Nuclear fission is a powerful phenomenon. When the conditions are right, atomic nuclei split, releasing neutrons that then split other nuclei in an ongoing chain reaction that releases enormous amounts of energy. This is how nuclear weapons work. In a more stable and controlled fashion, it’s how our nuclear reactors work too.
However, these chain reactions can also happen accidentally—with terrifying results. Though rare, criticality incidents – events where an accidental self-sustaining nuclear chain reaction occurs – serve as sobering reminders of the immense and unwieldy forces we attempt to harness when playing with nuclear materials.
Too Much Already
A criticality incident is when a nuclear fission chain reaction is caused by accident. The cause is usually quite simple. When it comes to fissionable material, like radioactive isotopes of uranium, there is a certain critical mass at which a chain reaction will occur. At this point, the natural radioactive decay of the material will release enough neutrons such that one might strike and split another atom. This then releases further neutrons, which split more atoms, and the chain reaction continues.
Calling it critical mass is a simplified way of saying it. More realistically, the critical mass depends on more factors—the shape of the radioactive material plays a role, too. As does the presence of any neutron reflectors that could bounce neutrons back towards more atoms to split.
Long story short, if you put too much fissionable material in one place, you’re asking for trouble. If it gets to that critical point and the chain reaction starts, it’s going to release a ton of radiation in a split second.
The most famous example of a criticality incident occurred when Louis Slotin was working with the Demon Core at Los Alamos back in 1946. The story has been told many a time, including on these hallowed pages. Start there if you’re curious, before we look at some more recent disasters.
America’s nuclear program hasn’t just had one awkward mistake like this. It’s had a few. One of the most serious criticality accidents in history occurred on December 30, 1958, once again at the Los Alamos National Laboratory in New Mexico. Chemical operator Cecil Kelley was processing plutonium-containing liquids in a large mixing tank as per his regular duties.
The tank was used for recovering and reusing plutonium solutions from various experiments, and was expected at that time to contain less than 0.1 grams of plutonium per liter of solution. Unbeknownst to Kelley, the tank actually held a far greater quantity of plutonium—over 3 kilograms—due to improper transfers of waste materials to the tank. The fluid in the tank wasn’t homogenous, either—there was a denser layer of aqueous solution at the bottom, topped with a lighter layer of organic solution which contained more of the plutonium.
The tank was already close to a critical state at rest. When Kelley switched on the mixer inside, the blades formed a vortex, pushing the dense aqueous layer of fluid outwards. In turn, the more plutonium-rich organic fluid was drawn to the center of the vessel, where it promptly went critical.
As Kelley stood on a ladder viewing the mixing tank, there was a sudden bright flash of blue light. A huge surge of neutron and gamma radiation flooded the room, delivering Kelley a lethal dose in a split second. His death was harrowing, and he passed away just 35 hours after the accident. While investigations were undertaken into the matter, there has never been a public explanation for how the excessively high concentration of plutonium ended up in the tank.
Fast forward to 1999, when carelessness caused a similar incident in Tokaimura, Japan. At a uranium processing facility, technicians were tasked with preparing a batch of fuel. Official regulations mandated that a uranyl nitrate solution be stored in a buffer tank, and added to a precipitation tank in controlled increments. However, as per a company operations manual that was unapproved by regulators, technicians were mixing chemicals in stainless steel buckets instead, rather than using the buffer tank that was designed to prevent criticality incidents. The crew were pouring the liquid directly into the precipitation tank, which had a cylindrical geometry that was favorable for inducing criticality.
The tank soon ended up with over 16 kg of uranium inside, well over the 2.4 kg limit set by regulators. As the seventh bucket was added, the tank went critical with a bright blue flash. Radiation alarms wailed as neutron levels shot up to 15,000 times normal. Three technicians received extreme radiation doses with severe ill effects; two of the three later died. The facility was irradiated, with residents in surrounding areas having to evacuate in the immediate aftermath.
Much like the Los Alamos event, the cause of the problem was simple. The technicians simply combined too much fissile material in one place.
CRITICALITY (1969) is a British documentary on the danger of criticality incidents, and how to avoid them. If you work with nuclear materials, you’ve ideally been educated with something more up-to-date. Still, the basic physics was well-understood back then, and the lessons here largely ring true today.
Los Alamos suffered an embarrassing incident in more recent times, too, though thankfully a near miss. Back in 2011, technicians had arranged a number of plutonium rods on a table in order to take a photo—the intent being to celebrate their successful production. A supervisor returning to the area noticed the close assembly of the rods and quickly instructed they be separated, lest a criticality incident occur. Disaster was averted before the dreaded blue flash occurred, but it was yet another harrowing example where fundamental safety rules around criticality had been ignored.
Lessons
So what can these unfortunate incidents teach us? Strict limits and controls on fissionable materials are key. Standard procedures that control the flow of fissionable material are important to achieve this. The Tokaimura incident showed how bypassing these protocols even briefly can be disastrous. Beyond that, it’s important that those working with these materials are cognicent of the risks at all times. Even something as simple as bringing together a few rods to take a photo could cause a major incident through carelessness.
But perhaps the biggest lesson is respecting the sheer power of fission itself. When a chain reaction starts, things go wrong fast. By the time the blue flash has told you something’s happened, it’s all too late. Radiation levels have spiked through the roof and the damage is done. There is no early warning sign in these cases. Proper procedure is the only real way to avoid disaster.
Fssion remains a fickle phenomenon that is not to be trifled with. When we do trifle with it, either by honest accident or gross negligence, the results can be swift and brutal. Each of these criticality incidents was a stern reminder to humanity to maintain the utmost vigilance and safeguards when working with fissionable materials. Failure to do so always ends up the same way.
I guess I really should restack those boxes.
Do you think this could easily generate over 1.21 giggawatts? Asking for a friend, this old dude down the block. Although come to think of it I haven’t seen him in a while.
Sure would be intimidating to have a DeLorean with 1.3 million horsepower under the hood
Dad was a witness to a Richard Feynman visit to Oakridge during the war. Feynman was shown a warehouse where product was being stored. He suggested that the stacks be lower and separated at twice the distance they were then arrayed at. He got some kickback from on e of the local military types that if what Feynman had suggested was done, the warehouse wasn’t big enough.
I can’t remmber how this was resolved.
Once again hit “report” instead of reply. Sorry, mods.
Feynman mentions an incident that sounds like that in his book, although I think he talks about carboys of solution being up against a wall, which doesn’t sound exactly like a warehouse.
Apparently he ended up having to get permission to give the Oak Ridge people more information about why they had to separate the stuff, because they didn’t know about the whole criticality thing at all. If I remember right, he also got permission to say “if Oak Ridge doesn’t separate this stuff, Los Alamos can’t be responsible for what happens”.
Pretty sure they separated the stuff in the end, since they didn’t all die.
I heard the story when I was in high school, 1959 so memory is probably defective.
Also recall that story. Array of well spaced drums in a room, some up against a wall. Feynman asked what was on the other side of the wall. Drums were moved away from BOTH SIDES of the wall.
That is the part I remember.
Years ago I visited the Hanford B reactor in Washington state (which is now open for tours under the National Park service – you should go if you’re ever in the neighborhood)
There is an area behind the reactor where the spent fuel rods get pushed out the back and fall directly into a pool of water where they get a few days to decay to a reasonable level. Then they are fished out and moved to a large dry storage area for further decay to a manageable point.
Both the pool floor and the racks in the storage area have geometry that enforces an extremely inefficient amount of space between the rods
I have worked in a fuel basin of a neighboring reactor of B Reactor getting it ready for demolition. It was an adventure walking out over a grating suspended above a pool full of radioactive debris.
Dr Manhattan says it’s all fine.
That picture at the end of the article is absolutely haunting/perfect. The caution tape and the sharpie for scale…
“Beyond that, it’s important that those working with these materials are cognicent of the risks at all times.”
Unless one of those working with these materials has suicidal tendencies. Then it might be better if they were NOT cognicent of the risks. :P
They say it’s the worst possible way to die.
The faster cells divide the faster radiation affects them.
So.. your nervous system is alive, fairly healthy and active as your body dies around it resulting in days of agony.
Don’t commit suicide. But if you do anyway this is not the method you are looking for.
‘Western’ attitudes!
Will lazy roundeyes improve the efficiency of fuel reprocessing by improving transfer methods using buckets?
No they won’t!
RIP hard working Japanese fuel reprocessers.
Actually that was manufacturing fuel and not reprocessing it.
The word you were looking for was “fissile.” While fissile material is also fissionable, piling up large amounts of fissionable material like U-238 is just fine.
https://en.wikipedia.org/wiki/Fissile_material#Fissile_vs_fissionable
This. Lots of isotopes are fissionable but very few are fissile (able to sustain a chain reaction). Fissile isotopes emit more than one neutron when they fission.
“When the conditions are right, atomic nuclei split” I’d be interested in hearing more about these conditions. It’s always been my understanding that atomic nuclei split all the time, willy nilly.
“If you see someone arranging nuclear materials like this for a quick photo, you’d be well advised to tell them to stop.” They were already told in training. You’d be well advised to di di mau out of the AO. It’s just like firearms safety: if someone ignores the rules you need to put a whole lotta gone between you and them.
Those Japanese guys reeeeeaaaaallly screwed up. I’ve worked in a lab, biochem, not nuke, and even there safety really is Job #1.
Well, they like to split if you can convince them to eat something they don’t like, or if you can wobble them around until they get dizzy, or failing that knock their block off.
“When the conditions are right, atomic nuclei split” I’d be interested in hearing more about these conditions. It’s always been my understanding that atomic nuclei split all the time, willy nilly.
“If you see someone arranging nuclear materials like this for a quick photo, you’d be well advised to tell them to stop.” They were already told in training. You’d be well advised to di di mau out of the AO. It’s just like firearms safety: if someone ignores the rules you need to put a whole lotta gone between you and them.
Those Japanese guys reeeeeaaaaallly screwed up. I’ve worked in a lab, biochem, not nuke, and even there safety really is Job #1.
You should change your name to “I Alone Post Twice” ;)
It’s Hackaday Jake. Seriously, I’m not doing it. And it happens with other posters here as well. A good website detects and does not allow duplicate posts. I’d apologize but it’s not my fault.
“Good men don’t need rules. Today is not the day to ask me why I have so many.”
is there a proximity joke extractable from this?
Have not heard that expression in a long time…. a long time….
(for those youngin’s “di di mau” / AO ….. Vietnamese for hurry up , AO = Area of Operation)
S.E. Asia ’68-’73
USMC (ret).
My favorite expression for “Go away” was “Un-ass my AO.”
Thanks for explaining that.
When I had a summer job at Savannah River, I had to take a class on how not to accidentally make a critical mass. One of the things they did in the area I worked was that they have zone that limit the amount of radioactive material in them. This was so that even if every zone that met at a corner put all their material in the corner, you still wouldn’t have enough for a critical mass.
“man dies” AND “wind turbine” returns more examples of deaths in the last 10 years than all of the criticality deaths of the last 80. Lessons were learned.
And deaths from burning carbon fuels are basically uncountable.
Yes, they need to fix safety, but Despite all the screw-ups, it’s still one of the safest ways to make power.
I’ve stood 30 feet over a reactor ( NCSU’s Pulstar), looked down, and seen the Cherenkov radiation. I’m pretty sure if I tried that with a Babcock and Wilcox coal-fired boiler, I would have died. :-)
Unless the B&W was under 30 feet of water, in which case it wouldn’t have stayed lit, but you know where I’m going with this.
If you ever get a chance to tour a reactor room, jump all over it. Cancel whatever appointments you have; skip class if you have to (You: “Reactor tour.” Faculty: “That’s an excused absence – and I’m supremely jealous. Damn you. You should have invited me.”)
What about a nuclear fusion facility?
yes, they are more deaths because there are more wind turbines than there are nuclear reactors/stockpiles in the world. I could also mention “research bias” here but I feel the point is moot.
It’s amazing how some people here want to make everything into an argument.
No we don’t !
B^)
I think the two criticality incidents above Nagasaki and Hiroshima might have killed more than wind turbines, but I’m not going to check
Chornobyl killed ~5000?
See M102 Birdcage
Back in the 80’s, I maintained a lab management computer system (HP3000) located at Argonne National Labs outside Chicago. Every lab room had a white board on the door with the (assumed) mass of plutonium in the lab. Add when you take a sample in, subtract when you take a sample out.
The best part was the safety briefing we got on arrival. The guard pointed out a big, red bell on the wall and told me that was the fire alarm. If I heard it ring, move as quickly as I could to the nearest exit. He next pointed out a big horn, and explained that was the criticality alarm, and I had a couple of options if I heard the distinctive ‘ah ooh gah’ sound. One, I could run as fast as I could in any direction, or two, I could sit down and kiss my a** good by. Either one was equally effective. Luckily, I never heard either.
I’m sure they would have thought of this, but shouldn’t there be a way to measure the amount of fissile materials in one of these tanks in real time? It seems like in both cases that was the real problem. There was no indicator that they were going way over the know limits. You’d think you could use a geiger counter or something, but the fact that the didn’t do that probably means it’s harder than it sounds.
Yeah, I’m sure it is really HARD to check out a Geiger Counter from the stock room just down the hall.
the problem with the geiger counter may be the same reading for a little, highly active, but non-fissible material and an almost critical mass of fissible material with lower spontaneous activity (so not knowing much about the details I’d probably go for “or something” option)
An industry where remote working from a room far away makes sense. Of course to do so you would need to reinvent some processes, but in the end it could be a far better safety culture.
A recent nuclear disaster?
Leonardo Mascheroni Los Alamos.
Also, do not pile those small squat bottles of pretty yellow liquid (enriched uranyl nitrate dissolved in water) in a neat stack lest they go supercritical, hose down the room with mixed radiation and melt, contaminating the whole room. Water (the solution) and polyethylene (the bottles) are excellent moderators and neutron reflectors.
I am surprised the the article did not mention either the SL1 or Chernobyl events which were both reactivity insertion accidents. The power levels reached during each of these events was many times the design rated power levels. They were not nuclear detonations, but the steam explosions that occurred when the energy got out of the fuel into the coolant were spectacularly destructive.
And then, of course, there was the Oklo reactor, in Africa, which went critical all by itself and “operated” without any intervention for a few hundred thousand years.
Mascheroni informed LANL that “a larger match – Mascheroni’s words” needed to achieve fusion energy ignition.
LANL did not like to hear this.
Fusion energy business game “~We are getting close to fusion energy ignition. ” ?
Send more money.
Graph Theory with Applications to Engineering and Computer Science (Dover Books on Mathematics) First Edition, First
by Narsingh Deo (Author)
told me, after a visit funded by the National Foundation, that LANL is what remains after all the good people have left.
There’s a good youtube channel that has covered many radiological accidents called “Plainly Difficult”.
The one criticality event that I can’t stop thinking about involved one of the workers inserting a rod of some sort into an apparatus manually. There was a steam explosion and he was pinned to the ceiling by said rod. If I recall, it took rescuers quite some time to find him…
Narsing Deo and I were travelling funded by NSF to try to develop a random number arbitrary distribution software library.
Bruce Barnes was NSF grant manager.
Barnes is reference in:
“The Puzzle Palace and threat of prosecution.
During the course of writing the book, Bamford discovered that the Justice Department in 1976 began a secret criminal investigation into widespread illegal domestic eavesdropping by the NSA. As a result, he filed a request under the Freedom of Information Act (FOIA)[10][11] for documents dealing with the investigation and several hundred pages were eventually released to him by the Carter administration. However, when President Ronald Reagan took office, the Justice Department sought to stop publication of the book and demanded return of the documents, claiming they had been “reclassified” as top secret. When Bamford refused, he was threatened with prosecution under the Espionage Act. In response, Bamford cited the presidential executive order on secrecy, which stated that once a document had been declassified it cannot be reclassified. As a result, President Reagan changed the executive order to indicate that once a document has been declassified it can be reclassified. However, due to ex post facto restrictions in the US Constitution, the new executive order could not be applied to Bamford and the information was subsequently published in The Puzzle Palace.”
NSA prevented library development, as explained by Bamford in the Puzzle Palace.
Bamford retaliated with:
Rigging the game spy sting?
https://www.baltimoresun.com/1995/12/10/rigging-the-game-spy-sting-few-at-the-swiss-factory-knew-the-mysterious-visitors-were-pulling-off-a-stunning-intelligence-coup-perhaps-the-most-audacious-in-the-national-security-agencys-long-war-on-f/
Positive grant result.
Charles Moore demonstrated forth for me on the day before Christmas 1995.
The result:
Embedded controller forth for the 8051 family.
https://www.google.com/search?q=embedded+controller+forth+for+the+8051+family&rlz=1C1QCTP_enUS1084US1084&oq=embedded+controll+forth&gs_lcrp=EgZjaHJvbWUqCAgBEAAYFhgeMgYIABBFGDkyCAgBEAAYFhgeMgoIAhAAGIAEGKIEMgoIAxAAGKIEGIkFMgoIBBAAGIAEGKIEMgoIBRAAGIAEGKIE0gEJMTg0ODBqMGo3qAIAsAIA&sourceid=chrome&ie=UTF-8
Correction 1975 not 1995. After lunch with Bess Rather paid for by NSF. :)
Bess consumed to glasses of red wine. :)
w h payne December 19, 2024 at 08:25
“Sam Altman Nuclear Startup Continues Hot 2024 With 12-Gigawatt Data Center Deal.”
“Virginia to host world’s first fusion power plant.” History of nuclear fusion https://en.wikipedia.org/wiki/History_of_nuclear_fusion
Send more money.
Real nuclear fusion goal?
Nuclear fusion ignition would hinder goal? Reply
Positive info:
gcc c labels as values have made fig forth and Intel MCS BASIC-52 relocatable
by storing the jump table at the start of the machine code.
If only relative and indirect jumps are used in a 8080 forth-like and 52 BASIC single task interactive incremental compile/assemble code modules, only the values
of jump table addresses need to be changed to make relocatable code.
:)++?