[en] Nuclear Safety Research Reactor in Japan Atomic Energy Research Institute is a TRIGA-ACPR (Annular Core Pulse Reactor) which is able to generate very sharp pulse power with the maximum of 23 GW and steady state power with the maximum of 300 kW. Many test fuel rods were irradiated in NSRR to study fuel behavior under Reactivity Initiated Accident conditions. However, the simulated power burst in the past tests was initiated from essentially zero power due to the limited capability of NSRR. The reactor control system of NSRR has been modified to extend the capability of the pulse operation and two new operation modes have become applicable. One is the shaped pulse operation mode which produces a controlled high power transient, and another is the combined pulse operation mode which is a combination of a high power transient and a sharp pulse power generation. In this article, characteristics of the shaped pulse operation is presented. NSRR is to be operated under the limitations of the maximum integral power of 110 MWs, the maximum core fuel temperature of 900degC, the maximum regulating rod speed of 75 mm/s and the maximum regulating rod position of 850 units. Through a number of test operations, characteristics of the shaped pulse mode under these limitations were obtained. The stability and capability of the various power shapes were certified. The maximum regulating rod position as a function of the integral reactor power and the limit of the operational ability in the shaped pulse mode were clarified. (author)