Cfd Modeling And Simulation Of Natural Circulation In Helium- Cooled Very High Temperature Reactors, Mohammad Sakib U. Abrar

Dissertations and Theses

This thesis investigates the thermal-hydraulic behavior of natural circulation in helium-cooled Very High Temperature Reactor (VHTR) systems, focusing on the performance and validation of passive safety features under Pressurized or Depressurized Loss of Forced Cooling (P-LOFC or D-LOFC) events. An experimental facility inspired by the General Atomics 350 MWt Modular High Temperature Gas-Cooled Reactor (MHTGR) was developed at The City College of New York. The setup consists of a plenum-to-plenum flow loop with four riser and four downcomer tubes, each equipped with heating coils, thermocouples, and pressure sensors. Natural circulation is driven by density gradients induced by asymmetric heating of …

Helium-Air Mixing In Simulated Reactor Cavities Of Very High Temperature Reactors, Abdullah Abubakar

Dissertations and Theses

Abstract

Very High Temperature Reactors (VHTRs) and High Temperature Gas Reactors (HTGRs) are Generation IV gas reactors that promise to deliver high temperature process heat and efficient electricity for both industrial and commercial purposes. They have a high level of inherent passive safety making them a viable alternative to traditional water-cooled reactors. These helium gas-cooled reactors use graphite containing U-235 TRISO fuel particles in their core, as a moderator to slow down neutrons for fission chain reactions and for general core support. In the event of a primary circuit pipe break, the coolant gas escapes into the surrounding reactor cavity …

Air Ingress And Heat-Driven Flow Relaminarization In A Very High Temperature Reactor (Vhtr), Apoorva Rudra

Dissertations and Theses

Very High Temperature Reactors (VHTRs) are one of six Generation IV reactors that have been proposed for DOE’s Next Generation Nuclear Plant. In addition to using gaseous coolants, VHTRs also display benefits of passive safety systems including intra-core natural circulation for heat removal in accident scenarios. However, a number of substantial engineering challenges are expected in VHTRs, and due to the high temperatures of the coolant involved, material behavior in various components needs to be better understood. Our work focuses mainly on two key phenomena that could lead to localized hot spots in the VHTR reactor core if not addressed …