Some passive safety systems for nuclear plants

Some passive safety systems for nuclear plants 

The passive systems and components discussed in the last few years range from complete reactor concepts to single components (Forsberg et al., 1989 Petrangeli, 1992). A rather arbitrary selection of a few of these proposals is presented in this section. They are all well-known concepts in the nuclear industry and they discussed here because they are considered among the most interesting ones. 

Passive plant reactors (e.g. the AP600W) are proposed future reactors that use the technology of current reactors, but include also significant changes in plant design and layout. Safety, in the event of an accident, depends on truly passive safety systems and on safety systems which are passive in operation although started up by a simple action such as valves opening. 

In nuclear power plants, the containment is the final barrier that prevents radioactive release to the environment during accident events. Because of containment importance in mitigating the consequences of an accident, it is necessary not only to assess its integrity during an accident, but also to ensure that it is and stays leakproof after the accident has occurred. 

Typical allowable primary containment leakage rates lie in the range of 0.1-1 per cent of volume a day, but the operating experience sometimes has indicated real-world values above these allowable limits. These are usually due to excessive valve or penetration leakage, valves or penetrations left open after testing, airlock failure, etc. 

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