Freeze Plug Design in Molten Salt Reactor with Consideration of Solidification


IV International (XVII Regional) Scientific Conference "Technogenic Systems and Environmental Risk", Obninsk, Russia, 19 - 20 April 2021, pp.13-15

  • Publication Type: Conference Paper / Summary Text
  • City: Obninsk
  • Country: Russia
  • Page Numbers: pp.13-15
  • Istanbul Technical University Affiliated: Yes


The effects of global warming increased rapidly over the last years. The main reason of global warming is high energy demand around the world. Human population, developed technology, and industry increase energy demand and consumption. It is not realistic to cut off industry or giving up modern life which requires high energy consumption. One solution could be limiting the energy consumption with energy efficient technologies. Actually, the solution should be based on using more clean energies such as renewable energy, nuclear energy and giving up fossil energy resources as much as possible. Nuclear energy has high importance in fighting against global warming as a carbon free base load energy production method.

However, after Fukushima accident, the popularity of nuclear energy has decreased. The main reason of this tendency is because of low public acceptance of nuclear energy due to safety issues. In order to increase the public acceptance in nuclear energy, safety issues should be solved both actively and passively and communicated to public very well.

Advanced reactor types are mostly based on passive safety systems [1]. In case of a power lost in nuclear power plant or in case of an accident, nuclear reactor must shut down automatically and remove decay heat passively. During this time, core material strength must be ensured to avoid any radiation propagating to atmosphere.

One of the advanced reactors is molten salt reactor (MSR). Many projects around the world continue developing several forms of molten salt reactor designs, such as solid or liquid fuel type MSR, thermal or fast neutron spectrum MSR, chloride or fluorine salt MSR etc. These reactor types mostly based on passive safety systems. MSR includes emergency passive safety systems that contains from freeze plug, draining shaft, draining tank and passive decay heat system. In case of a power lost or in case of an accident, freeze plug melts and fuel salt drains to draining tank via draining shaft. Draining tank is a subcritical zone and stops fission. Decay heat is removed by passive system.

Freeze plug is key component of emergency draining system. It shall melt passively when required conditions occur and stay in solid form in normal operational conditions. During normal operation, it must be cooled to create low temperature zone (under salt melting temperature). Many parameters such as wall material, wall thickness play important roles in melting and solidification of freeze plug [2].

In this study, the effect of wall thickness on solidification time is investigated via Ansys Fluent CFD code. Results show that duration of solidification increases with increasing wall thickness.