The Woodruff School

SUMMARY

This research determines the sensitivity of nonlinear ultrasound (NLU) to the changes in microstructure of heat treated Fe-1.0% Cu and Fe-0.1% Cu. The Fe-Cu material investigated in this research serves as a surrogate material to simulate the evolution of radiation damage that occurs in reactor pressure vessels (RPV) of light water power reactors. The formation of the Cu-precipitates in RPV steel is one of the main factors leading to radiation embrittlement. With RPVs seeing more neutron cycles than originally anticipated, it is imperative to develop nondestructive evaluation (NDE) techniques capable of evaluating the integrity of these structures. This research investigates the sensitivity of the NLU technique second harmonic generation (SHG) to the changes in the surrogate material microstructure. It is seen that as the surrogate material is heat treated the radii size of the Cu-precipitates, which is on the order of nanometers, grow. For the experimental procedure used in this research, longitudinal waves are propagated through the thickness of the specimens where higher harmonics are generated. The nonlinearity parameter, β, can then be calculated by relating the amplitude of the fundamental frequency to the amplitude of the second harmonic wave. Additionally, a theoretical model was developed to relate the change in β to the change in the Cu-precipitate radius. As will be seen in the results, there is a signification increase in β for the Fe-1.0% Cu specimens in contrast to there being very little change in β for the Fe-0.1% Cu specimens.

SUBJECT:	M.S. Thesis Presentation

BY:	Katherine Scott

TIME:	Tuesday, December 6, 2016, 1:30 p.m.

PLACE:	Love Building, 109

TITLE:	Characterization of Nuclear Reactor Pressure Vessel (RPV) Surrogate Specimens with Ultrasound

COMMITTEE:	Laurence Jacobs, Chair (ME, CEE) Jin-Yeon Kim (CEE) Karim Sabra (ME)

SUMMARY This research determines the sensitivity of nonlinear ultrasound (NLU) to the changes in microstructure of heat treated Fe-1.0% Cu and Fe-0.1% Cu. The Fe-Cu material investigated in this research serves as a surrogate material to simulate the evolution of radiation damage that occurs in reactor pressure vessels (RPV) of light water power reactors. The formation of the Cu-precipitates in RPV steel is one of the main factors leading to radiation embrittlement. With RPVs seeing more neutron cycles than originally anticipated, it is imperative to develop nondestructive evaluation (NDE) techniques capable of evaluating the integrity of these structures. This research investigates the sensitivity of the NLU technique second harmonic generation (SHG) to the changes in the surrogate material microstructure. It is seen that as the surrogate material is heat treated the radii size of the Cu-precipitates, which is on the order of nanometers, grow. For the experimental procedure used in this research, longitudinal waves are propagated through the thickness of the specimens where higher harmonics are generated. The nonlinearity parameter, β, can then be calculated by relating the amplitude of the fundamental frequency to the amplitude of the second harmonic wave. Additionally, a theoretical model was developed to relate the change in β to the change in the Cu-precipitate radius. As will be seen in the results, there is a signification increase in β for the Fe-1.0% Cu specimens in contrast to there being very little change in β for the Fe-0.1% Cu specimens.