Kurumisawa K.,Hokkaido University |
Nawa T.,Hokkaido University |
Owada H.,Radioactive Waste Management Funding and Research Center |
Shibata M.,Taiheiyo Consultant Co.
Cement and Concrete Research | Year: 2013
In this report, X-ray photoelectron spectroscopy (XPS) and 29Si-MAS-NMR was used for the evaluation of deteriorated hardened cement pastes. The deterioration by ammonium nitrate solution was accompanied by changes in the pore structure as well as by structural changes in the C-S-H in the hardened cement paste. The CaO/SiO2 ratio of the C-S-H decreased with the progress of deterioration, there was also polymerization of the silicate in the C-S-H. It was confirmed that the degree of polymerization of silicate of the C-S-H in hardened cement paste can be determined by XPS. It was also shown that the polymerization depends on the structure of the C-S-H. © 2013 Elsevier Ltd.
Kurumisawa K.,Hokkaido University |
Nawa T.,Hokkaido University |
Owada H.,Radioactive Waste Management Funding and Research Center
Cement and Concrete Composites | Year: 2012
A three-dimensional image of hardened cement paste was reconstructed using a backscattered electron image (BEI) and used to predict the diffusion properties of hardened cement paste. After the BEI observations, an autocorrelation function (ACF) was calculated for each phase of the hardened cement paste, including the unhydrated cement, portlandite, and large pores. A three-dimensional image was reconstructed on the basis of the ACF based on random distributions. The dynamic elastic modulus and diffusion coefficient were calculated using a finite-element or finite difference method with the reconstructed three-dimensional images. The elastic modulus of the C-S-H phase was determined by micro-indentation, and the diffusivity of C-S-H was calculated using this elastic modulus based on previous reports. The resulting predicted dynamic elastic moduli and diffusion coefficients were in good agreement with the experimental results. Although, it was observed that the predicted values of the diffusivity of the blended cement pastes is different from the measured values, a new relationship between diffusivity and porosity of C-S-H in blended cement pastes was developed in this study. © 2011 Elsevier Ltd. All rights reserved.
Kamaya M.,Japan Institute of Nuclear Safety System |
Kawakubo M.,Japan Institute of Nuclear Safety System |
Kawakubo M.,Radioactive Waste Management Funding and Research Center
International Journal of Fatigue | Year: 2015
Influence of mean stress on fatigue life and fatigue limit was investigated for Type 316 stainless steel. The results for prestrained specimens revealed that fatigue life was almost the same in the same strain range regardless of stress amplitude, maximum peak stress and mean strain. The fatigue life was shortened when applying the mean stress for the same strain range, whereas it was increased for the same stress amplitude. It was shown that the reduction in fatigue life was brought about by the change in the effective strain range, which was caused by the increase in minimum peak stress and the ratcheting strain. The fatigue life could be predicted conservatively even if the mean strain was applied by assuming the effective strain range to be equal to the total strain range (by assuming the crack mouth to be never closed). It was concluded that the mean stress correction was not necessary for the load-controlled cyclic loading and for the region where the ratcheting strain was constrained. © 2014 Elsevier Ltd. All rights reserved.
Agency: Cordis | Branch: H2020 | Program: RIA | Phase: NFRP-06-2014 | Award Amount: 9.66M | Year: 2015
The Modern2020 project aims at providing the means for developing and implementing an effective and efficient repository operational monitoring programme, taking into account the requirements of specific national programmes. The work allows advanced national radioactive waste disposal programmes to design monitoring systems suitable for deployment when repositories start operating in the next decade and supports less developed programmes and other stakeholders by illustrating how the national context can be taken into account in designing dedicated monitoring programmes tailored to their national needs. The work is established to understand what should be monitored within the frame of the wider safety cases and to provide methodology on how monitoring information can be used to support decision making and to plan for responding to monitoring results. Research and development work aims to improve and develop innovative repository monitoring techniques (wireless data transmission, alternative power supply sources, new sensors, geophysical methods) from the proof of feasibility stage to the technology development and demonstration phase. Innovative technical solutions facilitate the integration and flexibility of required monitoring components to ease the final implementation and adaptation of the monitoring system. Full-scale in-situ demonstrations of innovative monitoring techniques will further enhance the knowledge on the operational implementation of specific disposal monitoring and will demonstrate the performance of the state-of-the-art, the innovative techniques and their comparison with conventional ones. Finally, Modern2020 has the ambition to effectively engage local citizen stakeholders in the R&D monitoring activity by involving them at an early stage in a repository development programme in order to integrate their concerns and expectations into monitoring programmes.
Agency: Cordis | Branch: FP7 | Program: CP-FP | Phase: Fission-2008-1.1.2 | Award Amount: 5.11M | Year: 2009
The MoDeRn project aims at providing a reference framework for the development and possible implementation of monitoring activities and associated stakeholder engagement during relevant phases of the radioactive waste disposal process, i.e. during site characterisation, construction, operation and staged closure, as well as a post-closure institutional control phase. Monitoring provides operators and other stakeholders with in-situ data on repository evolutions, to contribute to operational safety, to help manage construction, operation and/or closure activities, and may allow for a comparison with prior safety assessments. It thus provides information to inform necessary decisions. If, in addition, monitoring activities respond to stakeholder needs and provide them with understandable results, they will contribute to transparency and possibly to stakeholder confidence in the disposal process. The project is structured into six work packages (WPs). The first four WPs are dedicated to (i) analyze key objectives and propose viable strategies, based on both technical and stakeholder considerations; to (ii) establish the state of the art and provide technical developments to match specific repository requirements; to (iii) conduct in-situ monitoring demonstration experiments using innovative techniques; and to (iv) conduct a case study of monitoring and its integration into staged disposal, including specific scenarii analysis aimed at providing guidance on how to handle and communicate monitoring results, in particular when these provide unexpected information. In order to provide a shared international view on how monitoring can be developed within a given national context, WP5 regroups key dissemination activities and WP6 will provide a reference framework integrating project results and describing feasible monitoring activities, suggesting relevant stakeholder engagement activities, and illustrating possible uses of monitoring results for decision-making.