The PWR (and related BWR) are bad at weapons plutonium production for two reasons: (1) there aren't a lot of excess neutrons to transform U238 -> Pu239, graphite reactors can be tuned up to make about twice as much Pu. (2) Either kind of LWR runs under pressure and it would be a big deal to shut the reactor down, bleed the pressure, and change the fuel; most other reactor types can be refueled online. The longer Pu239 stays in the reactor, the more of it adsorbs another neutron and becomes Pu240 which is bad for nuclear weapons because it creates a neutron background that causes predetonation.

Graphite reactors have a history for power production: see [1] and [2]. They might even have a future [3] but the German experience makes me think the prismatic type core makes more sense [4]

[1] https://en.wikipedia.org/wiki/Advanced_gas-cooled_reactor

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

[3] https://www.world-nuclear-news.org/Articles/Chinese-HTR-PM-D...

[4] https://inis.iaea.org/records/81760-q0060