The APEX lab is a one-quarter scale, reduced pressure, integral systems test facility that accurately models the Westinghouse AP1000 pressurized water reactor. The AP1000 contains passive safety systems that use gravity, natural circulation, condensation, and evaporation to cool the core.

APEX 1000 Design Certification Tests

This facility began as a research collaboration between OSU and Westinghouse to test the AP600. Later the facility became a partnership between the U.S. Nuclear Regulatory Commission (NRC) and OSU to perform confirmatory tests in the APEX facility. The tests investigated scenarios with two or more simultaneous failures of the AP1000 passive safety systems. The experiments also collected data for the evaluation of liquid entrainment and carryover of water to the automatic depressurization system during and after acutation of the fourth-stage valves. The tests were completed successfully in July 2004. The NRC issued final design certification for the AP1000 in 2006. It is the only Generation III+ reactor to receive NRC certification.

OSU is the only university in the world performing nuclear safety certification tests for AP1000 licensing.

Primary System

• 1:4 length scale, 1:2 time scale, 1:192 volume scale stainless steel construction

• 2 hot legs, 4 cold legs,

• 2 steam generators

• A pressurizer

• A reactor vessel with electronically heated rod bundle and upper plenum internals

Operating Conditions

  • Tests are initiated from steady-state conditions with a 1 MW electrically heated core

• Steam generator shell side pressure - 20 bar

• Pressurizer pressure - 25.5 bar

Instrumentation & Control

• Approximately 750 instruments

• High speed data acquisition system (DAS)

• AP1000 automatic logic simulation main steam line break (MSLB)

Testing Capability

• Hot & cold leg small break loss of coolant accident

• Main steam line break

• Inadvertent automatic depressurization systems

• Loss of passive residual heat removal system (PRHR)

• Partial loss of safety injection signal

• Core makeup tank balance line break

• Direct vessel injection line breaks

• Interactions between safety and non-safety systems

• Parametric core uncovery

• Station blackout

• Long term circulation

Passive Safety System

• 2 core makeup tanks

• 2 accumulators

• A passive residual heat removal heat exchanger

• A 4-stage ADS system