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Comment by LgWoodenBadger | Hacker News Reader

It is when you can get a 210MW S9G, along with an entire state-of-the-art fast attack submarine for 2.8 billion

I thought this was a sarcastic reply, so I checked the facts myself. I was stunned. You are spot on.

For those unaware, the submarine is Virginia-class[1] and is powered by a 210MW nuclear reactor called the "S9G"[2]. And yes, as of 2019 prices, each boat cost 2.8B USD. There are 28 of these subs active in the US Navy. This isn't some new, experimental reactor design. The US is pumping these out of their shipyards. Sheesh. 5B+ USD for a measly 300MW reactor... (without the nuclear sub!) looks way too expensive. What am I missing?

[1] https://en.wikipedia.org/wiki/Virginia-class_submarine

[2] https://en.wikipedia.org/wiki/S9G_reactor

You're missing the fact that a submarine tends to be submerged in the ocean, and that it is fueled with highly-enriched uranium.

Naval reactors and civil reactors look roughly the same at first glance, but as the folks at Three Mile Island found out the hard way, there are some rather crucial differences.

Weirdly, the "submerged in the ocean" part could be good for SMR to deflect the effects of a tsunami. This part is the most important: "it is fueled with highly-enriched uranium". Really, it makes me think, if the US military allowed it, what is wrong with a bunch of SMRs built in a low population density area using highly-enriched uranium? (For other readers, normally commerical nuclear reacors use low enrichment uranium: 3% to 5% uranium-235.)

That is 210 MW thermal. Which would produce about 70 MW electricity.

$2.8B for 70 MW is insanely expensive.

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