Fast, quantitative, and nondestructive evaluation of hydrided LWR fuel cladding by small angle incoherent neutron scattering of hydrogen

Abstract

a b s t r a c tA nondestructive neutron scattering method to precisely measure the uptake of hydrogen and the distribution of hydride precipitates in light water reactor (LWR) fuel cladding was developed. Zircaloy-4 cladding used in commercial LWRs was used to produce hydrided specimens. The hydriding apparatus consists of a closed stainless-steel vessel that contains Zr alloy specimens and hydrogen gas. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentrations were selected for the neutron study. Optical microscopy shows that our hydriding procedure results in uniform distribution of circumferential hydrides across the wall thickness. Small angle neutron incoherent scattering was performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Our study demonstrates that the hydrogen in commercial Zircaloy-4 cladding can be measured very accurately in minutes by this nondestructive method over a wide range of hydrogen concentrations from a very small amount (%20 ppm) to over 1000 ppm. The hydrogen distribution in a tube sample was obtained by scaling the neutron scattering rate with a factor determined by a calibration process using standard, destructive direct chemical analysis methods on the specimens. This scale factor can be used in future tests with unknown hydrogen concentrations, thus providing a nondestructive method for determining absolute hydrogen concentrations.

High Resolution Neutron Radiography and Tomography of Hydrided Zircaloy-4 Cladding Materials

“…1). The crystal orientation mapping by electron backscatter diffraction (EBSD) reveals that our samples are heavily textured (Yan et al, 2014), which might result in the circumferential hydrides, as shown in Fig. 1.…”

“…This naturally high sensitivity of hydrogen through neutron scattering techniques allows for a detailed, non-destructive study of zirconium cladding. Neutron radiography and scattering have been used to study the hydrogen distribution (Brosse et al, 2006, Lehmann et al, 2004, Yan et al, 2014, Yasuda et al, 2003, by which hydrogen content higher than a few hundred ppm can be quantitatively detected using the property of neutron attenuation due to absorption and scattering from hydrogen. This work shows that neutron radiography and tomography can be used for hydrogen analysis of hydrided Zircaloy-4 cladding samples with a wide range of hydrogen concentrations.…”

Hydriding, Oxidation, and Ductility Evaluation of Cr-Coated Zircaloy-4 Tubing

“…Because of the thin coating, the mechanical behavior after oxidation is rooted in the reduced oxidation and potentially reduced hydrogen pickup instead of an increased circumferential thickness. The hydriding system consists of a tube furnace with a stainless steel tube that is heated to high temperatures in the presence of hydrogen to introduce a desired quantity of hydrogen into the specimen [14]. Hydrogen uptake at elevated temperature results in the formation of hydrides, which are stable when cooled to room temperature.…”

“…The hydriding temperature was set to 425 °C, and the initial tube pressure was varied to adjust to the specimen's target hydrogen concentrations. The hydrogen content of the hydrided specimens was measured using the inert gas fusion technique per ASTM E1447-05 or the The hydriding system consists of a tube furnace with a stainless steel tube that is heated to high temperatures in the presence of hydrogen to introduce a desired quantity of hydrogen into the specimen [14]. Hydrogen uptake at elevated temperature results in the formation of hydrides, which are stable when cooled to room temperature.…”