* The Chernobyl disaster was a nuclear accident that occurred on April 26, 1986 at the #4 reactor in the Chernobyl Power Plant, near the city of Pripyat in the north of the Ukrainian SSR in the Soviet Union. Called the world’s worst-ever civil nuclear incident, it is one of only two nuclear energy accidents rated at seven,the maximum severity,on the International Nuclear Event Scale; the other being the 2011 Fukushima nuclear disaster in Japan. The initial emergency response, together with later decontamination of the environment, involed more than 500,000 personnel and cost an estimated 18 billion roubles-roughly $68 billion in 2019, adjusted for inflation. The accident occurred during a safety test.

* The International Nuclear Safety Advisory Group (INSAG) produced two significant reports on Chernobyl; INSAG-1 in 1986, and a revised report, INSAG-7 in 1972. In summary, according to INSAG-1, the main cause of the accident was the operator’s actions, but according to INSAG-7, the main cause was the reactor’s design. Both reports identified an inadequate “safety culture” at all managerial and operational levels as a major underlying factor of different aspects of the accident. This was stated to be inherent not only in operations but also during design, engineering, construction, manufacture and regulation.

* Views of the main causes were heavily lobbied by the different groups (i.e., finger pointing), including the reactor’s designers, power plant personnel, and the Soviet and Ukrainian governments. This was due to the uncertainty about the actual sequence of events and plant parameters; poor communications. After INSAG-1 more information became available, and  more powerful computing allowed better forensic simulations.

* The INSAG-7 conclusion of major factors contributing to the accident was: “The accident is now seen to have been the result of concurrence of the following major factors: specific physical characteristics of the reactor, specific design features of the reactor control elements, and the fact that the reactor was brought to a state not specified by procedures or investigated by an independent safety body. Most importantly, the physical characteristics of the reactor made possible its unstable behaviour.” 



* Which supports and barriers were in play?

* What were the dynamics?

* Who, or what, won the Tug-of-War?

* Discuss the outcome with your friends and family.

* Use Post #4 as a reference for the dynamics, and the relationships, between supports and barriers.