Laser-pulse vaporization of uranium dioxide and other refractory materials

Abstract

The nature of the vapor produced by pulse surface heating of UO2 and several other materials was investigated using normal-mode laser pulses with peak power densities between 104 and 106 W/cm2. Maximum surface temperatures measured by optical pyrometry ranged from 1900 to 4200 K. At temperatures below ∼2400 K for UO2, the vapor pulse followed the Hertz–Langmiur vacuum vaporization theory. More energetic transients produced gasdynamic blowoffs accompanied by significant supersaturation in the expanding plume. Neutron activation analysis of the collected vapor indicated that the total quantity of liquid UO2 evaporated in the pulse followed the Hertz–Langmuir formula. However, mass spectrometric analysis of the emitted vapor showed large deviations in the quantity and waveform shape of the monomer species. These and other features of the blowoff were satisfactorily explained in terms of nucleation and growth of polymeric species. Although UO2 clusters were undetectable by the mass spectrometer, polymers of MgO and ZrO2 were observed.

A Theoretical Study of the Structure and Bonding of UOX4(X=F, Cl, Br, I) Molecules: The Importance of InverseTransInfluence

“…The temperature of the solid surface (U or UO 2 ) was not reported in ref. 25, but it can be assumed to be between 2500 and 5000 K 67. Hence, on the basis of the available data (considering also some uncertainty in the computed results), we cannot make a decision for the observed species.…”

“…The temperature of the solid surface (U or UO 2 ) was not reported in ref. [25], but it can be assumed to be between 2500 and 5000 K. [67] Hence, on the basis of the available data (considering also some uncertainty in the computed results), we cannot make a decision for the observed species. From this point of view, the solution of the problem requires sophisticated calculations and a reliable estimation of the vapour temperature.…”

Laser Ablation Mass Spectrometry of Actinide Dioxides: ThO2, UO2, NpO2, PuO2 and AmO2

“…The key Observation was that the substantial qualitative differences between these An were consistently reproduced; thus, for example, UOJ and NpOJ were always significant species whereas only small amounts of PuOj and minuscule or undetectable amounts of ThOJ and AmOJ were produced. Although more accurate high-temperature thermodynamic data can be obtained by heating with long-duration (e.g., msec) laser pulses and careful control and measurement of experimental conditions [20], the present results demonstrate the value of the technique employed here for qualitatively assessing vaporization behavior and comparative stabilities of high-temperature species. It is noted that in contrast to previous LA-MS experiments with lanthanide samples [15], no significant amounts of oxide düster ions -e.g.…”

Laser pulse heating of nuclear fuels for simulation of reactor power transients

“…The presence of higher oxides in the surface and in the plume was expected from the temperature (believed to have gone above 3000 • C) and the ambient [4,5].…”