Research report summaries 2017–2018

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

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-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)