Abstract
The end product of the hot-spot analysis procedures described is a graph showing the relationship between measured mixed mean outlet temperature and the maximum number of pins at some small specified risk of exceeding the hot-spot limit. To arrive at this position, it is necessary to take account of 1. the variation of clad temperature with burn-up 2. the variation of initial clad temperature throughout the core due to transverse flux gradients 3. the problem of combining three categories of uncertainty associated with pins, sub-assemblies and reactor respectively. The first problem is resolved by one of two options involving, either, the use of a single temperature representative of clad temperature history or a burn-up dependent hot spot limit. The second problem is resolved by putting all pins in any small temperature interval in the same population, and treating each sub-population separately. The third problem is dealt with by a procedure which is desoribed in the.compansion paper “A Simple Procedure for the Combination of Fuel Pin, Sub-Assembly and Reactor Uncertainties in Fast Reactor Clad Hot-Spot- Temperature Assessment”.
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