Doctoral Dissertations

Date of Award

12-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Energy Science and Engineering

Major Professor

Jess C. Gehin

Committee Members

Brian D. Wirth, Arthur E. Ruggles, David J. Bjorndstad, Andrew T. Godfrey

Abstract

Beginning in the 1970's, power uprates in nuclear power plants began to cause an operational problem called Crud Induced Power Shift (CIPS). Over decades, a method has been developed and refined that has allowed industry to effectively avoid CIPS. However, increasingly challenging economic environments have caused power plants to utilize more aggressive core designs. The problem of CIPS still looms over many reactors as a potential hazard requiring conservative measures. CIPS is due to complex physical and chemical interactions. Current industry methods use multiple single-physics simulations in their analyses. However, improved 3D multi-physics models of CIPS can provide a better understanding of the interaction of the contributing physical phenomena. This increased understanding could help define and control the available margin and tradeoffs of operating with risk of having CIPS occur.

The Virtual Environment for Reactor Applications (VERA) has been developed within the Consortium for the Advanced Simulation of Light-water reactors to study the fundamentally 3D multi-physics phenomena that cause CIPS. The objective of this dissertation is to develop a methodology of applying VERA in industry to accurately determine the CIPS effects on varying core designs while providing information on their potential economic characteristics. The development and application of a methodology for advanced CIPS risk analysis has been performed by benchmarking of VERA models to plant data, improvements in VERA including the development a necessary boron hideout dissolution model, the comparative analysis of multiple core designs with differing CIPS risk, and the quantification of potential economic tradeoffs between the analyzed core designs. Application of the advanced CIPS risk methodology indicates that the feedback between multiple physics is critical to analyzing the effect of CIPS. This CIPS analysis shows relatively small differences in axial offset deviation for core designs with higher risk of CIPS, which translates to significant potential cost savings between core designs in all market scenarios with low additional risk from CIPS. This research provides insight into how varying core designs with specific maximum total core boron mass experience the effects of CIPS, what the magnitudes of those effects are, and the corresponding economic impacts of each core design.

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