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Chernobyl Disaster 1986 (what happened (Building of operators, workers and…
Chernobyl Disaster 1986
what happened
- Building of operators, workers and engineers conducted a test on a nuclear reactor to see how it would react when the power was reduced by half
- Reactor showed stable signs at first. Workers switched off one of two steam powered turbine engines. Emergency cooling system was turned off.
- After twelve hours, reactor was starting to become unstable, but Deputy Chief Engineer Anatoly Dyatlov chose to continue with the test. The power decreased to 30 MW thermal, but stabilised at 200 MW thermal, and did not rise further (The Chernobyl Gallery, 2018)
- Automatic emergency shutdown signals were disabled so they did not disturb the test being conducted. Operator forced the reactor to increase power by 70%; this was done by removing all but 6 control rods.
- Reactor core filled with water. Operator manually attempted to stop the flow of water filling the core, but could not close the valve. Remaining control rods began to rise due to the high water level and water temperature increases.
- Water begins to boil, and reactor begins to shake. Operator on shift pressed emergency button but control rods did not descend at full 7 metres inside the core. The reactor control showed no indication of water flow or failure of pumps (The Chernobyl Gallery, 2018)
- The reactor reached 120 times its full power, radioactive fuel disintegrated and pressure from excess steam broke pressure tubes, causing an explosion.
- This explosion lifted the 1000 ton steel lid, releasing radiation. Air reached the reactor and oxygen causing graphite fires. The metal of the fuel tubes reacted to the water, producing hydrogen in the chemical reaction. This created another explosion (The Chernobyl Gallery, 2018)
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People
Team Factors
Little to no communication between work crew - inadequate training and experience meant they assumed that orders given meant the operators in charge knew what they were doing
emergency crews spent several days cleaning up the mess - people were still being affected by radiation
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system life cycle
Commissioning
Controls
Main control room, back up control room
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Decommissioning
Reactor buckled under pressure, caused an explosion
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Workplace
Workplace factors
The team of operators and workers who conducted the test on the reactor did not follow the procedures put in place for operating the reactor mechanisms
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Management
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Information Transfer
Feedback
Numerous calls made to emergency services - fire station, police, radiation control
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Work crew
ordered to manually shut down the system - process was set to take four hours, time they did not have (The Chernobyl Gallery)
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why it happened
Technicians working the reactor were instructed to shut down the power regulating system and the emergency safety systems (World Nuclear Association, 2018)
(LATENT FAILURE)The reactor became increasingly unstable, and was not able to be shut down automatically or manually
Technicians removed all but 6 control rods, which were put in place to support the reactor core (World Nuclear Association, 2018)
The control rods could not be placed back inside the core, and therefore could not support the reactor whilst it was building up pressure (World Nuclear Association, 2018)
(MANAGEMENT FAILURE)Deputy Chief Engineer choosing to continue the test even though the reactor was becoming unstable
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