Why you don't mess with a nuclear weapon core

[MartG]

Interesting article about an accident with the core of a nuclear weapon

http://www.newyorker.com/tech/elements/demon-core-...

[Zod]

Interesting. Thanks.

[anonymous-user]

Right,

Don't mess with a nuclear weapon core.

That's added to my list of things not to try.

[MartG]

Movie recreation of the incident

https://www.youtube.com/watch?v=AQ0P7R9CfCY

[veccy208]

Pretty Interesting and scary stuff. So the 'pit' wasn't radioactive at all until it was activated?

[Top Banana]

veccy208 said:

Pretty Interesting and scary stuff. So the 'pit' wasn't radioactive at all until it was activated?

the pit was already radioactive, but changing the configuration made it go 'prompt critical' which effectively means for a split second it becomes intensely radioactive but not fully 'critical'

[rhinochopig]

It's not mentioned in the article, but IIRC, Slotin was instrumental in documenting the process of his demise to further the understanding of Radiation exposure.

ANother famous accident was SL-1 which had a far more gruesome outcome because the control rod pinned one of the operators to the ceiling when it was ejected following a prompt criticality.

This is how they had to move the body...the body is in the white bag at the end of the crane.



Full pictures and story here...

http://www.radiationworks.com/photos/sl1reactor5.h...

[veccy208]

Top Banana said:

veccy208 said:

Pretty Interesting and scary stuff. So the 'pit' wasn't radioactive at all until it was activated?

the pit was already radioactive, but changing the configuration made it go 'prompt critical' which effectively means for a split second it becomes intensely radioactive but not fully 'critical'

Ok, the reason I ask is, were these scientists getting dosed with radioactivity just by being near the pit, whether it was being prompted or not.

Sorry for being a bit thick but I've never understood what way these elements occur naturally/what state nuclear cores are in. Do they just spew all the time only in less quantities?

[Fugazi]

veccy208 said:

Ok, the reason I ask is, were these scientists getting dosed with radioactivity just by being near the pit, whether it was being prompted or not.

Sorry for being a bit thick but I've never understood what way these elements occur naturally/what state nuclear cores are in. Do they just spew all the time only in less quantities?

Interestingly, some geologists have recently found that self-sustaining fission reactors have been occurring naturally due to build ups of Uranium ore and these reactions where going on for a few hundred thousand years.

[anonymous-user]

el stovey said:

Right,

Don't mess with a nuclear weapon core.

That's added to my list of things not to try.

Mine too!!

[otolith]

veccy208 said:

Sorry for being a bit thick but I've never understood what way these elements occur naturally/what state nuclear cores are in. Do they just spew all the time only in less quantities?

The nuclei of the atoms of plutonium-239 are unstable. They spontaneously decay. They do this in several ways. One way in which they decay is to spit out an alpha particle and decay to uranium-235. This happens at a constant background rate. Alpha radiation interacts strongly with matter. This means that it doesn't penetrate much very far - a few centimetres in air, not far enough into skin to hit anything important. The downside of this is that if an alpha emitter actually gets inside you, it can do a lot of damage - so plutonium dust, sat in your lungs, is very likely to give you cancer.

Another way in which they decay spontaneously, which makes them of interest for nuclear weapons, is to split into two or more smaller nuclei, spitting out some neutrons and releasing some energy in the process. If those neutrons collide with other plutonium nuclei, they may also split, colliding with more and more and more... In a small lump of fissile material, most of these neutrons will escape without hitting anything and you won't get a self sustaining chain reaction. If you use a bigger lump, or you surround it with reflectors to bounce the neutrons back in, or you use high explosives to increase the density of the lump, or you use another nuclear reaction to generate a blast of fast neutrons, or all of the above and a few more wrinkles, you get a massive release of energy - an atomic explosion.

Slotin had a sub-critical lump of plutonium which was sat there spewing out alpha particles and the odd neutron and not really bothering anyone. He accidentally surrounded it with neutron reflectors. It started to approach the point of a self-sustaining fission chain reaction, and as a result the amount of radiation it was generating was massively increased - lots of neutrons, lots of gamma rays. It was never going to explode, it's not that easy to detonate an implosion type of device, it was just going to get very, very hot and very, very radioactive.

[rpguk]

I read an interesting article on the Goiânia accident recently. I'll try and dig it out but it's basically the story of a bit of radioactive material from an x-ray machine that ended up at a scrap dealers. Quite a few people came to see it and it didn't end well for them.

Edit to add - I think it was the wikipedia page I read - https://en.wikipedia.org/wiki/Goi%C3%A2nia_acciden...

[Halmyre]

rpguk said:

I read an interesting article on the Goiânia accident recently. I'll try and dig it out but it's basically the story of a bit of radioactive material from an x-ray machine that ended up at a scrap dealers. Quite a few people came to see it and it didn't end well for them.

Edit to add - I think it was the wikipedia page I read - https://en.wikipedia.org/wiki/Goi%C3%A2nia_acciden...

Spine-chilling.

[Guvernator]

Wow you learn something new every day. Initiating a nuclear reaction by hand? Really?? I realise it all had to start somewhere but I didn't know this was a thing. At any rate how did they persuade people to do this? I don't think any amount of money or patriotism would make me want to do that job.

I assume they were somewhat aware of the dangers or was this in a time when they didn't fully understand it? I guess if you are merrily setting off test nukes left right and centre, poking one with a stick doesn't seem so bad.

[otolith]

Guvernator said:

Wow you learn something new every day. Initiating a nuclear reaction by hand? Really?? I realise it all had to start somewhere but I didn't know this was a thing. At any rate how did they persuade people to do this? I don't think any amount of money or patriotism would make me want to do that job.

Even setting aside the war effort, I think you could probably explain it with simple curiosity. I think you'd still have people queuing up to work on the LHC even if it was a bit dangerous and killed the odd physicist. Would probably even attract some people. Also, the experiment Slotin was demonstrating was not intended to go prompt critical, he wasn't following protocol, he fked up.

[Guvernator]

otolith said:

Even setting aside the war effort, I think you could probably explain it with simple curiosity. I think you'd still have people queuing up to work on the LHC even if it was a bit dangerous and killed the odd physicist. Would probably even attract some people. Also, the experiment Slotin was demonstrating was not intended to go prompt critical, he wasn't following protocol, he fked up.

Scientists largely understand the LHC, even then there were scaremongering stories in a lot of papers about it creating a black hole.

I know Slotin didn't mean to start a nuclear reaction but sticking your hand\screwdriver in a nuclear core just seems very naive to me but I guess it was the start of the atomic age and they were very different times. Could you imagine H&S letting you try something like that now?

[otolith]

Close to. Not that close!

They did stop those manual criticality experiments after that incident, but in the early days they were racing against time with lots of lives on the line.

[hairykrishna]

Guvernator said:

I assume they were somewhat aware of the dangers or was this in a time when they didn't fully understand it?

He was fully aware and I'm sure at first he was extremely careful. He had just done it a load of times before so got a bit too casual about it. Story of many an industrial accident.

[Einion Yrth]

hairykrishna said:

He was fully aware

Not least because that core had already killed Harry Daghlian in a criticality accident.

[maffski]

otolith said:

Close to. Not that close!

They did stop those manual criticality experiments after that incident, but in the early days they were racing against time with lots of lives on the line.

Except if they'd just lifted one part up to the other rather than lowering it down it would have been fail safe.