[en] Reactor operation began at Penn State with the startup of the first University Park reactor. The first core was assembled from typical MTR fuel elements, and logged 2200 MW hours during its life. In the early 1960's, a concern for the integrity of the fuel assemblies, and a desire for increased capability developed. As a result, funding was obtained for a new core, and after a study of various alternatives the TRIGA reactor was selected. The new core and control system was installed in December of 1965 and on December 31, the 'new' Penn State reactor was loaded to criticality. The present low excess reactivity is not an operational problem because the reactor is operated on a two shift basis five days a week and is often operated at low power levels for various experiments, laboratory classes and training. Problems due to activation were experienced in December of 1968, when a detailed inspection of the core structure was accomplished. The objective of this was to reveal any deterioration of the structure. It was found that such an inspection was quite feasible