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 these tunnels were dry with no pooled water even though they were only 30-m below the bottom of Lake Ontario (NWMO 2011, p.121). The postclosure safety assessment evaluated the impacts for each of the cases shown in Figure 8.3 and 8.4 above. In all cases except for the shaft seal failure cases, the dose consequences were very low. In the case of the most severe shaft seal failure scenario (SF-ED), the repository saturation peaked at about 75%. This was the highest overall dose scenario, but the dose was due to the loss of gas from the repository up the shaft due to the poor seals, rather than due to resaturation of the repository. To bound uncertainty surrounding the impacts from repository resaturation, the NE-RS calculation case assumes a 100% saturated repository from closure (see Section 7.3.2.1 of QUINTESSA et al 2011). This case is not physical since it does not include any path for this water to have entered the repository; nor does it include gas generation. Rather, this case focuses on, and maximizes, the release of radionuclides from the wastes into groundwater. Although the early resaturation of the repository increases the corrosion of the wastes, the release of radionuclides from the wastes and repository via groundwater, and the calculated maximum dose, the dose remains orders of magnitude below the dose criterion and so the safety of the repository system is not compromised. References: GEOFIRMA. 2011. Postclosure Safety Assessment: Groundwater Modelling. Geofirma Engineering Ltd. report for the Nuclear Waste Management Organization NWMO DGR-TR-2011-30 R000. Toronto, Canada. (available at www.nwmo.ca/dgrpostclosuresafetyassessmentreports) GEOFIRMA and QUINTESSA. 2011. Postclosure Safety Assessment: Gas Modelling. Geofirma Engineering Ltd. and Quintessa Ltd. report for the Nuclear Waste Management Organization NWMO DGR-TR-2011-31 R000. Toronto, Canada. (available at www.nwmo.ca/dgrpostclosuresafetyassessmentreports) NWMO. 2011. Geosynthesis. Nuclear Waste Management Organization report NWMO DGR-TR-2011-11 R000. Toronto, Canada. (CEAA Registry Doc# 300) QUINTESSA and GEOFIRMA. 2011. Postclosure Safety Assessment: T2GGM Version 2: Gas Generation and Transport Code. Quintessa Ltd. and Geofirma Engineering Ltd. report for the Nuclear Waste Management Organization NWMO DGR-TR-2011-33 R000. Toronto, Canada. (available at www.nwmo.ca/dgrpostclosuresafetyassessmentreports) QUINTESSA, GEOFIRMA and SENES. 2011. Postclosure Safety Assessment. Quintessa Ltd., Geofirma Engineering Ltd. and SENES Consultants Ltd. report for the Nuclear Waste Management Organization NWMO DGR-TR-2011-25 R000. Toronto, Canada. (CEAA Registry Doc# 300) Page 29 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-04-123 � Section 12, Accidents, Malfunctions, and Malevolent Acts Information Request and Response Information Request: Is the shielding to be in place for ILW and LLW waste expected to provide any incidental barrier function? Will the additional shielding used during waste transport be retained during emplacement in the proposed DGR? Context: In the Reference Low and Intermediate Level Waste Inventory for the Deep Geologic Repository Report, Executive Summary, on page 7, it is stated that no extra processing/packaging will be required with the exception of shielding of most of the ILW and overpacking of a small portion of the LLW for waste retrieved from various storage structures at the Western Waste Management Facility (WWMF) and transferred to the DGR for emplacement. OPG Response: In general, the design purpose of shielding is to reduce the gamma radiation field outside waste packages to minimize radiation doses to workers during handling. Most Low Level Waste (LLW) packages do not require any additional shielding to meet this objective. Some Intermediate Level Waste (ILW) packages (e.g., reactor refurbishment waste containers) have substantial shielding built into their original designs. Other ILW packages will need to be provided with an add-on shield to protect workers while these waste packages are transferred underground. This shielding will sometimes be removed if safe to do so and re-used if practical, otherwise it will be retained on the waste after emplacement. In the case of resin liners, the intent is to leave the shield on the waste package in the repository (see Section 6.5.3.6 of the Preliminary Safety Report (PSR) (OPG 2011) for a discussion on handling of shielded resin liners). Any additional material provided around the waste could provide an additional barrier function, besides radiation shielding. Add-on shields are usually robust concrete or steel structures, and therefore could provide additional mechanical protection of the containers. In some circumstances they could also provide an additional layer of material that could delay the release of radionuclides (e.g., resin liner shields). In the preclosure safety assessment, the complete waste package is considered, including presence of shields, with respect to the likelihood and consequences of accidents (see Section 7.5.3.1 of the PSR). In the postclosure safety assessment, the waste containers, including shields, are conservatively not credited for any barrier function (see Section 8.6.2.1 of PSR). The materials (e.g., concrete and steel) represented by these shields are included in the reference inventory, specifically in Tables 2.9 and 2.10 of the Reference Inventory Report (OPG 2010) respectively for LLW and ILW. Page 30 of 69
Page 2 and 3: Dr. Stella Swanson September 28, 20
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CLOSURE WALL CAPACITY The shear str
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Title: Potential Inflows through Cr
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APPENDIX A Derivation of Conversion
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ATTACHMENT 2 Attachment to OPG lett
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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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