A review of pebble flow study for pebble bed high temperature gas-cooled reactor

Abstract

The pebble bed high temperature gas-cooled reactor is a promising generation-IV reactor, which uses large fuel pebbles and helium gas as coolant. The pebble bed flow is a fundamental issue for both academic investigation and engineering application, e.g., reactor core design and safety analysis. This work performed a review of recent progress on pebble flow study, focusing on the important issues like pebble flow, gas phase hydrodynamics, and inter-phase heat transfer (thermal hydraulics). Our group's researches on pebble flow have also been reviewed through the aspects of phenomenological observation and measurement, voidage distribution, geometric and parameter optimization, pebble flow mechanisms, flow regime categorization, and fundamentals of modelings of pebble flow and radiation. Finally, the major problems or possible directions of research are concluded which would be some of our focuses on the pebble bed flow study.

Parameter analysis and wall effect of radiative heat transfer for CFD-DEM simulation in nuclear packed pebble bed

“…Under norm and accidental operation conditions, the heat transportation is driven by forced convection and thermal radiation (Latifi et al, 2020). The design limitation of the temperature is about 1600 °C (Jiang et al, 2019) and the radiation becomes the dominate part.…”

Review of the experimental research on the thermal‐hydraulic characteristics in the pebble bed nuclear reactor core and fusion breeder blankets

“…Different from the rod‐type fuel in the existing water‐cooled nuclear reactors, the pebble‐type fuel has been adopted in some kinds of the fourth generation nuclear reactors, including the High‐Temperature Gas‐cooled Reactors (HTGRs), 1 Fluoride‐salt‐cooled High‐temperature Reactors (FHRs) 2‐4 and Water‐cooled Pebble Bed Reactors (WPBRs), 5,6 as shown in Table 1. The 6‐cm‐diameter or 3‐cm‐diameter pebble fuels contain fuel‐free graphite zone and the graphite matrix zone, where the microscopic TRIstructural‐iSOtropic (TRISO) coated fuel particles are embedded 1,2 . The temperature limit of such pebble fuels can be over 1600°C, leaving large safety margin for the reactors under design basis accident (DBA) 10,11 .…”

“…The temperature limit of such pebble fuels can be over 1600°C, leaving large safety margin for the reactors under design basis accident (DBA) 10,11 . In addition, the reactor output temperatures of the HTGRs (750°C‐950°C), and FHRs (700°C) can be much higher than those of the Pressurized Water‐cooled Reactors (PWRs, 325°C) 1,5,7,10,12 . Based on such pebble‐bed‐type nuclear reactors, the nuclear energy can be extended to provide an environmentally friendly solution to the hydrogen production, except for the traditional electricity generation 13 .…”

“…The packed pebble bed structure is widely adopted by the concept reactor core designs of HTGRs, FHRs, WPBRs and fusion breeder blankets. Fuel pebbles in the HTGRs, FHRs and WPBRs are recirculated in the reactor cores, with the refueling process performed by loading and discharging the fuel pebbles from the top or bottom of the reactor respectively 1,14 . The pebbles in the reactor core will be constant in the quantity when the pebble bed reaches the equilibrium state.…”

“…The pebbles in the reactor core will be constant in the quantity when the pebble bed reaches the equilibrium state. As the pebbles move at an extremely low speed, they can be treated as stagnant in the core for the majority of the designs 1 . Rots et al 15 and Mandal et al 16 proposed a different type of reactor core designs using the fluidized bed where the fuel pebbles were fluidized and cooled by the high‐velocity pressurized helium flow.…”