A Reliability Analysis of Personnel Protection Systems at the Spallation Neutron Source

In this paper we present and analyze field gathered system reliability data from the Oxygen monitoring and Access Control systems managed by the Protection Systems team at the Spallation Neutron Source at the Oak Ridge National Laboratory. The time span of the data varies from roughly fourteen years for systems in place as the linear accelerator was being built and tested, to a few months for the newest instrument beam lines. We analyzed the time to fail for the above systems, accounting for censored data, and developed a nonparametric probability model of the overall reliability for each system. From this probabilistic model, we were able to estimate the survivor and hazard functions, and find good correlation between these estimates and their empirical counterparts. Moreover, we used our model to find whether or not each system’s life distribution is New Better than Used.