at its simplest.

The new passive and modular features of the IMSR will make the final construction, licensing and operational costs lower. According to TEI’s chief executive Simon Irish, the reactor will cost about the same to build as a coal power plant, but will cost much less to run than a traditional nuclear plant. Economically the best of both worlds, socially it has a fresh new message – safe, secure, clean, carbon-free energy.

DOE’s support for TEI’s IMSR is a great start towards a robust and diverse energy future.

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