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Research report summaries 2016–2017

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

RSP-673.1, State of Policies and Practices on Substance Use in Safety-sensitive Industries in Canada

In April 2012, the Canadian Nuclear Safety Commission (CNSC) published a discussion paper titled DIS-12-03, Fitness for Duty: Proposals for Strengthening Alcohol and Drug Policy, Programs and Testing. This was followed by a draft version of a regulatory document that was presented at a CNSC Commission meeting on August 17, 2017, and published as REGDOC-2.2.4, Fitness for Duty, Volume II: Managing Alcohol and Drug Use on November 9, 2017.

REGDOC-2.2.4, Fitness for Duty, Volume II sets out requirements and guidance for managing the fitness for duty of workers in relation to alcohol and drug use and abuse and includes some provisions for alcohol and drug testing under various testing circumstances. For example, workers identified as substance-dependent are required to submit to follow-up alcohol and drug testing, and must be deemed fit by a duly qualified health professional before returning to safety-sensitive duties.

Health professionals have various certifications available to them to perform evaluations on and tailor treatment programs for substance dependent workers. However, there is no national-level certification relevant to the workplace, particularly for safety-sensitive industries.

Based on comments received from stakeholders during public consultation on draft REGDOC-2.2.4, Fitness for Duty, CNSC staff identified a need to strengthen the practice of substance dependence evaluation in the context of Canadian safety-sensitive workplaces. To that end, the CNSC engaged the Canadian Centre on Substance Use and Addiction (CCSA) to increase understanding of:

  • best practices in substance abuse evaluation
  • the regulatory framework in Canada that supports the decisions of substance abuse experts
  • the jurisprudence on the qualifications of ‘duly qualified health professionals’ that Canadian courts most readily accept as a substance abuse expert
  • the prevalence of substance use and abuse in communities where high security nuclear facilities are located

With the coming legalization of cannabis in Canada, CNSC staff also wanted to better understand the potential safety impact of medical and recreational marijuana use in safety-sensitive workplaces.

The CCSA developed and administered a survey to safety-sensitive industries across Canada and conducted a legal analysis on the qualifications of substance abuse experts most readily accepted by various Canadian courts. Prevalence data on substance use and abuse was taken from both federal and provincial survey data available from the Canadian Tobacco, Alcohol and Drugs Survey and the Centre for Addiction and Mental Health Monitor. To increase understanding of the potential impact of medical and recreational marijuana use on workplace safety, data was also gleaned from the American states of Colorado and Washington, where marijuana has been recently legalized. Additionally, a brief review of the literature was conducted to examine the evidence related to the impact and effectiveness of substance testing affecting the workplace.

Read the report (PDF)

RSP-665.1, Corrosion of Steel H-Piles at Nuclear Generating Stations

Canadian Nuclear Safety Commission (CNSC) licensees are required, where applicable, to demonstrate that the steel H-piles supporting all civil structures of their nuclear power plants (NPPs) will withstand the design loads with an appropriate margin until the end of their commercial operation and decommissioning.

As the steel H-piles are buried below concrete foundations, it is not possible to access the piles to measure their degree of corrosion without disturbing the soil. Instead, the AASHTO R27 standard provides a framework on how to conservatively estimate the corrosion rates of buried steel H-piles. The standard has been applied to ensure the safety of road infrastructures such as bridges and overpasses in North America.

The purpose of this research was to determine if the AASHTO R27 standard can be used to demonstrate that the steel H-piles supporting all civil structures of an NPP will withstand the intended design loads with an appropriate margin, and if pertinent, to provide guidance on how the AASHTO R27 standard could be used for such applications.

The report confirms that AASHTO R27 can be used by CNSC licensees to demonstrate that the steel H piles supporting all civil structures of an NPP will withstand, with appropriate margin, the design loads, during both normal operations and design basis accidents/events. The report also recommends that licensees carry out a systematic analysis of soil resistivity at the NPP site and collect soil samples from at least 12 representative locations at several depths following the guidelines offered by AASHTO R27. Subsequent analysis of these soil resistivity results will provide a sound and proven method for assessing the steel H piles corrosion situation.

Read the RSP-665.1-Final Report (PDF)

RSP-651.1, Review of Eye Protection Provided by Eyewear

The lens of the eye is one of the most radiosensitive tissues in the human body. The main health effect of concern is its opacification, which is termed cataract in its advanced stages. To prevent the incidence of radiation-induced cataracts, the CNSC has prescribed annual dose limits to the eye to protect both the public and nuclear energy workers (NEWs). However, a number of human epidemiological and experimental animal-based studies suggest that the development of cataracts may occur at exposure to significantly lower doses of ionizing radiation than previously thought. In response, and in alignment with International Commission on Radiological Protection recommendations, the CNSC is proposing to amend the Radiation Protection Regulations to lower the dose limit to the lens of an eye for a NEW, and to add a new dose limit to the lens of an eye for a NEW in a five-year dosimetry period.

The purpose of this report’s research is to determine the shielding factor offered by eyewear that is commonly used in the industry, or readily available for purchase and use.

The scope of this work included obtaining both experimental and theoretical data on the shielding capabilities of a range of standard (non-leaded) protective eyewear types when exposed to X-ray and beta radiation beams typical of CNSC-regulated nuclear activities. This range included six different types of eyewear that are readily available in Canada, and three different eyewear lens materials. Validation of the experimental data was completed through a comparison of the measurement data to Monte Carlo simulations, and multiple investigations were conducted with a variety of experimental geometries. Shielding factors were determined to be around 2.5–3 for the eyewear types tested with the beta radiation source Sr-90/Y-90. The study also found that found that the eyewear provided little shielding for X-rays and that no significant difference was observed in the shielding properties of the three materials tested. This work serves as a basis for future research to determine more realistic shielding factors considering a head phantom and different sources of beta radiation.

Read the RSP-651.1-Final Report (PDF)

RSP-646.1, Assessment of RELAP5 for Natural Circulation

The events of the Fukushima accident demonstrated that it is possible for a nuclear power plant’s normal electrical systems to become unavailable. In the event of a loss of all normal, standby and emergency power, natural circulation is relied upon to remove heat from the reactor core to the boilers. The thermal hydraulic behaviour of the reactor systems in natural circulation – including reflux condenser mode in the steam generators and intermittent buoyancy induced flow in the fuel channels – is not always well modelled by existing computer codes.

The purpose of this work was to assess the capability of the RELAP5 computer code to simulate the thermal hydraulic behaviour of primary and secondary cooling systems during natural circulation. The CNSC should have a benchmark of the RELAP5 code’s capabilities in the area of interest, as well as an indication of what further validation studies may be required.

The scope of the project included an examination of both empirical and theoretical models within RELAP. This was done by assessing their ability to predict the thermal hydraulic behaviour in a CANDU reactor channel undergoing the intermittent buoyancy induced flow (IBIF) mode of natural circulation. Validation of RELAP5 was performed based on available experimental data from the series of standing-start tests performed at the full-scale Cold Water Injection Test (CWIT) Facility. The experimental facility and imposed thermal hydraulic conditions were modelled using the RELAP5 code, and the resultant output compared with the experimentally-obtained data from the actual facility.

Read the RSP-646.1-Final Report (PDF)

RSP-637.1, Review of the applicability of EPRI recommendations for a flow-accelerated corrosion program to CANDU nuclear piping systems

Flow-accelerated corrosion (FAC) has resulted in several significant failures of balance-of-plant carbon steel piping systems in light-water nuclear power plants (NPPs) around the world. In response to the concerns over the potential for FAC-related degradation on pressure boundary systems and components, the U.S. industry, through the Electric Power Research Institute (EPRI), undertook the development of recommended practices to manage the degradation mechanism.

CANDU NPPs are unique in the respect that in addition to using carbon steel piping in balance-of-plant piping systems, carbon steel piping is also used in the large-diameter primary-side nuclear piping. In contrast, light-water NPPs generally use stainless steel or stainless-steel-clad piping for primary-side piping and carbon steel in the balance of plant. As such, in light-water NPPs, FAC is not a concern in the primary side. Primary-side water chemistry and operating conditions differ from the balance-of-plant piping systems the EPRI recommended practices were originally developed for.

EPRI has issued a recommended practices document and developed predictive modelling software (CHECWORKS) that have been adopted at U.S. and Canadian NPPs to implement and manage FAC-related degradation. In the CANDU NPPs, the recommended practices are applied to primary-side nuclear piping in addition to balance-of-plant piping. To date, FAC has not been detected in large-diameter CANDU nuclear piping, but given that the CANDU NPPs are entering periods of extended operation, a third-party technical review of the application of the EPRI recommended practices for FAC management was conducted. 

The outcome of the review provided useful information for CNSC staff to consider when making licensing decisions concerning aging management strategies and fitness-for-service evaluations for nuclear pressure boundary systems that are potentially susceptible to FAC.

The scope of the project included a dedicated literature review of publicly available documentation from EPRI and other sources to assess the applicability of the EPRI recommended practices to the management of FAC on CANDU nuclear piping systems.

The project findings suggest the recommended practices are applicable to large-diameter CANDU nuclear piping, but additional consideration should be given to the uniqueness of water chemistry, design and operation of CANDU heat transport system (HTS) in prediction methodologies.

Read the RSP-637.1 – Final Report (PDF)

RSP-613.3, Coordinated Assessment and Research Program (CARP): Age-Dating Fracture Infill Minerals

A deep geological repository in southern Ontario to permanently dispose of low- and intermediate-level radioactive waste is currently under review. Additionally, two southern Ontario municipalities are being investigated as potential hosts for a deep geological repository for Canada’s used nuclear fuel. Understanding of the geological history and tectonic stability of the host rock is an important part of assessing a site’s capability to provide an effective barrier to radionuclide migration. The ability of the host rock to provide containment of the waste is a crucial aspect in determining the suitability of a repository site.

The purpose of this research is to provide the CNSC with information that will help to evaluate a potential licence application for a deep geological repository in southern Ontario. Specifically, the project mapped brittle tectonic structures, assessed their deformation mechanisms and provided numerical (radiometric) age constraints on faulting across strategic sites in southern Ontario. This provides information concerning the regional long-term tectonic stability and geologic history of southern Ontario.

Detailed in the report are the findings of extensive field work in Prince Edward County, Ontario as well as the petrographic and geochemical analyses of the samples collected. Field work was conducted at sites where the surface-exposed rock was considered to be stratigraphically equivalent to the rock formations at a proposed deep geological repository site in the Bruce Peninsula. Field work included the mapping and collection of structural data on brittle structures preserved in the bedrock and the collection of samples of fracture-filling minerals, which were primarily calcite. Laboratory work included the geochemical analysis and dating of these samples.

Read the RSP-613.3-Final Report (PDF)

RSP-611.1, Bonded Pre-Stressed Concrete Slabs Open-Air Blast Testing

Pre-stressed concrete members are a common element in both current and future builds of nuclear containment structures. Considering the theoretical properties of pre-stressed steel and level of compression in concrete, lower ductility could be expected in pre-stressed concrete structures when compared to conventional reinforced concrete members. However, the current building standards outline much more stringent acceptance criteria for pre-stressed members, and the technical basis for this important difference is unclear. If appropriate, adopting more realistic acceptance criteria would be beneficial for vendors, designers and regulators.

The objective of this work is to aid in the potential refinement of acceptance criteria for pre-stressed concrete under impulse loadings. The output of this work should verify the actual response of pre-stressed concrete members to impulsive loading.

This project, conducted by the American Society of Mechanical Engineers (ASME), included the design, production and set-up of all necessary test specimens and the testing apparatus. The experiment involved impulsive loading tests conducted individually on eight simply supported two-way pre-stressed concrete slabs. Impulse loadings were applied by an explosive charge, and varied parameters included the level of loading, reinforcement ratios, and level of pre-stressing. For each test, measurements were taken to determine the support force, deflection, and re-enforcement and pre-stressing strains.

Read the RSP-611.1-Final Report (PDF)

RSP-608.1 – Independent (Geoscience) Advisory Group (IAG) Annual Report

In 2010, the Nuclear Waste Management Organization (NWMO) started a site selection process for a deep geological repository (DGR) for the long-term management of Canada’s used nuclear fuel.

It is international best practice for the regulator to be involved early in initiatives that may involve the long-term management of radioactive wastes, such as a DGR for used nuclear fuel.

To help CNSC staff prepare for the review of a future licence application by the NWMO for a DGR for Canada’s used nuclear fuel, an independent advisory group (IAG) was established.

The IAG provides CNSC staff with objective, independent advice on the geoscience aspects of a DGR initiative for Canada’s used nuclear fuel. In particular, the IAG was asked to identify any gaps in research or methodology that need to be addressed prior to a licensing request.

The IAG’s tasks included:

  • reviewing the NWMO’s geo-scientific research programs (NWMO annual research reports and specified technical documents)
  • reviewing the CNSC’s research program and providing advice on its effectiveness, as well as recommending future areas of research
  • advising on how the NWMO’s research program compares with repository research internationally

Besides interim reports on meetings, the IAG is required to submit an annual report on the progress achieved. This report summarizes the IAG’s activities and observations gathered through to March 31, 2016.

The advice made by the IAG is currently being reviewed by CNSC staff. The IAG’s report will be released shortly. It will be accompanied by a response from CNSC staff.

RSP-521.1, Testing and Development of Regulatory Requirements for Steel Plate Concrete Structures

As the nuclear industry grows, it is imperative for the CNSC to remain current and capable of regulating developing technologies in the nuclear sector. In an effort to explore new modular designs, the CNSC is proactively investigating composite steel plate concrete structures, as they are commonly used for reactor shielding buildings and reactor internal structures. Although modular composite structures are part of new-build designs, there are currently no regulatory requirements for this type of structure. In view of this fact, the study aimed to provide the CNSC with guidance regarding the development of the regulatory requirements for composite steel plate concrete structures.

The scope of the project included a dedicated literature review, analytical work, and the development of a testing program to accommodate physical testing and corresponding numerical simulations. Specifically, the study investigated the effects of out-of-plane (OOP) loading on the in-plane (IP) behaviour of steel plate composite wall piers, with a focus on the magnitude of the OOP load and the effect of tie-bar spacing.

The project findings suggest that special care should be taken when the combination of IP and OOP loading occurs, as this may significantly reduce structural capacity.

Read the RSP-521.1-Final Report (PDF)

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