As the cooling pumps require electricity to cool the reactor, in the event of a power failure, Chernobyl’s reactors had three backup diesel generators; these would start up in 15 seconds, but took 60–75 seconds to attain full speed and reach the 5.5‑megawatt output required to run the main pump.
http://chernobylgallery.com/chernobyl-disaster/cause/
The accident occurred during an experiment to test a way of cooling the core of the reactor in an emergency situation. The test was incorporated into a scheduled shutdown of reactor 4.
http://chernobylgallery.com/chernobyl-disaster/cause/
The 1986 Chernobyl disaster triggered the release of substantial amounts of radioactivity into the atmosphere in the form of both particulate and gaseous radioisotopes. It is one of the most significant unintentional releases of radioactivity into the environment to present.
https://en.wikipedia.org/wiki/Effects_of_the_Chernobyl_disaster
The issue of long-term effects of the Chernobyl disaster on civilians is very controversial. The number of people whose lives were affected by the disaster is enormous. Over 300,000 people were resettled because of the disaster; millions lived and continue to live in the contaminated area.
https://en.wikipedia.org/wiki/Effects_of_the_Chernobyl_disaster
General description of Chernobyl accident is given in the review. The accident causes are briefly described. Special attention is paid to radiation situation after the accident and radiation measurements problems. Some data on Chernobyl disaster are compared with the corresponding data on Fukushima accident.
http://www.sciencedirect.com/science/article/pii/S1350448712001680
First of all, it should be noted that the accidents at Chernobyl and Fukushima have different causes. The causes of the accident at Chernobyl NPS are described above. The accident at the Fukushima NPS is due to loss of cooling reactors and ponds for spent nuclear fuel (Strishov, 2011). The earthquake destroyed the system of stationary power supplies of NPS.
http://www.sciencedirect.com/science/article/pii/S1350448712001680
It presents brief analysis of the causes, consequences and problems of radiation measurements in the radiation situation which occurred after Chernobyl nuclear accident. Published materials as well as personal experience of one of the authors (V.
http://www.sciencedirect.com/science/article/pii/S1350448712001680
An increased incidence of thyroid cancer among children in areas of Belarus, Ukraine and Russia affected by the Chernobyl disaster has been firmly established as a result of screening programs and, in the case of Belarus, an established cancer registry.
https://en.wikipedia.org/wiki/Effects_of_the_Chernobyl_disaster
After the EPS-5 button was pressed, the insertion of control rods into the reactor core began. The control rod insertion mechanism moved the rods at 0.4 m/s, so that the rods took 18 to 20 seconds to travel the full height of the core, about 7 meters.
http://chernobylgallery.com/chernobyl-disaster/cause/
Chernobyl: Consequences of the Catastrophe for People and the Environment is an English translation of the 2007 Russian publication Chernobyl. It was published online in 2009 by the New York Academy of Sciences in their Annals of the New York Academy of Sciences.
https://en.wikipedia.org/wiki/Effects_of_the_Chernobyl_disaster
what caused the chernobyl accident
The Chernobyl accident caused  release of substantial amounts of radioactivity into the atmosphere in the form of both particulate and gaseous radioisotopes. The release of substantial amounts of radioactivity into the atmosphere in the form of both particulate and gaseous radioisotopes caused the chernobyl accident.