Highly technical probabilistic risk assessments at nuclear plants improve safety and pay for themselves many times over
Nuclear power plants are enormously complex systems, in which a failure in a seemingly simple component — a pressure-relief valve or an indicator light — can cascade into catastrophe.
That was the case at Three Mile Island in March 1979, when a pressure-release valve stuck open, allowing coolant around the core to escape. Because instruments in the control room wrongly indicated that the valve was closed, operators took a series of misinformed actions that caused the core to overheat and partially melt down.
Risk assessments are designed to identify potential hazards like a stuck relief valve and calculate the possible effects should they occur. The goal is to use the information to take steps to reduce or eliminate the danger.
For managers, though, it’s hard to know exactly how effective these risk assessments are, especially for the kind of low-probability, high-impact events that cause disastrous failure in complex systems like nuclear reactors, jetliners or spacecraft. Might the problem have been fixed without the time and expense of an assessment? How do you even measure whether it’s successful?
In a paper published in Risk Analysis, Ohio State’s Christian C. Blanco and UCLA Anderson’s Felipe Caro and Charles J. Corbett attempt to quantify the effect of probabilistic risk assessments (PRA) on the safety of U.S. nuclear power plants. Their analysis found that a PRA pays off — in the form of fewer safety-related incidents, reduced downtime and significant cost savings.