Not really a regionally significant nuclear accident then. About the same as a gas leak?
In any case the primary expense is going to be one of paying off all the people to get the right approvals. Crunching the numbers on how to safely rectify it and actually going through those actions will be dirt cheap compared to getting someone with the "right credentials" to tell the government, the insurers and whoever else that your obvious solution any highschooler can crunch the numbers on is in fact acceptable
[1] https://www.hemmings.com/stories/2017/10/17/misunderstood-ca...