Compact Double-wall Twisted-tube Heat Exchanger for the Fluoride salt-cooled High-temperature Reactor (FHR) with Implications for In-Service Inspection

摘要

Double-wall tubing, or "double containment" tubing has a history of use in applications where it is vital to protect against fluid leaks from the primary to secondary side for safety or contamination purposes. In heat exchangers where mixing between the two working fluids must be avoided, double-wall tubing has been used. Such heat exchangers have historically been used in both nuclear fission and fusion applications. Notable examples included double-wall steam generators in sodium fast reactors (SFRs) such as the Experimental Breeder Reactor Ⅱ (EBR-Ⅱ)in order to prevent sodium to water interactions as well as fusion applications where preventing tritium release to the environment is a major design challenge. This paper presents a novel concept for a compact double-wall heat exchanger for high Prandtl coolants (Pr = v/α, i.e. the ratio of momentum diffusivity to thermal diffusivity) where the inner tube is a conventional straight wall tube and the outer tube is a twisted elliptical tube (TET). In addition, we review options for tritium management utilizing these heat exchangers and discuss the implications for in-service inspection and non-destructive testing methods relevant to this design concept.