2023

Telkkä Joonas; Suikkanen Heikki; Räsänen Antti; Kotro Eetu; Hyvärinen Juhani

The MOTEL (MOdular TEst Loop) test facility, designed and constructed at LUT University, Finland, is an integral test facility representing a small modular reactor (SMR) operating with natural circulation. The design of the facility resembles the NuScale SMR with a helical coil steam generator consisting of 16 steam generator tubes in four tube bundles. A series of two steam generator experiments was performed with the MOTEL facility within the EU Horizon 2020 project McSAFER. The aim of the test series was to investigate the behavior of the helical coil steam generator and to provide data for the validation of thermal hydraulic codes. In the experiments, steady states with different heating powers were attempted. Particularly, the temperature behavior of the steam generator, both on the shell and tube sides, was studied; temperature distributions along the steam generator tubes were measured. One of the test series focused on lower heating powers of 75 kW, 100 kW, 125 kW and 150 kW, while the other investigated steam generator behaviour at higher heating powers of 250 kW, 500 kW, 750 kW and 1 MW. Steady behaviour and production of saturated steam was observed at lower heating powers. At higher than 250 kW powers superheating started to occur but in an oscillatory manner. Also, no clear steady states could be established at higher powers as the temperatures kept increasing towards the end of each step, signifying that the steam generator was incapable of transferring all the heat produced by the core in the conditions of the high-power experiments.