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Author: Guillaume Giudicelli Publisher: ISBN: Category : Languages : en Pages : 124
Book Description
This work aims at investigating the potential benefits of nitride fuel use in pressurized water reactors. The AP1000 is chosen as the reference power plant. Both oxide and nitride fuel are considered and compared using a steady state thermal hydraulics and mechanics parametric optimization study to achieve a maximal core power. A subsequent neutronics study determined the achievable energy extracted per fuel mass (burnup) and sets the core power that allows for an 18-months fuel cycle length. The impact of the change in the core operating temperature on the steam cycle efficiency is considered in order to provide a final evaluation of the electric power uprate. The steady state limits considered are pressure drop, minimum departure from nucleate boiling ratio, fretting and sliding wear and fuel average and centerline temperatures. These limits were set by the reference design's performance. Two strategies were used to raise the core power while remaining within specified limits: increasing the core mass flow rate and decreasing the core inlet temperature. These two strategies were implemented in a simplified MATLAB tool using correlations and a MATLAB-VIPRE (subchannel simulation tool) interface to better model cross-flows. Designs with smaller pins but with similar pitch-todiameter ratios compared to the reference design were found to be optimal with regards to these performances for both strategies. Fretting wear was found to be the limiting constraint for these designs for the first strategy, and additional spacer grids can be introduced to reduce fretting wear and to allow a further power increase. MDNBR was found to be the limiting constraint for these designs in the second strategy. The fuel temperature was not limiting for these designs and both oxide and nitride fuel can be utilized with the same uprates. Both tools provided similar results: smaller fuel pins with similar pitch over diameter ratios allow for better performances than the nominal design in the aforementioned criteria. The most promising strategy proved to be decreasing the core inlet temperature. With this strategy, the possible uprate is 16%, or 550 MWth, in both tools. Such an uprate requires an additional steam generator, and when lowering the core inlet temperature the efficiency of the steam cycle is lowered by 1% as we also need to lower the steam generator saturation pressure. This will require a larger high-pressure turbine. The optimized nitride-fueled design was compared with the oxide-fueled nominal core in terms of neutronics performances. I showed that the new design can reach an 18 month cycle length, at an uprated power, with a 4.3% enrichment and a 60 assembly feed using uranium nitride, compared with a 4.6% enrichment and a 68 assembly feed for the nominal design at the nominal power. With a higher enrichment and a higher feed, a two-year cycle length can be reached even with the uprate. The moderator temperature coefficient, the shutdown margin and the power coefficient of both designs satisfied licensing requirements. A 5% increase in fuel cycle costs was noted with the nitride optimized core, minor compared to the revenue of a 150 MWe uprate. Transient performances, and more extensive fuel performance studies are left for future studies.
Author: Guillaume Giudicelli Publisher: ISBN: Category : Languages : en Pages : 124
Book Description
This work aims at investigating the potential benefits of nitride fuel use in pressurized water reactors. The AP1000 is chosen as the reference power plant. Both oxide and nitride fuel are considered and compared using a steady state thermal hydraulics and mechanics parametric optimization study to achieve a maximal core power. A subsequent neutronics study determined the achievable energy extracted per fuel mass (burnup) and sets the core power that allows for an 18-months fuel cycle length. The impact of the change in the core operating temperature on the steam cycle efficiency is considered in order to provide a final evaluation of the electric power uprate. The steady state limits considered are pressure drop, minimum departure from nucleate boiling ratio, fretting and sliding wear and fuel average and centerline temperatures. These limits were set by the reference design's performance. Two strategies were used to raise the core power while remaining within specified limits: increasing the core mass flow rate and decreasing the core inlet temperature. These two strategies were implemented in a simplified MATLAB tool using correlations and a MATLAB-VIPRE (subchannel simulation tool) interface to better model cross-flows. Designs with smaller pins but with similar pitch-todiameter ratios compared to the reference design were found to be optimal with regards to these performances for both strategies. Fretting wear was found to be the limiting constraint for these designs for the first strategy, and additional spacer grids can be introduced to reduce fretting wear and to allow a further power increase. MDNBR was found to be the limiting constraint for these designs in the second strategy. The fuel temperature was not limiting for these designs and both oxide and nitride fuel can be utilized with the same uprates. Both tools provided similar results: smaller fuel pins with similar pitch over diameter ratios allow for better performances than the nominal design in the aforementioned criteria. The most promising strategy proved to be decreasing the core inlet temperature. With this strategy, the possible uprate is 16%, or 550 MWth, in both tools. Such an uprate requires an additional steam generator, and when lowering the core inlet temperature the efficiency of the steam cycle is lowered by 1% as we also need to lower the steam generator saturation pressure. This will require a larger high-pressure turbine. The optimized nitride-fueled design was compared with the oxide-fueled nominal core in terms of neutronics performances. I showed that the new design can reach an 18 month cycle length, at an uprated power, with a 4.3% enrichment and a 60 assembly feed using uranium nitride, compared with a 4.6% enrichment and a 68 assembly feed for the nominal design at the nominal power. With a higher enrichment and a higher feed, a two-year cycle length can be reached even with the uprate. The moderator temperature coefficient, the shutdown margin and the power coefficient of both designs satisfied licensing requirements. A 5% increase in fuel cycle costs was noted with the nitride optimized core, minor compared to the revenue of a 150 MWe uprate. Transient performances, and more extensive fuel performance studies are left for future studies.
Author: Nathan Christopher Andrews Publisher: ISBN: Category : Languages : en Pages : 230
Book Description
This work addresses several specific knowledge gaps that exist in the use of alternative fuel and cladding combinations in a pressurized water reactor (PWR) environment. In the switch from a UO2 with zirconium-based cladding to any other combination, there is a multitude of questions that need to be answered. This work examines three of these knowledge gaps: (1) the disposition of weapons-grade plutonium in thorium and silicon carbide cladding, (2) economics of accident tolerant fuel (ATF) claddings and (3) breeding of plutonium in uranium nitride fuel. Burning weapons-grade plutonium in a standard pressurized water reactor (PWR) using thoria as a fuel matrix has been compared to using urania. Two cladding options were considered: a 0.76 mm thick silicon carbide ceramic matrix composite (SiC CMC) and 0.57 mm thick standard Zircaloy cladding. A large benefit was found in using thoria compared to urania in terms of plutonium percentage and mass burned. A slightly smaller mass of plutonium is required in a core with SiC CMC cladding, due to its lower neutron absorption compared to Zircaloy. The thorium system was also better from a non-proliferation viewpoint, resulting in less fissile mass at discharge and more fissile mass burned over an assembly's lifetime. A limited safety comparison was made for two reactivity insertion accidents: (1) highest worth rod ejection accident (REA) and (2) main steam line break (MSLB). The MSLB accident demonstrated a safe value for the minimum departure from nucleate boiling ratio. The maximum enthalpy added to the fuel during the REA was also below current regulatory limits for PWRs. This indicates that the more negative moderator temperature coefficients of thoria-plutonia and urania-plutonia fuel, compared to a typical PWR design, were not limiting. For an ATF cladding to replace zirconium alloys, it must be economically viable by having similar fuel cycle costs to today's materials. Four proposed materials are examined: stainless steel (SS), FeCrAl alloy, molybdenum (Mo) and SiC CMC, each having its own development time and costs. The chosen cladding thicknesses were dependent on strength and manufacturing constraints. It was found that all options may end up requiring higher enrichment than zirconium-based claddings for the same fuel cycle length. If the present value of avoiding a reactor accident with a large radioactivity release is estimated using past experience for LWR large accidents and if it is assumed that ATF cladding is able to prevent such release, there is a definite net economic benefit relative to typical Zircaloy cladding only in using SiC, since it only results in a small fuel cycle cost increase. There is only a marginal benefit in using SiC to prevent a core-only loss without radioactivity release (TMI-type) accident and a large loss using metallic ATF concepts. The thermal hydraulic and neutronic feasibility of a nitride fueled pressurized water reactor (PWR) breeder design were examined. Because of its higher fuel density, nitride fuel would be preferable to traditional oxide fuel in attempting to achieve breeding in a PWR. The design chosen uses large hexagonal assemblies with 14 inner seed pin rows and 4 outer blanket pin rows. In this design, reactor grade plutonium of 12.75 wtHM was used as fuel. Nitride was also simulated as being 100% N-15, to limit neutronic penalties and C-14 production. The as specified assembly model only achieved a fissile inventory ratio (FIR) value above 1.0 when the thimble regions were assumed to be voided, which lowers the H/HM ratio in the assembly. This led to FIR values above 1.0 for the oxide, 85% theoretical density nitride (N85) and 95% theoretical density nitride (N95). All were at an FIR of 1.03 at 35 MWd/kgHM. However, the single batch discharge burnup of the voided assembly in MWd/kgHM was 32.2 for N95, 24.5 for N85, while only 15.6 for the oxide.
Author: Yigal Ronen Publisher: CRC Press ISBN: 9780849360817 Category : Technology & Engineering Languages : en Pages : 282
Book Description
The purpose of this book is to describe concepts related to advanced water reactors, with particular focus on Advanced Pressurized Water Reactors. It discusses the severe disadvantages which water reactors have with respect to uranium utilization. It also reveals new concepts in which the conversion ratio and the uranium utilization is improved. This interesting work includes information on various others ways used in addition to the increase in the conversion ratio. This is an informative, useful book for all nuclear scientists and engineers, and anyone who is interested in high converting water reactors.
Author: Dandong Feng (Ph. D.) Publisher: ISBN: Category : Languages : en Pages : 259
Book Description
(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.
Author: Richard Bartholomew Stout Publisher: ISBN: Category : Nuclear fuels Languages : en Pages : 316
Book Description
Fuel loading patterns which have a minimum power peak are economically desirable to allow power reactors to operate at the highest possible power density and to minimize the possibility of fuel failure. A computer code called SHUFLE was developed for pressurized water reactors which shuffles the fuel in search of the lowest possible power peaking factor. An iterative approach is used in this search routine. A radial power distribution is calculated from which the program logic Selects a movement of fuel elements in an attempt to lower the radial power peak. Another power calculation is made and the process repeated until a predetermined convergence is reached. The logic by which the code decides the fuel movement is presented, along with the criteria for accepting or rejecting the move after a power calculation of the new loading pattern is made. A 1.5 group course mesh diffusion theory method was used to obtain the power distribution for each SHUFLE iteration. Convergence to a final loading pattern varies from about 10 to 40 shuffling iterations depending on the initial loading presented to the code. Since the typical computer running time for a one-quarter core power distribution with this 1.5 group method is only one to a few seconds, depending on the loading, convergence to a good loading pattern takes on the order of one minute on a Univac 1108. The low computer cost plus ease of operation should make this code of considerable use in determining loading patterns with minimum power peaking for any given set of fuel elements. The program also has burnup capability which can be used to check power peaking throughout core life. A parametric analysis study of fuel cycle costs for a PWR is also presented. Cost parameters analyzed were variation in the cost of yellow cake, enrichment, money, fabrication, and reprocessing plus changes in burnup, load factors, power densities, and the effect of forced early discharge. Figures are presented to indicate total fuel costs as a function of burnup for these cost parameters. Linear relationships for minimum cost and optimum burnup are presented for each parameter.
Author: Charles P. Kliewer Publisher: ISBN: Category : Nuclear reactors Languages : en Pages : 320
Book Description
A significant amount of interest has been aroused recently concerning the advancement of the current pressurized water reactor core designs with a special emphasis towards improving the conversion characteristics of these reactors. Most reports have been divided into two camps; those that deal with the neutronic aspects and those that deal with the thersohydraulic concerns. Seldom do these two areas get combined for purposes of evaluating a new design. In this effort, the author takes a pragmatic approach to this area in so far as looking into ways of incorporating this advanced technology into current operational power plants. In so doing the Trojan Nuclear Power Plant was selected to serve as the reference design plant. This was done since it is a Westinghouse designed reactor, as are a large portion of the PWR's in the United States, and because it has one of the largest thermal power ratings in the nation as well. Both neutronic and thermohydraulic aspects are examined as well as an alternative fuel concept. In order to carry out the analysis computer codes COBRA-IV and LEOPARD were employed on a CYBER 170/710 mainframe computer. COBRA-IV was used to obtain results relating to the associated pressure loss and core temperature characteristics while LEOPARD was used for the neutronic aspects. A parametric study was initiated using fuel enrichment and pitch as the variables that would be systematically changed. As an additional factor to assure cross compatibility, the fuel rod diameter was held to a constant value throughout this analysis. Results of this research strongly indicate that current operational power plants can be effectively altered to become converters or low level breeders with only configurational changes in the core itself and no major equipment changes. Hence the author concludes that this concept is both feasible and readily attainable with the current level of technology. An additional benefit that would be realized under the adoption of this design would be the marked improvement in the utilization of uranium ore which ultimately becomes fuel. This would directly result in the extension of the power generation capability associated with nuclear power well into the next century.
Author: Joseph A. Sefcik Publisher: ISBN: Category : Nuclear fuel elements Languages : en Pages : 241
Book Description
Systematic procedures have been devised and applied to evaluate core design and fuel management strategies for improving uranium utilization in Pressurized Water Reactors operated on a once-through fuel cycle. A principal objective has been the evaluation of suggested improvements on a self-consistent basis, allowing for concurrent changes in dependent variables such as core leakage and batch power histories, which might otherwise obscure the sometimes subtle effects of interest. Two levels of evaluation have been devised: a simple but accurate analytic model based on the observed linear variations in assembly reactivity as a function of burnup; and a numerical approach, embodied in a computer program, which relaxes this assumption and combines it with empirical prescriptions for assembly (or batch) power as a function of reactivity, and core leakage as a function of peripheral assembly power. State-of-the-art physics methods, such as PDQ-7, were used to verify and supplement these techniques. These methods have been applied to evaluate several suggested improvements: (1) axial blankets of low-enriched or depleted uranium, and of beryllium metal, (2) radial natural uranium blankets, (3) low-leakage radial fuel management, (4) high burnup fuels, (5) optimized H/U atom ratio, (6) annular fuel, and (7) mechanical spectral shift (i.e. variable fuel-to-moderator ratio) concepts such as those involving pin pulling and bundle reconstitution. The potential savings in uranium requirements compared to current practice were found to be as follows: (1) O0-3%, (2) negative, (3) 2-3%; possibly 5%, (4) "15%, (5) 0-2.5%, (6) no inherent advantage, (7) 10%. Total savings should not be assumed to be additive; and thermal/hydraulic or mechanical design restrictions may preclude full realization of some of the potential improvements.
Author: International Atomic Energy Agency Publisher: ISBN: 9781523130191 Category : Fast reactors Languages : en Pages : 0
Book Description
"Based on a recommendation from the Technical Working Group on Fast Reactors, this publication is a regular update of previous publications on fast reactor technology. The publication provides comprehensive and detailed information on the technology of fast neutron reactors. The focus is on practical issues that are useful to engineers, scientists, managers, university students and professors. The main issues of discussion are experience in design, construction, operation and decommissioning, various areas of research and development, engineering, safety and national strategies, and public acceptance of fast reactors. In the summary the reader will find national strategies, international initiatives on innovative (i.e. Generation IV) systems and an assessment of public acceptance as related to fast reactors."--Résumé de l'éditeur.
Author: Kenneth D. Kok Publisher: CRC Press ISBN: 1315356309 Category : Science Languages : en Pages : 1328
Book Description
Building upon the success of the first edition, the Nuclear Engineering Handbook, Second Edition, provides a comprehensive, up-to-date overview of nuclear power engineering. Consisting of chapters written by leading experts, this volume spans a wide range of topics in the areas of nuclear power reactor design and operation, nuclear fuel cycles, and radiation detection. Plant safety issues are addressed, and the economics of nuclear power generation in the 21st century are presented. The Second Edition also includes full coverage of Generation IV reactor designs, and new information on MRS technologies, small modular reactors, and fast reactors.
Author: Guillaume Giudicelli
Author: Guillaume Giudicelli
Author: Nathan Christopher Andrews
Author: Yigal Ronen
Author: J. C. Ryman
Author: Dandong Feng (Ph. D.)
Author: Richard Bartholomew Stout![A Feasibil[i]ty Analysis of High Conversion Ratio Pressurized Water Reactor Designs PDF](https://books.google.com/books/content/images/frontcover/iZSfNwAACAAJ?fife=w80-h100)
Author: Charles P. Kliewer
Author: Joseph A. Sefcik
Author: International Atomic Energy Agency
Author: Kenneth D. Kok