A reactor building is a general term for a building that houses a reactor of some type. In particular, it often refers to a building containing a nuclear reactor

Nuclear reactor

A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

. This can also be used to refer to pressure sealed buildings containing nuclear reactor

Nuclear reactor

A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

s, though it would be more correct to call them containment building

Containment building

A containment building, in its most common usage, is a steel or reinforced concrete structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of radiation to a maximum pressure in the range of 60 to 200 psi...

s.

Although some buildings containing nuclear reactor

Nuclear reactor

A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

s are containment building

Containment building

A containment building, in its most common usage, is a steel or reinforced concrete structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of radiation to a maximum pressure in the range of 60 to 200 psi...

s, not all are. For instance, the Soviet RBMK

RBMK

RBMK is an initialism for the Russian reaktor bolshoy moshchnosti kanalniy which means "High Power Channel-type Reactor", and describes a class of graphite-moderated nuclear power reactor which was built in the Soviet Union. The RBMK reactor was the type involved in the Chernobyl disaster...

 reactors were not housed in containment building

Containment building

A containment building, in its most common usage, is a steel or reinforced concrete structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of radiation to a maximum pressure in the range of 60 to 200 psi...

s. This greatly increased the severity of the Chernobyl accident on April 26, 1986.