Hydro-mechanical effects of seismic events in crystalline rock barriers

Under ideal conditions, owing to its extremely low matrix permeability, crystalline rock can constitute a suitable hydro-geological barrier. Mechanically, its high strength and stiffness provide advantages when constructing a repository and for long-term stability. However, crystalline rock usually occurs in a fractured form, which can drastically alter hydromechanical (HM) barrier functions due to increased permeability and decreased strength. Seismic events have the potential to alter these HM properties by activating faults, increasing their transmissibility, creating new fractures or altering network connectivity (De Rubeis et al., 2010). Therefore, it is of high importance to build computational models to allow assessment of the HM effects of seismic events in a Deep Geologic Repository (DGR) in crystalline rock, as illustrated in Fig. 1. For this purpose, we consider a DGR in Russia (Yeniseysky site) for high-level waste in crystalline rock (Proterozoic and Archaean gneiss complexes) that is located close to a potentially seismically active area (Jobmann, 2016). Here, we present a coupled HM simulation, using OpenGeoSys (Kolditz et al., 2012), of a large-scale, three-dimensional finite-element model of the Yeniseysky site to assess the consequences of seismically induced stress-field changes on the local stress field and the fluid flow. This research also provides an outlook of current model development geared towards a more detailed assessment of seismically induced hydro-mechanical processes in porous and fractured rocks.

IAEA compiling state of knowledge and developing high level guidance in radioactive waste management

One endeavour central to the International Atomic Energy Agency's (IAEA) mandate is compiling the international state of knowledge (SoK), supporting transfer of knowledge and establishing high level guidance for all peaceful applications of nuclear technologies, including those specific to radioactive waste management (RWM). Building on the current state of experiences and knowledge shared with us from IAEA Member States, we are developing a comprehensive suite of documents on the technologies and solutions having the potential to address RWM needs and steps. This information can be used as a baseline to guide RWM in other countries. In a first approach, the information is compiled and developed in a sequence of documents covering a range of topical domains. These include: RW: inventory; characterization; use of waste acceptance criteria throughout all RWM steps. RWM steps: a series of handbooks presenting approaches to waste treatment, conditioning and storage; special applications supporting small inventory management needs (e.g. through mobile facilities); considerations specific to management needs of postaccident radioactive waste. Endpoints: introduction to design approaches and disposal concepts; managing site investigations; global compendium of Underground Research Facilities (URF) RD&D; special considerations for small inventory disposal. Programmatic considerations: a generic roadmap to deep geologic repository (DGR) implementation; cost estimation and funding of a disposal programme; stakeholder involvement in disposal. To improve on efficiency and to prove our capacity to compile and transfer an evolving state of knowledge on topics relevant to RWM, the IAEA is building a collection of online interactive contents based on these publications. This online interactive content ultimately aims at containing all our key guidance topics and is intended to provide easier and more rapid access to detailed information. The format would also allow its content to be expanded with descriptions and analyses of topical case studies.

A critical analysis of the deep geologic repository siting process in Ontario

This research paper is a case study of OPG’s siting process for a low and intermediate level radioactive waste facility. The chosen site is in Kincardine, Ontario, where nuclear waste is currently stored above ground. The Town of Kincardine is in support of the project; however, several individuals and organizations are actively opposing the facility. The objective of this paper is to understand why the facility is facing so much opposition, what steps could have been taken to prevent it and how to proceed with the project plan. An inductive analysis of qualitative data was performed using explanation building and pattern matching. Lessons were drawn from cooperative siting guidelines specific to nuclear waste repositories in Ontario. The conclusion was drawn that omission of extensive public consultation in the siting process resulted in significant public opposition. Increasing community involvement when moving forward with the project may assist in reducing public opposition.

A critical analysis of the deep geologic repository siting process in Ontario

This research paper is a case study of OPG’s siting process for a low and intermediate level radioactive waste facility. The chosen site is in Kincardine, Ontario, where nuclear waste is currently stored above ground. The Town of Kincardine is in support of the project; however, several individuals and organizations are actively opposing the facility. The objective of this paper is to understand why the facility is facing so much opposition, what steps could have been taken to prevent it and how to proceed with the project plan. An inductive analysis of qualitative data was performed using explanation building and pattern matching. Lessons were drawn from cooperative siting guidelines specific to nuclear waste repositories in Ontario. The conclusion was drawn that omission of extensive public consultation in the siting process resulted in significant public opposition. Increasing community involvement when moving forward with the project may assist in reducing public opposition.

Are Arid Regions Always that Appropriate for Waste Disposal? Examples of Complexity from Yucca Mountain, Nevada

The study of the hydrology of arid regions greatly expanded at the end of the 20th century as humans sought to reduce groundwater pollution from landfills, waste dumps and other forms of land disposal. Historically viewed as wastelands where little or no water percolated to the underlying water table, the discovery of large-scale contamination beneath arid disposal sites such as the Hanford nuclear complex in eastern Washington jumpstarted an industry in studying the hydrology of arid vadose zones and their transport behavior. These studies showed that, in spite of hyper aridity in many areas, precipitation often did infiltrate to deep water. The efforts at Yucca Mountain, Nevada to design a high-level nuclear repository stand out as one of the largest of such studies, and one that fundamentally changed our understanding of not only water flow in fractured rocks, but also of the range of our uncertainty of hydrologic processes in arid regions. In this review and commentary, we present some of the initial concepts of flow at Yucca Mountain, and the evolution in research to quantify the concepts. In light of continued stockpiling of high-level waste, and the renewed interest in opening Yucca Mountain for high-level waste, we then focus on the significant surprises and unanswered questions that remained after the end of the characterization and licensing period; questions that continue to demonstrate the challenges of a geologic repository and our uncertainty about critical processes for long-term, safe storage or disposal of some of our most toxic waste products.

Probabilistic Performance Assessment vs. the Safety Case Approach

ABSTRACTThe “safety case” approach has been developed to address the issue of evaluating the performance of a geologic repository in the face of the large uncertainty that results for evaluations that extend over hundreds of thousands of years. This paper reviews the concept of the safety case as it has been defined by the international community. We contrast the safety case approach with that presently used in the U.S. repository program. Especially, we focus on the role of uncertainty quantification. There are inconsistencies between the initial proposal to dealing with uncertainties in a safety case and current U.S. practice. The paper seeks to better define the safety case concept so that it can be usefully applied to the regulatory framework of the U.S. repository program.