Ontario Power Generation's Response to the Joint Review

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
Concentration (Bq/m 3 )
1.E-02
1.E-03
1.E-04
1.E-05
1.E-06
1.E-07
1.E-08
1.E-09
1.E-10
1.E-11
Information Request and Response
Cl-36: 5th Percentile I-129: 5th Percentile
Cl-36: 50th Percentile I-129: 50th Percentile
Cl-36: 95th Percentile I-129: 95th Percentile
1.E-12
100 1,000 10,000 100,000 1,000,000 10,000,000
Time (a)
Natural Cl-36 in Surface Water
Natural I-129 in Surface Water
Figure 2: Calculated Well Water Concentrations for Cl-36 and I-129 from Probabilistic
Sensitivity Calculations (NE-PC) Based on the Reference Case (Figure 8-55 of the PSR)
As noted above, the sorption values and solubility limits for contaminants were set deliberately low and high,
respectively. Within the uncertainties, the sorption values could also be higher and solubility limits lower than assumed.
No specific calculations were made to test this potential improvement as the dose rates are already low. However, as a
general observation it is noted that sorption, precipitation and solids exchange of C-14 are likely to occur to some
extent due to the large amount of carbon in the repository, shaft seals and host rock. This could appreciably reduce the
potential dose consequences of some disruptive scenarios such as the Severe Shaft Seal Failure Scenario.
(d) Interactions of Contaminants with Organics in Cap Rock
Interactions between contaminants and organic compounds in the cap rock are not explicitly considered. However,
many of the argillaceous rocks included in the review of sorption values in Appendix D of QUINTESSA and GEOFIRMA
(2011) are likely to include natural organics and so the impact of organics is implicitly included in the selected sorption
values. While the presence of organics is likely to increase sorption due to their large surface area, it is possible that
Page 20 of 69