I came across the article 'Don't make the mistake we did': Fukushima survivor to Queensland, which mentions the Japanese organization Peace Boat (Wikipedia, official website) opposing uranium mining in Australia. The Brisbane Times described the organization as a "disaster relief organisation", but a brief look at the Wikipedia article and their home page suggests that they're primarily an anti-war organization, with a bit of environmentalism thrown in. They have provided some help to those affected by war and by the Tohoku earthquake and tsunami (Japanese language Wikipedia link), though.
What I suspect, but is probably beyond the scope of this stack exchange, is that Peace Boat is mainly opposed to nuclear power because it makes it easier to build nuclear weapons, and that the Fukushima dai-ichi accident is merely being used as a supporting argument for a position it already held.
What I would like to know is whether it is or was common for anti-war groups to oppose nuclear power, even when they aren't politically active on any other environmental issues.