PASSIVE SAFETY SYSTEMS

Vendors, operators, and expert consultants jointly working to raise th e safety level of nuclear power plants in a continuous effort is a sym bol of a good safety culture. In view of the designs and technical lic ensing requirements of the commercial nuclear power plants currently i n operation or under construction dating from the sixties and seventie s, the present absence of construction activities in many countries ce rtainly offers an opportunity to think about new or, for that matter, earlier concepts. Also the costs must be taken into account, in additi on to effectiveness, greater simplicity and clarity and, in particular , improved reliability. One of the possibilities under intensive study is the use of so-called passive safety systems. The term ''passive'' denotes those systems which require no external power supply or a powe red only from batteries, compressed gas, or gravitation. The opposite of ''passive'' safety systems are ''active'' ones which, for instance in feed systems, require pumps, electric motors, Diesel engines, cooli ng systems for Diesel engines. Besides being less complicated in desig n, passive systems can also be less expensive than active ones. Hence the need to demonstrate that passive systems can function as well as a ctive systems.