XRD Analysis of Cement Paste Samples Exposed to the Simulated Environment of a Deep Repository - 12239
- Nuclear and Energy Research Institute, Sao Paulo (Brazil)
- Institute of Geosciences, University of Sao Paulo, Sao Paulo (Brazil)
Portland cement materials are widely used as engineered barriers in repositories for radioactive waste. The capacity of such barriers to avoid the disposed of radionuclides to entering the biosphere in the long-term depends on the service life of those materials. Thus, the performance assessment of structural materials under a series of environmental conditions prevailing at the environs of repositories is a matter of interest. The durability of cement paste foreseen as backfill in a deep borehole for disposal of disused sealed radioactive sources is investigated in the development of the repository concept. Results are intended to be part of the body of evidence in the safety case of the proposed disposal technology. This paper presents the results of X-Ray Diffraction (XRD) Analysis of cement paste exposed to varying temperatures and simulated groundwater after samples received the radiation dose that the cement paste will accumulate until complete decay of the radioactive sources. The XRD analysis of cement paste samples realized in this work allowed observing some differences in the results of cement paste specimens that were submitted to different treatments. The cluster analysis of results was able to group tested samples according to the applied treatments. Mineralogical differences, however, are tenuous and, apart from ettringite, are hardly observed. The absence of ettringite in all the seven specimens that were kept in dry storage at high temperature had hardly occurred by natural variations in the composition of hydrated cement paste because ettringite is observed in all tested except the seven specimens. Therefore this absence is certainly the result of the treatments and could be explained by the decomposition of ettringite. Although the temperature of decomposition is about 110-120 deg. C, it may be initially decomposed to meta-ettringite, an amorphous compound, above 50 deg. C in the absence of water. Influence of irradiation on the mineralogical composition was not observed when the treatment was analyzed individually or when analyzed under the possible synergic effect with other treatments. However, the radiation dose to which specimens were exposed is only a fraction of the accumulated dose in cement paste until complete decay of some sources. Therefore, in the short term, the conditions deemed to prevail in the repository environment may not influence the properties of cement paste at detectable levels. Under the conditions presented in this work, it is not possible to predict the long term evolution of these properties. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9-332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 22293527
- Report Number(s):
- INIS-US-14-WM-12239; TRN: US14V1182115051
- Resource Relation:
- Conference: WM2012: Waste Management 2012 conference on improving the future in waste management, Phoenix, AZ (United States), 26 Feb - 1 Mar 2012; Other Information: Country of input: France; 19 refs.
- Country of Publication:
- United States
- Language:
- English
Similar Records
A Study Of Geological Disposal Facility (GDF) Ageing Phenomena In Bentonite - 17605
Effects of Gamma Radiation on Cementitious Materials in Repository Environment - 16300