Some, but CO2 is not the only concern here. Greenpeace is a broad-spectrum environmental campaign group. As I've commented elsewhere, I'm not inherently anti-nuclear, but cost is not the only issue. The political and institutional demands nuclear places on societies are substantial — and I don't see much evidence anyone has risen to them yet. Even big pro nuke places like France don't have fully funded schemes to decommission old nuclear plants. And in the US money taxed from generators has been corruptly spent on other things... Whether it's "fair" or not, this is a strike against nuclear because until we can safely decommission plants and store waste it's unproven tech and the costs (including externalities) are not fully known.