ABSTRACT
When a reactor is first put into operation, fission products begin to accumulate in the core. They build up in the fuel rods, and start to absorb thermal neutrons. In thermal reactors, fission products primarily affect the thermal utilization of the fuel. In modern nuclear power plants, the control systems are designed to minimize the probability that a xenon transient will occur. The reactor accident in Chernobyl, Russia, was caused by a number of unfortunate events, but one of the most unfortunate of them was the buildup of Xenon-135 in the reactor core. The Chernobyl reactor was a military reactor designed to produce weapons-grade plutonium. The chapter discusses what the reactor operators did at Chernobyl in response to this buildup of Xenon-135 and how it ultimately caused the reactor accident to occur. The reactor operators panicked and made a decision to increase the power level by disabling the automatic safety systems that controlled the motion of the control rods.
