How likely is a Fukushima-style cooling-failure scenario after a huge tornado outbreak in the US?

I had a look at

http://www.fluther.com/87915/what-will-happen-when-an-f5-tornado-hits-a-nuclear-power/

which includes a discussion before the Fukushima accident. I think a new risk assessment must take the lessons learned into account.

Suppose a massive outbreak of tornadoes (like what we’ve seen over the past few days) including EF5 strength creates extensive damage. Suppose grid power is gone for several days. Suppose the backup diesel generators or the diesel tanks of a nuclear power plant are damaged as well. Suppose there’s a problem with the cooling water system because of the severe storm.

Can we really be sure that this doesn’t lead to a severe incident? The containment and the reactor core might withstand an EF5 tornado with wind speeds above 250 mph.

But what if cooling doesn’t work?

Can we really trust the nuclear lobby which still seems to be full of confidence? We know that the nuclear lobby has misled us before.

The United States averages about 1200 tornadoes per year.

How worried are you about nuclear power plants?

What about maximum credible accidents related to tornadoes?