Analysis of Unsteady Behaviour of Natural Circulation Helium Loop Matej Vach, Branislav Knížat, Marek Mlkvik, Róbert Olšiak, František Urban, František Ridzoň and Peter Mlynár MATEC Web Conf., 328 (2020) 03009 Published online: 18 November 2020 DOI: 10.1051/matecconf/202032803009