<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Heterogeneous catalytic recombination of hydrogen with oxygen is one of the methods used to remove hydrogen from the containment of a light-water nuclear reactor (LWR). Inside a passive autocatalytic recombiner (PAR), hydrogen and oxygen molecules are adsorbed at catalyst active spots and they recombine to yield water. Heat released in this exothermic reaction creates natural convection of gas in the spaces between the elements supporting a catalyst. Hot and humid gas flows upwards into the PAR chimney, while fresh, hydrogen-rich gas enters the PAR from below. Catalytic recombination should start spontaneously at room temperature and low hydrogen concentration. Computational fluid dynamics (CFD) has been used to study the dynamic behaviour of a plate-type Areva FR-380 recombiner in a quiescent environment for several test scenarios, including different rates of increase in hydrogen concentration and temporary catalyst deactivation. A method for the determination of pressure boundary conditions at the PAR exits was proposed and implemented into a CFD code. In this way, transient operation of PAR could be simulated without the need to model gas circulation outside the device. It was found that first a slow downward flow of gas is developed, which may persist until the temperature of the catalyst foils rises. As soon as the gas inside the PAR absorbs enough heat to become lighter than the gas outside the PAR, it starts to flow upwards. Criteria for determining the start-up time of PAR were proposed. Model predictions were also compared with experimental data obtained in tests conducted at the THAI facility.</p></abstract>

Heterogeneous catalytic recombination of hydrogen with oxygen is one of the methods used to remove hydrogen from the containment of a light-water nuclear reactor (LWR). Inside a passive autocatalytic recombiner (PAR), hydrogen and oxygen molecules are adsorbed at catalyst active spots and they recombine to yield water. Heat released in this exothermic reaction creates natural convection of gas in the spaces between the elements supporting a catalyst. Hot and humid gas flows upwards into the PAR chimney, while fresh, hydrogen-rich gas enters the PAR from below. Catalytic recombination should start spontaneously at room temperature and low hydrogen concentration. Computational fluid dynamics (CFD) has been used to study the dynamic behaviour of a plate-type Areva FR-380 recombiner in a quiescent environment for several test scenarios, including different rates of increase in hydrogen concentration and temporary catalyst deactivation. A method for the determination of pressure boundary conditions at the PAR exits was proposed and implemented into a CFD code. In this way, transient operation of PAR could be simulated without the need to model gas circulation outside the device. It was found that first a slow downward flow of gas is developed, which may persist until the temperature of the catalyst foils rises. As soon as the gas inside the PAR absorbs enough heat to become lighter than the gas outside the PAR, it starts to flow upwards. Criteria for determining the start-up time of PAR were proposed. Model predictions were also compared with experimental data obtained in tests conducted at the THAI facility.

Simulation of start-up behaviour of a passive autocatalytic hydrogen recombiner

Faculty of Chemical and Process Engineering

Nukleonika

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

{"article-title":"Simulation of start-up behaviour of a passive autocatalytic hydrogen recombiner"}

Heterogeneous catalytic recombination of hydrogen with oxygen is one of the methods used to remove hydrogen from the containment of a light-water nuclear...

Simulation of start-up behaviour of a passive autocatalytic hydrogen recombiner

Published Online: Jul 31, 2018

Page range: 27 - 41

Received: Mar 08, 2018

Accepted: May 25, 2018

DOI: https://doi.org/10.2478/nuka-2018-0004

Keywords
catalytic recombination, computational fluid dynamics, hydrogen safety, natural convection

© 2018 Antoni Rożeń, published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Simulation of start-up behaviour of a passive autocatalytic hydrogen recombiner

Published Online: Jul 31, 2018

Page range: 27 - 41

Received: Mar 08, 2018

Accepted: May 25, 2018

DOI: https://doi.org/10.2478/nuka-2018-0004

Keywordscatalytic recombination, computational fluid dynamics, hydrogen safety, natural convection

© 2018 Antoni Rożeń, published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Keywords
catalytic recombination, computational fluid dynamics, hydrogen safety, natural convection