This paper describes the results of neutron transport calculations and measurements that were performed for the concrete biological shield that surrounds a Westinghouse two-loop reactor. As a concrete shield ages a number of changes occur. Foremost among these, from a radiation shielding perspective, is the loss of water. The measurement of the neutron dose rate is a sensitive indicator of change in the biological shield concrete. For example, a 50% reduction in the water content of the shield as the result of age-related water loss results in a factor of 22 increase in the neutron dose rate but only a factor of three increase in the gamma ray dose rate. The measurements described herein employ solid state track recorders (SSTRs) and a multi-component shield assembly to separate the transmitted and background radiation field components.