Knowledge gained from foreign occurences of heat pipe fracture of steam raising units

Several dynamic calculations were performed on steam generator tube ruptures in German PWR's. These calculation revealed that, if disturbances occurred in the peripheral safety measures, even in German plants courses of incidents are conceivable which lead to an actuation of the emergency cooling criteria and a start of the safety injection. In such a case the situation could principally be compared to that of the analysed foreign plant. With this aspects in mind some importance is to be attributed to the experience gained there for the German PWR's. This statement, however, has to be modified insofar as the activation of the safety injection in German 4-loop-plants would certainly be performed later than in the affected 2-loop-plants, if comparable conditions prevail. Therefore, more time for additional manual interventions would be available to avoid a safety injection. (orig./RW)