TMI-2 core materials examination at CEA

In the framework of the OECD/CSNI Task Group on Three Mile Island 2, CEA examined five samples retrieved from the reactor damaged core: a slightly damaged fuel rod chunk from assembly L1 of the core external row, a rod remnant in position C7 hanging from the assembly head and three core bore rocks including a rock cut - G12-P1 (section D), K9-P3-M and O7-P5 - from both the ceramic and agglomerate regions of the damaged core. The scheduled analyses included visual observation, immersion density, metallography, microprobe analysis (WDX), X-ray diffraction, thermogravimetry, gamma spectroscopy and neutron activation analysis. The information gained from these examinations provided some assessments of the maximum temperatures reached locally during the accident, an insight into a possible fuel degradation mechanism for the rod in position C7, and indications about fission product and control or structure material behavior. Such data, involving a small number of samples, will be grouped with those from the other contributing laboratories in order to obtain an extensive data base and try to arrive at a consensus on the comprehension of the TMI-2 accident and, presumably, on the lessons to be learned in order to avoid the recurrence of a core melt