It is the AP 1000 reactor, a pressurized water reactor, sold by Westinghouse Electric Co.

WSJ: GE Steps Up Aid in Reactor Crisis

Finland is using a new breed of pressurized water reactor that is being built by a German-French consortium for around three billion euros.

FORBES: Magazine Article

The 825-megawatt pressurized water reactor at Three Mile Island, about 10 miles outside Harrisburg, Pennsylvania, has been in service since 1974 and can power about 800, 000 homes.

CNN: Pump triggers Three Mile Island reactor shutdown, NRC says