TY - GEN

T1 - Numerical model of fluid flow through heterogeneous rock for high level radioactive waste disposal

AU - Shirai, M.

AU - Chiba, R.

AU - Fomin, S.

AU - Chugunov, V.

AU - Takahashi, T.

AU - Niibori, Y.

AU - Hashida, T.

PY - 2007/5/11

Y1 - 2007/5/11

N2 - An international consensus has emerged that deep geological disposal on land is one of the most appropriate means for high level radioactive wastes (HLW). The fluid transport is slow and radioactive elements are dangerous, so it's impossible to experiment over thousands of years. Instead, numerical model in such natural barrier as fractured underground needs to be considered. Field observations reveal that the equation with fractional derivative is more appropriate for describing physical phenomena than the equation which is based on the Fick's law. Thus, non-Fickian diffusion into inhomogeneous underground appears to be important in the assessment of HLW disposal. A solute transport equation with fractional derivative has been suggested and discussed in literature. However, no attempts were made to apply this equation for modeling of HLW disposal with account for the radioactive decay. In this study, we suggest the use of a novel fractional advection-diffusion equation which accounts for the effect of radioactive disintegration and for interactions between major, macro pores and fractal micro pores. This model is fundamentally different from previous proposed model of HLW, particularly in utilizing fractional derivative. Breakthrough curves numerically obtained by the present model are presented for a variety of rock types with respect to some important nuclides. Results of the calculation showed that for longer distance our model tends to be more conservative than the conventional Fickian model, therefore our model can be said to be safer.

AB - An international consensus has emerged that deep geological disposal on land is one of the most appropriate means for high level radioactive wastes (HLW). The fluid transport is slow and radioactive elements are dangerous, so it's impossible to experiment over thousands of years. Instead, numerical model in such natural barrier as fractured underground needs to be considered. Field observations reveal that the equation with fractional derivative is more appropriate for describing physical phenomena than the equation which is based on the Fick's law. Thus, non-Fickian diffusion into inhomogeneous underground appears to be important in the assessment of HLW disposal. A solute transport equation with fractional derivative has been suggested and discussed in literature. However, no attempts were made to apply this equation for modeling of HLW disposal with account for the radioactive decay. In this study, we suggest the use of a novel fractional advection-diffusion equation which accounts for the effect of radioactive disintegration and for interactions between major, macro pores and fractal micro pores. This model is fundamentally different from previous proposed model of HLW, particularly in utilizing fractional derivative. Breakthrough curves numerically obtained by the present model are presented for a variety of rock types with respect to some important nuclides. Results of the calculation showed that for longer distance our model tends to be more conservative than the conventional Fickian model, therefore our model can be said to be safer.

KW - Fractional derivative

KW - Heterogeneous media

KW - High level radioactive waste disposal

KW - Non-ficluan diffusion

KW - Radioactive disintegration

UR - http://www.scopus.com/inward/record.url?scp=34248200028&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34248200028&partnerID=8YFLogxK

U2 - 10.1063/1.2721249

DO - 10.1063/1.2721249

M3 - Conference contribution

AN - SCOPUS:34248200028

SN - 0735404038

SN - 9780735404038

T3 - AIP Conference Proceedings

SP - 57

EP - 62

BT - WATER DYANMICS

T2 - 4th International Workshop on Water Dynamics

Y2 - 7 November 2006 through 8 November 2006

ER -