Application of the Systems Analysis Approach to a Natural Analogue Project
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Application of the Systems Analysis Approach to a Natural Analogue Project M.J. Stenhouse1, R. Arthur1, K. Ota2, T. Iwatsuki2, R. Metcalfe3 and H. Takase3 1
: Monitor Scientific, 3900 S. Wadsworth Blvd., Denver, CO 80235, USA
2
: Tono Geoscience Center, Japan Nuclear Cycle Development Institute (JNC), Toki, JAPAN
3
: Quintessa Japan, Yokohama, JAPAN.
Abstract The Tono uranium deposit (Gifu Prefecture, central Japan) was formed about 10 million years ago and available evidence suggests that this deposit has remained stable, i.e. uranium has not migrated significantly since then. Substantial field and modeling work is being carried out to better understand the hydrogeological and geochemical processes affecting or governing uranium transport and immobilization in and around the Tono uranium deposit. A systems analysis approach has been applied to the Tono deposit natural analogue project. Application of a systems analysis approach to a generic research project is novel and is different from prevailing applications. Previous applications of a systems analysis approach have been principally concerned with performance and safety assessments for radioactive waste disposal. The systems analysis approach provides a convenient framework for this project, having been used in the Tono Natural Analogue Project (TAP) to: • • • • •
define the system to be studied; identify features, events and processes (FEPs) associated with this system; identify external factors (EFEPs) which are likely to have influenced the Tono area or study site or uranium deposit; define interactions between pairs of FEPs; and develop credible scenarios for evolution of the area or uranium deposit. The results from the systems analysis approach allow us to:
• • • •
develop possible scenarios for how the Tono area or study site evolved, evaluate uncertainty and how it propagates backwards in time, link field characterization data with predictive modeling, and identify gaps in data and, hence, identify additional characterization needs.
Introduction The Tono uranium mine is located in the Gifu Prefecture, central Japan, about 350 km west of Tokyo (Figure 1). The Tsukiyoshi ore body, the subject of the Tono Natural Analogue Project (TAP), is one of four uranium deposits in the Tono area, and is located about 150 m below the surface. The uranium mineralization is dated at approximately 10 Ma [1]1 and occurs
1
Estimated by Fission Track Dating.
JJ8.6.1
in an organic-rich (lignite-bearing) formation, immediately above an unconformity with a granitic basement. The deposit spans an area of several hundred meters wide, is about 2-3 km long and a few meters thick [2].
(a) (b) Figure 1. Geological background for Tono Natural Analogue Project. (a): location and geological setting; (b) simplified lithostratigraphic column for the Tono mine.
The uranium deposit at Tono is one of several such deposits in Japan, most of which are of sandstone-type and occur in Tertiary sedimentary rocks overlying Cretaceous granites [3]. Since the igneous intrusion that r
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