• Reactor Running Normal

    Reactor was running in normal operation at the Chernobyl power plant.
  • Reactors start to lose power

    Reactors at the power plant as they progressed through a test that was used to observe the dynamics of a reactor with limited powerflow
  • Reactor reaches 50% of total power

    Twelve hours after power reduction started the reactor reached 50% power. Now only one turbine was needed to take in the decreased amount of steam caused by the power decrease and turbine #2 was turned off.
  • Reactor at 30% power

    Under the normal procedures of the test the reactor would have been reduced to 30% power, but the Soviet electricity authorities refused to allow this because of an apparent need for electricity elsewhere, so the reactor remained at 50% power for another 9 hours.
  • Power Reduction resumes

    The Chernobyl staff received permission to resume the reactor power reduction. One of the operators made a mistake. Instead of keeping power at 30%, he forgot to reset a controller which caused the power to plummet to 1% because of water which was now filling the core, and xenon which was building up in the reactor. This amount of power was too low for the test. The water added to the reactor is heated by the neuclear reaction and turned into steam to turn the turbines of the generator
  • Reactor forced to 7% power

    The operator forced the reactor up to 7% power by removing all but 6 of the control rods. This was a violation of porcedure and the reactor was never built to operate at such low power. The RBMK reactor is unstable when its core is filled with water. The operator tried to take over the flow of the water which was returning from the turbine manually which is very difficult because small temperature changes can cause large power fluctuations. The operator was not succesful in getting water flow.
  • Another test is started

    By 01:22, when the operators thought they had the most stable conditions, they decided to start the test. The operator blocked automatic shutdown on low water level and the loss of both turbines because of a fear that a shutdown would abort the test and they would have to repeat tests.
  • Turbine is shut down

    The remaining turbine is shutdown
  • Power in reactor begins to rise

    Power in the reactor began to gradually rise because of the reduction in water flow caused by the turbine shutdown which lead to an increase in boiling. The operator initiated manual shut down which lead to a quick power increase due to the control rod design.
  • Disaster Strikes

    The reactor reached 120 times its full power. All the radioactive fuel disintegrated, and pressure from all of the excess steam which was supposed to go to the turbines broke every one of the pressure tubes and blew off the entire top shield of the reactor.