The prompt neutron generation time for the Annular Core Research Reactor was experimentally determined using a prompt-period technique. The resultant value of 25.5 las agreed well with the analytically determined value of 24 ]as. The three different methods of reactivity insertion determination yielded +5%agreement in the experimental values of the prompt neutron generation time. Discrepancies observed in reactivity insertion values determined by the three methods used (transient rod position, relative delayed critical control rod positions, and s relative transient rod and control rod positions) were investigated to a limited ex_:_t. Rod-shadowing and low power fuel/coolant heat-up were addressed as possible causes of the discrepancies.

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