TMI-2 core bore acquisition summary report

Abstract

Core bore samples were obtained from the severely damaged TMI-2 core A description of the TMI-2 core bore during July and August, 1986. drilling unit used to obtain samples; a summary and discussion of the data from the ten core bore segments which were obtained; and the initial results of analysis and evaluation of these data are presented in thls report. the accident scenario is also discussed.The impact of the major findings relative to our understanding o f t i DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.. SUMMARYExaminations of the TMI-2 core indicated that a hard, nearly impenetrable layer of material exists across the core at approximately the mid-core elevation. It was hypothesized that this hard, basically ceramic material extended downward to about the 0.6-m elevation. material were required to complete the end-state characterization of the core configuration, as well as to improve understanding of the physical and chemical materials interactions and fission product retention of the core materials. A core bore machine has been designed and utilized to safely and efficiently provide the desired samples prior to the commencement of bulk defueling of the core by General Public Utilities Nuclear Corp. (GPU). Samples of thisThe core bore machine drilled 6-ft "core" samples approximately 2.5 in. in diameter, 'which were later removed from the reactor vessel (RV) for detailed physical and chemical examination. The hole remaining after sample removal provided access for closed-circuit te evision (video) inspections of the surrounding region. The central regions of the CSA do not contain significant amounts of previously molten fuel, which suggests that the major crust failure location was not in the central region of the core. primary migration path o f the previously molten material into the lower plenum appears to be located on the east side of the core near the periphery, primarily at assemblies P-5 and P-6. The3. -Based.on the limited video inspection data, the CSA appears to be undamaged. in those areas where previously mol ten ceramic mate...

The key role of sample analysis in Fukushima Dai-Ichi decommissioning, debris management, and accident progression investigation

“…After the upper head removal, samples were obtained as a byproduct of the core bore drilling. An examination of coolingsystem artifacts was also then performed, including the collection of samples such as debris from the plenum cover, filters from the makeup and letdown system, and control-rod components such as leadscrews and support tubes (Jensen et al, 1987;Tolman et al, 1987). These samples were analyzed using αand γ-spectroscopy, optical microscopy, and SEM EDS to confirm radionuclide and elemental composition.…”