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Integrated Systems Test (IST) facility

Integrated Systems Test (IST) facility is a pilot-scale thermodynamic power system commissioned by for the BWXT mPower™ small modular reactor (SMR).  The design and construction of the IST leveraged BWXT’s long-standing experience in energy systems coupled with contemporary objectives envisioned for new nuclear power plants.  In addition, given the rapid and continuous evolution of the BWXT mPower SMR, testing flexibility was incorporated into the plumbing, components and control systems to support design modifications and potential safety issue research.   
The current IST facility represents an investment of over $30 million. High fidelity systems, process equipment, control and data acquisition system, and process instrumentation comprise the facility enabling separate effects and integrated system testing.

  1. Core Heaters
    1. The IST heater bundle consists of 60 heaters, each containing one Inconel filament designed with a axial cosine heat flux profile, multiple (in some cases four) thermocouples, and a monel sheath.
    2. Heaters and associated hardware are capable of producing a calibrated 1.8 MW of electricity. The radial profile is controlled with programmable logic controller and is easily adjustable.
    3. Heaters were sourced from the industry-leading supplier in nuclear testing heaters – Stern Labs.
  2. Steam Generator
    1. The IST steam generator is a 19 tube (alloy 690) once through Babcock and Wilcox designed test-ready steam generator.
    2. 19 thermocouples span the entire elevation of the steam bundle providing insight into the heat transfer regions of the steam generator
    3. Nine differential pressure transmitters are located across each tube support plate with an additional transmitter spanning the entire length for water level measurement.
    4. Three steam samplers are located at different increasing elevations to pull a calculated volume of steam from the steam bundle, dry the steam, and measure the temperature. The temperature, as compared to the steam bundle (moist) temperature, provides the input necessary to determine the moisture content of the steam bundle at the elevation associated with each sampler.
  3. Pressurizer and Emergency Core Cooling System
    1. The pressurizer of the IST contains two connections to an emergency core cooling system. These connections lead to depressurization trains that flow to either a sparge nozzle in a 105 foot storage tank or directly to a pressure controlled containment simulation tank. Each location is capable of receiving RCS system maximum pressure, temperature, and “break” flow.
    2. The ECCS contains multiple flow control valves, flanged orifices for break simulations, measurement locations for flow, temperature, and pressure.
    3. Intermediate pressure injection tanks provide significant (relative) volume for injection. These tanks can be setup for passive injection and can be controlled to pressures up to 1500 psia to facilitate operation.
  4. Balance of Plant
    1. The BOP at IST contains a complete feed and steam system with the ability to control water temperatures at the inlet to the steam generator with fine control from ambient to over 400°F.
    2. Steam outlet from the steam generator flows through multiple flanges prior to entering an air-cooled main condenser. Flanged areas provide entrance to the steam lines where additional equipment and instruments can be installed and tested.
    3. Variable frequency drives control, with fine tuning and algorithmic capabilities, feed flow, feed pre-heater, main condenser fan.
    4. Control valves on the feed inlet and steam outlet are tuned for operations, load following sequences, securing flow to and from the steam generator, and design basis event scenarios.
  5. Reactor Coolant Inventory and Purification
    1. RCIP system contains a high pressure positive displacement pump capable of providing flow for letdown and make-up of the RCS and a low pressure pump designed for long-term decay heat cooling.
    2. Two regenerative and 3 non-regenerative heat exchangers temperature control the RCS fluid in the RCIP system.
    3. Chemistry evaluations, performed by in-line digital sensors, are continuously recorded and monitored remotely at the IST control panel
  6. Test control algorithms
  7. Test control algorithms are an important part of nuclear grade testing. Using algorithms ensures the operator – test interface does not confound the data coming from a test and allows the operator to maintain focus on plant safety. Algorithms give the researcher the ability to extract data and make decisions based on that data knowing there is no masking influence on the results.

    1. Algorithms to execute tests were created to produce specific conditions within the boundaries of systems to ensure fidelity.
    2. Order and timing of test execution is preserved through engineered requirements, training, and operational experience.
    3. Algorithms were installed for both the primary and secondary systems. Controlled parameters include (multiple locations for many listed below):
      1. Core heater power curves based on nuclear decay (ANS provided)
      2. Reactor coolant pump flow
      3. Steam pressure and feed flow (valves and pump)– isolating SG during transient
      4. ECCS break simulations and depressurization operations
      5. Heat tracing
      6. Trips for pumps, valves, and heaters
      7. Speed control of pumps
  8. Quality Program
    1. The IST instrument “data stream”; defined as signal inception at the instrument level, through communication architecture, conversion to digital data (temperature measurements), data acquisition and finally in storage media has been evaluated and documented using techniques from NQA-1 / 10 CFR Appendix B to Part 50.
    2. Data is verified continuously through a custom program built to evaluate information as it passes through the “data stream”.


    IST Data Stream. Data Stream is evaluated and documented using NQA-1.

  9. RELAP 5-3D Model of the IST
    1. A RELAP5 3-D model has been constructed to accurately represent the conditions in the systems of the IST
    2. Model supports licensing efforts, results compared to IST test results
    3. Ancillary benefits including pre-test predictions, test planning and training, test procedure development, and test analysis
  10. Additional Test Equipment (potential upgrades)
    1.  A five foot long, four inch diameter schedule 160 stainless steel removable section immediately above the core heaters can be replaced with  test sections including but not limited to:

    2. B&W IST - 5’ removable test section

      1. Sapphire window installation for optical access to process fluid
      2. Test heater installed within 5’ test fixture, separately heated to investigate corroded sheathing / materials.
      3. Use this section to create a slip-stream of flow from the top of the core for tertiary loop investigations with localized boundaries to lift cleanliness requirements of the IST RCS.  Addition of PIV required materials, dyes, chemicals into tertiary loop.
    3. A five inch diameter test port is installed in a perpendicular flange to the RCS where the riser spills over to the steam generator directly below the pressurizer. This area contains dynamic flow regimes from normal operation to design basis event scenarios. This test port allows access to this are for additional instrumentation installation and can accommodate, like the 5’ pipe above the core, optical windows for advanced instruments. This area was originally designed to install and remove thermocouples that would extend through the primary side of the steam generator for heat transfer coefficient data gathering. This hardware has not yet been installed and is on location at the CAER.

    4. B&W IST - 5” blind flange

      1. Coupled with the test location at the bottom of the riser / top of the core this location can provide detailed investigations into the fluid process conditions within the RCS.
      2. Flow, pressure, and temperature measurements in single and two-phase conditions can be assessed.
      3. During transient tests where the top of the RCS / pressurizer is open for depressurization this location contains superheated steam.
    5. Flanged steam lines from the exit of the steam generator to the main condenser are convenient locations to remove a steam for investigative and performance based research.