Life Cycle Analysis of Greenhouse Gas Emissions from the Mining and Milling of Uranium in Saskatchewan
This thesis presents a detailed study of life cycle greenhouse gas (GHG) emissions intensity during the uranium mining-milling phase of the nuclear fuel cycle for three paired uranium mine-mill operations in northern Saskatchewan (SK). The study period runs from 2006 – 2013 for two of the three pairs, and from 1995-2010 for the third. The life cycle analysis has been conducted based on the ISO 14040:2006 standard using a Process Chain Analysis methodology. This study differs from previous studies of GHG emissions intensity during the uranium mining-milling phase of the nuclear fuel cycle in two key respects. First, it has a very large system boundary which includes the uranium exploration and mine-mill decommissioning phases. Second, it utilizes a life cycle inventory database to include many processes which would normally fall outside of the system boundary due to their small individual contributions. These differences contribute to a more accurate result. The production-weighted average life cycle GHG emissions intensity is estimated as 45 kg CO2e/kg U3O8 at an average ore grade of 9.12% U3O8 based on relative U3O8 production volumes at Mine-Mill A, B, and C from 2006 to 2010. The 95% confidence interval for the production-weighted average result ranges from 42 to 49 kg CO2e/kg U3O8, indicating that overall uncertainty in the result is low. Life cycle GHG emission intensity for the three uranium mine-mill pairs are 84, 66, and 35 kg CO2e/kg U3O8 at average ore grades of 0.71%, 1.54%, and 11.5% U3O8 respectively. Nearly 90% of life cycle GHG emissions are associated with operation of the uranium mine-mills, primarily from energy consumption during operation (69% of total) transport of materials and personnel (7.0%), and use of reagents (5.6%). Remaining processes each individually account for less than 5% of the total. In calculating emissions from electricity consumption, the base-case emission intensities reported above use a province-wide electricity emission factor because the utility does not differentiate its emissions by region. However, the facilities included in this study are all located in Northern Saskatchewan, which is powered exclusively by hydropower. Application of a regional emission factor reduces the production-weighted average life cycle GHG emission intensity to 26 kg CO2e/kg U3O8 with a 95% confidence interval of 25 to 29 kg CO2e/kg U3O8. This represents a 42% reduction in life cycle GHG emission intensity from the base case. Due to the high uranium ore grades found in SK uranium deposits, life cycle GHG emissions intensity for uranium from SK is among the lowest in the world. Further, the life cycle GHG emission intensity estimate from uranium mining-milling in SK is a small (approximately 10%) contributor to the life cycle GHG emissions intensity from the nuclear fuel cycle for light water reactors overall, amounting to approximately 1.2 g CO2e/kWh electricity (0.6 g CO2e/kWh electricity calculated using the regional hydroelectric power source).
LCA, life cycle analysis, life cycle assessment, greenhouse gas, greenhouse gases, GHG, GHGs, uranium, yellowcake, mining, milling, Saskatchewan, SK, U3O8
Master of Science (M.Sc.)
Civil and Geological Engineering