Highly-trained and experienced operators can often compensate for a poor design; however, in the case of the Chernobyl disaster, the designers gave the operators too difficult a task. The design was not at all forgiving of operator mistakes. It may have been difficult for the operators to have compensated for design failures that they did not know about. Not only were the plant operators unaware of key design weaknesses, the designers were unaware as well. One example is the material used in the control rods. Control rods made of boron are lowered into the reactor core to slow the nuclear reaction. However, the tip of the control rods at Chernobyl were made of graphite, which temporarily increase the reaction as they enter the core. The emergency AZ-5 button reinserts all of the control rods, which shuts down the reaction. When this button was pressed as a last resort, the large number of descending graphite tips led to a huge surge in reactor power. Then, as parts of the system ruptured, the control rods were blocked from moving further down and so the graphite tips continued to accelerate the reaction, leading to the inevitable explosion. The operators at Chernobyl were under the impression that the AZ-5 button was a fail-safe shut-down. They were not aware of this design flaw. If they had understood, it may have influenced some of their decisions. To this day, some major companies continue to blame control room operators, pilots, train drivers and offshore drillers, rather than explore design issues or leadership behaviours that set these staff up to fail. The Chernobyl plant wasn’t just operated by humans, it was also designed by humans; and all humans can make mistakes.