[en] The pulse mode of operation for the Nuclear Science Center Reactor (NSCR) was reinitiated in February 1983 using Core VIII. Results of Phase I of the pulse test program were submitted to the USNRC and to the Texas A and M University Reactor Safety Board for review. It was concluded by the NSC management that the roll-off effect observed in fuel temperature and pulse energy for pulses greater than $1.50 was probably due to the prompt neutron lifetime of approximately 16 microseconds associated with FLIP fuel. At that time it was felt that the very short full width at half maximum (FWHM) values associated with the power transients prevented the transient rod from being removed fast enough to keep up with the pulse, and thus, the selected pulse reactivity was not inserted to its full value. It was decided to pursue this idea, and a procedure was developed to monitor both transient rod position and reactor power as a function of time. For each pulse the time for full rod withdrawal was determined and compared to the time at which peak reactor power occurred. The time difference between these two points was observed to decrease as the inserted pulse reactivity increased. Based on this most recent study it appears that pulses on the order of $2.00 would indeed cause reactor power to peak prior to full withdrawal of the transient rod. This is in disagreement with the NSC original report implying that the roll-off above $1.50 was due to rod ejection time. Although the cause of the roll-off at that level has not yet been determined, it is felt that the cause is something other than rod withdrawal times and will be investigated further in the near future