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DGR Postclosure Safety Assessment Reports

The preliminary postclosure safety assessment was completed, based on the preliminary design and site characterization data from all six deep boreholes. The safety assessment was undertaken in a systematic manner, consistent with CNSC guidance (CNSC Guidance G-320) and with international best practice.

 

The postclosure safety of the DGR is assessed through considering a range of potential future scenarios. These are not intended to predict the future, but rather to identify a range of possible future evolutions of the DGR against which the performance of the system can be assessed. Uncertainties are further addressed through evaluating a range of cases within each scenario. They are also addressed by use of conservative assumptions and parameter values.

 

Consistent with CNSC G-320 and the CEAA/CNSC Environmental Impact Statement guidelines, the scenarios are classified into those that consider the expected evolution of the DGR system with time (i.e., the Normal Evolution Scenario) and those that examine the potential impacts of low-probability events leading to penetration of barriers and abnormal loss of containment (i.e., Disruptive Scenarios or “What if” scenarios). The scenarios quantitatively evaluated are listed below. Other scenarios were considered but are either even more unlikely or are covered by these scenarios.

 

The Normal Evolution Scenario – The expected long-term evolution of the repository and site following closure. The scenario includes waste and packaging degradation, gas generation and build up, rockfall, earthquakes and, eventually, glaciation.

The Human Intrusion Scenario - Inadvertent intrusion directly into the DGR via an exploration borehole.

The Severe Shaft Seal Failure Scenario – Poorly constructed or substantially degraded shaft seals.

The Poorly Sealed Borehole Scenario – One of the deep site characterization boreholes near the DGR is poorly sealed or has substantially degraded seals.

The Vertical Fault Scenario – A transmissive vertical fault is present in the rock in the vicinity of the DGR.

 

The assessment results for the Normal Evolution Scenario indicate that the DGR system provides effective containment of the emplaced contaminants. Most radionuclides decay within the repository or the deep geosphere. The amount of contaminants reaching the surface is very small, such that the maximum calculated impacts for the Normal Evolution Scenario are much less than the public dose limit and the natural background radiation dose rate.

 

The isolation afforded by the location and design of the DGR limits the likelihood of disruptive events potentially able to bypass the natural barriers to a small number of situations with very low probability. Even if these events were to occur, the analysis shows that the contaminants in the waste would continue to be contained effectively by the DGR system such that risk criterion is met.

 

The preliminary postclosure safety assessment is documented in the Postclosure Safety Assessment Report and Supporting Technical Reports.

 

To view these documents scroll down to the Postclosure Safety Assessment Documents Roadmap. The Roadmap visually presents the documents and provides access to each, including both the Executive Summary and the full report. Click on a document to view its Executive Summary and from the Executive Summary access is provided to the full report.

 
     

 

 

If you cannot see the documents above, please click here

 

 

 

 

 
     

DGR Contact Information
Contact information for the DGR project is:
Box 7000, B21
Tiverton, Ontario
N0G 2T0 Canada
Tel: 519.368.1639
Fax: 519.368.1607
Email: dgrinfo@opg.com

 

 

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Sept-21-2014 06:08:26 PM EDT

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