Session: 11-01: Nuclear Power NDE

Paper Number: 135276

135276 - Eddy Current Probe Design for Graphite Pebble Inspection in Advanced Reactors 

Abstract: 

This paper describes the exploration of applying eddy current (EC) inspections to graphite pebbles, which are being used experimentally at Argonne National Laboratory as simulated fuel elements in high temperature reactor (HTR) design concepts. Eddy current inspection is a fast and economical non-destructive evaluation (NDE) technique that can detect flaws, impregnations, or manufactured discontinuities in the outer layer of graphite pebbles. Rapid testing for sorting pebbles is crucial when dealing with quantities of pebbles in the hundreds of thousands. In the existing paradigm, pebble batches can be sorted using their radioactivity levels, however, conventional radioactivity level sensors typically require lower operating temperatures, and therefore time for the pebbles to cool. With the current developments in high temperature EC probes, this NDE method could considerably reduce the downtime required for the sorting of marked pebbles under harsh environments. This paper describes the numerical electromagnetic modeling results and measurements on a sample pebble, which are used to optimize the EC probe design and frequency selection. We also present experimental data collected on a sample pebble with a thin film surface array probe, demonstrating the capability to detect flaws in the outer graphite layer of the pebble. We conclude that EC inspection is a promising technique for rapid and reliable testing of graphite pebbles for HTR applications.

Presenting Author: Thomas W. Elmer Argonne National Laboratory

Presenting Author Biography: Thomas Elmer II received a B.S. degree in physics with minors in math and computer science from La Sierra University in 1998 and an M.S. degree in Physics from the University of Illinois, Chicago in 2004. While at La Sierra, he worked for the physics department, writing and maintaining programs to run laboratory experiments. In 1999 he joined Argonne National Laboratory as a student intern, eventually staying as a Principal Software Engineer for the Sensors, Instrumentation & NDE Group of the Nuclear Science and Engineering Division. He writes programming for modeling, motion control, data acquisition, and data analysis in the microwave, millimeter-wave, and terahertz sensors labs. In 2007 he received an R&D 100 award from R&D Magazine and currently has five U.S. patents.

Authors:

Thomas W. Elmer Argonne National Laboratory
Eugene Koehl Argonne National Laboratory
Claudio Gariazzo Argonne National Laboratory
Sasan Bakhtiari Argonne National Laboratory