Innovative fuel designs for high power density pressurized water reactor

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, February 2006.Includes bibliographical references (p. 229-232).One of the ways to lower the cost of nuclear energy is to increase the power density of the reactor core. Features of fuel design that enhance the potential for high power density are derived based on characteristics of the pressurized water reactor (PWR) and its related design limits. Those features include: large fuel surface to volume ratio, small fuel thickness, large fuel rod stiffness, low core pressure drop and an open fuel lattice design. Three types of fuel designs are evaluated from the thermal-hydraulic point of view: conventional solid cylindrical fuel rods, internally and externally cooled annular fuel rods, and spiral cross-geometry fuel rods, with the major effort allocated to analyzing the annular fuel. Limits of acceptable power density in solid cylindrical fuel rods are obtained by examining the effects of changing the core operation parameters, fuel rod diameter and rod array size. It is shown that the solid cylindrical geometry does not meet all the desired features for high power density well, and its potential for achieving high power density is limited to 20% of current PWR power density, unless the vibration problems at the coolant higher velocity are overcome. The internally and externally cooled annular fuel potential for achieving high power density is explored, using a whole core model. The best size of fuel rods that fits in the reference assembly dimension is a 13x13 array, since the hot red will have a balanced MDNBR in the inner and outer channels. With proportional increase in coolant flow rate, this annular fuel can increase PWR power density by 50% with the same DNBR margin, while reducing by 1000 'C the peak fuel temperature. Five issues involving manufacturing tolerances, oxide growth on rod surfaces, inner and outer gap conductances asymmetry, MDNBR sensitivity to changes in core operation parameter and resistance to instabilities were also evaluated.(contd.) It is found that the main uncertainty for this design is associated with the heat split between the inner and outer channels due to differences in the thermal resistances in the two fuel-clad gaps. Annular fuel is found to be resistant to flow instabilities, such as Ledinegg instability and density wave oscillation due to high system pressure and one-phase flow along most of the hot channel length. Similar power density uprate is found possible for annular fuel in a hexagonal lattice. Large break loss of coolant accident (LBLOCA) for the reference Westinghouse 4-loop PWR utilizing annular fuel at 150% power is analyzed using RELAP, under conservative conditions. The blowdown peak cladding temperature (PCT) is found to be lower because of the low operating fuel temperature, but the flow rate from the safety injection system needs to be increased by 50% to remove the 50% higher decay heat. Loss of flow analysis also showed better performance of the annular fuel because of its low stored energy. The fuel design that best meets the desired thermal and mechanical features is the spiral cross-geometry rods. The dimensions of this type of fuel that can be applied in the reference core were defined. Thermal-hydraulic whole-core evaluations were conducted with cylindrical fuel rod simplification, and critical heat flux modification based on the heat flux lateral non-uniformity in the cross geometry. This geometry was found to have the potential to increase PWR power density by 50%. However, there are major uncertainties in the feasibility and costs of manufacturing this fuel.by Dandong Feng.Ph.D

The Cox model with staggered entry

Bibliography: p. 122-12

A comparison of the Cox model with an additive model

Bibliography: p. 117-121

The proportional hazards regression model with staggered entries: A strong martingale approach

The proportional hazards regression model, when subjects enter the study in a staggered fashion, is studied. A strong martingale approach is used to model the two-time parameter counting processes. It is shown that well-known univariate results such as weak convergence and martingale inequalities can be extended to this two-dimensional model. Strong martingale theory is also used to prove weight convergence of a general weighted goodness-of-fit process and its weighted bootstrap counterpart.Staggered entries Strong martingales Proportional hazards regression models

Patellar Inward Pushing Method Relieves Knee Osteoarthritis Via Regulating Cytokines

Background and Objective: &nbsp;Knee osteoarthritis (KOA) is a chronic degenerative disease characterized by pain, morning stiffness and swelling in the knee joints. And KOA is common in the elderly and seriously affects the exercise function and physical health of patients. This study aimed to explore the curative effects of patellar inward pushing method (PIPM) on KOA. Methods: &nbsp;In this study, we established rabbit animal models of KOA for the research by using the New Zealand white rabbits. A total of n=30 rabbits were divided into 5 groups by random number table method: blank group, model group, glucosamine hydrochloride (GH) group, PIPM group and PIPM combined with GH group. The rabbits were then modeled. Results: &nbsp;After 9-weeks cultured in groups, 5 ml blood was collected from the heart, and cytokines were detected. The result suggested that iNOS, NO and TNF-&alpha; were the pathogenic inflammatory factor of KOA, and aggravated cartilage damage and degeneration. Besides, this study indicated that PIPM combined with GH treatment significantly reduced the activity of inflammatory cytokines in serum and joint fluid of KOA models in rabbits. In addition, PIPM combined with GH therapy exhibited the best therapeutic effect among these treatments, which was working on KOA better than PIPM treatment alone or GH treatment alone. Conclusion: &nbsp;PIPM could effectively treat KOA via regulating cytokines, and the PIPM combined with GH therapy could be a novel therapeutic strategy for KOA.</p

High Performance Fuel Design for Next Generation PWRs: 11th Quarterly Report

Quarterly Report for Project DE-FG03-01SF22329 April 2004 – June 2004I. Technical Narrative: The overall objective of this NERI project is to examine the potential for a high performance advanced fuel for Pressurized Water Reactors (PWRs), which would accommodate a substantial increase of core power density while simultaneously providing larger thermal margins than current PWRs. This advanced fuel will have an annular geometry that allows internal and external coolant flow and heat removal. The project is led by the Massachusetts Institute of Technology (MIT), with collaboration of four industrial partners – Gamma Engineering Corporation, Westinghouse Electric Corporation, Framatome ANP (formerly Duke Engineering & Services), and Atomic Energy of Canada Limited

High Performance Fuel Design for Next Generation PWRs 2nd Annual Report

Progress Report for Work August 2002 through July 2003The overall objective of this NERI project is to examine the potential for a high performance advanced fuel design for Pressurized Water Reactors (PWRs), which would accommodate a substantial increase of core power density while simultaneously providing larger thermal margins than current PWRs. This advanced fuel employs an annular geometry that allows internal and external coolant flow and heat removal. The project is led by the Massachusetts Institute of Technology (MIT), with the collaboration of four industrial partners – Gamma Engineering Corporation, Westinghouse Electric Corporation, Framatome ANP DE & S (formerly Duke Engineering & Services), and Atomic Energy of Canada Limited. The project is organized into five tasks: 1. Task 1 Assess the thermal hydraulic performance of the internally and externally cooled annular fuel to identify the configuration with the highest potential for power density increase while maintaining ample thermal margins, as well as key aspects of mechanical design to ensure that new fuel will not perform outside established hydraulic and mechanical constraints, 2. Task 2 Determine the neutronic performance of the new fuel, and the design that will minimize fuel cycle cost and assures that reactor physics safety parameters are as good or better than those of current PWRs, 3. Task 3 Explore various methods of manufacturing of this advanced fuel, including new innovative fabrication processes to produce annular fuel elements with the required product characteristics, 4. Task 4 Evaluate fuel cycle cost and capital cost implications of high power density to determine the economic viability of the high-performance fuel, and 5. Task 5 Analyze fuel performance of the new UO2 annular fuel obtained by various production technologies including irradiation testing in the MIT reactor

High Performance Fuel Design for Next Generation PWRs Appendices B-I to FY-02 Annual Report

Progress Report for Work August 2001 through July 2002B.1.1 VIPRE modeling of PWR core with annular fuel: Optimization studies in the first year used an isolated channel and models for MDNBR analyses. These analyses provided sufficient knowledge of potential thermal hydraulic performance of annular fuels to select the 13x13 array as the most promising configuration. To obtain more realistic and accurate MDNBR, a whole core model is necessary. In particular, the major concern is correct representation of channel flow rate. The earlier models used the core-average mass flux, which does not account for flow rate reduction in the hot channels due to increased pressure drop in this channel as a result of higher subcooled, or possibly, saturated boiling. Therefore, it is expected that the MDNBR obtained from the full core VIPRE-01 model will be smaller than the values obtained from the isolated channel model