A comprehensive sensitivity analysis method has been developed with the aim of providing quantitative information in an efficient manner. This methodology is composed of the following two components: (1) a statistical method with random sampling of independent parameters, which identifies important parameters and extracts threshold values of parameters and/or combinations yielding a 'successful condition' where maximum dose does not exceed a target value, (2) A nuclide migration model that as far as possible incorporates a comprehensive set of phenomena occurring within the repository. This approach was applied as part of a safety assessment of the geological disposal of transuranic (TRU) waste in Japan (TRU-2). It was shown that the concept of TRU waste disposal is robust from the point of view of safety.Mater. Res. Soc. Symp. Proc. Vol. 985

A demonstration-scale steam-assisted pyrolysis system was designed and tested for the treatment of the radioactive organic wastes which are difficult to incinerate such as halogenated organic compounds and phosphate esters. The steam-assisted pyrolysis system comprises a decontamination process for the gasification/separation of organic waste from nonvolatile radioactive nuclides by pyrolysis and a destruction process by submerged combustion. This two-step treatment system provides a high-volume reduction of waste and a very small amount of radioactive secondary waste. Tri-n-butyl phosphate/n-dodecane waste contaminated with uranium and simulated halogenated organic wastes stored in Japan Atomic Energy Agency were treated using the steam-assisted pyrolysis system. These wastes were reduced by 98 to 99.4% in weight during the treatment without any trouble using acidic compounds that are produced by the pyrolysis of wastes. Uranium was retained in the gasification chamber and the uranium concentration of secondary waste water was very low, thus permitting the discharge of neutralized waste water to the environment.

Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to demonstrate the reaction mechanisms of alkali-activated materials (AAMs) and the early stage of structure formation in the materials. The effects of different types of alkali activator solutions on the structure formation and reaction mechanisms of AAMs were studied. The results revealed that the main peaks of the ATR-FTIR spectra of the AAMs in the 1300–650 cm−1 range shifted to a low wavenumber with changing patterns, depending on the activator solution used, indicating that the dissolution and reorientation of metakaolin had occurred. Silica and alumina monomers were dissolved by the NaOH solution to produce crystalline zeolites. Although the reaction between metakaolin and Na2SiO3 solution is slow, the condensation between the Al-OH from metakaolin and the Si-OH from Na2SiO3 solution bonded the chain to be longer. Therefore, the Na2SiO3 solution acted as a template-bonded monomer, formed long chains of Si–O–Si and Si–O–Al, and produced an amorphous AAM structure. In the mixed solution, when the NaOH in it dissolved the Si and Al monomers, the Na2SiO3 in the solution also bonded with monomers and produced a complex structure. The different reaction that metakaolin had with different alkali activator solutions reflected the different phases, microstructures, and mechanical properties of the AAMs produced.

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