scholarly journals Investigations of Near-Field Thermal-Hydrologic-Mechanical-Chemical Models for Radioactive Waste Disposal in Clay/Shale Rock

2011 ◽  
Author(s):  
H.H. Liu ◽  
L. Li ◽  
L. Zheng ◽  
J.E. Houseworth ◽  
J. Rutqvist
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
Near Field ◽  
Radioactive Waste Disposal ◽  
Clay Shale ◽  
Shale Rock ◽  
Chemical Models

Chemistry and Performance of Blended Cements and Backfills for use in Radioactive Waste Disposal

1996 ◽  
Vol 465 ◽  
Author(s):  
S. Duerden ◽  
F. P. Glasser ◽  
K. Goldthorpe ◽  
J. Pedersen ◽  
K. Quillin ◽  
...  
Keyword(s):  
Fly Ash ◽  
Radioactive Waste ◽  
Portland Cement ◽  
Waste Disposal ◽  
Radioactive Waste Disposal ◽  
Blended Cements ◽  
Ph Changes ◽  
Chemical Models ◽  
Magnesium Silicates ◽  
And Performance

ABSTRACTThe ability of NaCl and MgSO4 to impair the performance of Portland cement, blended cements containing slag and fly ash and of a permeable backfill have been measured. Performance is determined by decrease in pH, changes in mineralogy and loss of physical coherence. Experiments have been made at 25°, 55° and 85°C and extensively backed up by chemical models of cement performance. NaCl, up to 1.5M, has a comparatively slight impact on performance but MgSO4 rapidly and almost quantitatively reacts, lowering system pH's to < 10, conditioned by mixtures of Mg(OH)2 and magnesium silicates with gypsum.

General discussion

1986 ◽  
Vol 319 (1545) ◽  
pp. 189-189
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
Near Field ◽  
Radioactive Waste Disposal ◽  
Radiological Protection ◽  
Individual Dose

R. H. Flowers. We have seen during this meeting that near-field, tar-field and biosphere all represent effective barriers to limit the risk from radioactive waste disposal. It therefore seems that the operators of disposal sites will have no difficulty in meeting ICRP limits on individual dose. The principal concern will be with the understanding and application of ALARA in a practical way. Can Mr Webb, who gave us that very clear paper on radiological protection procedures, offer any advice to the industry on how to apply ALARA in practice?

scholarly journals A Coupled Modeling Simulator for Near-Field Processes in Cement Engineered Barrier Systems for Radioactive Waste Disposal

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 767
Author(s):  
Steven J. Benbow ◽  
Daisuke Kawama ◽  
Hiroyasu Takase ◽  
Hiroyuki Shimizu ◽  
Chie Oda ◽  
...  
Keyword(s):  
Finite Element ◽  
Radioactive Waste ◽  
Waste Disposal ◽  
Near Field ◽  
Coupled Model ◽  
Element Model ◽  
Simulation Software ◽  
Radioactive Waste Disposal ◽  
Hydrogeological Model ◽  
Coupled Modeling

Details are presented of the development of a coupled modeling simulator for assessing the evolution in the near-field of a geological repository for radioactive waste disposal where concrete is used as a backfill. The simulator uses OpenMI, a standard for exchanging data between simulation software programs at run-time, to form a coupled chemical-mechanical-hydrogeological model of the system. The approach combines a tunnel scale stress analysis finite element model, a discrete element model for accurately modeling the patterns of emerging cracks in the concrete, and a finite element and finite volume model of the chemical processes and alteration in the porous matrix and cracks in the concrete, to produce a fully coupled model of the system. Combining existing detailed simulation software in this way with OpenMI has the benefit of not relying on simplifications that might be necessary to combine all of the modeled processes in a single piece of software.

A long term baseline and variability of natural radionuclides in groundwater at the Vaalputs low-level radioactive waste disposal facility, Namaqualand, South Africa: regional implications

2020 ◽  
Vol 123 (1) ◽  
pp. 105-116 ◽  
Author(s):  
H.C.F. Pretorius ◽  
M. Tredoux ◽  
M.A.G. Andreoli ◽  
P.D. Vermeulen
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
Structural Damage ◽  
Near Field ◽  
Natural Radionuclides ◽  
Radioactive Waste Disposal ◽  
World Health ◽  
Disposal Site ◽  
Spent Fuel ◽  
Disposal Facility

Abstract Vaalputs is the only South African nuclear waste disposal facility; it is licensed to dispose of low and intermediate level radioactive waste. Possible disposal of long-lived waste, potentially including spent fuel rods, prompted a study to establish a baseline of naturally-occurring radionuclides from the U and Th decay chains in the groundwater of Vaalputs. This baseline was created by investigating a dataset containing 25 years of analyses of the groundwater at the Vaalputs site. The behaviour over time, of 23 radionuclides in groundwater samples from 13 annually and three quarterly sampled boreholes, was evaluated and integrated in order to establish changing trends in the activities of radionuclides, the relative contributions of individual radionuclides to total radiation levels and how these were influenced by groundwater conditions. 238U levels showed a natural anomaly in the near-field of the disposal site that was attributed to the underlying basement rocks (granites) which are anomalously enriched in U. A set of duplicate samples from 2009 determined that the activity ratio of 234U/238U in the groundwater of Vaalputs is 4.1; this is ascribed to more rapid leaching of 234U relative to 238U, because of increased crystal structural damage around sites surrounding 234U atoms. High levels of 226Ra, unsupported by 238U, were found in groundwater from boreholes on the western side of the property: this groundwater yielded low values for 234U/238U, lower pH and stronger oxidizing conditions than groundwater from the rest of the area. The absence of overlying sedimentary rocks, which tend to ameliorate the effects of high radiation from granites by absorption, is suggested as the reason for the different geochemical conditions of the groundwater from boreholes in the west. This suggestion may apply to those boreholes elsewhere in Namaqualand with low published concentrations of 238U, but exceptionally high levels of α -and β-emitters. 232Th and its daughter radionuclides yielded radiation levels far below the guideline of 1 Bq.L-1 specified by the World Health Organization; this result is in line with the known low mobility of Th in groundwater systems.

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