The detection of trace amounts of H and D present in Zr-2.5%Nb in the form of ZrH and ZrD, respectively, by LIBS was explored. The intended use case for this experimentation was CANada Deuterium Uranium (CANDU) nuclear reactor pressure
tube inspections where hydride buildup can lessen the mechanical strength of these
components. As these tubes carry coolant and house the fuel bundles, their integrity
is paramount. A LIBS inspection method is of interest in the nuclear industry due
to the operational flexibility it would introduce and its ability to reduce the cost,
time, and radiation dose associated with inspection campaigns of pressure tubes in CANDU nuclear reactors.
Using LIBS, simultaneous detection of H and D was achieved in a low-pressure air environment using a microjoule, picosecond pulsed laser and emission being captured by a high-resolution spectrometer. The emission lines of the two species were blended, however, two peaks can be seen. Experiments using a milijoule, nanosecond pulsed laser in a LIBS setup were also conducted at atmospheric pressures. These experiments failed to show D emission, however.
In addition to detecting emission from H and D, a Monte Carlo algorithm was developed for estimating the error associated with a LIBS inspection of a pressure tube segment. ZrH and ZrD form heterogeneous structures in the bulk of the Zr-2.5%Nb pressure tube material, meaning that a single measurement would not be indicative of the entire tube. Using metallographs of artificially hydrided pressure tube samples, the error within a given confidence interval was found as a function of number of measurement sites and ablation diameter.
Furthermore, the impacts to Zr-2.5%Nb based on intense laser-matter interactions
was investigated by optical microscopy and interferometry, allowing for 3-dimensional
reconstructions of ablation craters. The morphology of millijoule, nanosecond pulsed laser-matter interaction and microjoule, picosecond pulsed laser-matter interaction were the subjects of this investigation. The salient difference between the two interactions is the evidence of substantial melting and subsequent re-deposition of material in the case of nanosecond interactions, whereas picosecond ablation yielded little melting.
These results support the further development of a LIBS-based inspection method
for determining the concentration of H and D in Zr-2.5%Nb. It was found that a
vacuum environment allows for the simultaneous detection of H and D emission.
Further experimentation should explore using low-pressure buffer gas environments
as a method to further distinguish emission between the two species. / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25778 |
| Date | January 2020 |
| Creators | Kurnell, Mitchell D. |
| Contributors | Novog, David, Preston, John, Engineering Physics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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