Australian Nuclear Science & Technology Organisation Australian Nuclear Science & Technology Organisation Appraisal of a Cementitious Cementitious Material Material Appraisal of a for Waste Disposal: Neutron Imaging for Waste Disposal: Neutron Imaging Studies of Pore Structure and Studies of Pore Structure and Sorptivity Sorptivity Peter McGlinn, , Frikkie de Beer Frikkie de Beer, , Laurence Aldridge Laurence Aldridge, , Mabuti Mabuti Peter McGlinn Radebe, , Robert Nshimirimana Robert Nshimirimana, , Daniel Brew Daniel Brew, , Timothy Timothy Radebe Payne, , Kylie Kylie Olufson Olufson Payne ANSTO NECSA
Aim Aim To characterise and to evaluate the durability, To characterise and to evaluate the durability, structural properties and sorptivity sorptivity of a candidate of a candidate structural properties and wasteform for ILW and gain an understanding of for ILW and gain an understanding of wasteform the factors that control water movement through the factors that control water movement through the matrix and the resultant the resultant degradation process. degradation process. the matrix and
Background Background • Australia has a small amount of low and intermediate • Australia has a small amount of low and intermediate level radioactive waste from medicine, research and level radioactive waste from medicine, research and industry. industry. • In addition, ILW from reprocessing of spent fuel will • In addition, ILW from reprocessing of spent fuel will be returned from Dounreay Dounreay as cement. as cement. be returned from • In 2004, the Australian Government announced a a • In 2004, the Australian Government announced plan to establish a nuclear waste facility by 2011. to establish a nuclear waste facility by 2011. plan • ANSTO has established a project to undertake • ANSTO has established a project to undertake research relevant to the safety case for the facility. research relevant to the safety case for the facility.
Material Material • The samples tested simulated the Materials Testing The samples tested simulated the Materials Testing • Reactor (MTR) wasteform wasteform (AEA Technology in UK). (AEA Technology in UK). Reactor (MTR) • Formulation of 9:1 ground granulated blast furnace slag Formulation of 9:1 ground granulated blast furnace slag • to Ordinary Portland Cement (OPC). to Ordinary Portland Cement (OPC). • Waste liquor contained detectable amounts of some Waste liquor contained detectable amounts of some • simulant fission products, although in much lower simulant fission products, although in much lower concentrations than normally encountered in typical concentrations than normally encountered in typical MTR cement. MTR cement.
Methodology Methodology • Characterisation of un Characterisation of un- -leached and leached cement leached and leached cement – – • bulk solids composition; mineralogy; microstructure microstructure bulk solids composition; mineralogy; • Durability testing of cement: testing of cement: • Durability previous studies → → long - previous studies long- -term non term non- -replacement replacement - tests tests current studies → → replacement tests (ANS 16.1) - current studies replacement tests (ANS 16.1) - • Neutron imaging (radiography and tomography): (radiography and tomography): • Neutron imaging - residual water residual water - - sorptivity sorptivity (comparison with ASTM gravimetry (comparison with ASTM gravimetry- -based based - protocol) protocol) - pore size, volume and distribution pore size, volume and distribution -
Methodology Methodology Characterisation (before and after leaching) Characterisation (before and after leaching) • Mineralogy Mineralogy – – XRD XRD • • Bulk solids elemental analysis Bulk solids elemental analysis – – XRF XRF • • LOI LOI - - TGA TGA • • Microstructural and compositional changes of cement Microstructural and compositional changes of cement • matrix (primary phase for waste encapsulation) - - SEM/ SEM/ matrix (primary phase for waste encapsulation) EDS EDS
Methodology Methodology Durability testing Durability testing • Previous studies - - non non- -replacement replacement in deionised water in deionised water • Previous studies for 1, 3, 6 mths mths (40 (40° °C) and 92 months (first 12 months C) and 92 months (first 12 months for 1, 3, 6 at 40° at 40 °C, thereafter RT); SA/V = 0.03 mm C, thereafter RT); SA/V = 0.03 mm - -1 1 ; whole ; whole specimens specimens • Current studies – – ANS 16.1 ANS 16.1 - - leachate leachate replacement replacement • Current studies (deionised water at RT) – – 2 h to 90 d 2 h to 90 d; ; SA/V = 0.01mm SA/V = 0.01mm - ; (deionised water at RT) -1 1 ; sections of interior matrix and surface layer sections of interior matrix and surface layer • Leachate Leachate analysis analysis – – ICP ICP- -MS and ICP MS and ICP- -AES for Na, Mg, AES for Na, Mg, • Al, Si Si, S, K, Ca, Ti, , S, K, Ca, Ti, Mn Mn, Fe, , Fe, Sr Sr, , Zr Zr and and Ba Ba Al,
Current durability studies Current durability studies Previous durability studies Previous durability studies (ANS 16.1) (ANS 16.1) 1.5 cm 4 cm Interior Interior 1.5 cm 8 cm Epoxy resin Epoxy resin m Surface Surface c 2 NB: Same SA:V ratio (0.01 mm -1 ) for interior and surface samples
Methodology Methodology Sorptivity testing testing Sorptivity • Samples enclosed in Al tape with only the base • Samples enclosed in Al tape with only the base exposed, facilitating water transport in one direction exposed, facilitating water transport in one direction only (upwards). only (upwards). • Base continuously immersed in water - - adsorption adsorption • Base continuously immersed in water measured over periods of 1, 2, 4, 6, 9, 12, 16, 20 and measured over periods of 1, 2, 4, 6, 9, 12, 16, 20 and 25 minutes (up to a month where possible). 25 minutes (up to a month where possible). • • At the end of each time interval the samples were At the end of each time interval the samples were removed from the water, weighed removed from the water, weighed and then and then transferred to the Nrad transferred to the Nrad facility to collect facility to collect 2 2- -D D radiographic data and chart water ingress. radiographic data and chart water ingress. 2 cm 2 cm • Water contents were computed from the image. • Water contents were computed from the image. • At the end of the final acquisition period a 3- -D D • At the end of the final acquisition period a 3 tomography was carried out on the specimens to tomography was carried out on the specimens to construct macro- -pore distributions. pore distributions. construct macro
Methodology Methodology Sorptivity testing testing Sorptivity • Samples enclosed in Al tape with only the base • Samples enclosed in Al tape with only the base exposed, facilitating water transport in one direction exposed, facilitating water transport in one direction only (upwards). only (upwards). • Base continuously immersed in water - - adsorption adsorption • Base continuously immersed in water measured over periods of 1, 2, 4, 6, 9, 12, 16, 20 and measured over periods of 1, 2, 4, 6, 9, 12, 16, 20 and 25 minutes (up to a month where possible). 25 minutes (up to a month where possible). • • At the end of each time interval the samples were At the end of each time interval the samples were removed from the water, weighed removed from the water, weighed and then and then transferred to the Nrad transferred to the Nrad facility to collect facility to collect 2 2- -D D radiographic data and chart water ingress. radiographic data and chart water ingress. 2 cm 2 cm • Water contents were computed from the images. images. • Water contents were computed from the • At the end of the final acquisition period a 3- -D D • At the end of the final acquisition period a 3 Water tomography was carried out on the specimens to tomography was carried out on the specimens to construct macro- -pore distributions. pore distributions. construct macro
Methodology Methodology Neutron Imaging Neutron Imaging • Penetrating; complementary to X- -ray and gamma ray and gamma • Penetrating; complementary to X radiography. radiography. • Require strong, stationary, n sources for good beam • Require strong, stationary, n sources for good beam collimation and for a high spatial resolution ⇒ ⇒ reactor reactor collimation and for a high spatial resolution or accelerator based. or accelerator based. • For Ntom Ntom, require fixed beam line, stationary detector, , require fixed beam line, stationary detector, • For and rotating turntable for sample. and rotating turntable for sample. • Advantage over X- -rays is their high interaction rays is their high interaction • Advantage over X probability with H and lower attenuation in several probability with H and lower attenuation in several heavy elements. heavy elements.
SANDSTONE FROM LIVERINGA GROUP SANDSTONE FROM LIVERINGA GROUP
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