Canadian Nuclear Safety Commission Research Articles

A Multiphysics Model for the Near-Field Evolution of a Geological Repository of Radioactive Waste

The safety and robustness of Deep Geological Repositories (DGRs) are of paramount importance for the long-term management of spent nuclear fuel from electricity generation. The introduction of a multi-barrier system, which includes the host rock formation and an engineered barrier system (including the bentonite buffer), has been a widely used approach to ensure the safety of DGRs. The assessment of the long-term safety of DGRs involves the mathematical modeling of the coupled thermal–hydraulic–mechanical–chemical (THMC) processes that occur in the near-field of the DGRs and their impact on the behaviour and engineering properties of the bentonite buffer. This paper presents a review of the THMC-coupled processes that arise in the bentonite buffer as well as a mathematical model governing such coupled processes. The model is verified against existing analytical solutions and validated against measured data of a thermal diffusion experiment in a sand bentonite column. Also, scoping analyses were performed to assess the influence of coupled THM processes on solute transport in clayrocks. The results of the numerical model closely matched those of the analytical solutions and experimental data demonstrating the capability of the provided mathematical model as well as the numerical approach in enhancing our comprehension of DGR behaviour. This enhanced comprehension will be valuable for safety prediction and assessment in the context of DGRs. The work presented in this paper is part of the Canadian Nuclear Safety Commission’s (CNSC) regulatory research to gain independent knowledge on the safety of the geological disposal of radioactive waste.

Natural Analogue Studies in Support of Post-Closure Safety Assessment of Deep Geological Disposal

Natural analogues are systems that have evolved over geological timescales with features similar to one or several components of a deep geological repository (DGR). Natural analogues complement short-duration laboratory studies since they are existing reflections of many long-term processes that might affect the performance of a repository. Mathematical models are often used for the post-closure safety assessment of a DGR. Confidence in the models’ predictions is enhanced when the models successfully simulate the past evolution of a natural analogue. This paper summarizes the Canadian Nuclear Safety Commission’s (CNSC’s) recent research on natural analogues to inform on (1) glacial erosion, (2) engineered barrier system, and (3) uranium reactive transport in the context of DGRs for radioactive wastes. Glaciation and its erosion are prominent factors impacting the performance of future DGRs at high latitudes in the northern hemisphere. The authors have reviewed the field data from the Greenland Analogue Project, developed a conceptual and mathematical model for the simulation of the thermal conditions within the Greenland ice sheet, as well as the thermal-hydraulic conditions at its base and the ice sheet velocity, and eventually estimated the erosion rate at the site. The Cigar Lake Analogue demonstrates the long-term radionuclide containment capability of the illite clay zone enveloping the ore body, serving as an analogy to the engineered clay barriers. The CNSC and University of Ottawa analyzed 129I in the Cigar Lake core samples, and modeled and correlated the diffusion-dominated transport of radionuclides over the geological evolution of the Cigar Lake deposit. The results provide information on the mobility of fission products and significant radionuclides in conditions analogous to the source, engineered barriers, and near-field host rock of a DGR. The reactive transport and geochemistry of the Kiggavik-Andrew Lake uranium deposit mineralization and remobilization was another natural uranium deposit analogue studied by the CNSC. A reactive transport model was established according to the conceptualized geochemical processes and run under specified boundary and initial conditions to validate the geochemical processes. The geometry, timing, geochemistry, and fluid composition were used as model constraints.

Radiation exposure in fluoroscopy guided spinal interventions: A prospective observational study of standard practice in a physiatry academic center

ContextFluoroscopy is the recommended image guidance modality for most spinal pain interventions. However, it exposes interventional pain physicians to chronic ionizing radiation, with known risks to the eye, skin, and hand. The use of protective glasses and gloves is variable among pain physicians. ObjectivesTo document the total radiation exposure (mSv) by pain physicians to their eyes, hands and chest in an academic setting including various spinal interventions. MethodsFour pain physicians wore a finger, head/collar (equivalent to eye exposure) and chest dosimeter over and under their lead apron during a three-month period where they performed their usual fluoroscopy-guided interventions, including close supervision of trainees. We calculated an average exposure per intervention and extrapolated the recorded exposure to a maximum, worst-case scenario of a caseload of 13 procedures per day, 5 days a week and 52 weeks per year. ResultsFour pain physicians of variable experience performed 15 different types of procedures on 607 patients throughout the study period. The yearly maximum exposure scenarios for each pain physician were all below the Canadian Nuclear Safety Commission thresholds for nuclear energy workers: for the hands (31.56 mSv, 25.67 mSv, 20.59 mSv, 21.51 mSv; threshold = 500 mSv), eyes (16.01 mSv, 18.64 mSv, 24.08 mSv, 18.68 mSv; threshold = 50 mSv) and chest over the lead apron (28.27 mSv, 46.91 mSv, 30.00 mSv, 40,03 mSv; whole body threshold = 50 mSv), with some doses even below general population thresholds. The exposure under the lead apron was 0 mSv for each pain physician. ConclusionThe standard practice of an interventional pain physician using fluoroscopy in this academic setting is below radiation exposure regulations, even in a theoretical, worst-case, maximum exposure scenario. Standard radiation protection practices such as the use of lead aprons and thyroid shields should still be used. However, this data is reassuring for pain physicians with a practice in fluoroscopy-guided interventions who wish to not use protective glasses or gloves.

Electron Paramagnetic Resonance Measurements of Lifetime Doses in Teeth of Durham Region Residents, Ontario.

The Canadian Nuclear Safety Commission (CNSC) and Ontario Power Generation (OPG) determined the total dose contribution of nuclear power plants in Durham Region populations by analyzing environmental samples from the surrounding areas of both nuclear generating stations (Pickering and Darlington). However, the total doses from the various sources were unknown in Durham Region populations, Ontario. Electron paramagnetic resonance (EPR) dosimetry with tooth enamel has been successfully established as an effective tool for gamma dose assessment for chronic and acute exposures in individuals, groups, or populations to reconstruct the absorbed dose down to 30 mGy. This study collected the extracted teeth from people of different ages in Durham Region, Ontario, and analyzed them using the x-band continuous wave (CW) EPR spectrometer. The total dose rate from the natural and anthropogenic sources was 1.9721 mSv y-1. The anthropogenic dose rate from the various sources was 0.6341 mSv y-1, about 47.39% of the natural background dose (1.338 mSv y-1) in Durham Region, Ontario. The combined anthropogenic doses from these sources were lower than the local background dose in Durham Region and lower than the regulatory annual effective dose limit of 1 mSv y-1 in Canada. Based on these data, this study concluded that the anthropogenic dose contribution was lower than the regulatory limit to the local populations.

Current status of eye-lens dosimetry in Canada

For occupational exposures in planned exposure situations International Commission on Radiological Protection (ICRP) publication 118 recommends an equivalent dose limit for the lens of the eye of 20 mSv yr−1 averaged over five years with no single year exceeding 50 mSv. This constitutes a reduction from the previous limit of 150 mSv yr−1. The Canadian nuclear regulator, the Canadian Nuclear Safety Commission, responded to the ICRP recommendation by initiating amendments to the Radiation Protection Regulations through a discussion paper which was published for comment by interested stakeholders in 2013. The revised equivalent dose limit of 50 mSv in a one-year dosimetry period for nuclear energy workers came into effect in January 2021. This paper presents the outcome of discussions with Canadian stakeholders in diverse fields of radiological work which focused on the implementation of the reduced occupational equivalent dose limit for the lens of the eye in their respective workplaces. These exchanges highlighted the existing practices for monitoring doses to the lens of the eye and identified current technological gaps. The exchanges also identified that, in many cases, the lens of the eye dose is anticipated to be well within the new dose limit despite some of the gaps in technology. The paper also presents the monitoring and eye-lens dose assessment solutions that are available based on different methods for eye-lens monitoring; presented together with criteria for their use.

Management of radioactive waste from application of radioactive materials and small reactors in non-nuclear industries in Canada and the implications for their new application in the future

<abstract> <p>A large number of artificial-origin radionuclides from irradiation in small reactors and/or nuclear reactions in accelerators are currently used in non-nuclear industries such as education, oil and gas, consumer merchandise, research, and medicine. Radioactive wastes from the use of these radionuclides in non-nuclear industries include expired sealed radioactive sources, biological materials, radionuclide-containing chemicals, contaminated equipment, and very small quantities of used nuclear fuel. Although being less challenging and complex than nuclear energy production and research waste streams, these wastes are subject to the common nuclear regulations by the Canadian Nuclear Safety Commission, and are managed following domestic and international standards and guidelines made by the Canadian Standards Association, International Atomic Energy Agency, and International Organization for Standardization. Management practices used in the nuclear industry in Canada are commonly applied to the non-nuclear industry radioactive waste streams, such as waste handling, treatment, packaging, storage, transportation, clearance and exemptions, and disposal. The half-lives of radionuclides in non‑nuclear applications range from hours to thousands of years, and their activities in non-nuclear industrial applications can be as low as their clearance level or as high as the upper limits for intermediate level radioactive waste. Waste containing only short half-life radionuclides is placed in temporary storage to allow decay, and then is cleared and disposed of through non-radioactive waste routes. Non‑clearable waste materials are treated, consolidated, and managed along with radioactive waste generated from the nuclear industries at designated radioactive waste management sites.</p> </abstract>

Approach to Regulatory Pre-Licensing SMR Vendor Design Review

The Canadian Nuclear Safety Commission (CNSC) has recently completed the first phase of the pre-licensing vendor design review (VDR) for the SMR-160 small modular reactor (SMR) designed by Holtec International (USA). This event is an example of early involvement of the regulatory authority into review of the safety assessment for SMR design developed in compliance with standards and rules of another country. This example deserves a detailed analysis considering that the introduction of SMR technology is potentially attractive for Ukraine and there is national interest in this area. The paper presents an overview of the regulatory framework governing the pre-licensing VDR by CNSC: objective, initial conditions, main stages, technical content and general expected results of this process. According to the first phase of the review performed for the SMR-160 design, information on the main aspects addressed for each technical area and the main review findings are provided. Since the implementation of relevant advanced practices is reasonable and relevant, the paper proposes to consider the development and implementation of regulatory framework for the national nuclear regulatory authority to perform further pre-licensing reviews of designs using the latest foreign technologies.

Small Modular Reactors and Advanced Reactor Security: Regulatory Perspectives on Integrating Physical and Cyber Security by Design to Protect Against Malicious Acts and Evolving Threats

How can future nuclear technologies and Small Modular Reactors (SMRs) deter and prevent organized crime groups, terrorists, and malicious actors from attempting to steal or sabotage nuclear materials and facilities? This paper presents the benefits of integrating Security by Design (SeBD) into a regulatory framework to allow more a flexible and effective design of physical protection systems for SMRs. During its effort to modernize the Nuclear Security Regulations, the Canadian Nuclear Safety Commission (CNSC) licensing application process provides for the option of SeBD in moving toward a performance-based approach with less prescriptive requirements. CNSC also recognizes the need for a graded approach using risk-informed criteria for nuclear security. As part of the SMR Vendor Design Review (VDR) process, CNSC reviews SeBD proposals as well as interfaces with safety (robustness), safeguards (Nuclear Material Accounting and Control), operations, and sustainability. The CNSC also recognizes the need to share relevant, nuclear, sensitive information from the National Design Basis Threat (DBT) with SMR designers so they can consider credible and evolving threats in their proposed SeBD. Finally, the interfaces between nuclear security and system engineering specialists within the VDR process allow one to look at both physical and cyber security systems in a more holistic approach. This allows the regulator to look at how SMR developers propose to optimize nuclear safety to mitigate or protect against potential acts of sabotage and radiological release.

THE CANADIAN NUCLEAR SAFETY COMMISSION’S READINESS TO REGULATE SMALL MODULAR REACTORS

Over the course of the last several years the Canadian Nuclear Safety Commission (CNSC) has engaged with numerous vendors and potential licenses of small modular reactor (SMR) technology. This paper discusses what an SMR is and what potentially makes them different from standard nuclear power plants (NPP). Readiness activities for the potential licensing of SMRs are described as well as modifications being made to the CNSC’s existing regulatory framework to facilitate the same, without reducing safety. The role of the CNSC’s discussion paper DIS-16-04, Small Modular Reactors: Regulatory Strategy, Approaches and Challenges (DIS 16-04) and how feedback received on it helped confirm the CNSC’s modifications to be undertaken to the regulatory framework, as well as areas requiring further clarity, are highlighted. Finally, the role of the CNSC Vendor Design Review process is described as well as other readiness activities undertaken by the CNSC that are helping to ensure that the CNSC will be ready to accept and evaluate a license application for an SMR.

Consideration of Administrative Monetary Penalties in Nuclear Safety and Security

An Administrative Monetary Penalty (AMP) is a penalty imposed by the Canadian Nuclear Safety Commission (CNSC), without court involvement for a violation of a regulatory requirement. An AMP can be applied against any individual or corporation subject to the Nuclear Safety Control Act, which regulates the development, production and use of nuclear energy and the production, possession and use of nuclear and radioactive material. However, AMPs are not the same as criminal offences. They are civil sanctions which try to secure compliance through the application of monetary penalties for non-compliance with regulatory requirements. The AMP program was introduced in 2013 in Canada and to this date over 30 penalties have been issued. In all of these cases, the violations were related to handling and security of radioactive material. Based on these issued penalties investigations were conducted to discover pros and cons of the AMP system and to propose potential improvements for future implementation. This paper also addresses some of the complicated issues of the system, such as the economic aspect of the process, and the subjectivity and relative ease of issuing these penalties. In order to improve nuclear security in Canada, the regulator must be aware of possible violations of the Nuclear Safety Control Act and work on prevention of these violations. It is postulated that current AMP policy may not motivate individuals or corporations to report violations. The paper gives recommendations on modifications which could be implemented to motivate self – identification of violation, and give significant benefit to the AMP system. Other than the issued AMPs, the paper will analyze data obtained through the survey conducted on human readiness to self – identify violations in the nuclear industry under different circumstances. This confirms that the modified AMP policy would improve the body of knowledge and provide significant information on violations of the Nuclear Safety Control Act and improve nuclear security.

Special Section: ICONE-26

This Special Section in this issue of the ASME Journal of Nuclear Engineering and Radiation Science is dedicated to selected papers from the 26th International Conference on Nuclear Engineering (ICONE-26) held in London, United Kingdom, during July 22–26, 2018. The selected ICONE-26 papers were revised and reviewed to meet the journal standards and requirements.The ICONE conference is a premier global annual conference on nuclear engineering, science, and technology that has a quarter century history and is organized by the Nuclear Engineering Division (NED) of the ASME, the Japan Society of Mechanical Engineers (JSME), and the Chinese Nuclear Society (CNS). The first conference, ICONE-1, was held in 1991 in Tokyo with the JSME and ASME as sponsors. In 2005, the Chinese Nuclear Society (CNS) formally joined as the third sponsor and hosted ICONE-13 in Beijing. The ICONE-series of conferences are global significant events of choice for nuclear professionals to stay technically current, follow industry trends, promote professional development, and provide a platform for information exchange and dissemination. The contributions from industry, government, and academia lead to the success of ICONE as the quality and number of the technical presentations steadily increased. In addition to the archival paper publications, ICONE assists the nuclear industry in developing future generations of nuclear professionals to meet industry needs. This is achieved through an excellent student paper competition program that includes a significant number of students from around the globe, supported and partially funded by the conference sponsors (60 finalists in total consisting of 15 students from each of the following four regions: North America, Europe, China, and Japan with Asia at large).Based on the turnout and the comments received from many of the nearly 900 registered participants, the 26th International Conference on Nuclear Engineering (ICONE-26), held in London, UK, was a great success. In total, 57% of the participants were from academia, 29% from the industry, and 11% from government. Geographically, the largest part of participants came from China (45%), European Union (20%, including 7% from UK), Japan (16%), USA and Canada (11%), and South Korea (6%). More than 670 final technical papers and 760 presentations were made during the ICONE-26 conference from countries worldwide in a total of 15 technical tracks. These statistics show emphatically that ICONE presents a truly worldwide view on Nuclear Power, and there is no better venue to express viewpoints or share information with likeminded professionals.The ICONE-26 organizers invited the authors to submit their revised and augmented papers for journal publication consideration. The selected final papers presented in this special section cover a wide area of topics in nuclear science and technology. Reflecting the state of the nuclear industry, there are several papers dealing with analysis, simulation, management, experiments, context evaluation, and consequences of postulated design basis and severe accidents. This special issue also contains papers related to research and development challenges into advanced reactors, fusion technology, decontamination and decommissioning, radiation protection, and other related topics.The guest editors want to warmly thank the authors and reviewers for their efforts and support in producing this journal issue. During the editorial process, the papers went through the rigorous peer-review process. The ICONE-based special issue or section of the Journal of Nuclear Engineering and Radiation Science is now already traditional and we hope to continue the journal publication of selected augmented papers from the future ICONE conferences. The guest editors would like to extend their thanks to the editorial board of the journal and, in particular, the editor, Dr. Igor Pioro, for their support during the preparation of this special section. Finally, we hope that the readers enjoy this special ICONE-26 based section.Guoqiang Wang, Ph.D. ICONE-26 Conference Chair Fellow ASME Westinghouse Electric Company LLC, Pittsburgh, PA 15235 e-mail: WangG@Westinghouse.comShripad Revankar, Ph.D. ICONE-26 Technical Program Chair Fellow ASME School of Nuclear Engineering,Purdue University,West Lafayette, IN 47907e-mail: shripad@purdue.eduLeon Cizelj, Ph.D. ICONE-26 Conference Co-Chair Fellow ASME Reactor Engineering Division, Jožef Stefan Institute, Ljubljana 1000, Slovenia e-mail: Leon.Cizelj@ijs.siRobert Stakenborghs ICONE-26 Steering Committee Chair Fellow ASME ILD, Inc., Baton Rouge, LA 70808 e-mail: bob@ildpower.comJovica Riznic, Ph.D. ICONE-26 Organizing Committee Co-Chair Fellow ASME Canadian Nuclear Safety Commission, Ottava, ON K1P 59S, Canada e-mail: jovica.riznic@canada.ca

Licensing Framework of CANDU Reactors in Canada, and Alternatives for Crediting EME in Safety Analysis

This paper summarizes the existing framework of safety analysis and licensing of CANDU reactors in Canada, established by the Canadian Nuclear Safety Commission (CNSC), and explores enhancements to better capture and implement lessons learned from the Fukushima accident, in conducting nuclear safety analysis for the existing and new reactors. This paper compares the Canadian regulatory requirements with other international nuclear regulatory guidelines, in terms of dealing with Beyond Design Basis Accidents (BDBA) and Severe Accidents, and also reviews the past and present event classification principles in safety analysis, set by the CNSC. The CNSC have published regulatory documents and technical papers outlining the challenges to be addressed with respect to implementations of the Design Extension Conditions (DEC). The DEC concept has interfaces with the other safety concepts such as Defence-in-Depth in Deterministic Safety Analysis (DSA) of the Design Basis Accidents (DBA), and Best-Estimation in Probabilistic Safety Assessment (PSA) of Beyond Design Basis Accidents (BDBA). This paper explores the current requirements and the principles of the regulatory framework in Canada, and compare it with alternative practical solutions, such as using portable/mobile Emergency Mitigating Equipment (EME) primarily for mitigation of Severe Accidents consequences, versus preventing them. Systematic examination of CANDU PSA results shows, crediting mobile EME in Level 1 PSA accident sequences have challenges. Although, adding another layer of redundancy to backup support systems (electrical power, cooling water and air) further reduces the frequency of Severe Core Damage (SCD), portable EME can only have a short-term mission time, and the main benefit in using crediting them in Level 1 PSA, is to delay the consequences. This paper proposes a thorough review of PSA before allocating EME to AIM/EOP or SAMG, with the objective of maintaining a balance between prevention and mitigation of severe core damage and large release. Maintaining this balance is paramount and instrumental to public safety. Instead of focusing on reducing the “probability” of accidents by crediting every available EME in Level 1 PSA, an alternative would present a better balance between prevention and mitigation of accidents.

A direct-AMS multi-isotope survey of uranium ore concentrates

Uranium ore concentrate (UOC) is an important nuclear material of interest for Canada. A large scale analytical program is being led by the Directorate of Security and Safeguards (DSS) of the Canadian Nuclear Safety Commission (CNSC) to establish a reference dataset of UOCs that have passed through and/or are currently under Canadian regulatory control. Isotopic ratios are among the signatures being captured under the reference dataset. Accelerator Mass Spectrometry (AMS) has been used for the measurement and assessment of 236U/238U and 187Os/188Os, respectively. Furthermore, since UOCs have uranium typically concentrated to ≥70% by weight, a direct-AMS assay method is possible wherein the samples can be measured without time consuming chemical digestion and processing. Using this direct-AMS approach, several related ratios (231Pa/238U, 230Th/238U, 226Ra/238U) were also assessed within the data acquisition sequence used for measuring the 236U/238U ratios, and 185Re, 187Re and 187Os, 188Os, 191Ir and 193Ir in the sequence for the 187Os/188Os ratios. The sum of these results can be shown together in a “bar-code” pattern to strengthen the capability for UOC source identification. Unexpectedly large 236U/238U ratios (up to ≥1 × 10−7) have been found in several UOC samples. The 187Os/188Os ratio has also been shown for the first time to be a viable supplementary signature of UOCs. This work shows that the direct-AMS method has the potential to become an effective tool for nuclear forensics provenance assessment applications with UOCs. The implications of the results, and the need for further refinement of the sputter target preparation, as well as the Cs+ sputter ion source itself, are also discussed.

Fire development in multi‐compartment facilities: PRISME 2 project

Fire development in multi‐compartment facilities: PRISME 2 project

Material, structural and modelling aspects of alkali aggregate reaction in concrete

Concrete nuclear structures have been identified as suffering from alkali aggregate reaction (AAR) in both Canada and the United States. Although much research effort has been directed toward understanding its effect on reinforced concrete structures, unresolved issues still remain. Among them are the effect of multiaxial stress states, commonly developed in nuclear structures, on the response of AAR-affected concrete; also of concern is the possible invalidity of conventional methods of analysis for structural assessment due to the induced anisotropy in the mechanical properties of concrete. The Canadian Nuclear Safety Commission initiated and funded an extensive study aimed to reveal the implications of concrete deterioration due to AAR on structural integrity, which included material and structural testing and modeling. This paper presents an overview of the entire research program and discusses the key results.

Modelling a heater experiment for radioactive waste disposal

This paper presents the Canadian Nuclear Safety Commission’s modelling of coupled thermal, hydraulic and mechanical (THM) processes and their influence on the performance of the engineered barrier system (EBS) and the host rock. The coupled THM processes were monitored during a heater experiment called HE-E, performed in an Opalinus Clay formation at the Mont Terri Rock Laboratory in Switzerland. The HE-E experimental set-up consisted of two EBS sections emplaced in an existing tunnel of the Underground Rock Laboratory. This paper focuses on the model development, parametric analysis, model calibration and verification with the field test data. The influence of THM processes on the EBS and host rock performance and the implications on the design and safety assessment of geological disposal repository systems are discussed.

A Crisis of Our Own Making: Prospects for Major Natural Resource Projects in Canada

Announcements of new energy and mining projects slowed after 2015, and, between 2017 and 2018, the planned investment value of major resource sector projects has plunged by $100 billion – an amount equivalent to 4.5 percent of Canada’s gross domestic product. Many projects in Canada have faced environmental assessments that take much longer than in comparator jurisdictions: Canadian timelines for mining projects are substantially longer than in Australia, and Canadian pipeline approvals are protracted relative to those in the United States. Environmental assessments play a critical role in mitigating negative externalities on the environment and human well-being and resolving asymmetric information between project proponents and affected stakeholders. Assessment processes, however, should not discourage socially beneficial projects by imposing excessively high regulatory costs, protracted review timelines and excessive uncertainty around the finality of approvals. Under Canada’s federal legislation for environmental assessments, most project approvals since 2012 have withstood court challenges. However, courts’ findings that federal governments failed to fulfill their constitutional duty to consult affected Indigenous peoples has resulted in the quashing of three approvals, including those for the Northern Gateway pipeline and Trans Mountain Expansion. The Minister of Justice and Minister of Crown-Indigenous Relations should update guidance for federal officials to ensure consistent consultation of Indigenous peoples – particularly prior to Cabinet’s decision – that satisfies the requirements from the past decade of case law on the duty to consult. With investment in Canada’s resources sector already depressed, the federal government’s proposed Bill C-69 could further discourage investment in the sector by congesting the assessment process with wider public policy concerns and exacerbating the political uncertainty facing proponents with a highly subjective “public interest” standard that would likely apply to every project subject to an assessment. To address fundamental problems in Bill C-69, legislation for impact assessment must: specify considerations for assessing projects that can be scoped and applied with reasonable consistency and predictability; preserve the role of independent and expert life cycle regulators (specifically, the National Energy Board/Canadian Energy Regulator and Canadian Nuclear Safety Commission) in leading assessments; require a ”significant” standard for a project’s effects before involving political decision makers in approving the project; and specify a standard for “standing” that ensures review panels can focus proceedings on relevant submissions. The federal government should undertake to compile and annually report on timelines for federal environmental assessments across major projects in Canada, as well as regularly and publicly benchmark performance relative to timelines for provinces and other countries – such as the United States and Australia.

International Atomic Energy Agency's Analytical Laboratories for the Measurement of Environmental Radioactivity network: Experiences and perspectives in the North and Latin America region

The International Atomic Energy Agency (IAEA) Network of Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA) is a worldwide network of laboratories capable of providing reliable and timely analysis of radionuclides in environmental samples during normal or accidental/intentional events that result in the release of radioactivity in the environment. ALMERA is coordinated by the Environment Laboratories of the IAEA and organized into five regional groups, including the North and Latin America region (NLAR), led by the Canadian Nuclear Safety Commission. Capacity building in the NLAR for the measurements of environmental radioactivity is achieved through qualitative study that consists of experiences of ALMERA core activities and perspectives of the regional initiatives, respectively. Outcomes' analysis showed that the ALMERA core activities have contributed to the improvements of the analytical capacity and capability, and the regional initiatives assisted in the strengthening of the collaboration and networking, in the NLAR region. The immediate impact of these achievements consisted of gaining technical competence in measuring environmental radioactivity and establishing a network of laboratories. In the long term, sustained efforts between ALMERA and the regional coordination will continue upgrading national and regional competence in the radio analytical services.

Hydro-mechanical behavior of an argillaceous limestone considered as a potential host formation for radioactive waste disposal

The Canadian Nuclear Safety Commission (CNSC), Canada's nuclear regulator, conducts regulatory research in order to develop independent knowledge on safety aspects related to the deep geological disposal of radioactive wastes. In Canada, the Cobourg limestone of the Michigan Basin is currently considered as a potential host formation for geological disposal. The understanding of the hydro-mechanical behavior of such a host rock is one of the essential requirements for the assessment of its performance as a barrier against radionuclide migration. The excavation of galleries and shafts of a deep geological repository (DGR) can induce damage to the surrounding rock. The excavation damaged zone (EDZ) has higher permeability and reduced strength compared to the undisturbed rock and those factors must be considered in the design and safety assessment of the DGR. The extent and characteristics of the EDZ depend on the size of the opening, the rock type and its properties, and the in situ stresses, among other factors. In addition, the extent and characteristics of the EDZ can change with time due to rock strength degradation, evolution of fractures within the EDZ, and the redistribution of pore pressure around the excavation. In this research project initiated by the CNSC, the authors conducted experimental and theoretical research in order to assess the hydro-mechanical behavior of the Cobourg limestone under undamaged and damaged conditions, both in the short and long terms. The short-term behavior was investigated by a program of triaxial tests with the measurement of permeability evolution on specimens of Cobourg limestone. The authors formulate a coupled hydro-mechanical model to simulate the stress-strain response and evolution of the permeability during those triaxial tests. Using creep and relaxation data from a similar limestone, the model was extended to include its long-term strength degradation. The model successfully simulated both the short- and long-term hydro-mechanical behavior of the limestone during those tests. This provides confidence that the main physical processes have been adequately understood and formulated.

Thermo-Hydro-Mechanical-Chemical processes in geological disposal of radioactive waste – An example of regulatory research

Deep geological disposal is being considered in Canada and many other countries as the most viable option for the long-term management of radioactive waste. The disposal method consists of emplacing the waste in a repository built at hundreds of metres depth in a suitable host rock. A multi-barrier system, that includes the host rock formation as a major component, would be provided in order to protect humans and the environment from the harmful effects of the waste for very extensive time periods. Many events and processes are expected to occur during the lifetime of the repository, such as heat generation from the waste, seismicity and glaciation. As a result of those events and processes the Thermal-Hydraulic-Mechanical-Chemical (THMC) regimes in the natural and engineered components of the multi-barrier system will be perturbed, and the evolution of the THMC regimes and how this evolution affects the multi-barrier performance need to be understood. The Canadian Nuclear Safety Commission (CNSC), Canada’s nuclear regulator, has been conducting independent experimental and theoretical research on coupled THMC processes for several decades. As part of this research, the CNSC used experimental data from laboratory tests and large-scale experiments at underground research laboratories (URL) in order to develop a mathematical framework for the simulation of coupled processes in engineered and natural barriers for geological disposal. In this paper, we describe that mathematical framework and show examples of how it was adapted and applied to several situations: water and gas injection experiment at an URL, a heater experiment at an URL, and the effects of nine glacial cycles in a sedimentary rock formation. Cited as : Nguyen, T.S. Thermo-Hydro-Mechanical-Chemical processes in geological disposal of radioactive waste – An example of regulatory research. Advances in Geo-Energy Research, 2018, 2(2): 173-189, doi: 10.26804/ager.2018.02.06