Improving the reliability and safety of nuclear power plant piping systems

Nuclear power remains one of the biggest drivers of Ontario’s economy. The province’s 18 commercial reactors produce about 60 per cent of the province’s electricity. All nuclear power plants in Canada use the CANDU (CANada Deuterium Uranium) design – pressurized heavy water reactors that utilize natural uranium to generate electricity. CANDU reactors are highly regarded worldwide for their safe and reliable technology. A researcher at the University of Ontario Institute of Technology (UOIT) is investigating how to make CANDU reactors even more reliable.

• Related link: How a nuclear power plant works (Canadian Nuclear Safety Commission)

Associate Professor Atef Mohany, PhD, with the university’s Faculty of Engineering and Applied Science (FEAS), has received new federal research funding to examine the complex and robust piping systems and pumps that support the transfer of heat from the core of the CANDU reactors to their steam generators.

“Piping systems used in many industrial applications are liable to generate pressure pulsations, vibrations which need to be eliminated to maintain structural integrity,” says Dr. Mohany. “These unwanted pulsations arise from the use of reciprocating pumps and/or the dynamic instability of valves. But In nuclear power plants, if the frequencies of other pulsating sources match the frequencies of the reactor’s piping system, this can produce an acoustic condition leading to excessive pressure fluctuation. Referred to as Acoustic Induced Vibrations (AIV), it can cause leakage due to gasket and seal ruptures, valve failure, and in serious cases, fatigue and fracture of the piping system as well as nuclear fuel bundles, affecting the reliability of the plant.”

To prevent such an event from happening, Dr. Mohany has been awarded a Collaborative Research and Development grant by the Natural Sciences and Engineering Research Council of Canada (NSERC) valued at more than $530,000. His research partners – the CANDU Owners Group and the University Network of Excellence in Nuclear Engineering (UNENE) – have each contributed significant cash and resources to the project. Dr. Mohany is also collaborating with a research colleague Dr. Marwan Hassan at the University of Guelph.

“In 1990, one of the fuel bundles in the Darlington nuclear power plant was damaged as a result of excessive vibration in the fuel channels, an incident that led to the replacement of the pump impellers to change the frequency of the pulsations they induce,” says Dr. Mohany. “In addition to our experimental work, our research will develop a three-dimensional model to numerically simulate and predict the dynamic response of CANDU fuel bundles to acoustic pressure pulsations. These findings will provide practical design guidelines for implementation of new passive acoustic damping devices in reactor piping systems to prevent system vibration.”

Quick facts

• Nuclear engineering and nuclear safety is an area of research strongly aligned with the university’s academic programming and strategic research plan.
• Prior to joining the university, Dr. Atef Mohany worked with Atomic Energy of Canada Limited’s (AECL) Chalk River Laboratories (now known as Canadian Nuclear Laboratories). At AECL he was involved in several projects related to the design of key components in the advanced CANDU reactor, as well as the operation of existing CANDU reactors in Canada and abroad.

Media contact
Bryan Oliver
Communications and Marketing
Ontario Tech University
905.721.8668 ext. 6709
bryan.oliver@uoit.ca