Nuclear should be considered part of clean energy standard, White House says

I hope that the federal government can provide incentives to keep reactors running that would otherwise close prematurely.

5.1 gigawatts of American reactors are expected to retire this year: https://www.eia.gov/todayinenergy/detail.php?id=46436

It's a shame that the US is retiring working reactors while still burning fossil fuels for electricity. Reactors are far safer and cleaner than fossil electric generation. It's mostly the low price of natural gas that is driving these early retirements. Low gas prices have also retired a lot of coal usage -- which is good! -- but we'd make more climate progress if those low prices didn't also threaten nuclear generation.

Some states like New York already provided incentives to keep reactors running for climate reasons:

https://www.eia.gov/todayinenergy/detail.php?id=41534

Federal policy could be more comprehensive.

About Iowas Duane Arnold plant that is being closed:

"The Mark I containment was undersized in the original design; the Nuclear Regulatory Commission's Harold Denton estimated a 90% probability of explosive failure if the pressure containment system were ever needed in a severe accident.[18] This design flaw may have been the reason that the tsunami in 2011 led to explosions and fire in Fukushima Daiichi nuclear disaster.[19]" (Wikipedia)

It's likely that many old power plants are just not safe and too costly to operate reliably.

The follow-on question is why aren't these plants retrofitted to be secure? I'd somewhat naively expect that its simpler to upgrade an existing plant than permit a new plant in.a separate location.

Each plant is unique, and not perfectly understood. Often the people that did understand it have forgotten, died, moved on, etc.

Understanding, improving, testing, and certification of a plan to protect against the huge risks involved is expensive and often in practice timelines and budgets often go significantly over.

There's numerous MUCH newer designs that: are much smaller, much easier to scale, absolutely identical, well understood, robust in the face of failure, and don't even need operators. Additionally since they are identical they get economies of scale and only need a finite number of experts on hand, not a group of them per site. You literally need a flat site, water, and electrical hookups. If you don't provide enough water for cooling they shut down. After their useful service life you put them back on a train car and ask for a replacement.

Some of these projects are ready to deliver, but the early customers have been cancelling. Bill Gates funded a project, and there's several around.