thorium molten salt reactor meltdown impossible

Photo: US Department of Energy / Frank HoffmanĪs so often happens these days, this great “American” idea emigrated to China. US Atomic Energy Commission Chairman Glenn Seaborg is at the controls.

Startup at Oak Ridge, Tennessee, October 10, 1968, of molten salt reactor operating with uranium-233 fuel. Unfortunately, the program was discontinued as part of the process that led to the virtual monopoly of light water reactors in nuclear power generation. Alvin Weinberg, one of the fathers of nuclear energy in the United States, looked upon the MSR as a future workhouse for world development. A small prototype, the 8 MWt Molten Salt Reactor Experiment (MSRE), was built and operated from 1957 until 1976 at the Oak Ridge National Laboratory in the United States. The MSR first emerged in the context of the US effort, launched in the late 1940s, to develop nuclear-powered aircraft. A variant of an MSR, a liquid fluoride thorium reactor (LFTR), will be able to use abundant thorium as a fuel. MSRs can run on uranium and existing stockpiles of plutonium and nuclear waste. This simplicity also allows MSRs to be smaller in size, which in turn makes them ideal for factory manufacture. Having far fewer systems and parts makes MSRs inherently cheaper.

MSRs can be made cheaply because they are simple compared with conventional reactors, not requiring large, pressurized containment domes and many complicated additional safety systems found in the conventional systems.

In a certain sense this is the opposite of the dreaded “meltdown” scenario in conventional reactors. In case the fuel-carrying liquid somehow leaks out of the primary circuit, it will quickly cool to below its melting temperature, solidifying and trapping the radioactive substances contained in it. All of this happens without human intervention. If for any reason the liquid should become too hot for the reactor to operate safely, a special plug at the bottom of the reactor melts, letting the fluid drop down into emergency dump tanks. If the reactor heats up, the liquid expands, the reactions slow down and after a certain point the fuel is no longer dense enough for the chain reaction to sustain itself. Without the graphite moderator to interact with, in fact, the neutrons have the wrong energies and cannot trigger fission reactions effectively. The composition of the fuel solution is such that chain reactions can only occur when it is surrounded by the graphite moderator.

A very high degree of passive (or inherent) safety.

This type of design has numerous advantages, including: Along the way the fluid can be processed, various reaction products removed and new material added, as desired.

Leaving the core at a higher temperature, the fluid runs through a heat exchanger, transferring the extra heat energy to a secondary circuit. In the core, the liquid-carrying channels are surrounded by neutron-moderating material (mainly graphite), which provides the conditions for fission chain-reactions to occur in the dissolved fuel. What is the molten salt reactor, and why all the interest? The basic idea is to dissolve the nuclear fuel in a liquid – a molten salt at 600-700 degrees C – that is continuously circulated through the reactor core. A 2013 conference presentation by Jiang Mianheng on nuclear energy in China is available online. Jiang Mianheng received his doctorate in electrical engineering from Drexel University in the United States and has headed up a variety of technology programs in China. The leading figure in China’s MSR effort is Jiang Mianheng, son of the former Chinese president and Communist Party general secretary Jiang Zemin and presently director of the Shanghai branch of the Chinese Academy of Sciences.

The MSR has been a significant area of technical cooperation between the two countries.Ĭhina occupies a unique position, not only because it is currently the only country in the world that is actually building a molten salt reactor, but also because the Chinese Academy of Sciences has chosen MSR technology as an essential component of China’s medium- and long-term energy strategy. The clear leaders in the field of molten salt reactors are the United States – where the MSR was invented – and China.

Thorium molten salt reactor meltdown impossible