For example, 20kg of 5% enriched uranium in a reactor would provide 10MW for 13 weeks (around 80TJ total), which is enough to power 1000 homes, and costs like $20000 (admittedly at earth market rates) However, if that energy isn't stored chemically or emitted from the ship in some way (that is, is used in some fashion that eventually becomes heat in a closed system, whether it be lights, electricity, and so on), that also produces enough heat to raise the temperature of the Wolfen by 1C over that 13 weeks... if we assumed that it was a solid brick of iron 150m by 150m by 1000m. If it weighs less than 177 megatons, you're looking at proportionately more temperature gain (depending on the specific heat of the composing materials, but water only has 10x as much specific heat). For reference, the Saturn V rocket is 3 kilotons. If we assume the Wolfen had similar density to Saturn V, it would be about 7 megatons, so that would be a 2 C temperature increase every week, which would be completely unsustainable. Presumably a lot of that goes to engines, which admittedly emit energy from the ship, but we don't really use those when grounded. Also maybe shields, but if those behave analogously to something like an electromagnet, they should only draw significant power when actually repelling something, otherwise, it's just based on resistance in the wiring, which means you're producing more heat.
And that's just 20kg of fuel, which is produced from about 1.5 tons of uranium ore. Admittedly, however, that's an unrealistically low amount of energy production for a nuclear reactor (only very tiny reactors generate that little. Big reactors are 100x that much or more, and consume proportionately more fuel), but if the reactor is bigger, the heat problem gets proportionately worse. And I'm pretty sure that assumes near-100% conversion of power to electricity, when the real % is more like 30-40. There's a reason nuclear plants are built by big rivers.
Also, the Wolfen being that big makes me wonder how much impact force it should have. 7 megatons moving at 100m/s (slightly faster than terminal velocity of a human, but feels like a lowball estimate: You'd accelerate to that speed in less than a kilometer of freefall, which seems pretty close), you'd be looking at 35TJ of energy, or about 9kt. That's about half of a small fission bomb. Presumably Lord Camelot just tells Newton's third law to eat it and makes most of that vanish, though (otherwise Mash would be very far underground). However, this also makes me realize that for the Wolfen to actually accelerate to a decent speed in space will take a lot of that reactor power I was hyping up as being a heat problem (Notice accelerating the entire thing to a mere 100m/s takes around 10kg of enriched uranium, and velocity requires quadratically more energy, so if you want to go 1 km/s (4 days to the moon), you need a full ton of uranium, then another to decelerate. Presumably gravity slingshots are a very important part of travel), so I can definitely see needing that generation capacity when accelerating. If you're not using it for that though, heat problems are significant.