The reactor primary equipment, the pressure circuit and associated systems are provided with high integrity containment, which forms the final principal barrier against release of radioactive material to the environ­ment in the event of a fault. The containment is de­signed to accommodate without failure the affects of LOCAS, steam and feed line breaks (SLB, FLB) aris­ing from equipment failures inside the reactor con­tainment building, and various other faults involving mass and energy release. The containment function is performed primarily by buildings and structures, but various systems and equipment also contribute to containment integrity and effectiveness.

The requirements which the various elements of the containment must satisfy are in three main categories:

• Control of radioactive release.

• Control of containment atmospheric conditions.

• Control of hydrogen.

These requirements are satisfied in the following manner,