On Tuesday, TerraPower, the US nuclear power plant backed by Bill Gates, announced that it has selected a location for its first reactor. Kemmerer, Wyoming, about 2,500 residents, was the site of the Naughton coal-fired power station, which is being closed. The TerraPower project will replace it with a 345 megawatt reactor, which would breach a number of technologies that were previously not in commercial use.
These include a reactor design that requires minimal refueling, liquid sodium cooling, and a molten salt heat storage system that gives the plant the flexibility it needs to better integrate with renewable energy.
Although the TerraPower name is clearly associated with the project, many other parties are also involved. The company is perhaps best known for having the backing of Bill Gates, now chairman of the board, who promoted nuclear power as a partial solution to the climate crisis. The company was selected by the U.S. Department of Energy to build a demonstration reactor, a designation that guarantees at least $ 180 million for construction and could earn billions of dollars over the next several years.
The reactor itself is not a pure TerraPower project either. The reactor design is being jointly developed with GE Hitachi Nuclear Energy. A company called Bechtel will help with construction, which employs around 80 percent of Kemmerer’s population.
The design will incorporate a range of technologies that have rarely or never been tried. So this won’t be an easy project. TerraPower and GE Hitachi call the design Sodium, and they have set up a website to describe it. We’ll discuss some of the key differentiators here.
Initially, the plant will not use water to transfer heat from the reactor; instead, liquid sodium is used. This has the great advantage that sodium does not boil at any of the temperatures it should be exposed to in the reactor. This means that no hardware holding the coolant is subjected to high pressures, which makes things a lot easier. However, sodium reacts readily with air and explosively with water, raising a number of concerns.
Only about 25 large reactors with sodium coolant have been built worldwide. Many were built for research purposes only, and only a handful are still in use. The last one in the US was built in 1965 and the last one started operating in 1994. So it can be said that the companies don’t have a lot of hands-on experience.
In contrast to water cooling, sodium-cooled designs do not slow down the neutrons produced by fission reactions; For this reason they are often referred to as “fast reactors”. Fast neutrons have the ability to convert isotopes that don’t make useful fuel, so they can produce more fuel while operating.
In the case of TerraPower, the design surrounds a core of enriched fuel with many less useful isotopes. The reactor is powered by the enriched core while converting extra material into useful fuel that does the job when the first is exhausted. This process can repeat itself over several shifts of conversion, limiting the downtime required to refuel. But again, it has not seen any commercial use before.
The reactor will have a number of features that should allow passive safety, thereby limiting its internal heat even if the cooling circulation fails.
Plays well with others
After all, TerraPower does not convert the heat extracted from the reactor directly into electricity; Instead, it is stored as molten salt. As a result, although the reactor is rated at 345 MW, the plant will be able to generate up to 500 MW during periods of high demand or scale down to lower production when demand is reduced. This enables the system to better follow the daily demand cycles. In addition, the heat storage facility enables the Kemmerer site to be better integrated into the increasing use of renewable energies (Wyoming is a major wind power producer).
Overall, each of these differences carries risks. The combination of all of them in a single design means that this will be an extremely difficult project, especially over the planned seven year period. If this succeeds, however, we can finally get a feel for whether the cost of advanced nuclear concepts can stay competitive with the ever-decreasing cost of renewable energy with storage.
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