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Gamma radiation induces hydrogen absorption by copper in water.

Lousada CM, Soroka IL, Yagodzinskyy Y, Tarakina NV, Todoshchenko O, Hänninen H, Korzhavyi PA, Jonsson M - Sci Rep (2016)

Bottom Line: One of the most intricate issues of nuclear power is the long-term safety of repositories for radioactive waste.Several countries have considered copper as an outer corrosion barrier for canisters containing spent nuclear fuel.At a dose of 69 kGy the uptake of hydrogen by metallic copper is 7 orders of magnitude higher than when the absorption is driven by H2(g) at a pressure of 1 atm in a non-irradiated dry system.

View Article: PubMed Central - PubMed

Affiliation: Division of Materials Technology, Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden.

ABSTRACT
One of the most intricate issues of nuclear power is the long-term safety of repositories for radioactive waste. These repositories can have an impact on future generations for a period of time orders of magnitude longer than any known civilization. Several countries have considered copper as an outer corrosion barrier for canisters containing spent nuclear fuel. Among the many processes that must be considered in the safety assessments, radiation induced processes constitute a key-component. Here we show that copper metal immersed in water uptakes considerable amounts of hydrogen when exposed to γ-radiation. Additionally we show that the amount of hydrogen absorbed by copper depends on the total dose of radiation. At a dose of 69 kGy the uptake of hydrogen by metallic copper is 7 orders of magnitude higher than when the absorption is driven by H2(g) at a pressure of 1 atm in a non-irradiated dry system. Moreover, irradiation of copper in water causes corrosion of the metal and the formation of a variety of surface cavities, nanoparticle deposits, and islands of needle-shaped crystals. Hence, radiation enhanced uptake of hydrogen by spent nuclear fuel encapsulating materials should be taken into account in the safety assessments of nuclear waste repositories.

No MeSH data available.


Related in: MedlinePlus

Amounts of H2 () and H2O () measured in samples of copper metal irradiated in water as a function of the total dose of γ-radiation deposited (D) (kGy). The measurements of H2 and H2O were performed after irradiation. Each data point corresponds to a different irradiation experiment. Both sets of data are normalized for the background values. The linear regression is given by: y = 4 · 10−6x + 0.085; R2 = 0.827.
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f2: Amounts of H2 () and H2O () measured in samples of copper metal irradiated in water as a function of the total dose of γ-radiation deposited (D) (kGy). The measurements of H2 and H2O were performed after irradiation. Each data point corresponds to a different irradiation experiment. Both sets of data are normalized for the background values. The linear regression is given by: y = 4 · 10−6x + 0.085; R2 = 0.827.

Mentions: The γ-radiation-induced hydrogen charging of copper was investigated as a function of total radiation dose (D). For each total radiation dose, blanks or background samples were prepared. The background samples consist of non-irradiated copper exposed to water for the same period of time as that of the irradiated samples. The background samples are necessary because copper has some amount of hydrogen from the manufacturing and even without the influence of ionizing radiation copper can induce the formation of minute amounts of H2(g) when exposed to water3738. This is because water can adsorb dissociatively on some copper surfaces and this process leads to the formation of both HO• and H•, the latter is a precursor of H238. In Fig. 2 the amount of H2(g) measured in copper that was irradiated in aqueous media is plotted as a function of the total dose (D) corrected for the background values. It is known that desorption of dissociatively adsorbed water from metal and oxide surfaces can occur via a channel that leads to the formation of H2(g)39. This is due to the recombination of surface adsorbed H-atoms that occurs when the temperature is increased in the temperature-programmed desorption (TPD) experiment40. In order to exclude the hypothesis that the H2 measured in our samples originates from the recombination of products of dissociatively adsorbed water at the copper surface, we also determined the amount of H2O that is adsorbed at the surface of the copper samples and investigated possible correlations with the amount of H2 measured. In Fig. 2 it can be seen that the amount of H2O present in the copper samples does not correlate with the amount of H2 detected. This fact excludes the possibility that the H2 measured originates from the recombination of products of dissociatively adsorbed water at the copper surface. The H2(g) was measured post-irradiation which indicates that H• and/or H2 are stable in copper. Previous investigations of desorption of H2 from copper show that bulk H2 desorbs in the same temperature range41 as the H2 that was detected in our irradiation experiments (Fig. 3). This indicates that the majority of the hydrogen measured originates from the copper bulk because surface-adsorbed hydrogen desorbs at lower temperatures in the TPD measurements. It can be seen in Fig. 3 that the irradiated sample has a considerably higher hydrogen content that desorbs at temperatures corresponding to bulk hydrogen, T > 500 K. The hydrogen content of the irradiated samples is also higher at the surface and at a few subsurface layers—this is for T < 500 K. A scanning electron microscopy investigation showed that the surfaces of both non-irradiated and irradiated samples exposed to water became covered with particles of approximately 100 nm in size (Fig. 4). There are no significant differences in morphology or size of the particles formed at the surface of non-irradiated and irradiated samples. However, besides the formation of nanoparticles, irradiated samples display extensive surface erosion and the presence of islands of needle-shaped crystals (Figs 4c,d, 5 and 6), which were not observed on non-irradiated samples. Erosion features are present all over the surface of the sample but are more pronounced in areas nearby islands of needle-shaped crystals (Fig. 5a–e). Here they reach considerable depth, affecting the material subsurface layers up to several hundred33 nm. As a result of erosion, a diversity of porous structures, cavities and ravines are formed (Fig. 5b–e). Needle-shaped crystals occur either as large islands (of approximately 50–200 μm) or as very small crystals surrounding eroded areas (Fig. 5e). Interestingly, all observed islands of needle-shaped crystals have a core part (central nucleation point (Fig. 6d)), which is surrounded by a circle of nucleation points consisting of smaller crystal islands that are in turn encircled by very small crystals (indicated by white arrows on Fig. 6e). Energy-dispersive X-ray microanalysis and X-ray photoelectron spectroscopy performed at these areas confirmed the presence of oxygen, copper and a small amount of carbon in the crystals (Fig. 6e). According to previous studies on the radiation chemistry of copper/water interfaces, the corrosion products formed are most likely oxygen-containing products—mostly cuprite, Cu2O—resulting from the oxidation of copper33. All islands of needle–shaped crystals have a light blue color (Fig. 6d). This suggests the presence of copper (II) hydroxide or copper (II) hydroxy carbonate because cuprite has a red-pink color42.


Gamma radiation induces hydrogen absorption by copper in water.

Lousada CM, Soroka IL, Yagodzinskyy Y, Tarakina NV, Todoshchenko O, Hänninen H, Korzhavyi PA, Jonsson M - Sci Rep (2016)

Amounts of H2 () and H2O () measured in samples of copper metal irradiated in water as a function of the total dose of γ-radiation deposited (D) (kGy). The measurements of H2 and H2O were performed after irradiation. Each data point corresponds to a different irradiation experiment. Both sets of data are normalized for the background values. The linear regression is given by: y = 4 · 10−6x + 0.085; R2 = 0.827.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834571&req=5

f2: Amounts of H2 () and H2O () measured in samples of copper metal irradiated in water as a function of the total dose of γ-radiation deposited (D) (kGy). The measurements of H2 and H2O were performed after irradiation. Each data point corresponds to a different irradiation experiment. Both sets of data are normalized for the background values. The linear regression is given by: y = 4 · 10−6x + 0.085; R2 = 0.827.
Mentions: The γ-radiation-induced hydrogen charging of copper was investigated as a function of total radiation dose (D). For each total radiation dose, blanks or background samples were prepared. The background samples consist of non-irradiated copper exposed to water for the same period of time as that of the irradiated samples. The background samples are necessary because copper has some amount of hydrogen from the manufacturing and even without the influence of ionizing radiation copper can induce the formation of minute amounts of H2(g) when exposed to water3738. This is because water can adsorb dissociatively on some copper surfaces and this process leads to the formation of both HO• and H•, the latter is a precursor of H238. In Fig. 2 the amount of H2(g) measured in copper that was irradiated in aqueous media is plotted as a function of the total dose (D) corrected for the background values. It is known that desorption of dissociatively adsorbed water from metal and oxide surfaces can occur via a channel that leads to the formation of H2(g)39. This is due to the recombination of surface adsorbed H-atoms that occurs when the temperature is increased in the temperature-programmed desorption (TPD) experiment40. In order to exclude the hypothesis that the H2 measured in our samples originates from the recombination of products of dissociatively adsorbed water at the copper surface, we also determined the amount of H2O that is adsorbed at the surface of the copper samples and investigated possible correlations with the amount of H2 measured. In Fig. 2 it can be seen that the amount of H2O present in the copper samples does not correlate with the amount of H2 detected. This fact excludes the possibility that the H2 measured originates from the recombination of products of dissociatively adsorbed water at the copper surface. The H2(g) was measured post-irradiation which indicates that H• and/or H2 are stable in copper. Previous investigations of desorption of H2 from copper show that bulk H2 desorbs in the same temperature range41 as the H2 that was detected in our irradiation experiments (Fig. 3). This indicates that the majority of the hydrogen measured originates from the copper bulk because surface-adsorbed hydrogen desorbs at lower temperatures in the TPD measurements. It can be seen in Fig. 3 that the irradiated sample has a considerably higher hydrogen content that desorbs at temperatures corresponding to bulk hydrogen, T > 500 K. The hydrogen content of the irradiated samples is also higher at the surface and at a few subsurface layers—this is for T < 500 K. A scanning electron microscopy investigation showed that the surfaces of both non-irradiated and irradiated samples exposed to water became covered with particles of approximately 100 nm in size (Fig. 4). There are no significant differences in morphology or size of the particles formed at the surface of non-irradiated and irradiated samples. However, besides the formation of nanoparticles, irradiated samples display extensive surface erosion and the presence of islands of needle-shaped crystals (Figs 4c,d, 5 and 6), which were not observed on non-irradiated samples. Erosion features are present all over the surface of the sample but are more pronounced in areas nearby islands of needle-shaped crystals (Fig. 5a–e). Here they reach considerable depth, affecting the material subsurface layers up to several hundred33 nm. As a result of erosion, a diversity of porous structures, cavities and ravines are formed (Fig. 5b–e). Needle-shaped crystals occur either as large islands (of approximately 50–200 μm) or as very small crystals surrounding eroded areas (Fig. 5e). Interestingly, all observed islands of needle-shaped crystals have a core part (central nucleation point (Fig. 6d)), which is surrounded by a circle of nucleation points consisting of smaller crystal islands that are in turn encircled by very small crystals (indicated by white arrows on Fig. 6e). Energy-dispersive X-ray microanalysis and X-ray photoelectron spectroscopy performed at these areas confirmed the presence of oxygen, copper and a small amount of carbon in the crystals (Fig. 6e). According to previous studies on the radiation chemistry of copper/water interfaces, the corrosion products formed are most likely oxygen-containing products—mostly cuprite, Cu2O—resulting from the oxidation of copper33. All islands of needle–shaped crystals have a light blue color (Fig. 6d). This suggests the presence of copper (II) hydroxide or copper (II) hydroxy carbonate because cuprite has a red-pink color42.

Bottom Line: One of the most intricate issues of nuclear power is the long-term safety of repositories for radioactive waste.Several countries have considered copper as an outer corrosion barrier for canisters containing spent nuclear fuel.At a dose of 69 kGy the uptake of hydrogen by metallic copper is 7 orders of magnitude higher than when the absorption is driven by H2(g) at a pressure of 1 atm in a non-irradiated dry system.

View Article: PubMed Central - PubMed

Affiliation: Division of Materials Technology, Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden.

ABSTRACT
One of the most intricate issues of nuclear power is the long-term safety of repositories for radioactive waste. These repositories can have an impact on future generations for a period of time orders of magnitude longer than any known civilization. Several countries have considered copper as an outer corrosion barrier for canisters containing spent nuclear fuel. Among the many processes that must be considered in the safety assessments, radiation induced processes constitute a key-component. Here we show that copper metal immersed in water uptakes considerable amounts of hydrogen when exposed to γ-radiation. Additionally we show that the amount of hydrogen absorbed by copper depends on the total dose of radiation. At a dose of 69 kGy the uptake of hydrogen by metallic copper is 7 orders of magnitude higher than when the absorption is driven by H2(g) at a pressure of 1 atm in a non-irradiated dry system. Moreover, irradiation of copper in water causes corrosion of the metal and the formation of a variety of surface cavities, nanoparticle deposits, and islands of needle-shaped crystals. Hence, radiation enhanced uptake of hydrogen by spent nuclear fuel encapsulating materials should be taken into account in the safety assessments of nuclear waste repositories.

No MeSH data available.


Related in: MedlinePlus