Comparison of an exact and moments calculation of reliability

Present methods for calculating the reliability of reactor systems usually assume constant failure rates for individual components of the system. In principle, if the uncertainty in component failure rates can be expressed in terms of a probability density function, then the probability density function for the overall system reliability can be obtained. The system reliability distribution can then be used to calculate confidence bounds, for example. The probability distribution for the system reliability can also be found by an approximate method, namely the method of moments. In order to compare the exact and approximate results, a simple two element series system is modeled.