Integral Molten Salt Reactor

Integral Molten Salt Reactor (IMSR) is a type of nuclear reactor that uses a liquid mixture of salts as both fuel and coolant. This technology is a part of the broader category of molten salt reactors (MSRs), which have been under development since the mid-20th century.

History

The concept of the IMSR was first proposed in the 1950s by Alvin Weinberg, then director of the Oak Ridge National Laboratory. The idea was to create a reactor that could operate at high temperatures without the need for high pressure, thus reducing the risk of a catastrophic failure. The first experimental MSR, the Molten-Salt Reactor Experiment, was built at Oak Ridge and operated from 1965 to 1969.

Design and Operation

The IMSR design incorporates the primary reactor components, including the fuel salt, moderator, and heat exchanger, into a single, sealed vessel. This "integral" design simplifies the reactor and reduces the number of potential failure points.

The fuel salt is a mixture of lithium and beryllium fluorides, known as FLiBe, with dissolved uranium or thorium as the nuclear fuel. The salt is heated by the nuclear reactions to temperatures of around 700 degrees Celsius, and then pumped through a heat exchanger to transfer the heat to a secondary salt loop. This secondary loop is then used to generate steam for electricity production.

Advantages and Challenges

The IMSR has several potential advantages over traditional nuclear reactors. These include improved safety, due to the low pressure operation and the ability of the fuel salt to absorb and dissipate heat; the potential for load-following operation, due to the strong negative temperature coefficient of reactivity; and the ability to use thorium as a fuel, which is more abundant than uranium.

However, there are also significant challenges to the commercialization of IMSR technology. These include the corrosive nature of the fuel salt, the need for advanced materials to withstand the high temperatures and radiation levels, and the need for a solution to the management of the radioactive waste produced by the reactor.

Current Development

Several companies and research institutions are currently working on the development of IMSR technology. These include Terrestrial Energy, a Canadian company that is developing an IMSR design for commercial power generation, and the Shanghai Institute of Applied Physics, which is researching the use of an IMSR for heat and hydrogen production.

See Also

• Nuclear Power
• Generation IV Reactor
• Liquid Fluoride Thorium Reactor