I think their position is: 1) don't shut don't existing nuclear plants to replace them with fossil fuels and 2) wind and solar should make up the new energy mix. But for what it's worth, the membership has diverse views. I'm pro-nuclear.

CCL tends to be more pragmatic and have many more nuclear proponents.

Im very much pro science and have no strong feelings on nuclear either way but I havent quite understod the pro nuclear arguments. What are they? From the very very limited understanding about energy systems I have wind (and sometimes solar) seems to be more economic. And to complement wind and solar you need some type of power source which can be switched on and off depending on current weather and nuclear is not really suited for that. The energy simulations I’ve seen for my own country (Sweden) only shows nuclear as a small part of a future sustainable and economic energy system. But I’m really interested in the pro arguments.

There is really no "they". There are various not well defined groups pushing for some kind not well defined "Green New Deal". There are some who are anti-nuclear and some who aren't. The thing is, you can still use the momentum of GND to push for your preferred climate change mitigation action. You don't have to subscribe 100% to the ideology of someone else.

Science behind ideology, or ideology behind science?

If you look at sociology and anthropology, the evidence of the ability of human civilizations to handle problems with the time scale nuclear waste requires seems to be lacking. That the physics says it can be done safely does not prove that the other fields of science say it is likely to be done safely.

It's also important not to let the perfect be the enemy of the good. I agree that nuclear is a requirement to stemming climate change, but I still support the GND because it represents a lot of good steps in the right direction. We can always patch up the imperfect bits later.

Well, it advocated stopping travel by plane in favor of trains... which in terms of practically is almost literally insane. So, there was more wrong with it than just being anti-nuclear (which it was).