Characterization and mitigation of crud at pressurized water reactor conditions
Characterization and mitigation of crud at PWR conditions
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering.
Michael P. Short and Lin-wen Hu.
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The nuclear industry is no exception when it comes to those affected by fouling deposit problems. Fouling deposits on fuel rods in nuclear reactors, known as crud, can cause a variety of undesirable effects including axial power shifts, accelerated corrosion, increased primary circuit radiation dose, and possible fuel failure. This study revisits the crud problem once again using a newly constructed Internally Heated Testloop For PWRs (IHTFP) and new analytical techniques, and attempt to find a way to prevent or mitigate crud, or at least better understand it. This is the first time that fuelrod coatings are examined as a way of countering crud growth. These coatings are chosen based on their surface chemical properties and robustness at PWR conditions. For the goal of gaining a better understanding of crud, this study is the first to apply fractal analysis to characterize crud. To achieve both of these goals, the IHTFP was built to obtain crud grown under the PWR thermal-hydraulic and chemical conditions. The crud-resistant coatings experiments show significantly reduced crud surface coverage, indicating reduced crud adhesion, for TiC and ZrN coatings. The results roughly agree with London-van der Waals theoretical force predictions, suggesting that London-VDW forces are responsible for the adhesion of crud to fuel cladding. This knowledge can be useful in designing better crud-resistant materials. The fractal analysis can provide a simple, effective way to characterize the macro-scale behavior of crud with its micro-scale properties. The fractal analysis experimental study found R2 values to be very close to one when applying the box-counting method to crud, which is one piece of evidence to support the usage of fractal analysis on crud. Moreover, a strong logarithmic relationship trend between fractal dimension and porosity was found. This relationship applies to both the IHTFP's and Westinghouse loop's crud, even though the two experimental setups used different crud precursors and heat flux. This could indicate that crud's fractal dimension is dependent only on porosity. This relationship could simplify crud modeling and lead to better predictions of crud's behaviors. Better predictions can lower margins, leading to more efficient reactors.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 448-467).
DepartmentMassachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology
Nuclear Science and Engineering.