Reactor Designs Aren't the Problem

Wednesday, November 6th 2019
Why we don't have time to focus on molten salt reactors right now and where we should be spending money instead.

Current Reactors

We get 22% of our energy from nuclear reactors. One ton of a uranium fuel in a reactor can produce 44 million kilowatt hours of electricity. Producing an equivalent amount of power using fossil fuels would require burning 20,000 tons of coal or 8.5 million cubic meters of natural gas. Atomic power plants today use second generation reactors. Reactor designs, much like airplanes, are always being improved using lessons learned and new third generation reactor designs are receiving significant investment.

Fuel

Today, we produce a surplus of commercial nuclear fuel for use in the second generation reactors at power plants. They use an isotope of Uranium, U-235. This isotope is fissile, meaning it is capable of sustaining a nuclear chain reaction. Most of mined uranium is made up of a different isotope that cannot sustain a chain reaction, U-238. About 99.3% of uranium ore is U-238 and while the U-235 isotope makes up just under 0.7%. In order to be used to power reactors, Uranium must first be 'enriched' to contain 3-5% of the fissile U-235 isotope. Because U-238 has 3 more neutrons than U-235, the difference in mass can be used to seperate them in centrifuges until the desired ratio of isotopes is met. Stuxnet, the most advanced computer virus to date, was able to greatly reduce Iranium Uranium enrichment capacity by simply targeting their centrifuges.

Waste Management

When nuclear fuel is used up, it still contains about 96% of its original Uranium. When it is removed from the reactor it continues to emit radiation and heat and is immediately placed in storage ponds at the reactor facility. It remains in water for around a year to cool. Once cooled, the used fuel is highly recyclable and can be reprocessed into fissionable uranium and plutonium. After processing, only about 3% of used fuel (about 750kg per year from a large reactor) becomes high-level radioactive waste. Public concern over radioactive waste and lack of funding hampered the development of deep geological repositories where waste is initially recoverable for re-use before being permanently sealed. The planned Yucca Mountain nuclear waste repository in New Mexico was defunded by the Department of Energy and closed in 2011. There is not a pressing need to build these facilities as there is only a small volume of waste and it becomes less dangerous over time. Naturally-occuring radioactive elements are relatively common, so assuming we can start burying the unrecoverable fuel waste, we'll just be putting it back from where it came.

Arandis Uranium mine. The worldwide production of uranium in 2015 amounted to 60,496 tonnes.   
Yucca Mountain, a nuclear waste storage facility   

The Atom's Perception Challenge

Nuclear disasters like the Three Mile Island Accident in 1979, the Chernobyl Disaster in 1986, and the Fukushima Daiichi Accident in 2011 have contributed to governments resisting nuclear reactors. In addition to these incidents, nuclear weapons have occupied society’s collective consciousness since their first use in 1945. After almost 70 since the Chicago Pile-1, the first artificial atomic chain reaction, less than 100 deaths have directly resulted from atomic energy. Reactor designs and nuclear power stations have reached an airline level safety. But, unlike plane crashes, nuclear reactors carry more baggage: prior meltdowns, association with nuclear weapons, and misunderstanding of radiation leading to public fear. This has led to just a trickle of new reactor projects in recent years, even as nuclear research booms.

There are some upcoming reactor designs that have been shown to be meltdown resistant alternatives to U-235 reactors. They run by mixing Thorium and trace amounts of U-235 in a molten salt solution. These alternative reactor designs have been around for a long time but the last reactors running these reactions were shut down in the 1960s. Even today, molten salt reactors are still not a viable source of power. Next-generation molten salt reactors will require at least 7-15 years of development before they can become commercially viable. As meltdown resitant as they are, they will also need to accumulate a safety record to temper public fear which will only further delay implementing the designs at scale.

When compared with coal, atomic energy, regardless of how it is generated, is not only much easier to control, but also does not produce greenhouse gases or toxic ash.

Dr. Strangelove   

Atomic Politics

Bill Gates' nuclear company, TerraPower, developed a third generation U-235 reactor design. It was more compact and safer than previous designs. However, the cost of producing just one reactor was prohibitively expensive, so they had to find a way to manufacture and sell multiple reactors for the design to be economically viable. They found a partner in China willing to help them accomplish this.

However, the ongoing trade war between the United States and China has blocked the sharing of nuclear technology and blocked TerraPower from working with their partner. China has built the largest number of nuclear reactors, but they meet a smaller percentage of their electricity demand. It seems like a global market could be an accelerant for scaling nuclear, but international relations prevents it.

Politicians have recently expressed interest in new molten salt reactor technology due to their safety characteristics. Very few have acknowledged the level of safety we have achieved with existing technology. Thorium reactor technology is not yet fully understood and have yet to be run on the grid. Even if we were to have a viable molten salt reactor design by 2020, meeting the required scale of reactor production to offset coal will still take significant time. We are not even producing U-235 reactors at the rate we should be. To remove energy-related carbon emissions, nuclear power construction will need to increase by more than 400%.

Compared to new technologies, U-235 reactors have a significant head start. They already have the supply chain in place and constructing them is well understood. They are a better choice because we must massively scale up reactor production. Thorium reactors should be left to be developed by private industry until we can build them as scalably as U-235 reactors.

U.S. reactor spending should be entirely focused on deploying U-235 reactors to reduce carbon emissions. We should be building support for an increased number of nuclear projects using well-understood reactor technologies. The more reactors we build, the more efficient their deployment will become.

Climate change is a global problem, so the U.S. Federal Government should focus on prioritizing a global nuclear manufacturing marketplace. Maybe even the construction of state-owned nuclear power stations.

It's not worth the risk of trying for thorium reactors without first scaling atomic power generation by any means necessary. Luckily, the reactor designs we have been using for decades are very efficient, safe, and well understood. To avoid losing control of climate change, we need to think in terms of decades. Running the U.S. grid on atomic power is a crucial step to cut 33% of our total CO2 emissions.

TerraPower   

At the same time, climate change is beginning to happen on human-perceptible timescales which is, sadly, a good thing. We are being forced to face the reality of time as we work to prevent a true global disaster.

Running water over hot Uranium is the only carbon-free energy solution we have available right now that can meet power needs both today and for decades to come. Solar, wind, and other renewables are projected to cover 22% of energy needs. Sure, these nuclear water boilers produce radioactive waste, but we can bury it. Given it's where it originally came from, I would rather have Uranium buried underground. than fires, rising seas, and toxic air. Buried Uranium cannot hurt us, but climate change can. Replacing as many carbon-based power plants with nuclear reactors is the only option we have to reduce atmospheric carbon levels without impacting growth.

We would be foolish to focus on molten salt reactors, a technology that is decades away, when the one available solution to our electricity generation problem has already been on the grid for decades.

W.H.