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Research report summaries 2021–2022

Contractors’ reports are only available in the language in which they are submitted to the CNSC.

RSP-593.2 Implementation of 4D/4P tool for all NPPs

In the event of a nuclear reactor accident, the diagnosis and prognosis of the accident and its progression are essential in emergency response. A reactor assessment tool methodology was developed by the Canadian Nuclear Safety Commission (CNSC) in collaboration with Canadian Nuclear Laboratories (CNL), the International Atomic Energy Agency (IAEA), CANDU Owners Group and the nuclear industry. An automated tool to allow for efficient assessment of the accident was presented to the CNSC by the Canadian Nuclear Laboratories (CNL) in early 2020. Following this, a user manual was created, and the final version of the software was delivered to the CNSC in February 2022. The tool includes 4D/4P (Diagnosis/Prognosis) assessment grids, and the Reactor Assessment Tool (RAT). The automatic tool provides an efficient accident assessment capability for Canadian Nuclear Power Plants.

The CNSC Emergency Operations Centre (EOC) is activated in the event of a nuclear emergency. The EOC assesses the safety systems and safety functions for better understanding of the reactor state during accident conditions and potential accident progression. The 4D/4P RAT tool is used for accident assessment in CNSC’s EOC. The accident assessment information collected in the 4D/4P grids are used as inputs of the RAT which generates graphical outputs of the current and future plant status. The graphical outputs are used to communicate important information both internally and externally in even of a nuclear emergency.

Request the RSP-593.2 final report

RSP-723.2 Technical Basis for Flood Protection and Flood Hazard Assessment for Canadian Nuclear Facilities

A severe flood may simultaneously affect all the structures, systems, and components important to the safety of a nuclear installation site. It is essential to understand flood mechanisms to estimate realistic flood magnitude and occurring frequency, and its potential impacts to nuclear facilities.

This report is a technical basis document on flood protection and flood hazard assessment for Canadian nuclear facilities. The purpose is to provide a detailed review, summary and discussion of national and international up-to-date studies and best practices for flood protection and flood hazard assessment that could be applicable to the Canadian nuclear facilities under the changing climate.

Flood hazard assessments are essential for the safety-related structures, systems, and components important to safety of a nuclear power plant against the adverse effects of flooding. Flood hazard assessment approaches include deterministic methods such as estimating the probable maximum precipitation (PMP) and probable maximum flood (PMF), and hydrological and hydraulic modeling. Flood hazard assessments can also be based on a probabilistic approach such as flood frequency analysis (FFA). Both deterministic and probabilistic methods need to take into consideration of uncertainty characterization and impact of climate change.

It’s expected that this technical basis document will provide the technical background for developing a guidance document on how to conduct flood hazard assessment for existing and new nuclear facilities.

Report Limitations

The Report and maps were prepared by the author for the Canadian Nuclear Safety Commission. The statements, analyses, conclusions, and recommendations given in this Report are applicable only to the Flood Protection and Hazard Assessments of Canadian nuclear facilities. Assumptions made in the analyses, conclusions, and recommendations are not all documented in the Report.

Conclusions and recommendations stated in the Report reflect the author’s judgement in light of the information available at the time the Study was undertaken, but they may change if that information changes or new information becomes available.

In addition, the report is still under a peer review process. Parts of the report may be revised as a result.

Request the RSP-732.2 final report

RSP-222.2 Radon Exposure and the Risk of Lung Cancer Incidence and Mortality: Final Update of the Cohort of Newfoundland Fluorspar Miners

The relation between occupational radon exposure and mortality, specifically lung cancer and circulatory diseases (i.e., heart disease), was analyzed in the cohort of Newfoundland Fluorspar miners. The mining of fluorspar in St. Lawrence, Newfoundland began in 1933. Underground miners were exposed to high radon exposures until mechanical ventilation was introduced in the mines in 1960. This report provides over 65 years of mortality follow-up to assess the long-term health risks of lung cancer and circulatory disease mortality from occupational radon exposure. The research was performed to:

  • Assess the risk of lung cancer mortality among miners with both high and lower levels of radon exposure
  • Assess how the risk of lung cancer differs with increasing time since last radon exposure
  • Assess how cigarette smoking alters the relationship between radon exposure and lung cancer mortality
  • Examine associations between radon and circulatory disease mortality among 1,080 miners with known smoking status

The mortality of the cohort was followed-up by linking individual occupational records to national death data. Individual estimates of exposure to radon and its progeny for each miner (in working level months) was calculated for each year of employment. Of the 2,050 miners in the cohort, 1,363 died sometime from 1950-2016. Of these, 236 died from lung cancer and 210 died from circulatory diseases. Comparisons between underground miners and the Newfoundland’s male population found a statistically significant excess of deaths in miners for only lung cancer. The study found a strong increased risk of lung cancer with cumulative radon exposure that was modified by a miner’s time since last radon exposure and his cigarette smoking status. The study did not find an increased risk of circulatory disease mortality from radon exposure. These findings contribute to the scientific evidence to support radiation protection regulations, specifically for radon in occupational settings.

Request the RSP-222.2 final report

RSP-762.1, Review of the Canadian Nuclear Safety Commission’s Regulatory Framework for Readiness to Regulate Fusion Technologies

Reviewing the implementation of the CNSC’s current Regulatory Framework with respect to novel technologies is an area of broad interest and concern. Fusion is widely viewed as a cleaner, safer, and cheaper means of producing power. To date no entity has succeeded in commercializing fusion as all research fusion reactors require more energy in to maintain criticality than energy outputted. There are, however, fusion organizations on a path with established utilities to build demonstration facilities to prove the feasibility of commercial fusion technology. The CNSC is working under the assumption that there may be fusion technology companies that will seek to enter into a formalized Vendor Design Review (VDR) agreement in the near future.

The purpose of this project was to establish an external research contract to review the CNSC regulatory framework’s readiness for regulating fusion, and to suggest areas where modification may be required as appropriate. This research helps ensure that the CNSC’s regulatory framework reflects the necessary readiness and agility to review license applications for fusion technology.

The scope of this project involved the following elements:

  • Developing hypothetical preliminary descriptions of fusion facilities covering a range of approaches to fusion to use to test the Regulatory Framework
  • Researching and interviewing regulators and stakeholders on their approach to regulation of fusion technologies in the USA, UK, France, and Japan, as well as relevant IAEA reports
  • Assessing the readiness of the CNSC’s Regulatory Framework to license a fusion facility using the hypothetical models

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RSP-739.1, Regulatory Oversight Program for Authorized Inspection Agencies (AIA) at Nuclear Facilities

In Canada, an integral part of the safety culture for pressure boundary construction and operation is independent inspection. As the nuclear regulator in Canada, the Canadian Nuclear Safety Commission (CNSC) designates the organizations that can conduct independent inspections. Authorized Inspection Agencies (AIA) are provincial organizations who provide services established in the governing standards and other functions that the CNSC requires. In the non-nuclear industry, inspection service is carried out by the provincial regulatory body for construction and insurance and other companies approved as an AIA for most in-service work. The qualification of AIAs is controlled provincially.

Gaps have been identified in the current AIA designation and oversight program and the CNSC is taking action to improve regulatory oversight for the AIA service at nuclear power plants (NPPs). These gaps warrant a modified regulatory oversight program that will assist the CNSC in designating an AIA and provide more verifiable oversight of the AIA activities at NPPs. This study reviewed international best practices to develop alternative solutions to improve qualification of AIAs. In identifying the issues and creating recommendations a consistent, practical, and feasible approach to the regulatory oversight of the AIAs can be made across Canada.

Request the RSP-739. 1 final report

RSP-726.1, High Temperature Gas Reactor Technical Seminar

The Canadian Nuclear Safety Commission (CNSC) is preparing to perform pre-licensing vendor design reviews and technical assessments of licensing submissions related to advanced reactor technologies. The CNSC contracted Argonne National Laboratory to provide a technical seminar on High Temperature Gas Reactor (HTGR) technologies to enhance CNSC staff’s understanding of key design aspects and safety features of HTGRs. Argonne National Laboratory provided several presentations on specific topics related to HTGR technologies including nuclear physics, chemistry, and materials. Specific topics of interest for the CNSC staff included:

  • Retention of fission products at the source (TRISO fuel) under standard operation or accident conditions
  • Irradiation of graphite causing geometrical and structural changes
  • Nuclear core design and neutronic calculations
  • Guaranteed shutdown state
  • Method for the selection of initiating events
  • Risk assessment for HTGRs
  • Mechanical design
  • Behaviour of high temperature structural materials and their degradation mechanisms

Request the RSP-726. 1 final report

RSP-720.1, Class II Equipment Servicing Accreditation Program

This report, prepared for the Canadian Nuclear Safety Commission, describes the potential safety hazards associated with maintenance and repair of linear accelerators and cyclotrons. The Canadian Nuclear Safety Commission (CNSC) seeks to identify the hazards associated with accelerator maintenance beyond the radiation hazards, in order to ensure that Canadian technicians who service this equipment have the appropriate knowledge of these hazards. The results of this report may lead to some form of accreditation process, knowledge requirement or teaching aid for these technicians.

Safety in accelerators is a vast subject. Despite this, very few resources are available to train maintenance personnel. Training courses are provided by the equipment manufacturer, however these are mostly technical in nature and do not teach the Canadian regulations or safety standards. This work supports the development of a training program for service technicians so they understand and are prepared to address safety hazards within the accelerator environment. Unique hazards encountered during accelerator maintenance are discussed. A review of Canadian safety regulations and standards that apply to accelerator maintenance is provided.

The CNSC conducted a survey of Canadian accelerator maintenance workers to obtain information on their training and the nature of their work. Results from this survey are discussed here. The survey found that the level of training which maintenance workers receive is not consistent. While the majority of workers attended manufacturer’s training courses, most reported not having received formal in-house training. Some reported having received no training other than informal on-the-job training and self-learning.

Training in safety and in the regulations are regulatory requirements in Canada. While the CNSC regulates the use of particle accelerators from a radiation safety perspective, their regulations do not cover other aspects of the work such as electrical or chemical hazards, or rules for working on pressure vessels. This report recommends that a safety training program be developed for Class II equipment maintenance personnel which covers three principle training paradigms- technical training, safety, and regulatory training, in order to meet the definition given of competency as given in the regulations.

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RSP-690.1, Best Practices for Probabilistic Fracture Mechanics Evaluations

This study reviewed current practices for Probabilistic Fracture Mechanics (PFM) assessments, identified strengths and gaps, and ultimately recognized a set of best practices for PFM assessments. Based on this information, a guideline document for best practices for PFM analyses and evaluations was developed to assist in future PFM applications and regulatory considerations. This project was a two-year study that began in July 2019 and was funded by the CNSC.

Fracture mechanics assessments for pressure boundary components are typically performed using deterministic evaluation methodologies where uncertainties are recognized and implicitly accounted for through the selection of bounding values for input parameters and the use of safety factors.  Deterministic methodologies have been widely adopted by standards bodies and incorporated into nuclear power plant regulations in many countries. Development of PFM approaches began in the late 1990s in the nuclear industry, which explicitly consider the uncertainty in input parameters and models and the effects of those uncertainties on the results of a fracture mechanics calculation. With advancements in computational technologies, significant developments in PFM analysis since the late 1990s include specification of useful PFM models and uncertainties, development of PFM software, understating the limitations of PFM and regulatory decision-making using PFM results. In recent years, the Canadian nuclear industry has expressed interest in wider spread adoption of PFM to evaluate the condition of pressure boundary components.

The scope of the project involved the follow key elements:

  • Performing a literature review of best practices for PFM assessments in nuclear and non-nuclear industries
  • Identification of critical elements of PFM based on the literature review
  • Development of draft guidelines for PFM best practices that summarizes the team’s experience, results, and decisions, including uncertainty analysis

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