The Steam Generator Tube Rupture (SGTR) accident has been analyzed with RELAP5/MOD3 thermal hydraulic system analysis code under the conditions that the safety valve of affected SG is stuck open.The AFW is unavailable
and only one HPSI pump is available.It can be mitigated successfully if the operators take actions to cooldown and depressurize RCS within 150 min after the safety injection signal.The results show that the active core is covered by coolant before the break flow is terminated with the balance between primary and secondary side of affected SG at atmospheric pressure.