Radioluminescence experiments have been performed on single- and polycrystal CsI at the pulsed TRIGA nuclear reactor of the University of Illinois. 95% of the 100 krad dose (SiO 2) was contributed by gamma-rays, the rest by neutrons. The radioluminescence was measured in the near infrared (up to 5.5 μm) and in the visible range. At the peak of the radiation pulse (dose rate of 6.9 Mrad/s), single-crystal CsI emits ∼ 40 mW/cm 2 in the infrared, against virtually nothing for the polycrystal CsI. In the visible range, however, the emission intensity is much larger, ranging from 300 mW/cm 2 for the polycrystal CsI to more than 5 W/cm 2 for the single-crystal CsI. It was also found that dose accumulation by consecutive pulsing causes the luminescence to decrease. The rate of decrease depends on the sample, on the proportion of thallium as a dopant and on the wavelength range considered. Increasing the temperature of CsI also causes a decrease in radioluminescence and repairs the damage to the crystal by annealing the quenching centers, essentially allowing full recovery of the radioluminescence intensity.