I suppose I should start by noting that I don’t frequent YouTube, Snapchat, TikTok, or any other social media or video sites, although I do watch occasional funny videos sent to me by friends, family, and coworkers. I haven’t played with any of the AI sites much either, although I will confess that I once used ChatGPT to rewrite an email in sonnet form, which was surprisingly well-received. I stream TV shows and movies, shop online, do an awful lot of searches for my research, and much more.
I know you’re probably not highly interested in my internet habits; however, despite my relatively frugal use of social media, online videos, and AI, all of this requires finding and moving a lot of digital bits around the country, involving data stored on tens (maybe hundreds) of thousands of computers.
Power Up
In the last few months, Microsoft has announced it’s planning to use power from a restarted nuclear reactor at Three Mile Island; Oracle has announced plans to power a data center with a handful of small modular reactors (SMRs), as have Amazon and Google, with other tech firms considering the same. The reason is that the vast server farms at data centers suck up massive amounts of power, and only nuclear energy offers a reliable source of carbon-free baseline power. The wind doesn’t always blow, the sun doesn’t always shine, and rivers don’t always flow (all while the planet is heating up) – but American nuclear power stations are online over 90% of the time. No other form of energy is carbon-free and virtually always there. That makes nuclear energy – especially in the form of small modular reactors – ideal for powering data centers. But is it safe? Are cat videos, AI-generated sonnets, shopping, and home entertainment worth the risk of installing dozens – eventually, perhaps hundreds or even thousands – of nuclear reactors, however small, around the country?
Small Modular Reactors (SMR)
I’ve written about SMRs before, so I won’t get too into the weeds on the subject. The big picture summary is that the new SMR designs are relatively low-power, factories will be able to crank out identical reactors the way Airbus cranks out jets, and between advanced engineering and the use of passive safety systems, SMRs can make a strong argument for being inherently safer than the larger reactors (primarily designed in the 1970s and 1980s), making it possible for them to remain cool in an emergency even in the absence of offsite power to run reactor coolant pumps.
SMRs have another interesting characteristic: Consider, for example, a data center (or a city, for that matter) powered by, say, a fleet of 10 SMRs, each putting out 50 MW instead of a single 500 MW reactor. Any accident with a single reactor shuts down the entire power supply; the reactor is either operating or not. If the reactor suffers a major accident, we have 500 MW worth of fission products that can potentially be released. With a network of SMRs, a reactor accident will only take 10% of power offline, and a single reactor only has 10% of the radioactivity that might be released. This redundancy makes the SMR cluster more resilient, while the lower inventory of fission products in any single reactor reduces the amount of radioactivity that can be released.
This is all on paper, of course, and as Yogi Berra famously said,
“In theory, there is no difference between theory and practice. In practice, there is.”
How can we know that it will all work out in practice?
We actually have some experience with SMRs (defined by the NRC as reactors that produce less than 1000 MW thermal and less than 300 MW of electrical power) – quite a bit, in fact. For example, the Navy’s Nuclear Power Program has operated multiple units of standardized reactor designs for more than 70 years, the great majority of them producing less than 1000 MW of thermal energy, amassing more than 5400 reactor years of operation in the process, all accident-free. The Navy’s reactors are all pressurized-water designs, which run the risk of steam explosions and loss of coolant if severely damaged; the Navy has avoided this through rigorous training, a fantastic quality control system, and strict adherence to procedures. On the other hand, some of today’s SMR designs use liquid metal, molten salt, or even circulating gas to keep the reactor cool. If they lose offsite power, the core is kept cool using basic principles of physics rather than engineering an emergency cooling system that relies on electrical power to run cooling pumps.
I should also note that liquid metal, molten salt, gas-cooled, pebble-bed, and other SMR designs have been around for several decades, including some used in nuclear submarines, test reactors, and commercial plants. This means the designs are familiar to nuclear engineers, who have updated them to take advantage of modern materials and improved designs.
Putting all these factors together is why powering data centers using SMRs fills me with more interest than dread. To recap, new designs are less likely to suffer serious accidents, passive cooling systems will keep them from melting down without the need for electrical power, and smaller reactors limit the amount of radioactivity that can be released if something does happen as well as reducing the impact on overall power production. While the technology has been updated, the concepts and designs have been around long enough to feel comfortable with them. So, load up the next cat video, and I think I will see if ChatGPT can convert this piece into Shakespearean English.
