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Fusion Science and Technology
Penfield and Enos: Outage planning in the COVID-19 era
Energy Harbor’s Beaver Valley plant, located about 34 miles northwest of Pittsburgh, Pa., was one of many nuclear sites preparing for a scheduled outage as the coronavirus pandemic intensified in March. The baseline objective of any planned outage—to complete refueling on time and get back to producing power—was complicated by the need to prevent the transmission of COVID-19.
While over 200 of the plant’s 850 staff members worked from home to support the outage, about 800 contractors were brought in for jobs that could only be done on-site. Nuclear News Staff Writer Susan Gallier talked with Beaver Valley Site Vice President Rod Penfield and General Plant Manager Matt Enos about the planning and communication required.
Beaver Valley can look forward to several more outages in the future, now that plans to shut down the two Westinghouse pressurized water reactors, each rated at about 960 MWe, were reversed in March. “The deactivation announcement happened in the middle of all our planning,” Enos said. “It’s a shame we haven’t had a chance to get together as a large group and celebrate that yet.”
While the focus remains on safe pandemic operations, the site now has two causes for celebration: an outage success and a long future ahead.
B. Zhao, S. A. Musa, S. I. Abdel-Khalik, M. Yoda
Fusion Science and Technology | Volume 72 | Number 3 | October 2017 | Pages 300-305
Technical Paper | dx.doi.org/10.1080/15361055.2017.1333828
Articles are hosted by Taylor and Francis Online.
The leading candidate for the DEMO divertor is the helium-cooled modular divertor with multiple jets (HEMJ) design, which is to date the only design that has been experimentally shown to accommodate incident steady-state heat fluxes greater than 10 MW/m2. In the HEMJ, the divertor target plates are cooled by 25 jets of different diameters that impinge upon a curved tungsten (W)-alloy surface brazed to a hexagonal W tile. Given the difficulties in manufacturing such a complicated geometry in W and W-alloys, numerical simulations were performed to determine if simplified versions of the HEMJ design could provide similar thermal-hydraulic performance. Parametric studies were performed at fully prototypical conditions using one-way coupled thermo-mechanical and fluid dynamics simulations in ANSYS® Workbench® to determine the effect of varying the jet-to-cooled surface distance, the number, diameter, and spacing of the jet holes (the jets were all assumed to have the same diameter), and the curvature of the cooled surface on the thermal-hydraulic performance. The results for the evaluated 75 different jet array configurations suggest that similar and even superior thermal-hydraulic performance can be provided by several designs. These HEMJ variants with fewer jets and larger holes may reduce fabrication costs and improve reliability. For example, the simulations suggest that a configuration involving flat surfaces with six holes surrounding one central hole, all with a diameter of 1.18 mm at a jet-to-cooled surface distance of 1.25 mm provides a 6.6% higher average heat transfer coefficient (HTC) at a 4.8% lower pressure drop when compared with the HEMJ. The maximum temperature of the outer shell and cooled surface stress are also lower for this design. In all cases, the simulations also suggest that the jet-to-cooled surface distance decreases by approximately 0.2 mm when the temperature increases from ambient to prototypical conditions due to differential thermal expansion of the jets cartridge and the W-alloy pressure boundary.