Chronology of events that occurred in 19864/25•The power of the plant decreases, indicating the start of the reactor shutdown.•The emergency core cooling system has been deactivated.•The automated regulation system has been turned off.•The power has been reduced to 30 Mwt.•Resumption of power reduction.4/26•The operating reactivity margin is reduced to less than 30 bars. •Increased power to 200 Mtw by removing the bars as well as starting two additional recirculation pumps.◦Decreased vacuum.◦All but six bars have been removed. ◦Emergency protection signals obstructed by operators. •Feed water flow to steam drums increased.◦Control room displays excessive responsiveness.◦This required an immediate shutdown, however, l The warning was ignored and the test was initiated. • Feed water flow to the steam drums decreased - 30 seconds later reactor inlet temperatures begin to rise. • Recirculation pumps begin to slow down with the turbine.◦Reactor flow rate decreases.•Turbine feed valves are closed.◦Power increased.◦Test was complete.◦An operator noticed rods moving on the heart map. • Emergency scram initiated by button AZ-5. This decision was driven because:◦Doppler decreased reactivity addition.◦Fuel fragments caused rapid draining.◦Steam drum power and pressure increased rapidly.•Power increased rapidly in due to the positive vacuum effect.•An explosion occurred, then a second explosion occurred a few seconds later.Summary of what happened: The operators were carrying out tests to see how the reactor would behave in case of electrical failure, when a fault in the reactor has triggered a serious overvoltage. The heart had not been stopped before running the test. The power surge triggered events that sent the nuclear reaction out of control, causing the two explosions. The reactor was not equipped with a containment structure... middle of paper ... their cooling systems would also be able to function. What happened: When a huge earthquake struck, the following tsunami destroyed the electricity at TEPC and caused many problems for workers who struggled to repair and maintain water levels. water in damaged reactors. Water was desperately needed to keep the fuel rods from overheating and there was a huge risk of radioactive exposure due to the lack of cooling water and the rods overheating. I do not believe this accident could have been avoided as the main damage was a result of the tsunami and the rest was due to the damaged reactors causing damage to others that were not affected by the tsunami. I think as a society we have learned that ultimately we will never be able to create a completely safe, radiation-free nuclear power plant...