Except it's not a capital cost, it's collected over the life of the plants as part of the rate paid.
Say for example, Diablo Canyon OPEX is $0.038/kWh, but rate paid is $0.040 as it includes a $0.002/kWh rate rider for decom and post-operation fuel management. That sounds tiny, right?
Diablo Canyon is ~2,400MW. Assuming CF is in-line with the rest of the US fleet at ~93%, that's 19.6TWh/year; 19.55 billion kWh. That means that $0.002/kWh rider yields $39 million/year. Assuming a 60 year lifespan (most US reactors are licensed for 60 years, a couple 80 years now), that's $2.35 billion in the decom fund, which is invested and produces a yield over the life of the plant as it accrues, which is how we ended up at $20 billion for ours in Ontario.
Pretty sure the plant falls under a given companies capex?
Someone has to make the capital commitment to the plant.
Operating license timeframe does not equal time in operation - back to san onofre.