Identification of exhaust stack sampling location of a research reactor considering ANSI/HPS N13.1-2011 mixing criteria using computational fluid dynamics

ABSTRACT

Research Reactors have exhaust stacks that emit filtered radioactive gaseous waste into the atmosphere. In this research work, to check whether the radioactive gaseous waste met the requirements of ANSI/HPS N13.1–2011 mixing criteria, computational fluid dynamics (CFD) analysis was performed. According to ANSI criteria, Coefficient of Variance (COV) of velocity uniformity, flow angle, tracer gas, and aerosol particles concentration should be less than 20%. Therefore, the COV of the four parameters at different sampling positions along the stack height, with eight tracer gas and eight particles injection cases, were analyzed. The COV of velocity at 6 m height is 17.5% and flow cyclone is 9.8 degree. The results indicated that the 6 m height of the stack is enough for cyclone angle and COV of velocity to fulfill the ANSI mixing criteria. The COV of tracer gas concentration in one to eight injection cases is 10%, 4.8%, 7.5%, 17%, 2.5%, 6%, 13%, and 5% at 14 m stack height so the tracer gas also satisfied the standard mixing criteria in a concise length of 14 m because of the minimal difference in densities of tracer gas and air. However, due to their much higher density, aerosol particles took much longer to mix into the air. At 60 m stack height, the COV of aerosol particle concentration in one to eight injection cases is 14.8%, 18%, 8%, 12%, 11%, 15%, 15.5%, and 2%, respectively. As a result, when the stack height is set to 60 m, the COV of velocity, cyclone flow angle, tracer gas concentration, and aerosol particle concentration are found to meet the ANSI mixing criteria. Therefore, the minimum recommended height of the stack is proposed to be 60 m for the case under consideration.

KEYWORDS:

• ANSI/HPS N13.1-2011
• tracer gas
• aerosol particles
• stack height
• stack sampling location
• coefficient of variance

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Muhammad. Ajaz Ashraf

Mr. Muhammad Ajaz Ashraf is currently working as research assistant in Mechanical Engineering Department of Pakistan Institute of Engineering & Applied Sciences (PIEAS), Pakistan. He received his MS Degree in 2022 from PIEAS, Pakistan. His research interests are Computational fluid dynamics (CFD), Advanced nuclear reactors and systems, Compressible flows, Thermal-hydraulics, Turbulent flows.

Aitazaz Hassan

Mr. Aitazaz Hassan is currently pursuing PhD in Chemical and Material Engineering at University of Alberta, Canada. Previously, he was working as lecturer at Department of Chemical Engineering at Pakistan Institute of Engineering and Applied Sciences (PIEAS). His research interest includes Process Engineering, Process Modeling and Control, Process Identification, Optimal and Distributed Parameters System Control, Model Predictive Control, Computational Fluid Dynamics (CFD).

Arif

Dr. Arif is currently working as process systems designer, visiting faculty member and technical expert. He has received his PhD degree in Chemical Engineering from North-West University, Potchefstroom-South Africa in 2018. His research interests are process systems design, process & CFD modeling, flue gas desulfurization, electrostatic precipitators, research reactors, nuclear-renewable hybrid energy systems and climate change.

Ahmed Raza

Mr. Ahmad Raza is currently working as Junior Engineer at Pakistan Institute of Nuclear Science and Technology, Nilore, Islamabad. He received his degree of Masters in Mechanical Engineering from Pakistan Institute of Engineering and Applied Sciences in 2020. His research interests are Computational Fluid Dynamics, Process flow and equipment design, Biomedical Isotopes Production and Engineering Civil Structures.

Maham Fatima

Maham Fatima is currently working as process engineer and visiting faculty member. She has received her MS degree in Nuclear Engineering from PIEAS, Islamabad-Pakistan. Her research interests are process systems design, process & CFD modeling and research reactors.

Atta Ullah

Atta Ullah is currently working as a Professor of Chemical Engineering at Pakistan Institute of Engineering and Applied Sciences (PIEAS). He received his PhD in Chemical Engineering in 2013 from Institute of Process Engineering (IPE), Chinese Academy of Sciences (CAS), Beijing, China. His research interests include modeling and simulations of multiphase and energy systems.