Publications

Rochau, Gary E.; Rochau, Gary E.; Caffey, Thurlow W.

A major cause of failures in heat exchangers and steam generators in nuclear power plants is degradation of the tubes within them. The tube failure is often caused by the development of cracks that begin on the outer surface of the tube and propagate both inwards and laterally. A new technique was researched for detection of defects using a continuous-wave radar method within metal tubing. The experimental program resulted in a completed product development schedule and the design of an experimental apparatus for studying handling of the probe and data acquisition. These tests were completed as far as the prototypical probe performance allowed. The prototype probe design did not have sufficient sensitivity to detect a defect signal using the defined radar technique and did not allow successful completion of all of the project milestones. The best results from the prototype probe could not detect a tube defect using the radar principle. Though a more precision probe may be possible, the cost of design and construction was beyond the scope of the project. This report describes the probe development and the status of the design at the termination of the project.

Weiss, Chester J.; Caffey, Thurlow W.

Borehole radar systems can provide essential subsurface structural information for environmental evaluation, geotechnical analysis, or energy exploration. Sandia developed a prototype continuous-wave Borehole Radar (BHR) in 1996, and development of a practical tool has been continuing at a Russian institute under a Sandia contract. The BHR field experiments, which were planned for the summer of 2001 in Russia, provided a unique opportunity to evaluate the latest Sandia algorithms with actual field data. A new three-dimensional code was developed to enable the analysis of BHR data on modest-sized desktop workstations. The code is based on the staggered grid, finite difference technique, and eliminates 55% of the massive storage associated with solving the system of finite-difference linear equations. The code was used to forward-model the Russian site geometry and placement of artificial targets to anticipate any problems that might arise when the data was received. Technical software and equipment problems in the Russian field tests, conducted in August 2001, invalidated all but one of the data sets. However, more field tests with improved equipment and software are planned for 2002, and analysis of that data will be presented in a future report.

Caffey, Thurlow W.

A major cause of failures in heat exchangers and steam generators in nuclear power plants is degradation of the tubes within them. The tube failure is often caused by the development of cracks that begin on the outer surface of the tube and propagate both inwards and laterally. A new technique will be described for detection of defects using a continuous-wave radar device within metal tubing. The technique is 100% volumetric, and may find smaller defects, find them more rapidly, and find them less expensively than present methods. Because this project was started only recently, there is no demonstrated performance to report so far. However, the basic engineering concepts will be presented together with a description of the milestone tasks and dates.