Ontario Power Generation's Response to the Joint Review

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Attachment 1 to OPG letter, Albert Sweetnam to Dr. Stella Swanson, “Deep Geologic Repository Project for Low and Intermediate Level Waste – Submission of Responses to the Final Sub-set of Package #4 Information Requests”, CD#: 00216-CORR-00531-00143. IR# EIS Guidelines Section Information Request and Response on the conservative assumption of no grouting, it is estimated that groundwater inflow from these formations will be 0.38 L/s. However, during shaft sinking it is expected that these formations will be grouted, as required, to primarily reduce groundwater inflow later during DGR operations (see below). Once shaft sinking is complete and both shafts are fully lined with concrete, groundwater inflow through concrete liners is estimated to be 0.45 L/s (GOLDER 2012). This estimate is based on the assumption that the majority of inflow occurs from Salina A1 and Guelph Formations through a “leaky liner” and these two formations are ungrouted (see responses to IR-LPSC-01-17 (OPG 2012a) and Undertaking TIS 11 (OPG 2012b)). However, since it is expected that these formations will be grouted during shaft sinking, the groundwater inflow will be less than 0.45 L/s. During lateral development at the repository level, the usage of process water for equipment, construction and dust mitigation is assumed to be about 20 L/s (average). This estimate is very conservative to allow for a wide variety of equipment selection and water demand criteria. The estimate has been derived using high water demand equipment (e.g., high efficiency multi-boom drilling jumbos), high utilization estimates for operating hours per day, continuous water suppression during operating hours and an allowance for continuous civil construction activities (e.g., floor concrete). As well, this estimate does not take into consideration options for recirculation of process water. The expected inflow rates during normal operations are described in the response to Undertaking TIS 11 (OPG 2012b). During normal operations, the majority of groundwater inflow will be through both shaft concrete liners and as described above is conservatively estimated to be 0.45 L/s. Due to the very low permeability of the Cobourg Formation Lower Member, groundwater inflow at the repository level is expected to be negligible (0.006 L/s). This rate of groundwater inflow would likely be less than the rate at which the water would evaporate and thus would not flow to the underground dewatering system. A small allowance (0.06 L/s) has been made in the discharge water estimate to reflect potential condensation in the ventilation shaft during summer conditions. The underground dewatering system used for operations will be sized to handle both the aforementioned normal inflow plus additional groundwater inflow that might occur during a postulated abnormal operations event. In the Preliminary Safety Report (OPG 2011, Section 6.3.10.4) it was assumed that an abnormal ’in-rush scenario’ would lead to an additional groundwater inflow of 15 L/s. Further assessment of potential additional inflow due to shaft liner impairments has been completed (GOLDER 2011, enclosed). This assessment shows that a 1:2500 year seismic event, which is consistent with the National Building Code of Canada (2010 edition) requirements, could lead to cracking of shaft liners and an additional 0.1 L/s inflow. A further analysis was conducted for a beyond-design-basis 1:100,000 year seismic event which resulted in a potential inflow of 3.4 L/s. References: GOLDER. 2011. Potential Inflows through Cracked Hydrostatic Concrete Shaft Liner. Golder Associates Ltd. Technical Memorandum 1011170042-TM-G2100-0001-01 R01. (enclosed) GOLDER. 2012. Underground Services (WP2-10) Underground Repository Dewatering – Preliminary Estimate of Groundwater Inflow under Normal Operating Conditions. Golder Associates Ltd. Technical Memorandum No. Page 53 of 69
Attachment 1 to OPG letter, Albert Sweetnam to Dr. Stella Swanson, “Deep Geologic Repository Project for Low and Intermediate Level Waste – Submission of Responses to the Final Sub-set of Package #4 Information Requests”, CD#: 00216-CORR-00531-00143. IR# EIS Guidelines Section EIS-04-153 � Section 13, Demonstrating the Long term Safety of the DGR Information Request and Response 1011170042-TM-G2100-0002-02. OPG. 2011. OPG’s Deep Geologic Repository for Low and Intermediate Level Waste – Preliminary Safety Report. Ontario Power Generation report 00216-SR-01320-00001 R000. Toronto, Canada. (CEAA Registry Doc# 300) OPG. 2012a. OPG Letter, A. Sweetnam to S. Swanson, “Deep Geologic Repository Project for Low and Intermediate Level Waste - Submission of Responses to Information Requests”, CD# 00216-CORR-00531-00108, March 9, 2012. (CEAA Registry Doc# 363) OPG. 2012b. OPG Letter, A. Sweetnam to S. Swanson, “Deep Geologic Repository Project for Low and Intermediate Level Waste – Responses to Undertakings from Technical Information Session #1”, CD# 00216-CORR-00531-00132, August 15, 2012. (CEAA Registry Doc# 692) Information Request: Explain how long it will take for the bentonite/sand materials used as the primary shaft seal to saturate with groundwater, thus generating swelling pressures that aid the development of a tight seal against the shaft wall. Provide the relevant geologic and hydrogeologic data and assumptions. Include a discussion of the uncertainty associated with the time estimate. Include this information in an evaluation of the current uncertainty analysis of the postclosure assessment, with emphasis on how assumptions used in the assessment regarding the issue of shaft sealing build confidence in the assessment. Context: The time required for saturation of the bentonite/sand materials may be considerable, dependent upon the degree of groundwater inflow from the sides of the shaft and then the migration up and down within the bentonite/sand column from the point of groundwater inflow. Therefore, the time required for a “tight seal” with the shaft wall may also be considerable. This has implications for the postclosure safety assessment; in particular, the uncertainty analysis for that assessment, the “confidence-building” assumptions used in the assessment (as per Table 3.5) and the degree to which the precautionary (conservative) approach was balanced with realistic assumptions. OPG Response: Shaft resaturation was modelled explicitly in the T2GGM model of gas generation and transport which includes consideration of two-phase flow (e.g., GEOFIRMA and QUINTESSA 2011, Sections 5.1.2, 5.2.2 and 5.3.2). The shaft seal materials were initially at as-emplaced liquid saturations. For the bentonite-sand sealing material, this was 80% initial liquid saturation (QUINTESSA and GEOFIRMA 2011, Section 4.7.5). Subsequent to emplacement, the bentonite-sand resaturates at a rate that is primarily controlled by the ability of the adjacent shaft rock damaged zone and rock formations to supply water. Relevant data and associated uncertainties for the bentonite-sand seal are discussed in Section 4 of the Data report (QUINTESSA and GEOFIRMA 2011), specifically Sections 4.4.3, 4.5.2.2, Page 54 of 69
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Dr. Stella Swanson September 28, 20
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Attachment 1 to OPG letter, Albert
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Page 74 and 75: Title: OPG’s Deep Geologic Reposi
Page 76 and 77: Table of Contents CLOSURE WALL CAPA
Page 78 and 79: Figure 1: Access tunnel geometry. C
Page 80 and 81: CLOSURE WALL CAPACITY and are the s
Page 82 and 83: CLOSURE WALL CAPACITY The shear str
Page 84 and 85: (H-a) = 4.25 m Figure 5: Return air
Page 86 and 87: Golder Associates Ltd. 6700 Century
Page 88 and 89: Title: Potential Inflows through Cr
Page 90 and 91: Serge Clement 1011170042-TM-G2100-0
Page 100 and 101: APPENDIX A Derivation of Conversion
Page 102 and 103: External radius of liner =
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8. Letter from A. Sweetnam to S. Sw
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OPG’s L&ILW Deep Geologic Reposit
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Ontario Power Generation's Response to the Joint Review

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