Sensia (formerly Schlumberger, formerly Cameron) contracted Verdantas (then Alden Research Laboratories) to perform flow testing of the full-scale section of the prototype NuScale Reactor Pressure Vessel (RPV) constructed and initially tested by us in 2017. Our objectives for the 2017 testing were to show proof of concept for the use of the Ultrasonic Flow Meters (UFMs) for resolving the reactor flow rate, to help validate isothermal CFD analysis, and to determine the ideal circumferential locations for the UFMs where the sensitivity to the exact inlet profile is minimized. However, the 2017 testing concluded a higher than anticipated/ desired uncertainty for UFM flow measurement. The contributing factors for the higher than anticipated uncertainty were electrical interference, low experimental reproducibility, significant influence of near field geometry, unclear sensitivity to upstream flow distortion, and the original design of the physical devices used to induce predicted levels of flow distortion in the physical model. In order to decrease the total uncertainty in UFM measurement, a second series of testing was conducted by Verdantas with the original UFMs along with 8 additional newly designed UFMs installed in the model and tested in 2020.

The evaluations of distorted flow within the model during the 2020 testing sequence were based on predictions of isothermal CFD analysis of the prototype RPV. We designed the RPV model in 2017 with input from Sensia and NuScale, as a 1 to 1 truncated section of the RPV Prototype. The model was modified in 2020 to include 8 additional UFMS with a different path angle and removal of some internal geometry due to design changes. The facility was re-commissioned at Verdantas’ Alden campus in Holden, MA, following the modifications to the model and the facility test loop. The model and the facility were inspected to meet the very tight requirements on internal geometry (better than ±1/16” on over 10 ft diameter pipe, for example). Once the model and facility were inspected, the commissioning of the test loop proceeded with electrical interference testing, followed by low flow testing, and concluding with distortion and repeatability testing. Testing was successful in determining the optimum locations for the UFMs with the lowest possible uncertainty with the applied levels of flow distortion.