Even if solar and storage do actually turn out to be cheaper in the long term, that isn't the same thing as destroying the full amount of money you put into a nuclear plant. The amount of money you're out is only the difference between the initial cost and the price you can sell electricity at in competition with solar and storage. You could plausibly get back less than you put in but still get back 90% of it.
And if that does happen, there is a good reason for it, which is that we're not actually sure that solar and storage will make it to that point, and there's a non-trivial chance that they don't. Or even if they do eventually, that they don't do so quickly.
If we get a significant carbon tax before the existing fossil fuel generating plants are decommissioned then the price of electricity is going to rise significantly until their capacity is replaced. That could take 20 years or more. In the meantime that nuclear plant is more than paying for itself -- it could pay off its full capital cost in that time at the higher generation price -- so that by the time solar and storage gets cheaper the nuclear plant only has to cover its operating cost and continues to be cost competitive for the remainder of its operating life.
It's basically a speculative investment against the chance that solar and storage don't get cheaper fast enough. You could lose some money, or you could win big if we get a carbon tax and the storage technology comes up short for a long period of time. Which also makes it a good hedge against investments in storage technologies.
And if that does happen, there is a good reason for it, which is that we're not actually sure that solar and storage will make it to that point, and there's a non-trivial chance that they don't. Or even if they do eventually, that they don't do so quickly.
If we get a significant carbon tax before the existing fossil fuel generating plants are decommissioned then the price of electricity is going to rise significantly until their capacity is replaced. That could take 20 years or more. In the meantime that nuclear plant is more than paying for itself -- it could pay off its full capital cost in that time at the higher generation price -- so that by the time solar and storage gets cheaper the nuclear plant only has to cover its operating cost and continues to be cost competitive for the remainder of its operating life.
It's basically a speculative investment against the chance that solar and storage don't get cheaper fast enough. You could lose some money, or you could win big if we get a carbon tax and the storage technology comes up short for a long period of time. Which also makes it a good hedge against investments in storage technologies.