A modelling approach to assess the environmental/radiological impact of C-14 release from radioactive waste repositories

Charalampos Doulgeris, Paul Humphreys

Research output: Contribution to journalArticle

Abstract

Assessments of the environmental impact of C-14 disposal often assume that C-14 is converted into gases that are able to migrate to the surface, where they pose a radiological risk. However, uncertainties, associated with the long-term release of C-14 from graphite and the evolution in the post-closure environment of a geological disposal facility (GDF), exist. In this paper, an integrated modelling framework has been developed to investigate these uncertainties. The modelling framework consists of a biogeochemical near field model which interfaces with a geosphere/biosphere model and it is verified by comparing the results to those obtained from other models. A sensitivity analysis discloses that a faster mid chain scission rate of stopped cellulose about four orders of magnitude assesses a twice higher effective dose. In another scenario, which is related to the control of microbial activity by pH and the availability of carbon dioxide to microbes, the effective dose is two orders of magnitude higher compared with a reference scenario. This modelling work illustrates also the importance of far field parameters, such as the rock permeability and the release area of gas pathway, to the assessment of effective dose.
Original languageEnglish
Pages (from-to)61-71
Number of pages11
JournalJournal of Environmental Radioactivity
Volume205-206
Early online date15 May 2019
DOIs
Publication statusPublished - 1 Sep 2019

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Radioactive Waste
Radioactive wastes
repository
radioactive waste
Uncertainty
Environmental impact
environmental impact
Gases
Graphite
Carbon Dioxide
Cellulose
modeling
Permeability
gas
graphite
biosphere
Sensitivity analysis
microbial activity
sensitivity analysis
cellulose

Cite this

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title = "A modelling approach to assess the environmental/radiological impact of C-14 release from radioactive waste repositories",
abstract = "Assessments of the environmental impact of C-14 disposal often assume that C-14 is converted into gases that are able to migrate to the surface, where they pose a radiological risk. However, uncertainties, associated with the long-term release of C-14 from graphite and the evolution in the post-closure environment of a geological disposal facility (GDF), exist. In this paper, an integrated modelling framework has been developed to investigate these uncertainties. The modelling framework consists of a biogeochemical near field model which interfaces with a geosphere/biosphere model and it is verified by comparing the results to those obtained from other models. A sensitivity analysis discloses that a faster mid chain scission rate of stopped cellulose about four orders of magnitude assesses a twice higher effective dose. In another scenario, which is related to the control of microbial activity by pH and the availability of carbon dioxide to microbes, the effective dose is two orders of magnitude higher compared with a reference scenario. This modelling work illustrates also the importance of far field parameters, such as the rock permeability and the release area of gas pathway, to the assessment of effective dose.",
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A modelling approach to assess the environmental/radiological impact of C-14 release from radioactive waste repositories. / Doulgeris, Charalampos; Humphreys, Paul.

In: Journal of Environmental Radioactivity, Vol. 205-206, 01.09.2019, p. 61-71.

Research output: Contribution to journalArticle

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AU - Humphreys, Paul

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AB - Assessments of the environmental impact of C-14 disposal often assume that C-14 is converted into gases that are able to migrate to the surface, where they pose a radiological risk. However, uncertainties, associated with the long-term release of C-14 from graphite and the evolution in the post-closure environment of a geological disposal facility (GDF), exist. In this paper, an integrated modelling framework has been developed to investigate these uncertainties. The modelling framework consists of a biogeochemical near field model which interfaces with a geosphere/biosphere model and it is verified by comparing the results to those obtained from other models. A sensitivity analysis discloses that a faster mid chain scission rate of stopped cellulose about four orders of magnitude assesses a twice higher effective dose. In another scenario, which is related to the control of microbial activity by pH and the availability of carbon dioxide to microbes, the effective dose is two orders of magnitude higher compared with a reference scenario. This modelling work illustrates also the importance of far field parameters, such as the rock permeability and the release area of gas pathway, to the assessment of effective dose.

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