Nuclear plants were originally designed small, as for submarines. For some reason the design trend has been towards larger plants. Perhaps for economies of scale?
An interesting watch is Adam Curtis' documentary "A is for Atom", which covers the history of nuclear power.
The larger reactors were supposed to improve the economics of nuclear power once they reached series production. Making the minimum size larger seems to have impeded progression toward series production, zeroing out (and then some) the expected reduction in cost-per-megawatt from larger units.
For example, the 1117 MWe AP1000 design that's driven Westinghouse to bankruptcy derives from the AP600 design of only 600 MWe. After-the-fact criticism is too easy, but it seems to me that Westinghouse and its US partners would have suffered less if they were trying to build 4x 600 MWe reactors, and the projects fell behind schedule/over budget, than in their actual situation where they're behind schedule/over budget on 4x 1117 MWe reactors.
Would it be possible to make them modular? As in, build X number of the best submarine-size reactors and drop them in side-by-side in essentially secure concrete warehouses cooled by water pumped from a nearby lake? Kind of like racking servers is what I'm picturing.
That's the "small modular reactor" concept, under development by a few companies. I think that the concept has considerable merits. I hope that it will be tested in practice. I'm pretty bullish on renewables but nuclear power is very low emissions over its life cycle, safe enough (IMO), and nuclear construction capability should be (again IMO) maintained as a complement/alternative to renewable generation for the post-fossil era. For continued viability new nuclear construction needs lower, more predictable costs or steady long-term support from governments; I think that cost improvements would be the better of the two.
One advantage submarine reactors have is that they can use fully enriched uranium (bomb-quality, >90% U-235). You can still make pretty small reactors with non-weapons uranium (defined as <20% enriched) but they are not as performant or long-lasting as the pure U-235 submarines.
Yes. Plutonium from disassembled nuclear weapons is also used this way, under the name "mixed oxide fuel". Some reactor designs are better at burning "MOX" than others; CANDU reactors are particularly good at this, and in the early post-cold-war years there was a very active US-Canada-Russia programme to use Canadian reactors to burn surplus Russian fuel, funded by the USA (which was very concerned about the potential for fuel from decommissioned Russian weapons to get onto the black market).
Absolutely. In fact, from 1993 to 2013, fully 10% of the electricity in the USA came from dismantled ex-Soviet nuclear bombs through just such a arms reduction effort [1]. The material was downblended with U-238 to take it from weapons-grade to reactor-grade. The bombs that were once pointed at American cities ended up powering them. It was glorious.
For example, the 1117 MWe AP1000 design that's driven Westinghouse to bankruptcy derives from the AP600 design of only 600 MWe. After-the-fact criticism is too easy, but it seems to me that Westinghouse and its US partners would have suffered less if they were trying to build 4x 600 MWe reactors, and the projects fell behind schedule/over budget, than in their actual situation where they're behind schedule/over budget on 4x 1117 MWe reactors.