Testing/training reactor used for research and to train nuclear engineers.
Considered a zero power reactor with a nominal rating of 0.1W
Used 90% enriched Uranium
Overconfidence
Many years of accident free operation, may have caused overconfidence to be a factor that lead to ignoring protocols
Moderator fluid was not fully drained
Two fuel assemblies, which were supposed to be removed, were left inside the reactor in contact with the graphite reflector
The sequence in which the fuel assembly repositioning was performed reduced the system's subcriticality
Two fuel assemblies were inserted without their cadmium control plates
No safety officer was present
Exposure
In about 50 milliseconds, 10 megajoules of energy was released (about the energy of 5lbs of TNT)
In that moment, experienced operator Osvaldo Rogulich, received an estimated whole body dose of 1,400 rads (14Gy) of fast neutrons and 500 rads (5Gy) of gamma
17 other people in adjacent rooms also received alarming, but not critical, doses of gamma and neutron radiation
About 3.5Gy will result in the death of 50% of people within 60 days
Health Effects
25 minutes after exposure, the operator began to show symptoms of acute exposure (vomiting, headaches, diarrhea)
He was unconscious much of the second day and had worsening GI symptoms
At dawn on the third day he developed radiopneumonitis of the right lungh, and edema of the right arm
At 1645 on the third day since his exposure, the operator died from severe inflammation of the lungs
Reactor Shutdown
Following the incident, the reactor was decommissioned
Between 1984 and 1989 the building was dismantled and sections of the building exposed to radiation were recovered
In 2005 all effected facilities were reopened for unrestricted use
Many years of accident free operation, may have caused overconfidence to be a factor that lead to ignoring protocols
