Making NuclearEnergy Safer

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. Dr. Mohany, Professor in the Mechanical and Manufacturing engineering department, is leading a research group to study the structural dynamics of CANDU fuel bundles to ensure their safe and reliable operations under different loading conditions and fluid excitation forces including acoustic pressure pulsations from the primary system heat transport pumps.

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. Piping systems used in many industrial applications are liable to generate pressure pulsations, vibrations which need to be eliminated to maintain structural integrity. 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.

Over the past few years, his research group has received over $900 thousand for two collaborative research and development projects to improve the safety and reliability of critical components in nuclear power plants using state-of-theart experimental and numerical techniques. The projects are supported by the Natural Sciences and Engineering Research Council of Canada in collaboration with CANDU Owners Group, University Network of Excellence in Nuclear Engineering, and the Canadian Nuclear Laboratories.

Dr. Atef Mohany, Professor and Chair of the Mechanical and Manufacturing Engineering Department

Before joining Ontario Tech in 2012, Dr. Mohany was a Nuclear R&D Scientist at Atomic Energy of Canada Limited (AECL), Chalk River Laboratories (now known as Canadian Nuclear Laboratories). During his tenure at AECL, Dr. Mohany was involved in several strategic projects related to the design of key components in the advanced CANDU reactor as well as the operation of nuclear power plants in Canada and around the world and is currently serving on the international standards organization –technical committees (ISO/TC) in Acoustics, Noise, and Boilers and Pressure Vessels.

His research is interdisciplinary covering the areas of acoustics, vibrations, aeroacoustics, fluidstructure interaction, flow-induced vibration, structural dynamics, and noise and vibration control.