
SL-1: The only fatal nuclear reactor accident in US history - herendin
https://passingstrangeness.wordpress.com/2015/07/20/sl-1-murder-by-nuclear-reactor/
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MurMan
I was a power plant operator on a nuclear submarine. We were shown a
classified film that about the SL-1 incident as part of our training.
Recalling that film still gives me chills.

A lot was learned about reactor safety as result of that disaster.

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angersock
What else was in the film?

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MurMan
Nice try! :-)

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Animats
The SL-1 story is well known in the industry. The Atomic Energy Commission has
a video.[1] SL-1 was an experimental reactor at the National Reactor Testing
Station in Idaho, an 8000 square mile AEC reservation. It's an isolated area,
and the test reactors were many miles apart, just in case.

[1]
[https://www.youtube.com/watch?v=qOt7xDKxmCM](https://www.youtube.com/watch?v=qOt7xDKxmCM)

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timr
Here's another youtube video that goes more extensively into the mechanics of
the accident. It's pretty remarkable that they were able to work out the
position of the control rods, given that they were blasted around the room
during the accident, bent, broken and (in some cases) embedded in the ceiling:

[https://www.youtube.com/watch?v=phbaE_0LANc](https://www.youtube.com/watch?v=phbaE_0LANc)

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angersock
Or in the personnel:

 _Fifteen minutes later they found Legg, also dead—he had been impaled to the
ceiling by one of the plugs used to seal the unused control rod channels_

That's pretty metal, I've got to say.

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abecode
That part of Idaho is interesting to drive through. It's near craters of the
moon national park. The Idaho Nuclear Laboratory is pretty big. I remember it
being nearly 50 miles along one side of the road with all barbed wire fences.
It's pretty lonely and creepy out there. There was one cliff in Atomic City
that was covered with graffiti of large random numbers. It turned out that the
numbers were from high school graduating classes but the numbers weren't in
order so it seemed like some random code.

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stymaar
Fortunately, this reactor was moderated by water, so after the incident, all
the water was gone and the nuclear reaction stopped by itself. I don't want to
imagine what would have happened if the moderator was Graphite instead :/

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retrogradeorbit
"...killed by the only fatal reactor accident in US history."

Is that really true?

'“Nobody died at Three Mile Island” — unless you count babies.'

[http://www.counterpunch.org/2015/03/27/cancer-and-infant-
mor...](http://www.counterpunch.org/2015/03/27/cancer-and-infant-mortality-at-
three-mile-island/)

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rdl
Somewhat crazy, but: One more level of abstraction, and lots of people die at
nuclear plants _because they 're not built yet_ (or existing ones were
delayed, or in maintenance), due to the coal power which they would displace.

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InclinedPlane
Even weirder, the rates of cancer are higher around nuclear power plant
locations. Even when the plants haven't been built yet. Turns out, such things
tens to get built in old industrial areas that are already heavily
contaminated.

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HCIdivision17
This is going to be my go-to factoid on nuclear plant nimby-ism.

My uncle had an interesting experience in this vein. It was well understood
that high voltage power lines caused all manner of health issues, from cancer
to various degenerative diseases. He understood that EM radiation from the
lines really shouldn't be very dangerous, though, and didn't think much of the
leg of a line tower in his back yard. Then one day the power company came
through to clear out the underbrush growing around the base of the line's
tower. In just two days after the spraying all vegitation was _thoroughly_
dead. Turns out they spray an Agent Orange-like chemical to keep the towers
maintained from plant overgrowth. You can bet he moved shortly after noticing
that. (This was some years ago, and likely has been (hopefully) rectified.)

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anabis
Does the Demon Core count as a reactor?

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tyho
Yes it does:

[https://en.wiktionary.org/wiki/nuclear_reactor](https://en.wiktionary.org/wiki/nuclear_reactor)

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rosser
No, it doesn't.

The definition you're citing says, "Any _device_ in which a _controlled_ chain
reaction is maintained", emphasis added.

First of all, the Demon Core wasn't a "device", but a shaped lump of
plutonium, which briefly — and _accidentally_ — went super-critical. (Yes,
twice. And, yes, subsequently deliberately.) A "reactor" is the entire
assembly, not just the "hot" stuff.

Secondly, it wasn't exactly designed for _controlled_ criticality.

EDIT: corrections.

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tyho
It was controlled using a screw driver. What makes a device? For me 2
plutonium spheres and a screw driver rotated to adjust the gap counts.

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JohnGB
I find the term "accident" a somewhat meaningless distinction. Millions of
people have gotten cancer (statistically) from the radiation in the atmosphere
as a result of nuclear tests. Does it really matter that the tests were
intentional or not?

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pixl97
Well, mostly because it would make discussing anything difficult and
meaningless. And, in that case, if we wanted to talk about the about the
largest nuclear 'accident' involving the most deaths, we'd discuss coal
burning power plants.

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regehr
Pretty good book about this incident: [http://www.amazon.com/Idaho-Falls-
Americas-Nuclear-Accident/...](http://www.amazon.com/Idaho-Falls-Americas-
Nuclear-Accident/dp/1550225626/)

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infinotize
Whoa:

> In the split second it took for the rod to travel the remaining 8.3cm, the
> reactor spiked to 20 GW, 6300 times its safe operating capacity.

(Up from that days' configured power output of 3 MW, happened while operator
was lifting a control rod)

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gh02t
Yeah, the reactor went prompt-critical, which is pretty much the worst thing
that could possibly happen. In the reactor normally there's two classes of
neutrons present - "prompt", which are emitted directly from fission, and
"delayed", which are secondary neutron emissions from decay of fission
byproducts.

Prompt neutrons are emitted on a very very short timescale and so if the power
were controlled solely by them it'd be impossible to control a reactor because
any change in the control rod position would cause an extremely rapid change
in the power. Instead, reactors are designed to be subcritical considering
only prompt neutrons and then be made critical via the remaining delayed
neutrons. This extends the reactor period (time it takes for the power to
change by a factor of exp(1)) from milliseconds to minutes.

However, if there isn't enough control material in the core that the
proportion of prompt neutrons is enough to make the reactor critical by itself
then it goes "prompt critical" and exactly what happens in the article occurs.
Reactors are _supposed_ to be operated with enough margin that this won't ever
happen (which isn't that difficult), but it sounds like they were deliberately
operating right on the limit, which scares me.

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stymaar
Interesting explanation thanks !

However, I think you made a mistake (probably a typo but I think it's worth
noting it to avoid confusion of other readers) in that sentence: “However, if
there isn't enough control material in the core that the proportion of FAST
neutrons is enough to make the reactor critical”.

Prompt neutron (short time between fission and neutron emission) should not be
mistaken with fast neutron (high kinetic energy, see
[https://en.wikipedia.org/wiki/Neutron_temperature](https://en.wikipedia.org/wiki/Neutron_temperature))

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gh02t
Oh, you're right. I know the difference, just a typo. I corrected it.

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hudibras
For what it's worth, I like the original title on the article better.

