Ask your Representative or Senator to co-sponsor or support the Energy Innovation and Carbon Dividends Act (H.R 763 and S. 3791)

The primary reason for US nuclear plant closures and lack of new reactor construction is that nuclear is now slightly more expensive than competing fossil (mainly gas) generators.  However, this is due to the fact that fossil generators are allowed to release massive amounts of CO2 and other harmful pollutants directly into the environment for free.  Given that clean air and reducing global warming are things of significant, tangible value, this is a significant market failure.  If this market failure is corrected by placing a price on CO2 emissions, nuclear plant closures would stop, and building new reactors would be a far more attractive option.

The Energy Innovation and Carbon Dividends Act places a significant and steadily rising fee on fossil fuels at the point of extraction or import (based on how much CO2 they would emit when burned), and returns all the collected money back to the people.  Thus, it increases the cost of using fossil fuels (and in turn, fossil power generation) and lets the market decide how to respond.  It is a technology-neutral policy which gives all means of emission reduction (including nuclear) the same level of support. That, as opposed to having the government decide how to reduce emissions and pick winners and losers, based on political considerations (which often acts against nuclear).

For the above reasons, this policy will help nuclear more than any other policy that has come along.  Furthermore, it helps nuclear (to the same degree as renewables, finally!) w/o being specifically about supporting nuclear.  That allows the policy to attract a much wider range of political support than overtly pro-nuclear policies. Many people who are not supportive of nuclear support the idea of carbon pricing, and letting emissions reduction options compete on a fair playing field.

More info here: https://citizensclimatelobby.org/energy-innovation-and-carbon-dividend-act/