Laser etching of Thoria pellets for microstructural investigations

Nanosecond laser ablation of Thoria fuel pellets for microstructural study

“…The laser wavelength was taken to be 532 nm corresponding to the second harmonic emission from a Nd:YAG laser. Our experimental observations on laser etching of Thoria used a single shot of laser pulse [7]. Hence calculations reported here have been carried out for laser based etching using a single laser pulse.…”

“…I S (x, t) denotes the instantaneous laser irradiance at the sample surface determined by the temporal and spatial profile of the incident laser pulse. For our experimental laser surface etching system a pulsed Nd:YAG laser operating at its second harmonic wavelength of 532 nm has been employed [7]. The temporal profile of the laser pulse is typically depicted by a Gaussian in time having a full width at half maxima (FWHM) of 5 ns.…”

“…This, to the best of our knowledge, is the first report on theoretical simulation of laser ablation of Thoria. In keeping with our experimental observations related to the specific application of laser based surface preparation of Thoria pellets for metallographic investigations [7], we have considered the particular case where a nanosecond pulsed laser is utilized to laser ablate Thoria fuel pellets. Through this simulation model we seek to develop an understanding of the process of laser based etching of Thoria and make theoretical estimates of process features such as time evolution of temperature distribution in the target, melt depth and ablation rates.…”

“…Therefore, both these etching techniques prove to be inappropriate for surface preparation of irradiated Thoria pellets. However, recently laser based etching has been reported as a potential alternative etching technique that has successfully revealed the microstructure of Thoria fuel elements thus enabling their subsequent metallographic investigation [7]. This laser based etching technique permits strongly localized heat or photo-treatment of materials and thus has several advantages as compared to conventional etching techniques.…”

Fabrication of Thorium and Thorium Dioxide

“…Thoria pellets could be readily thermal etched to be able to see well defined grain boundaries. A Laser etching technique has been developed for etching thoria for micro structural investigation in reprocessing [24]. Sometimes a cored structure is visible in fractured sintered ceramic pellets.…”