Conductivity monitoring for leak detection in a double-walled plutonium container

• Main Author: Nelson, Mark Andrew
• Format: Dissertation
• Language: English
• Subjects: energy; engineering, nuclear
• ISBN: 0493024514; 9780493024516

A methodology using ionizing radiation to determine the amount of non-noble gas in an otherwise noble gas environment as well as the activity of and type of radiation was examined. The movement of charge carriers in a weak electric field was modeled as well as the response of a charge-sensitive preamplifier that would be used to measure the charge carriers. Free-electron and ion pulses were determined to have collection times on the order of microseconds and milliseconds respectively. The electron and ion pulse maximum amplitudes were determined to be on the order of picoamps and femtoamps respectively.
An apparatus was assembled to test the model and three modes of radiation-detector operation were investigated; pulse mode, current mode, and mean square voltage (MSV) mode. The pulses resulting from positive ions and free-electrons created by an alpha particle in argon were collected and fit to the previously determined model. Positive and negative pulses in zero-air were also measured but the preamp response function did not correctly model the resulting pulses.
The current and MSV modes were subsequently examined. It was determined that non-noble constituents in an otherwise noble gas could be detected by monitoring the negative current arriving on the anode in the MSV mode. Monitoring the cathode in the current mode is the best method to determine total activity present.
This methodology has application in determining the integrity of a double-walled storage container.