Qualitative Reasoning about a Large System Using Dimensional Analysis

We present a simple qualitative model of a large system, viz . a nuclear power plant using a pressurized water reactor . We use the technique of dimensional reasoning, which has recently been shown to be useful in the traditional small-scale problems of qualitative physics, such as springs, boilers, etc . Here we extend the technique so that it can be applied to large systems . Our model is devoted to one aspect of the system, its thermal hydraulic.i . Using this model we are able to capture the effects of a sudden loss of water on the secondary side of the plant and reach conclusions similar to those reached by a conventional numerical simulation . The dimensional aphTOach, although restricted, has a wide range of applicability, and appears useful because it uses the symbolic content, of physics.