Post-closure biosphere assessment modelling: comparison of complex and more stylised approaches

Walke, Russell; Kirchner, Gerald; Xu, Shulan; Dverstorp, Björn

doi:10.1016/j.jenvrad.2015.06.006

Cited by 8 publications

(4 citation statements)

References 4 publications

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“…1 are based on similar conceptual models to those used by the applicant, but the modelling software, parameter values and detailed modelling assumptions differ somewhat. In general, however, results from direct attempts to reproduce the applicant's consequence assessment calculations are in agreement with those presented in SR-Site, with calculated doses at a similar level and general trends being in good agreement (Walke et al, 2015;Xu et al, 2015).…”

Section: Results From Consequence Analysissupporting

confidence: 81%

Exploratory what-if analysis of some debated canister failure modes in the review of a licence application for the construction and operation of a spent nuclear fuel repository in Sweden

2019

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Regulatory review of the licence application for construction and operation of a spent fuel repository at the Forsmark site in Sweden involves detailed assessment of both expected and hypothetical failure modes of the copper canister. The copper canister, which is supported by the bentonite buffer and the surrounding crystalline rock in the KBS-3 concept, is expected to provide complete containment of radioactive elements for very long timescales. Detailed assessment shows that there is a small probability on such timescales of canister failure due to corrosion following loss of buffer as well as mechanical failure due to large earthquakes. During the regulatory review process, it was proposed that canisters might also fail due to: (i) corrosion in anoxic oxygen gas free water, (ii) pitting corrosion, (iii) stress corrosion cracking, (iv) creep brittle failure, (v) hydrogen embrittlement. We here provisionally accept a number of alternative assumptions related to these processes as a basis for what-if analysis of their implications. The focus is not to determine the merit or to estimate probability of these cases, but rather to explore their potential significance in the context of the available knowledge about the repository environment. Simplified estimates are made of the consequences in terms of number and timing of canister failures as well as radiological impact. It is judged that poor creep ductility of copper would have larger potential consequences compared to localised corrosion phenomena. Potential corrosion failures are expected to be associated with the small fraction of deposition holes that are most extensively exposed to corrodants.

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Section: Results From Consequence Analysissupporting

confidence: 81%

Exploratory what-if analysis of some debated canister failure modes in the review of a licence application for the construction and operation of a spent nuclear fuel repository in Sweden

2019

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“…Whereas system understanding relating to the highest exposure can arguably be derived from a much simpler model as discussed by Walke et al (2015), we are confident that the present biosphere model has a level of detail that is fit for purpose, namely to robustly demonstrate protection of humans and the environment over very long time periods in a heterogeneous landscape going through considerable change.…”

Section: Dose To Humansmentioning

confidence: 89%

The impact of low and intermediate-level radioactive waste on humans and the environment over the next one hundred thousand years

Kautsky

Saetre

Berglund

et al. 2016

Journal of Environmental Radioactivity

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In order to assess the potential radiological risk to humans and the environment from a geological repository for radioactive waste, a safety assessment must be performed. This implies that the release and transfer of radionuclides from the repository into the surface environment are calculated and that the effects in the biosphere are evaluated for an assessment period up to one hundred thousand years according to Swedish regulations. This paper discusses the challenges associated with the modelling of surface ecosystems over such long time scales, using the recently completed assessment for the extension of the existing repository for the low- and intermediate-level nuclear waste (called SFR) in Forsmark, Sweden as an applied example. In the assessment, natural variation and uncertainties in climate during the assessment period were captured by using a set of climate cases, primarily reflecting different expectations on the effects of global warming. Development of the landscape at the site, due to post-glacial isostatic rebound, was modelled, and areas where modelling indicated that radionuclides could discharge into the biosphere were identified. Transfers of surface water and groundwater were described with spatially distributed hydrological models. The projected release of radionuclides from the bedrock was then fed into a biosphere radionuclide transport model, simulating the transport and fate of radionuclides within and between ecosystems in the landscape. Annual doses for human inhabitants were calculated by combining activity concentrations in environmental media (soil, water, air and plants) with assumptions on habits and land-use of future human inhabitants. Similarly, dose rates to representative organisms of non-human biota were calculated from activity concentrations in relevant habitats, following the ERICA methodology. In the main scenario, the calculated risk for humans did not exceed the risk criteria or the screening dose rate for non-human biota, indicating that the repository design is sufficient to protect future populations and the environment. Although the combination of radionuclides, land-uses/habitats, type of most exposed population and area of exposure that contribute most to the total dose shifts over time, the total calculated dose shows limited variability. Significant reductions in the dose only occur during submerged periods and under periglacial climate conditions. As several different water and food pathways were equally important for endpoint results, it is concluded that it would be difficult to represent the biosphere with one or a set of simplified models. Instead, we found that it is important to maintain a diversity of food and water pathways, as key pathways for radionuclide accumulation and exposure partly worked in parallel.

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“…If resource limitations mean that assumptions have to be made, and this is very likely in the context of environmental assessments (Funtowicz and Ravetz, 1994;Rowe and Frewer, 2000;Kloprogge et al, 2011;Krueger et al, 2012;Duncan, 2013;Walke et al, 2015), these assumptions need to be assessed and tested (Lipshitz and Strauss, 1997;Tarantola et al, 2002;Canter and Atkinson, 2010). The entire set of assumptions (or hypotheses) to be analyzed concerning the possible outcomes or impacts needs to be consistent with the available knowledge and data on the options.…”

Section: Identifying Options and Impacts For A Projectmentioning

confidence: 99%

“…Tullos, 2009), or when the assumptions made are not easily verifiable (e.g. Attanayake and Waterman, 2006;Walke et al, 2015). Uncertainty is also present when: (i) there is no agreement as to the criteria to use to evaluate the importance of the impacts (e.g.…”

Section: Introductionmentioning

confidence: 99%

Coping with uncertainty in environmental impact assessments: Open techniques

Cárdenas

Halman

2016

Environmental Impact Assessment Review

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Post-closure biosphere assessment modelling: comparison of complex and more stylised approaches

Cited by 8 publications

References 4 publications

Exploratory what-if analysis of some debated canister failure modes in the review of a licence application for the construction and operation of a spent nuclear fuel repository in Sweden

Exploratory what-if analysis of some debated canister failure modes in the review of a licence application for the construction and operation of a spent nuclear fuel repository in Sweden

The impact of low and intermediate-level radioactive waste on humans and the environment over the next one hundred thousand years

Coping with uncertainty in environmental impact assessments: Open techniques

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