Helical coil steam generator stability experiments with the MOTEL test facility

Small modular reactors (SMRs) are under extensive development globally. Some SMR concepts have design features that are rare in traditional pressurized water reactors (PWRs). One such feature is a helical coil steam generator which differs from traditional horizontal and vertical inverted U-tube steam generators in several ways. The helical coil steam generator is a once-through design where the primary side flow runs in the shell side and the secondary side flow runs inside the tubes and can generate superheated steam. Boiling instabilities in helically coiled tubes are a crucial research question due to their potentially negative impact on steady plant operation. The MOTEL (MOdular TEst Loop) facility at LUT University is a model of an integral SMR with a helical coil steam generator representing an integral pressurized water reactor. A large variation of core power and feedwater flow values were tested to map MOTEL operating conditions in which the steam production in the helical coil steam generator is stable.