A Review of the Effect of Irradiation on the Corrosion of Copper-Coated Used Fuel Containers

Radiation induced corrosion is one of the possible modes of materials degradation in the concept of long-term management of used nuclear fuel. Depending on the environmental conditions surrounding the used fuel container, a range of radiolysis products are expected to form that could impact the corrosion of the copper coating. For instance, γ-radiolysis of pure water produces molecular oxidants such as H2O2 and the radiolysis of humid air produces compounds such as NOx and HNO3. This review is confined to a discussion of the effect of γ-radiation on the corrosion of copper-coated containers. A simplified mixed-potential model is also presented to calculate the extent of copper corrosion by using the steady-state concentration of H2O2 generated during the first 300 years of emplacement, when the radiation field is significant.

Electron-induced radiolysis and sputtering on the surface of icy moons: insights from laboratory experiments

<p><strong>Abstract</strong></p> <p>The surfaces of Jupiter's icy moons are continually irradiated by charged particles from the Jovian plasma environment. This irradiation triggers chemical reactions in the surface ice and also acts as an atmospheric release process. Remote observations, theoretical modelling, and laboratory experiments must be combined to understand<br />this plasma-ice interaction. Here, we present new experiment results concerning the chemistry of irradiated water ice samples relevant for icy moons and other icy objects in the solar system. </p> <p><strong>Introduction</strong></p> <p>The University of Bern is developing the neutral gas mass spectrometer for ESA's Jupiter Icy moons Explorer (JUICE, Grasset et al. 2013), <br />planned to reach the Jupiter system in 2029. We therefore strive to fill knowledge gaps about the basic physics of the surfaces and atmospheres of Jupiter’s icy moons before the arrival of JUICE. We combine the available facilities for developing and calibrating mass spectrometers and ion/electron spectrometers (Marti et al. 2001) with the sample preparation techniques and diagnostics of the Planetary Imaging Group (Pommerol et al. 2019).</p> <p><strong>Experiment setup</strong></p> <p>To study the effects of electrons irradiating water ice, we subjected a variety of ice samples (thin amorphous ice films and macroscopic samples of porous ice with customizable grain size) to an electron beam of energies between 200 eV and 10 keV at pressures and temperatures representative for the surfaces of Jupiter's icy moons. The physical and optical properties of these macroscopic ice samples make them realistic analogues for planetary surfaces beyond the ice line. The effect of chemical impurities in the water ice, such as NaCl, can also be investigated. The particles released from the ice were monitored with a newly designed time-of-flight (TOF) mass spectrometer and (in the case of the water ice film) with a microbalance. </p> <p><strong>Preliminary results</strong></p> <p>Electron irradiation of pure water ice results mostly in the creation and release of H<sub>2</sub> and O<sub>2</sub> from H<sub>2</sub>O in a stoichiometric 2:1 ratio, which is in agreement with the results based on an older quadrupole mass spectrometer (Galli et al. 2018). This seems to hold true for any type of water ice sample, independent of grain size and crystallinity. We also derive upper limits for rare radiolysis products (such as OH and H<sub>2</sub>O<sub>2</sub>) and the time scales for the build-up and release of radiolysis products. The O<sub>2</sub> release lags behind the immediate H<sub>2</sub> release by typically ~ 10 s and is reminiscent of the time-dependent sputtering yield of O<sub>2</sub> from water ice upon ion irradiation (Teolis et al. 2005). This delayed O<sub>2</sub> release has implications for the O<sub>2</sub>/H<sub>2</sub>O ratio observed at the surface of icy objects in the solar system, such as Ganymede, Europa, Callisto (Calvin et al. 1996, Spencer and Calvin 2002), and 67P/Churyumov-Gerasimenko (Bieler et al. 2015).</p>

Electron irradiation of water ice samples in the laboratory - Implications for icy moons and comets

<p>The surfaces of icy bodies in the solar system are continuously irradiated by charged particles from planetary magnetospheres or from the solar wind. This irradiation induces chemical reactions in the surface ice and also acts as an atmospheric release process. Remote observations, theoretical modelling, and laboratory experiments must be combined to understand this plasma-ice interaction. In this presentation, we concentrate on laboratory experiments with electron irradiation (energy range of 0.1 to 10 keV) of water ice. The samples include thin ice films on a microbalance as well as thick layers of porous ice, resembling regolith. The physical and optical properties of the latter make them realistic analogues for the surfaces of icy moons.</p><p>We measure the sputtering yield and monitor the irradiation-induced alterations in the ice samples with a dedicated new time-of-flight mass spectrometer.<br>Previous results obtained with an earlier quadrupole mass spectrometer (Galli et al. 2018, Planetary and Space Sciences) indicated that most water escaping the ice sample upon electron irradiation does so in the form of the radiolysis products H<sub>2</sub> and O<sub>2</sub>. The freshly produced H<sub>2</sub> appeared to leave the porous water ice sample immediately whereas the O<sub>2</sub> escape slowly increased until reaching a steady-state ratio of 1:2 of O<sub>2</sub> to H<sub>2</sub>. With the new mass spectrometer, we investigate the release and storage of radiolysis products at a higher temporal resolution and sensitivity for a variety of ice sample porosities and thicknesses. We pay special attention to less abundant radiolysis products such as H<sub>2</sub>O<sub>2</sub> and to the O<sub>2</sub>/H<sub>2</sub>O ratio in the irradiated water ice layer.</p>