[en] 1 - Description of test facility - The LOBI-MOD2 test facility is a high pressure integral system blowdown refill test facility designed, constructed and operated at the Joint Research Centre of the European Communities, Ispra Establishment, Italy. It represents and extensive modification of the original MOD1 configuration and was put into operation after shutdown of the MOD1 configuration in June 1982. The LOBI facility is a 1/700 scale model of a four loop PWR and has two primary loops, the intact loop representing three loops and the broken loop representing one loop of a four-loop PWR. The reactor pressure vessel model contains an electrically heated rod-bundle with 64 rods and a heated length of 3.9 m. The nominal heating power is 5.3 MW. The downcomer is of annular shape. An upper head simulator is connected to the vessel. Each of the two primary loops contains a pump and a steam generator. The different mass flows in the loops are established by different pump speeds, since the two pumps are identical. ECC water can be supplied from two accumulators, one for each loop. Cold or hot leg as well as combined injection can be simulated. Heat is removed from the steam generators by a secondary system. In the MOD2 configuration, emergency core cooling (ECC) water can be supplied by the high pressure injection system (HPIS) and by the accumulator injection system (AIS). The LOBI test facility is the only high pressure integral test facility within the European Communities (1982), built and operated in the Joint Research Centre, Ispra, Italy. In the LOBI experiments the thermal-hydraulic behavior of the facility during a transient, caused by a simulated loss of coolant accident (LOCA), is investigated to provide an experimental basis for analytical model development and code verification. 2 - Description of test - Test A2-81 simulates a 1% cold leg break in the main coolant pipe of a pressurized water reactor. Cooldown is effected via the secondary loop at a rate of 100 K/h. Emergency cooling water is injected into the primary loop by cold leg high pressure injection (HPIS) representative of two injection pumps; of the remaining two pumps in the reference plant, one is assumed to be in maintenance and the other connected to the broken loop