Technology Validation

Technology Validation and Industry Expertise

Pressurized water-cooled reactors (PWRs) have benefited from billions of dollars of research and development (R&D) and millions of hours of operating experience over the past 50 years. While this R&D provides a strong foundation, NuScale’s small modular reactor (SMR) technology truly stands out through the cutting edge testing it performs at state-of-the-art facilities worldwide, including:

  • NuScale Integral System Test (NIST-2) facility located at Oregon State University in Corvallis, Oregon
  • Fuels Thermal Hydraulic and Mechanical testing at Framatome’s Richland Test Facility (RTF) in Richland, Washington
  • Critical Heat Flux testing at Stern Laboratories in Hamilton, Ontario Canada
  • Critical Heat Flux testing at Framatome’s KATHY loop in Karlstein, Germany
  • Control Rod Assembly (CRA) drop / shaft alignment testing at Framatome’s GmbH Technology Center in Erlangen, Germany
  • Steam Generator Thermal Hydraulic Performance testing at SIET SpA in Piacenza, Italy
  • Steam Generator Flow Induced Vibration (FIV) testing at SIET SpA in Piacenza, Italy
  • Steam Generator Inlet Flow Restrictor testing at Alden Laboratory, Holden, MA, USA
  • Emergency Core Cooling System (ECCS) Valve Proof of Concept, Demonstration and Proof Tests, Target Rock, NY, USA

Information obtained from these tests is used to validate our thermal-hydraulic and design computer models for predicting the thermal efficiency, performance, and safety of NuScale’s SMR. Data from these tests also is used to validate our reactor design and to gain manufacturing, assembly, and material handling insights.


Domestic Testing

NIST-2 Integral Testing Facility

NuScale designed and built the state-of-the-art NuScale Integral System Test (NIST-2) facility located at Oregon State University in Corvallis, Oregon. The exclusive access NIST-2 facility provides NuScale with a tremendous advantage for modular prototype testing. It holds a one-third scale prototype that replicates the entire NuScale Power Module™ (NPM) and reactor building cooling pool. It provides an electrically-heated core to bring the system up to operating temperature and pressure. Stability testing ensures that throughout the expected operating conditions, natural circulation flow is stable.

The facility has demonstrated the strong safety case and viability of the NPM, and provides an enhanced representation of NuScale’s current reactor design. NIST-2 includes a new data acquisition and control system as well as extensive instrumentation additions which provide the measurements necessary for safety analysis code and reactor design validation.

Steam Generator Tube Inspection Feasibility Study

NuScale completed a feasibility study to evaluate the use of eddy current probes to inspect the NuScale helical coil steam generator tubes. Specifically, we addressed the ability of a conventional probe system to traverse the NuScale helical coil steam generator design. Helical coils with prototypic lengths, diameters, curvatures, and inclination angles were traversed using a conventional eddy probe system, indicating acceptable insertion capability of a conventional eddy probe system.

Steam Generator Inlet Flow Restrictor Testing

NuScale commissioned Alden Laboratory to conduct a series of Steam Generator Inlet Flow Restrictor (IFR) tests. Testing used Reynolds similitude to characterize form loss and vibration response for several candidate flow restrictor designs over a range of operating conditions, including flow velocities up to several times that which would occur in service. Test results showed excellent performance characteristics for the NPM IFR design, with no occurrence of leakage flow instability or turbulent buffeting. Post-test inspection confirmed lack of wear on the flow restrictor and inside of the steam generator tube.

Emergency Core Cooling System (ECCS) Valve Tests

NuScale’s SMR utilizes a simplified, reliable, ECCS system consisting of three reactor vent valves located in the pressurizer, and two reactor recirculation valves in the downcomer. During a LOCA scenario, primary pressure decreases and the valves open when their low pressure setpoint is reached. Once open, a natural circulation flow path is established between the reactor pressure vessel and containment to provide long term core cooling.

Target Rock has been contracted by NuScale to design and test these ECCS valves. Testing has been implemented in several phases, beginning with an initial proof-of-concept test to assess first-of-a-kind design features, followed by more rigorous demonstration tests that assessed functionality at operating temperatures and pressures, and lastly, by proof testing using fully prototypic valves. Proof-of-concept and demonstration testing has confirmed that the ECCS valve design functions properly, and that the low pressure setpoint, which is governed by a unique inadvertent actuation block, reliably prevents valve opening at elevated pressures. Valve proof testing will be used to demonstrate consistent and dependable valve operation in a LOCA environment.

NuScale employees working on module

International Testing

SIET Separate Effects And Prototype Steam Generator Testing

NuScale’s SMR uses compact, highly efficient helical coil steam generators with many proprietary design features. NuScale contracted with Società Informazioni Esperienze Termoidrauliche (SIET) in Piacenza, Italy to obtain test data to validate the steam generator design under conditions that result from natural circulation flows in the NuScale reactor coolant system. Tests, completed in early 2014, focused on the secondary side performance and consisted of an electrically-headed, highly-instrumented, full-length 3-tube bundle. A second set of tests, completed in 2015, focused on overall primary and secondary side performance and consisted of a prototypic tube bank (252-tube bundle) operated at plant primary and secondary flow conditions.

Thermal-Hydraulic and Mechanical Testing Of Preliminary and Final Fuel Designs

NuScale’s SMR uses natural circulation-driven flows in the reactor coolant system to provide reliable core heat removal, both during normal plant operation and for accident conditions. To obtain critical heat flux (CHF) test data suitable to validate the fuel bundle design, NuScale completed a major test program for its preliminary fuel design at Stern Laboratories in Ontario, Canada. Testing was conducted over a wide range of natural circulation flow rates and pressures, with both uniform and non-uniform power profiles. Results from the Stern testing have been used to characterize performance margin and to inform design optimizations and testing of the final fuel design.

Testing of the final fuel design was completed at the Framatome KATHY multifunction thermal-hydraulic test loop in Karlstein, Germany. This facility tested both steady-state and transient thermal-hydraulic behavior of the fuel assemblies.

Thermal-hydraulic fuel testing requirements extend beyond the need for CHF characterization, and the Framatome Richland Test Facility has been employed to complete lift-off, pressure drop, and hydraulic characterization of the final fuel design. Additionally, mechanical testing of the new fuel design was conducted at the Richland Test Facility to measure the physical capabilities of the design under different seismic conditions.

Control Rod Assembly and Drive Shaft Drop Alignment Test

Drop Alignment Tests were conducted in 2018 at the Framatome GmbH (formerly AREVA) Technical Center in Erlangen, Germany. These tests assessed control rod insertion for a variety of control rod drive shaft alignment conditions. Prototypical test hardware included a control rod assembly (CRA), control rod drive shaft structures, CRA guide tube assembly, and fuel assembly. Testing confirmed that the scram curves used in our safety analyses are conservative.

Flow Induced Vibration Tests

NuScale has enlisted SIET to fabricate a full-scale prototypic mock-up of our helical coil steam generator to support flow induced vibration testing of steam generator internals. Goals of this test program include determination of natural frequencies and mode shapes of steam generator tubes, determination of system damping characteristics, and determination of primary flow characteristic behavior at normal operating flow rates and above. Additionally, valuable steam generator fabrication, assembly, and material handling insights will be obtained as part of this test program.