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The safe disposal of radioactive nuclear wastes using multi-barrier systems requires a good understanding of their transport properties in geological materials. When groundwater flow is very slow, the most important mechanisms of transport and retardation are diffusion through and sorption onto geological materials, and an evaluation of relevant parameters, particularly the effective diffusion coefficient and rock capacity factor (or sorption coefficient), is of fundamental importance to any safety assessment. Although laboratory diffusion tests can be used to determine these two parameters, conventional through-diffusion testing has some limitations, such as the need for a relatively long test time, cumbersome test procedures and the possibility of errors due to differences between analytical assumptions and actual test conditions. In this paper, we offer a rigorous solution to the through-diffusion test. Boundary conditions are improved by taking into account concentration changes in both the source and the measurement cells. A companion approach for back-calculating the effective diffusion coefficient and rock capacity factor is also proposed. The effectiveness and advantages of this improved technique are demonstrated using experimental data derived from a sedimentary rock sample taken from a research site in Japan.

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%675$&7The accurate hydraulic characterization of low permeability geological materials and formations has important practical implications, such as the geological disposal of radioactive nuclear waste. In this paper, we discuss pressure pulse techniques, which are methods that are commonly adopted both in the laboratory and LQ VLWX for testing low permeability geological materials and formations. The results obtained in this study illustrate that: 1) the use of nominal values for water compressibility will lead to significant underestimation of permeability from the pressure pulse tests; 2) specific storage is also an important parameter that should be evaluated simultaneously with permeability; 3) to shorten the time required to measure low permeability in the laboratory, it is advisable to use disk-shaped specimens; 4) when a geological formation is anisotropic, the value of permeability calculated using an isotropic model is between the maximum and minimum permeabilities of the geological formation; 5) the values of permeability and specific storage derived from an LQ VLWX pressure pulse test may only reflect the hydraulic properties of the domain closely surrounding the test well. Caution should be exercised when interpreting data derived from the pressure pulse tests for the purpose of safety assessment. ,1752'8&7,21There is international consensus concerning the geological disposal of radioactive nuclear waste in deep and stable geological formations. Through a system of multiple containment barriers, this strategy would isolate the waste from the biosphere for extremely long periods of time, and ensure that residual radioactive substances reaching the biosphere after many thousands of years would be at harmless levels. As a natural barrier to retard the migration of radionuclides accompanying underground flow of water, the most important feature of such geological formations should be low permeability.Although several methods are available for measuring the hydraulic properties of geological materials both in the laboratory [1] and LQ VLWX [2], the pressure pulse techniques are commonly adopted because the times required for testing low permeabilities are much shorter than those required by other techniques. In this study, we discuss what factors may affect the results obtained by pressure pulse tests. The capabilities and accuracies of the pressure pulse techniques were examined because errors in permeability measurements could lead to significant misinterpretation of the suitability of a potential waste facility.35(6685( 38/6( 7(&+1,48(6 &RQFHSWV DQG VROXWLRQVThe laboratory pressure pulse technique was originally proposed by Brace HW DO [3]. This technique involves connecting the specimen ends to two fluid reservoirs, instantaneously increasing the fluid pressure in one reservoir, and measuring the corresponding pressure decay Mat. Res. Soc. Symp. Proc. Vol. 807

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