I cringe at the sight of this person! But I have to ask, WTF happened?
Tokaimura, Japan, at the JCO (Japan Nuclear Fuel Conversion Co.) experimental fast breeder plant. September 30, 1999.
31 year old Hisashi Ouchi was one of three overnight shift technicians in charge with running tests on the Joyo Experimental Water-Moderated Fast Reactor System. The system used an aqueous solution of U-235 nitrate with water as the neutron barrier. At the point of the flash, the tank already contained 16 kilograms of uranyl nitrate. One technician was in an office upstairs monitoring the radiation output. Two others, including Ouchi, was in the reactor room. The overwatch tech noticed a fluctuation of output from the tank and warned the other two via radio that they were to immediately cease adding any more solution and leave the room. The second tech warned Ouchi to step away from the tank, but Ouchi insisted that the protocol called for all of the buckets of uranyl nitrate to be mixed into the tank. He was leaning directly over the tank during this time. Upon the addition of the seventh bucket, the mass of uranium in the tank reached full critical capacity.
Both techs, as well as the third man watching the cameras observed a tremendous flash of bluish white Cherenkov light emit from the tank, so intense that objects nearby seemed "ghostly". Radiation alarms immediately began to sound throughout the facility. The flash was mostly comprised of gamma and X-rays.
Ouchi, who was still directly over the aperture of the device, received 17 sieverts of radiation in a split second. The second tech who was by the door received 10 sieverts. Both men immediately began showing the signs of acute radiation exposure. By the time Ouchi had been transported to the hospital, his entire body had been covered with third degree burns and the skin had completely "degloved". A blood sample showed no viable blood cells present at all, with only a soup of destroyed cells and amino acids. Not one sample of intact DNA could be isolated anywhere on his body either. Remarkably, Ouchi was still alive and remained conscious during the entire ordeal. Researchers who wanted to study the full effects of radiation poisoning basically had found their prize specimen. Despite Ouchi continuously begging for the scientists to remove his feeding tubes and allow him to be free of the pain, they kept him alive for over 83 days, running various experiments on him. Ouchi eventually succumbed to infection as his entire immune system had been virtually wiped out. The other tech who had received the 10 SV dose had been long dead by then.
For reference, 8 sieverts of exposure is enough to kill an adult human. The exposed core of the Chernobyl reactor was emitting 9-12 sieverts when the first rapid response team descended onto the roof via helicopter. Japanese safety standards mandate that 3 millisieverts is the maximum amount any plant worker or scientist is allowed to be exposed to without permanent and long term damage.