Hydrogen generation by water radiolysis with immersion of oxidation products of Zircaloy-4

Abstract

In order to predict the hydrogen gas generation from seawater or water in which debris would be included by the severe accident of nuclear power plant, we investigated the effect of ZrO 2 and the oxidation products of Zircaloy-4 on hydrogen gas generation by radiolysis of water since the radiolytic generation could be affected by materials immersed in water. Powders of well-characterized oxides and oxidation products were immersed in either seawater or distilled water, and irradiated by gamma ray from a Co-60 source. The observed hydrogen yield, G(H 2 ), was measured as a function of the weight fraction of oxide in water up to 50 wt%. The enhancement of the hydrogen generation by radiolysis of water with the commercial oxides and the oxidation products of Zircaloy-4 was quite small or absent in seawater. But the enhancement was observed in the presence of the oxides or the oxidation products at low weight fraction in distilled water. This enhancement in distilled water seemed to be dependent on specific surface area or particle size, but its dependence on the crystal structure was not apparent in the experimental results. The enhancement was saturated at higher ZrO 2 weight fractions and it was not apparent in the seawater.

The influence of various sized zircaloy-4 oxidation products on hydrogen generation of the water solution by Co-60 gamma radiolysis

“…In our previous study which used two commercial zirconium oxides indicated that the G(H 2 ) of yttria-stabilized tetragonal zirconia (t-ZrO 2 ) was larger than monoclinic zirconia (m-ZrO 2 ). The G(H 2 ), median particle diameter, and specific surface area of m-ZrO 2 were 2.1E -08 mol/J, 3 μm, and 19.6 m 2 /g and these of t-ZrO 2 were 4.2E -08 mol/J, 3 μm, and 63.2 m 2 /g (Matsumoto et al, 2015). However, in the experiments with water containing two different oxidation products of zry-4, the G(H 2 ) of the oxidation product T never exceeded the oxidation product M. We have calculated and compared the G(H 2 )/S of the oxidation products and two commercial zirconium oxides.…”

“…We have oxidized the zry-4 under various conditions and crushed them to investigate the effects of the oxidation products on the H 2 generation by water radiolysis. The enhancement of H 2 generation seemed to be dependent on either the specific surface area or the particle size of the oxidation product, but it was not certain which is the predominant factor (Matsumoto et al, 2015). The characterization of the aerosol source term emitted during the laser cutting of fuel debris assumes that the particle mass size distributions corresponding to particle aerodynamic diameters between 0.01 and 10 µm (Porcheron et al, 2018).…”

Characterization of ZrN, ZrO2 and β′–Zr7O11N2 nanoparticles synthesized by pulsed wire discharge

“…The formation mechanisms of these phases were complicated and would require extra information from the accident product analysis. On the other hand, characterization of the oxidation products of Zircaloy is also relevant in considering the hydrogen safety in fuel debris storage . In some cases, ZrN, Zr oxynitrides, and ZrO 2 coexisted in a fine microstructure for which nanoscale analyses should be necessary, for those circumstances, transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) are useful methods.…”