The OSU APEX test facility is a one-fourth height, one-half time scale, reduced pressure integral systems facility. A formal scaling analysis has been performed to assure that it accurately models the details of the AP600 geometry including the primary system, the passive safety systems, and parts of the non-safety grade Chemical and Volume Control System (CVS) and Residual Heat Removal System. The geometry of the interconnecting pipe routings are also duplicated. All of the primary system components are fabricated of stainless steel and are capable of prolonged operation at 2760 kPa (400 psia) and saturation conditions.

Because data from the facility will be used as part of the AP600 certification process, the applicable sections of ASME NQA-1 have been satisfied . In particular, requirements for instrument calibration and records have been established in accordance with Appendix B of Title 10 Part 50 of the Code of Federal Regulations . Quality assurance (QA) procedures were implemented in accordance with the Project Quality Plan . The NRC, Westinghouse QA, and the U.S. Department of Energy performed facility audits. Numerous safety audits were performed by national, state and local safety and licensing agencies. General layouts of the APEX facility are presented in Figure 3-1 through Figure 3-3.

The APEX test facility primary system includes the following components:

The APEX test facility includes the following passive safety systems:

• Two Core Makeup Tanks (CMTs) each have a pressure balance line that connects the CMT head to the cold leg. Each CMT also has an injection line that permits draining of the CMT into one of two Direct Vessel Injection (DVI) Lines connected to the reactor downcomer. Check valves and isolation valves have been included.
• An In-Containment Refueling Water Storage Tank (IRWST) has two injection lines that connect to the DVI lines. The IRWST is capable of being pressurized to 550 kPa (80 psia) to simulate containment back-pressure.
• An Automatic Depressurization System (ADS) includes three valves on the top of the PZR. The flow from these valves is vented to a sparger inside the IRWST. The ADS1-3 Flow nozzles are sized to represent two-trains of the AP600 ADS1-3. A single valve located on the top of each of the hot legs models the fourth stage of the ADS. The ADS flow nozzles are sized to model two trains of ADS 4 on each hot leg. The fourth stage ADS flows are vented into the primary sump.
• Two Accumulators (ACCs) pressurized with nitrogen provide safety injection during depressurization events. Each accumulator has an injection line that connects to one of the two DVI lines.
• A Passive Residual Heat Removal (PRHR) heat exchanger is located inside the IRWST. The PRHR is a passive natural circulation heat exchanger which draws water from a hot leg, rejects the heat to the IRWST, and returns the cooled water to the cold leg channel of one steam generator.

The Break and ADS Measurement System (BAMS) is used to measure two-phase flows from breaks and the four stages of the Automatic Depressurization System (ADS). The two-phase flow is directed to one of four separators where the flow is separated into single-phase liquid and single-phase vapor. Since the initial liquid level in the break separator is equal to the loop seal discharge elevation, the liquid entering the break separator will displace liquid in the loop seal. The liquid flow through the loop seal is measured using a magnetic flow meter and directed to the appropriate tank (IRWST or Primary Sump). The vapor flow from the break and ADS 4 is measured with a vortex flow meter and vented from the test facility. Vapor flow from the ADS 1-3 separator is measured and directed into the IRWST. Electrical strip heaters are used to maintain boundary conditions at approximately 93 ºC (200 ºF). The system is capable of being pressurized to 550 kPa (80 psia) to simulate containment back-pressure. As partially shown in Figure 3-4, the BAMS contains the following components:

• A Primary and a Secondary Sump simulate the containment compartment volumes below the normal flood-up elevation. The sump tanks are capable of being pressurized to 550 kPa (80 psia) to simulate containment back-pressure. Return lines to the DVI lines are provided to represent the lower containment recirculation lines.
• Four Moisture Separators are sized based on maximum expected flow rates. Separation is primarily accomplished by the use of gravity and a swirl vane moisture separator element. Each separator is provided with a loop seal line on the liquid discharge to ensure vapor flow does not bypass the separator.
• Containment Sump Return System provides heated water from a hold-up tank to be pumped into the primary sump and the IRWST at a mass flow rate equivalent to the mass flow rate of the vented steam. This heated liquid simulates the flow of condensate from the steam vented into the containment building. This steam would be condensed and drain into the IRWST or the containment (primary) sump.

Instrumentation is provided to record the necessary data to calculate mass and energy balances. Approximately 750 channels are continuously recorded by the Data Acquisition System (DAS). The APEX test facility includes the following types of instrumentation:

• Thermocouples are used to measure the temperature of the coolant in the primary and secondary systems, and the supply and component cooling water systems. They are also used to measure the temperature distribution in the CMT walls and the core heater rods. Premium grade thermocouples have been used and connected to the data acquisition system (DAS) through controlled purity thermocouple wire.
• Magnetic Flow Meters are used to measure all single-phase liquid flow rates.
• Pressure Transducers are used to measure the static pressures within the various tanks and vessels.
• Differential Pressure transducers are used to measure the liquid levels in various tanks, vessels, and pipes. They are also used to determine pressure drop in system piping and across various fittings and components.
• Vortex Flow Meters are used to measure all vapor flow rates.
• Heat Flux Meters are used to measure heat loss from individual tanks and components.
• Load Cells are used to measure the weight of liquid inside large tanks.
• Ambient air temperature, humidity and barometric pressure are also recorded.
• All of the instruments are monitored by the DAS, which records the data on computer files.

The Data Acquisition and Control System (DAS) includes all the equipment necessary to receive, transmit, process and record the voltage or current signal outputs from the individual sensing instruments. This includes amplifiers, signal conditioners, transmitters, interconnecting wiring, analog to digital converters, interfacing boards, switching panels, computers, displays and other recording devices as needed to access the instruments. The DAS selected for this project is a FLUKE HELIOS system linked to three DEC 486 PC Based computers. A Labview software package to process the incoming data has been developed, validated and fully tested. The DAS is capable of storing and maintaining all data retrieved and recorded during a single test. The DAS includes on-line data graphics for process monitoring and a Compact Disk (CD) Writer, which provides for permanent storage of all test-data on CD.

APEX includes a fully developed control panel capable of modeling all of the important safety logic of the AP600. All control actions, such as valve openings and closures, pumps starts, and safety signals are monitored and recorded using the WONDERWARE software package (same package used for NASA's space shuttle program). This package provides a time history of all control actions that occur during a test. The WONDERWARE software package has been fully validated and tested.