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- 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
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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
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- 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
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- 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
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- 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