[thunderbird120]

Because submarine style high enrichment pressurized water reactors are both a nuclear proliferation concern due to their fuel type (i.e. much closer to weapons grade uranium than normal reactors use) and INCREDIBLY expensive. The reactors built for nuclear submarines are performant, not economical.

[avar]

A HN comment chain claiming the opposite of what you're arguing here, that they're much cheaper: https://news.ycombinator.com/item?id=26348839

[thunderbird120]

A1Bs are not submarine reactors but I guess that's not important. If it were as simple as just taking a carrier reactor and plopping it in the middle of a corn field everyone would be doing it already. For their cost calculation that user is that user is making lots of mistakes. You cannot compare the A1Bs thermal power output and to the electrical power output of power stations while also ignoring all of the cost of all of the additional systems which have to be built into the power stations themselves to manage them. These systems also have to be built into aircraft carriers but they seem to be glossing over those costs. Its also necessary to look at lifetime costs. The peak power output of naval reactors is very high relative to their size because they need to make ships go fast sometimes. Key word sometimes. If you run a naval reactor at its listed max power output its expensive highly enriched fuel is not going to last nearly as long as its supposed to. This gives people incorrect ideas about lifetime cost since you are comparing to power stations meant to put out a lot of power near constantly. If you take into account all the costs naval reactors are not at all competitive with normal civilian nuclear reactors and that should not be surprising to anyone. Civilian nuclear engineers are not stupid. Nuclear power plants don't just neglect naval reactors for no reason.

Also, as previously mentioned, naval reactors have nuclear proliferation concern. The reason naval reactors get to go 30 years between refuels is because they use use uranium enriched to >90% rather than the 3-5% used in commercial reactors. Not only is this very expensive, it adds a long list of concerns to the already long list of concerns surrounding nuclear energy.

[AnonymousPlanet]

Also, as far as I know, no one has ever dismantled a navy reactor. Every such reactor that has ever been built is in service or sitting in some yard. Any scheme that would make use of navy sized reactors would create a stream of reactors no one knows how to safely dispose off after use.

Compare this to civilian reactors for which dismantling and repurposing of the location is part of the cost calculation nowadays.

[avar]

> A1Bs are not submarine reactors but I guess that's not important.

I'll admit I was assuming that these naval are broadly similar, at least in cost per MW.

> If it were as simple as [...] everyone would be doing it already.

I think the main implicit claim here (and it's usually more explicit) is that using naval reactors is the only viable end-run around the morass that is civilian nuclear regulation.

> You cannot compare the A1Bs thermal power output and to the electrical power output [...]

True, but "thermal power station"[1] part of any nuclear plant is a well-solved off-the-shelf problem, as opposed to all the bespoke nuclear parts of it.

> The peak power output of naval reactors is very high relative to their size because they need to make ships go fast sometimes. Key word sometimes.

Do you have a source for this? I'm not doubting that you're right in practice, i.e. that naval nuclear reactors have variable power output, and spend a low part of their overall lifetime at a high percentage of the potential power output).

But by extension that means that they've got some average power output at which they could run perpetually over their shortened lifetime. What's that output?

> Civilian nuclear engineers are not stupid. Nuclear power plants don't just neglect naval reactors for no reason.

I don't think they're stupid, but they're clearly working within the narrow constraints given to them.

It's literally true that if our entire planet's electricity supply were generated with the RBMK-1000 design used in Chernobyl our mortality per MW would be vastly lower than it is today (look at current mortality statistics from coal etc.). So our current nuclear safety culture has clearly gotten out of hand.

> naval reactors have nuclear proliferation concern.

I don't think anyone's suggesting giving naval nuclear reactors to states that don't have nuclear weapons already, or at least those that are nuclear capable (e.g. Germany, Japan, etc. if they want highly enriched Uranium nothing's stopping them now).

If they're limited to those states I think these proliferation concerns can be dismissed.

1. https://en.wikipedia.org/wiki/Thermal_power_station

[sgarland]

> Do you have a source for this [power output profile of naval reactors]

I was a submarine nuke reactor operator. Can confirm, we spent most of the time at essentially idle. There are effectively three things that will cause you to operate at high power on a submarine:

* Boat needs to get somewhere _right now._ I've spent days at All Ahead Flank, which is mildly unnerving at first, because every parameter you can think of is just absolutely maxed out. Imagine Le Mans, but for multiple days, and when it's done you don't get to rebuild everything.

* Coners (non-nukes) are practicing maneuvers.

* Return To Port. While your Squadron more or less dictates this, I have definitely seen dates flex a little if your boat mysteriously makes far better time than expected.

Carriers AFAIK have a somewhat higher average output, because they use their steam for flight ops as well as propulsion and electricity, and the topsiders have their own schedules.

> ...they've got some average power output at which they could run perpetually over their shortened lifetime. What's that output?

Actual power output for current naval reactors is classified. You can find guesses in various places, some of which are close, and some of which is hilariously wrong.

[avar]

The question isn't what the current usage pattern of these reactors is, but whether they'd be amenable to different usage patterns.

Just like you might only use your car for 2 hours every day, but using its engine for 18 hours per day is probably fine.

[cripblip]

Thanks! I knew someone would have the details. Are there alternatives you think would work in a distributed model like this that address these concerns ?

[unsung]

There's a push these days to move towards HALEU fuel in the US; it's basically downblended submarine fuel stock [0]. It'll take about a decade to really start the downblending and distribution process at commercial scale in earnest [1], and there's some projects for instrumentation, transport containment, and so on in the works. Once commercial scale feedstock production is proven out, we'll start seeing shovels breaking ground on new reactor sites.

[0] https://www.nrc.gov/materials/new-fuels/haleu.html [1] https://www.orano.group/usa/en/our-portfolio-expertise/advan...