Sub-surface disposal systems are expected to contain a large amount of carbon steel as containers for radioactive waste or rebar of concrete pits. Corrosion expansion of the steel can cause cracking or expansion of cementitious materials and deteriorate the performance of low diffusivity of the systems. This study evaluated available literature with regard to the corrosion rate and corrosion expansion of the steel, with the aim of determining the most likely parameter values that are requested for performing safety assessment of the likely scenario by the former Japanese regulatory body. Furthermore, polarisation, electrolytic corrosion, and hydraulic tests considering the disposal conditions were conducted to verify the validity of some of the values.
This paper describes the method for quality control of the cementitious materials used in radioactive waste disposal facility in Japan. The influence of the fly-ash quality and the methods of the early-age curing on the fresh properties, mechanical properties and the effective tritium diffusion coefficient is investigated. In addition, the applicability of nondestructive test for quality control of these cementitious materials is also investigated. The test for the those investigation are done in the simulated actual conditions during construction and exposure environment of the disposal facilities. Test results indicate that the variability in the quality of fly-ash has no remarkable influence on the property of the cementitious materials in this case, and that the compressive strength can be calculated from the surface strength tested with the rebound hammer of the nondestructive test.
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