Scientists at the Nuclear Research and Consultancy Group (NRG) in Petten, Netherlands, have commenced the world’s first thorium molten salt reactor (TMSR) experiment in more than 45 years (Figure 1). The SALt Irradiation ExperimeNT, or SALIENT, was developed in cooperation with the European Commission Joint Research Center’s Institute for Transuranium Elements, which is located near Karlsruhe, Germany.
|1. A shining resource. This image gives a glimpse inside the test reactor in Petton, Netherlands, where experiments are now being conducted using thorium salt. Courtesy: Thorium Energy World|
SALIENT will involve a series of tests, each building on the previous results. The first phase focuses on creating cleaner reactor fuel by removing noble metals from thorium fuel as it transmutes to uranium and undergoes fission while exposed to a radiation field from a high flux reactor. Noble metals are a group of metals that resist oxidation and corrosion in moist air, and that acids do not easily attack.
Nuclear fuels expert, Ralph Hania, who is one of the lead NRG scientists for the SALIENT experiments, was interviewed for a story published by the Thorium MSR Foundation—an organization focused on educating people about the use of TMSR technology. Hania explained that managing noble metals in the salt stream is particularly important to sustaining MSR operation. The experiments will help determine if nickel can be used to precipitate the noble metals for removal from the system.
During SALIENT’s second phase, researchers plan to test the resilience of ordinary materials used in the construction of TMSRs. Corrosion resistance is one important aspect, but excellent mechanical strength and the ability to withstand intense radiation are also essential. Later SALIENT tests will focus on more specialized materials, such as 316 stainless steel, Hastelloy, and a titanium-zirconium-molybdenum alloy.
If test results prove promising, it would be a significant step toward commercialization of TMSRs. The International Thorium Energy Organisation’s (IThEO’s) website—thoriumenergyworld.com—notes that only three countries (China, India, and Indonesia) are currently working on TMSRs. It said China intends to operate a molten salt cooled pebble bed reactor as an intermediate step toward TMSR implementation. In Indonesia, three companies signed a memorandum of understanding in October 2015 with Martingale Inc. to plan, develop, and build TMSRs based on Martingale’s ThorCon design. India, meanwhile, has a couple of TMSR designs on the drawing board, but its scientists have been more focused on thorium-fueled advanced heavy-water reactors than on the MSR design, according to the IThEO.
The Thorium MSR Foundation points to numerous advantages of thorium power over other fuel types. The inherent safety of the plants is near the top of the list. By design, the salt prevents hazardous materials from escaping, and meltdown, hydrogen blasts, and pressure explosions are said to be impossible. The proliferation risk is considered very low with TMSRs, and they can actually be used to help safely eliminate existing nuclear weapons material.
Thorium is about three to four times more abundant than uranium in the Earth’s crust, and it is easier to extract. There is a marked difference between the waste produced from TMSRs and typical light-water reactors too. Specifically, nuclear waste produced by traditional nuclear power plants must be stored for tens of thousands of years before radioactivity decays to the level of natural uranium ore, whereas TMSR waste takes roughly 300 years to do so.
“This is a technology with much perspective for large scale energy production,” Sander de Groot, NRG reactor core expert, was quoted on the IThEO website as saying. “We see this as a commercial opportunity for the long-term.”
—Aaron Larson is POWER’s executive editor.