Portland cement paste behaviour under gamma radiation field in geological repository - 15272
- Instituto de Pesquisas Energeticas e Nucleares (Brazil)
- Institut de Cienca de Materials de Barcelona (Spain)
- Hemholtz-Zentrum Berlin fur Materialien und Energie - HZB (Germany)
The Radioactive Waste Management Laboratory at the Nuclear and Energy Research Institute in Sao Paulo, Brazil (IPEN-CNEN-SP), is developing the concept of a repository for disposition of disused sealed radioactive sources in a deep borehole in which cement paste is intended to be used as a backfill between the steel casing and the geological formation around the borehole. The cement paste is intended to function as structural material, a blockage against the transport of water between the different strata of the geological setting, and as an additional barrier against the migration of radionuclides. The assessment of the cement paste behaviour in long term is necessary to increase the confidence that the material will perform as required during the service life of the facility. Under radiation, pore water present in cement paste suffers radiolysis and some products can be highly reactive, as electrons and hydroxyl radicals and hydrogen peroxide. These radiolysis products will interact with cement paste and its hydration products, forming a wide range of compounds. Previous work focused on assessing the synergic effects of radiation and environmental conditions, like higher temperature and aggressive groundwater chemicals, on cement paste. Examination of samples detected small differences in mineralogy and microstructure. However, the radiation dose to which samples were exposed (400 kGy) was only a fraction of the expected accumulated dose in cement paste until complete decay of some sealed sources in the repository. Therefore, several thousand kilo-grays must be tested the possibility of radiation to alter cement mineralogy and, as a consequence, its durability The objective of this research is to evaluate the changes in mineralogy and microstructure of irradiated cement paste specimens, in an attempt to establish a relationship between irradiation and durability. Cubic Portland cement specimens were casted and exposed to the gamma radiation of a 60 Co multipurpose irradiator, at IPEN-CNEN/SP. The effects of doses between 1000 kGy and 4000 kGy are evaluated by X-Ray Diffraction, Scanning Electron Microscopy, X-ray micro tomography, neutrongraphy and neutron scattering. This report presents the changes in cement paste mineralogy when samples are examined by XRD. Results indicate that durability can be affected because of the observed changes. Results are expected to indicate the induced changes in cement paste under high radiation doses and to provide hints on its behaviour in the long-term and service-life. The results can be used in safety analysis for deep geological repositories that use cement based materials as engineered barriers. (authors)
- Research Organization:
- WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
- OSTI ID:
- 22822793
- Report Number(s):
- INIS-US-19-WM-15272; TRN: US19V0783067708
- Resource Relation:
- Conference: WM2015: Annual Waste Management Symposium, Phoenix, AZ (United States), 15-19 Mar 2015; Other Information: Country of input: France; Available online at: http://archive.wmsym.org/2015/index.html
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BOREHOLES
BRAZILIAN CNEN
COBALT 60
ELECTRONS
GAMMA RADIATION
GEOLOGIC FORMATIONS
GROUND WATER
HYDRATION
HYDROGEN PEROXIDE
HYDROXYL RADICALS
MICROSTRUCTURE
MINERALOGY
NEUTRON DIFFRACTION
PORTLAND CEMENT
RADIATION DOSE UNITS
RADIATION DOSES
RADIATION EFFECTS
RADIOACTIVE WASTE MANAGEMENT
RADIONUCLIDE MIGRATION
SAFETY ANALYSIS
SCANNING ELECTRON MICROSCOPY
SEALED SOURCES
SERVICE LIFE
STEELS
TEMPERATURE RANGE 0400-1000 K
TOMOGRAPHY
WEAR RESISTANCE
X-RAY DIFFRACTION