I don't like commenting on things I know only a little about, however, one thing is getting overlooked when people make this argument.

The newer designs are usually PWRs which are stable by design as loss of water or power slows down the reaction. Unfortunately, they are expensive to build (billions of dollars) and have a limited life due to the challenges of containing pressure with metals exposed to radiation. This makes them barely economic over their lifetime at todays energy prices.

The UK has allowed the planning and building of new PWRs. Unfortunately, the companies involved are reluctant to go ahead without some sort of subsidy or carbon tax.

If any of the above is wrong, I'd like to be corrected. However, I feel this is a valid point that is rarely made.