A multiple steam generator tube rupture transient, which was simulated on the Bethsy French experimental facility (test 4.3b), has been analyzed with ASTEC V1.2 for CESAR thermal-hydraulic module validation purposes. The experimental transient takes into account the involved protections and the operator actions according to the appropriate emergency operating procedures. The Bethsy facility model used in previous analysis of Bethsy experiments has been slightly improved to take into account the peculiarities of the experiment 4.3b. The behaviour of primary and secondary circuits during the experimental transient is in general well simulated by CESAR. The reasons of main discrepancies between code results and experimental data have been investigated by sensitivity studies.