Proposed design criteria for containments in Germany

Till now all containments of German nuclear power plants have been fabricated in steel. However the nuclear power plants Gundremmingen II (KRB II) and Schmehausen II (HTR) will have prestressed concrete containments. The construction of these plants will probably start in 1975. Containments have to fulfill special tasks differing from those of pressure vessels. Because of this, design criteria for pressure vessels are not applicable to containments. On the other hand normal regulations for prestressed concrete structures are insufficient for containments. The containments KRB II and HTR are buildings of different types. KRB II is located in the interior of the reactor building of the SW-72-type. It is surrounded by a thick-walled concrete structure. HTR has the classical shape for concrete containments - vertical cylinder with spherical cap. It surrounds the reactor-building. The containment has to withstand aircraft impact forces. This influences its liner too. Design criteria have been developed for both containments, taking into consideration the special properties of these buildings. Design criteria are discussed for service-load conditions, test conditions, various forms of accident and for the ultimate load conditions. The influence of extreme external loads on the design is described. (author)