Not sure why this is regarded as "leakinng badly" though...
Six tanks leaking at rates of a few to a few hundred gallons PER YEAR doesn't seem like a serious leak.
The problem should definitely be dealt with, but we're talking replacing only six tanks (each holding "tens of thousands of gallons" (not "millions") of radioactive wastes), pumping the old tanks' contents into the new tanks, then disposing of the old tanks and cleaning up under them to the extent that's practical.
In other words, TFS blows the problem up to sound much bigger and scarier than it actually is. But what else is new?