The last engineered barrier: a steel-lined reinforced concrete or steel structure enclosing the reactor coolant system, designed to withstand the pressure and temperature of a major pipe break and to leak only a tiny fraction of its volume per day. PWRs mostly use large dry containments; BWRs use a drywell around the reactor and a suppression pool to condense steam. Leak-rate tests, isolation valves and penetrations are tracked closely because a bypass defeats it.
Containment isolation went in on the high-pressure signal, verify all the outboard valves shut.
Real containment problems are usually bypass paths, such as a valve left open or a failed penetration seal, not the concrete itself.
Also heard as
- containment building
- primary containment
Related terms
Fission product barrier
One of the successive physical barriers that keep radioactive fission products away from people and the environment.
LOCA
Loss of coolant accident: a break or leak in the reactor coolant system that lets coolant escape faster than it can be replaced.
Severe accident
An accident involving significant damage to the reactor core, with possible fuel melting and large releases.
Source term
The amount, type, timing and chemical form of radioactive material released, or assumed released, in an accident.