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Developing a new regulatory framework for advanced reactors: Update on Part 53
White
The American Nuclear Society’s Risk-informed, Performance-based Principles and Policy Committee (RP3C) on March 29 held another presentation in its monthly Community of Practice (CoP) series. The presenter, Patrick White with the Nuclear Innovation Alliance (NIA), talked about the current status of efforts to develop a new regulatory framework for advanced reactors—known as 10 CFR Part 53 or simply Part 53. White serves as the research director of the NIA, where he leads their research as well as analysis-based stakeholder and policymaker engagement and education. White’s March 29 presentation is publicly available on YouTube and at ANS’s publication platform Nuclear Science and Technology Open Research (NSTOR).
RP3C chair N. Prasad Kadambi opened the CoP with brief introductory remarks about the RP3C before he welcomed White as the session’s presenter.
White covered three main topics: the history of the existing regulatory frameworks for new reactors, progress to date on the development of the Part 53 rule for advanced reactors, and the current status and next steps for the Part 53 rulemaking process.
C. S. Brown, I. A. Bolotnov
Nuclear Science and Engineering | Volume 184 | Number 3 | November 2016 | Pages 363-376
Technical Paper | doi.org/10.13182/NSE15-126
Articles are hosted by Taylor and Francis Online.
The spectral analysis of turbulent single- and two-phase direct numerical simulation (DNS) data in flat plane channel, circular pipe, and reactor subchannel geometries is performed using the recorded DNS velocity fluctuations as a function of time and applying the fast Fourier transform. This results in an energy spectrum of the liquid turbulence in a frequency domain. The complexity of multiphase flow results in a mixed velocity time history coming from either the liquid or the gas phase. A modified single-phase signal that mimics the presence of bubbles (“pseudo-void”) is developed to quantify the effect of the liquid signal intermittency as the bubble passes through a virtual probe.
Comparisons of single-phase, pseudo-void, and two-phase results quantify the changes to the expected −5/3 slope of the energy spectrum for single-phase flows due to turbulent interactions caused by the wakes behind a bubble. The two-phase energy spectra show a slope close to −3 and similar shape in the different geometries while single-phase energy spectra exhibit the expected −5/3 slope. Pseudo-void results indicate that the change to the energy spectrum in bubbly two-phase flows is due entirely from liquid turbulence interactions with the bubble wakes.
A comprehensive spectral analysis for different geometries and different Reynolds number flows at varying distances from the wall is an essential step in developing physically sound closure models for bubble-liquid interactions. The comparison between different geometries demonstrates the direct applicability of various models to reactor-relevant geometries.