The night of the explosion, Chernobyl’s number 4 reactor was undergoing a safety check, which should’ve been done before the reactor ever opened. The test is see what will happen if, for any reason, the reactor fails and the back up generators need to be switched on. The point of this test was to check the delay time between the reactor failing and the generators powering up, ideal time being 40 seconds.

This test should’ve been done when the reactor was function at 700-1000 megawatts. The higher the voltage being produced by the plant, the more water consumed. Realizing this, the head supervisor that night decided to drop power to 200 megawatts. Workers changed settings in the reactor core and power fell, but didn’t stop falling until it hit 0 megawatts.

Workers restarted the reactor, but a glitch in the base of the reactor core saw vast, unmonitored quantities of heat being realized. Once the reactor had started, workers hurried to start the test, making sure water consumption was that needed for 200 megawatts of power produced. However, unknown to the supervisor and workers, the glitch in the base of the reactor core was boiling the water much too fast, producing immense amounts of steam to accumulate in the reactor.

Water is not only used to produce steam, but also to keep the reactor cool and most of this water was being evaporated almost instantly, disallowing the cooling cycle to take place.

The incredible pressure the steam put on the reactor, combined with the heat inside the reactor saw the first explosion, shortly followed by a second.

On April 26th, 1986, at 1.23am, just two minutes after the safety test began; Chernobyl’s number 4 reactor overheated and caught fire. The result was 50 tonnes of radioactive material such as graphite and uranium being released into the atmosphere.

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Part 4

Part 5

Part 6