TMI-2 leadscrew debris pyrophoricity study

Debris removed from the surface of a leadscrew from the TMI-2 Reactor Building was examined to assess the potential for the debris to become pyrophoric. Elemental analyses were performed to identify candidate phases that could be pyrophoric, and x-ray diffraction was used to determine if any of these phases was actually present. However, none of the candidate phases were found. Based on differential scanning calorimetry, no exothermic reactions were observed upon heating the debris to 5000C in air. Particle size distributions for the debris were obtained from analyses of micrographs of the debris. A light blockage instrument was also used to determine the particle size distribution. These analyses indicated that particles larger than 10 μm accounted for most of the debris volume, although the majority of the particles were actually smaller than 10 μm. Gamma spectroscopy indicated that most of the radioactivity in the debris, and on the leadscrew after debris removal, was due to mixed fission products such as 137Cs and 134Cs