Thermo hydraulic analysis of the PBMR fuel handling and storage system
Le Roux, Philip Louis
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The work done for this dissertation is based on actual thermo–hydraulic design work done during 2002 to 2006 on one of the subsystems of the Pebble Bed Modular Reactor (PBMR). The Pebble Bed Modular Reactor is a proved revolutionary small, compact and safe nuclear power plant. It operates on a direct closed Brayton cycle. One of the unique features of this concept is its ability to easily regulate the power output depending on the electricity demand. The PBMR fuel comprises particles of enriched uranium dioxide coated with silicon carbide and pyrolytic carbon. The particles are encased in graphite to form a fuel sphere or pebble about the size of a billiard ball. The core of the reactor contains approximately 360 000 of these fuel spheres for a 400 MW design reactor. The fuel spheres are continuously circulated through the reactor core via a closed loop helium conveying system, referred to as the Fuel Handling and Storage System (FHSS). The system is also responsible for discharging spent–fuel spheres to the spent–fuel storage area and recharging the reactor with fresh fuel spheres. The focus of this dissertation is the thermo–hydraulic design of the FHSS system, with specific focus on the FHSS helium circulator, referred to as the FHSS blower. The FHSS blower is a single–stage centrifugal machine, submerged in an enclosed pressure boundary, which forms part of the closed–loop helium pressure boundary. The aim of the dissertation is to simulate all the operating parameters of the system to determine the volumetric flow rate and pressure rise the impeller of the blower has to deliver. Due to the complexity of the simulation model and lack of experimental data a Sensitivity and Monte Carlo study was also done. The output of the study is sufficient thermo–hydraulic data to design all the major components of the FHSS system. For components such as the piping and pressure boundary this includes (i) temperature, (ii) pressure and (iii) heat transfer through the material at all the operating conditions. For the blower it includes; (i) blower mass flow rate, (ii) pressure ratio, (iii) inlet pressure and (iv) inlet temperature at all the operating conditions.
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