canduene krever vel minst like store reaktortanker? Vertfall på designen av selve kjernen?
Siden tungtvannet er dårligere på moderering enn lettvann.

Fra wikiepedia:
Since heavy water is less efficient than light water at slowing neutrons,[13] CANDU needs a larger moderator-to-fuel ratio and a larger core for the same power output. Although a calandria-based core is cheaper to build, its size increases the cost for standard features like the containment building.