A steel-lined concrete reactor containment building (RCB) accommodates all primary reactor systems, including the reactor assembly and associated valves and piping. A compound building (CPB), and an auxiliary building (AB) surround the RCB. A single base-mat accommodates the RPB, CPB and AB. The plant building layout is designed to reduce the surface silhouette and direct access to the RCB. Similar to the operating PWRs in the Republic of Korea, the RCB contains the radioactive fission products protects against primary coolant leakage to the environment. The RCB protects the entire reactor systems from any external air collisions.