Gamma 60Co-irradiation of organic matter in the Phosphoria Retort Shale

Lewan, Michael D.; Ulmishek, Gregory F.; Harrison, W.; Schreiner, F.

doi:10.1016/0016-7037(91)90163-y

Cited by 20 publications

(23 citation statements)

References 28 publications

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“…This water is radiolytically transformed into hydrogen, but, in the presence of oxygen (under air atmosphere), the reaction rate is smaller, conversely, as the main source of hydrogen is organic matter in other types, hydrogen generation is only due to organic matter radiolytic decomposition -radiation induced crosslinking-as previously demonstrated on polymers [5] and natural organic matter [6]. In such systems, the main source of hydrogen is water from the fluid inclusions, and not the decomposition of organic matter.…”

Section: Influence Of Integrated Dose (Figs 1 A-i and 2)mentioning

confidence: 90%

Compared Study of Radiolysis-Induced Gas Liberation in Rocksalt from Various Origins

et al. 1992

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The evolution of impure rocksalt samples under irradiation has been investigated and compared to the evolution of pure halite, concerning the radiolytic release of gases. Four different types of rocksalt (pure halite, anhydrite-bearing, sylvinite-bearing, and marneous) have been irradiated with spent fuel at doses ranging from 10 4 Gy to 10 7 Gy, under synthetic air or helium at 50'C, 150'C, and 200'C. Marneous and anhydrite-bearing salt produced higher amounts of gas than the two other types, especially for H 2 , CO, and CH 4 . Radiolytic gas production essentially originates from the decomposition of traces of different kind of impurities : fluid inclusions, which can be composed of brine and/or organic fluids and gases; minerals such as carbonates, sulfates, or hydrated minerals; organic matter, in general (kerogen). Pure halite decomposes only at very high doses (more than 10 7 Gy) giving off some Cl 2 and other corrosive gases. Gas production increases steadily with dose for H 2 , CO, and CH 4 , contrary to what is observed for the pure Asse salt, where H 2 and CO, respectively, peak at 106, and 105 Gy. The increase, with dose, in the production of CH 4 , C 2 H 6 , and C 3 H 8 is far higher for marneous salt and higher for anhydrite-bearing salt. The decrease of the 0 2 /N 2 (oxygen consumption) ratio in the irradiation atmosphere is in the following order: marneous>anhydrite>halite=sylvinite. The overall effect of 'y-irradiation on impure rocksalt can be described as follows : destruction of organic matter that produces chemically reduced gases (H 2 , CO, hydrocarbons), after an initial stage of oxygen consumption, which is reached more or less quickly, depending on the availability and quantity of organic matter. The use of impure, i.e, organic matter-bearing salt, as host-rock or engineered barrier for nuclear wastes, may be questioned, because of the high amount of gases produced in the immediate vicinity of the container (explosion hazards, pressure build-up). The present study will be followed by a modelling of the in-situ radiolytic gas production, taking into account: 1) the dose distribution with time, 2) the temperature distribution with time, and 3) the geometry of the repository, and will allow us to estimate the potentiel safety impact of radiolytic gas production in the case of a repository emplaced in impure rocksalt.

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Section: Influence Of Integrated Dose (Figs 1 A-i and 2)mentioning

confidence: 90%

Compared Study of Radiolysis-Induced Gas Liberation in Rocksalt from Various Origins

et al. 1992

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“…Intensive radiolysis may cause polymerization and condensation of functionalized lipids thus reducing the amount of aliphatics in altered bitumen (Lewan et al, 1991;Landais, 1996b and references therein). A proposed mechanism for this is by the crosslinking of hydrocarbons due to interaction with a free radical.…”

Section: Radiolysismentioning

confidence: 99%

“…When a free radical interacts with another hydrocarbon, a hydrogen atom is abstracted and a C-C bond is formed. Such a mechanism may continue until alkanes and long-chain polymers are rendered infusible (Lewan and Buchardt, 1989;Lewan et al, 1991). Another mechanism that causes polymerization of hydrocarbons is gradual construction from methane (Court et al, 2006).…”

Section: Radiolysismentioning

confidence: 99%

“…Uranium enrichment and associated radiation will affect the composition of sediment OM by reducing the relative proportion of hydrogen (as monitored by HI or the H/C ratio) or dehydrogenation and in parallel increase the oxygen proportion (OI or O/C ratio kerogen) in the bulk kerogen or black shale (Zumberge et al, 1978;Nakashima et al, 1984;Leventhal et al, 1986;Dahl et al, 1988;Lewan and Buchardt, 1989;Disnar and Sureau, 1990;Landais, 1996b;Court et al, 2006;Greenwood et al, 2013). Most of the radiation resulting from 238 U decay in natural systems will be emitted in the form of a-radiation (Lewan et al, 1991), which has a shallow penetration depth of <100 microns, followed by less intensive gradiation which penetrates several decimeters. In natural systems it must be noted that distribution of radiation-emitting elements is not uniform and hence intimate spatial association of OM and U can lead to significant alteration despite the shallow penetration depth of a-rays.…”

Section: Effects Of Radiolysis On Ommentioning

confidence: 99%

“…Several experiments that have artificially applied radiation to natural OM have been conducted (e.g. Lewan et al, 1991), based on the use of g-radiation that might not be representative for near natural conditions where a-radiation is of higher relevance. No formation of ketones was observed in these artificial radiolysis experiments.…”

Section: Effects Of Radiolysis On Ommentioning

confidence: 99%

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