Source: IGN
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25th of April 1986 an experiment took place in the 4th block of the Chernobyl power plant. A team of engineers and scientists wished to verify that the turbines could produce enough power in the case of a total failure of electricity, thus ensuring that the emergency cooling would function correctly. To allow the experiment to take place under realistic conditions, the emergency program "Average Protection" was turned off. In so doing, all the important security functions such as the emergency cooling and the emergency retraction of the brake rods, were taken offline. However, the launch of the experiment was postponed, and the unprepared night shift undertook the experiment, failing to understand that the test environment that took place earlier in the day had left the reactor unprotected.