Coupled CFD-DEM analysis of molten salt-cooled pebble-bed reactor experiment

Mardus-Hall, R; Ho, MKM; Yeoh, GH; Timchenko, V

Coupled CFD-DEM analysis of molten salt-cooled pebble-bed reactor experiment

Date

2017-06

Authors

Publisher

Americian Nuclear Association

Abstract

The development of new nuclear reactor designs is an area of ongoing investigation, and a focus of dedicated work for various laboratories around the world. Despite the steadfast and reliable service of Light Water Reactors (LWR), the ideal power reactor, with a combination of high operational temperature, passive safety, proliferation resistance, economic build and waste minimization remains elusive. One promising design that might address these diverse, and at times contradictory requirements, is the Molten Salt Reactor (MSR). In its most radical form, a liquid fueled (LF) MSR has the nuclear fuel dissolved in the molten-salt primary coolant itself, as demonstrated by Oak Ridge National Lab (ORNL) in 1965 to 1969. An alternative fuel arrangement is to retain conventional, solid fuel elements. A proposed method is to implement pebble fuel elements, as have been used in previous gas-cooled reactors, with the gas coolant being replaced with a molten salt. This is referred to as pebble-bed, molten-salt reactor (PB-MSR). The spherical fuel pebbles used within PB-MSRs contain TRISO particles dispersed throughout the pebble’s graphite matrix. Many pebbles are constrained to form a porous bed within the core region of a reactor. Coolant molten-salt passes through the pebble bed to remove heat produced due to the nuclear fission taking place within the fuel pebbles’ TRISO particles. Various benefits are apparent with the PB-MSR design. When considering the choice of fuel elements, they are a geometry that has been produced and utilized in a similar way in the past, within gas-cooled reactors. The fuel pebbles are also able to be added to, and removed from, the core during operation, enabling on-line refueling. When considering the coolant choice, molten-salts have much higher boiling points (1703K at 1 atm. for FLiBe) than conventional coolants such as water (630K at 150 atm.), and are capable of reaching these temperatures at atmospheric pressure. This in turn removes the need for high pressure containment that is present in light water reactors and gas cooled reactors. The future implementation of new reactors, and the search for improvements in efficiency and safety in current designs, require the advancement of simulation tools, which this work ultimately aims to address.

Keywords

Molten Salt cooled reactors, Pebble bed reactors, Reactors, Temperature range, Atmospheric pressure, Gas cooled reactors, Radioactive waste disposal, Fuel elements, Fission

Citation

Mardus-Hall, R., Ho, M., Yeho, G., & Timchenko, V. (2017). Coupled CFD-DEM analysis of molten salt-cooled pebble-bed reactor experiment. Paper presented to the American Nuclear Society 2017 Annual Meeting, June 11-15, 2017, San Francisco, CA. In Transactions of the Amercian Nuclear Society, Vol. 116,(1), 1506-1509.