For engineering purposes, risk is defined as the expected losses (lives lost, persons injured, damage to property, and disruption of economic activity) caused by a particular phenomenon. Risk is a function of the probability of particular occurrences and the losses each would cause. Other analysts use the term to mean the probability of a disaster occurring and resulting in a particular level of loss. A societal element is said to be at risk, or vulnerable, when it is exposed to known disaster hazards and is likely to be adversely affected by the impact of those hazards if and when they occur. The communities, structures, services, or activities concerned are described as elements at risk. Also, the FEMA damage and casualty production model for simultaneously handling multiple nuclear attacks to produce the spectrum of likely attack results and determine their associated possibilities. A pre-attack planning tool. (Simeon Institute 1992)