Nuclear is cheap in Illinois because Exelon, the company that runs the Nuclear plants, bribed the state to give their plants subsidies. https://www.bizjournals.com/chicago/news/2020/11/19/ex-comed...
And given that construction is so expensive, it ruins the economic case for building new nuclear plants (imho).
In this graph you have the marginal cost of traditional generation compared to total cost of new built renewables.
https://www.lazard.com/media/451885/grphx_lcoe-07.png
From Lazard Levelized Cost of Energy 2021.
https://www.lazard.com/perspective/levelized-cost-of-energy-...
I didn't find all that much to go on. Aside from a French Court of Audit report in 2012, this information seems to be mostly non-public? Anyway, it looks like the answer is staffing and maintenance. It seems to be common for nuclear power plants to employ 500 to 1000 people. Fessenheim in France employed 700 people at the time of its closure, plus an additional 600 to 2000 during maintenance (per Wikipedia).
Meanwhile, nuclear seems to be very technically complicated with a bunch of weird Advanced Physics-y shit that can go wrong. Like, water pipes exploding because the nuclear radiation caused water molecules to split up by radiolysis and a design flaw allowed the hydrogen to collect somewhere. Or borated water eating through steel.
And now that I type this, it occurs to me that you can't just turn off the plant for safe maintenance work -- inside the dome is always going to be irradiated and probably require hazmat suits.
And, as you alluded to, nuclear plants use the steam based thermodynamic cycle but run cold because they have to maintain water in a liquid state while absorbing heat from the reactor. The power achievable from the Carnot cycle depends on the magnitude of the temperature difference: nuclear plants run at 300° C, coal plants about 570° C, and CCGT at 1000° C up to 1500° C.
"Study of Equipment Prices in the Power Sector"
https://esmap.org/sites/default/files/esmap-files/TR122-09_G...
From table ES3 we can see that steam based plants are expensive in pure equipment costs. Which makes sense comparing a tiny gas turbine giving direct mechanical force. Then you can use the waste heat for steam generation if that makes sense in your location.
Comparing this to coal and nuclear plants huge boiler and turbine setup with about the same output. Nuclear adding even more complexity of different loops and safety requirements.
Haven't dug deeper into that report than the executive summary though.
Admittedly you need much less storage (until a tsunami comes along). But pumped storage only costs around $1/watt. (The unit of $/watt rather than $/kWh because the dam is only a minor fraction of the cost of pumped storage, and it drops quadratically with size.) Storage + renewable generation still costs less than 1/2 of nuclear.
https://en.wikipedia.org/wiki/Base_load#Description
It is a straight LCOE shoot out. Storage may help at the limits but is a pure loss from a system perspective.
> After three days and 64 rounds of bidding, the U.S. Department of the Interior Bureau of Offshore Energy Management (BOEM) on Friday concluded the nation’s highest-grossing offshore energy lease sale ever, with winning bids from six companies totaling approximately $4.37 billion.
> Not only does the amount raised in the New York Bight lease sale far exceed the more than $400 million raised during the previous offshore wind sale in 2018, it even surpasses the highest amount raised during any offshore oil and gas lease sale ever in U.S. history.
> The results are a major milestone in the Biden-Harris administration’s goal of reaching 30 gigawatts of offshore wind energy by 2030.
https://gcaptain.com/new-york-bight-offshore-wind-lease-auct...
I got one news article that said they gave nuclear $130 millions each year in 2019, but then other sources say it is a number between $19 and $52 millions. Then in 2021 I find an article that they increased subsidies for renewables by an additional $350 millions per year. In one article that the total subsidies to build new solar and wind has a total of $600 millions per year. An other said that the total of subsidies for renewables are well above $1 billion per year. I couldn't find an article that estimates Illinois fossil fuel subsidies, but one said that the US spend around $20 billions per year.
Naturally each article want to either inflate or deflate those numbers to drive a political point, so it would be nice if anyone could bring some authoritative numbers that give the exact number of what Illinois actually spend in terms of energy subsidies.