From the journal Science, June 2017:
Technicians at the government's Los Alamos National Laboratory settled on what seemed like a surefire way to win praise from their bosses in August 2011: In a hi-tech testing and manufacturing building pivotal to sustaining America's nuclear arsenal, they gathered eight rods painstakingly crafted out of plutonium, and positioned them side-by-side on a table to photograph how nice they looked.
At many jobs, this would be innocent bragging. But plutonium is the unstable, radioactive, man-made fuel of a nuclear explosion, and it isn't amenable to showboating. When too much is put in one place, it becomes "critical" and begins to fission uncontrollably, spontaneously sparking a nuclear chain reaction, which releases energy and generates a deadly burst of radiation.
The resulting blue glow — known as Cherenkov radiation — has accidentally and abruptly flashed at least 60 times since the dawn of the nuclear age, signaling an instantaneous nuclear charge and causing a total of 21 agonizing deaths. So keeping bits of plutonium far apart is one of the bedrock rules that those working on the nuclear arsenal are supposed to follow to prevent workplace accidents. It's Physics 101 for nuclear scientists, but has sometimes been ignored at Los Alamos.
As luck had it that August day, a supervisor returned from her lunch break, noticed the dangerous configuration, and ordered a technician to move the rods apart. But in so doing, she violated safety rules calling for a swift evacuation of all personnel in "criticality" events, because bodies — and even hands — can reflect and slow the neutrons emitted by plutonium, increasing the likelihood of a nuclear chain reaction. A more senior lab official instead improperly decided that others in the room should keep working, according to a witness and an Energy Department report describing the incident....
....MUCH MORE
"Does Iran have a secret plutonium bomb program?"
Plutonium, no good....
Bill Gates' nuclear firm TerraPower and the China National Nuclear Corporation have signed an agreement to develop a world-first nuclear reactor, using other nuclear reactors' waste....
