Tuesday Daily Plenary Session

From the early days of the development of nuclear power, people realized that there were a lot of uncertainties in the estimation of the frequency of accidents and the consequences of accidents. So they had to develop methods to manage this uncertainty when in fact they could not quantify it. We’re talking now about way back in the 60s and early 70s. They came up with this very clever idea in my opinion of defense in depth, which is a term that is not used uniformly everywhere. But it means to employ multiple layers of protection so if one fails another one hopefully will save you.