[virtue3]

https://en.wikipedia.org/wiki/Three_Mile_Island_accident

We got super super lucky. And there's some debate about how bad the accident was with regards to NRCs monitoring.

Frankly, the whole plant was a disaster in the making. There was tons of warning lights and other systems but they were essentially useless because they constantly flashed and for poorly understood reasons.

3mile island is an excellent engineering study of what not to do with monitoring. We got very VERY lucky it was as small as it was.

[garmaine]

Sure, all of which are problems which we've since fixed. But the core point is that there wasn't a major release of radiation like Chernobyl, and the reason why is because there were a regulator-imposed safeguard in place: the containment building.

There were a lot of things that went wrong in 3MI. Many of the lessons learned from that were incorporated into future designs. But one thing that went very right was that there was defense in depth, so that a N different things would have to go wrong to create a nuclear disaster. And in this case the number of failures was less than N. That's an engineering and regulatory success story.

[ncmncm]

"Wasn't a major release" meaning what?

A large amount of radioactive krypton gas was "vented", meaning it was released to spill down to the river and gas anyone who lived nearby. There was no tracking, so we don't know who or how many were exposed, or how much.

[garmaine]

We can certainly ballpark estimate how much gas was vented--we knew the pressures and duration of the vent.

But this is a night-and-day comparison with, say, Chernobyl where the core was exposed and burning unmitigated for nine days. Many more orders of magnitude more release of radiation.

[ncmncm]

Everybody agrees Chernobyl was the worst. But that doesn't mean the others were picnics. A common thread is systematically discounting harm to people exposed. With such pervasive dishonesty throughout the industry, rigorous oversight has proved impossible, in practice.

The nuke navy is always cited as having no incidents, but that doesn't pass the smell test. Military failures are easily classified and buried.

[sir_bearington]

There was no luck about it. It was a meltdown, and the pressure vessel was compromised. Secondary containment saved the day. Three Mile Island didn't become a Chernobyl not because of luck, but because the US didn't cheap out and skip building concrete condom over the reactor like the Soviets did.

[Covzire]

Even if Chernobyl would have had a containment vessel, what would have been the best case scenario? I'm not an expert but the blast threw the multi-ton slab of steel and concrete lid into the night sky, surely the containment vessel would have had a giant hole in it, albeit saving some of the radiation from the atmosphere of course but not all of it. One reason I think Three Mile Island wasn't as bad is because nobody in the west was crazy enough to build an RBMK.

[sir_bearington]

The whole point of the containment building is to contain a pressure vessel failure. American containment buildings are built to withstand impact of a fully loaded passenger airliner. That's why the containment vessels are reinforced concrete more than a meter thick.

If Chernobyl had secondary containment, the burning fuel rods would not have been exposed directly to atmosphere. Basically, if you have a fire emitting toxic soot it's a lot better to have this fire happen in a concrete dome versus totally exposed.