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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: 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: David Michael Carpenter Publisher: ISBN: Category : Languages : en Pages : 189
Book Description
(cont.) Because of the fuel geometry, the average fuel temperature is significantly lower, and the stiffness of the SiC cladding helps to maintain the geometry of the annulus during extended irradiation. Experimental projects have been undertaken to study the performance of both the annular fuel rods and silicon carbide duplex cladding. A post-irradiation examination of prototype annular fuel rods with VIPAC fuel, irradiated in the MIT reactor, has been designed and executed. Through this non-destructive examination, the disposition of the fuel grains is examined, and fuel burnup and fission gas release is estimated. These experimental results correlate well with computer calculations. A new irradiation facility was also planned and constructed that consists of a closed loop, operated at pressurized water reactor pressure, temperature, and chemistry conditions. This facility contains silicon carbide duplex cladding samples of various constructions, and it will be irradiated in the core of the MIT reactor for several months.
Author: International Atomic Energy Agency Publisher: IAEA ISBN: Category : Business & Economics Languages : en Pages : 232
Book Description
This publication presents a variety of innovative water cooled, gas cooled, liquid metal cooled and non-conventional small and medium sized reactor (SMR) designs developed worldwide, and examines technology and infrastructure development needs that may be common to several concepts or lines of such reactors. It also gives an updated definition of small reactors without on-site refuelling and a preliminary review of the passive safety design options for SMRs.
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: Jun Wang Publisher: Elsevier ISBN: 0323999468 Category : Science Languages : en Pages : 465
Book Description
Nuclear Power Reactor Designs: From History to Advances analyzes nuclear designs throughout history and explains how each of those has helped to shape and inform the nuclear reactor designs of today and the future. Focused on the structure, systems and relevant components of each reactor design, this book provides the readers with answers to key questions to help them understand the benefits of each design. Each reactor design is introduced, their origin defined, and the relevant research presented before an analysis of its successes, what was learned, and how research and technology advanced as a result are presented. Students, researchers and early career engineers will gain a solid understanding of how nuclear designs have evolved, and how they will continue to develop in the future. Presents reactor designs through history to present day, focusing on key structures, systems and components Provides readers with quick answers about various design principles and rationales Includes new approaches such as the micro-reactor and small-modular reactors
Author: Zhiwen Xu Publisher: ISBN: Category : Languages : en Pages : 305
Book Description
This work is focused on the strategy for utilizing high-burnup fuel in pressurized water reactors (PWR) with special emphasis on the full array of neutronic considerations. The historical increase in batch-averaged discharge fuel burnup, from ~30 MWd/kg in the 1970s to ~50 MWd/kg today, was achieved mainly by increasing the reload fuel enrichment to allow longer fuel cycles: from an average of 12 months to about 18 months. This also reduced operating costs by improving the plant capacity factor. Recently, because of limited spent fuel storage capacity, increased core power output and the search for increased proliferation resistance, achieving burnup in the 70 to 100 MWd/kg range has attracted considerable attention. However the implications of this initiative have not been fully explored; hence this work defines the practical issues for high-burnup PWR fuels based on neutronic, thermal hydraulic and economic considerations as well as spent fuel characteristics. In order to evaluate the various high burnup fuel design options, an improved MCNP-ORIGEN depletion program called MCODE was developed. A standard burnup predictor-corrector algorithm is implemented, which distinguishes MCODE from other MCNP-ORIGEN linkage codes. Using MCODE, the effect of lattice design (moderation effect) on core design and spent fuel characteristics is explored. Characterized by the hydrogen-to-heavy-metal ratio (H/HM), the neutron spectrum effect in UO2/H2O lattices is investigated for a wide range of moderation, from fast spectra to over-thermalized spectra. It is shown that either wetter or very dry lattices are preferable in terms of achievable burnup potential to those having an epithermal spectrum. Wet lattices are the preferred high burnup approach due to improved proliferation resistance. The constraint of negative moderator temperature coefficient (MTC) requires that H/HM values (now at 3.4) remain below ~6.0 for PWR lattices. Alternative fuel choices, including the conventional solid pellets, central-voided annular pellets, Internally- & eXternally-cooled Annular Fuel (IXAF), and different fuel forms are analyzed to achieve a wetter lattice. Although a wetter lattice has higher burnup potential than the reference PWR lattice, the requirement of a fixed target cycle energy production necessitates higher initial fuel enrichments to compensate for the loss of fuel mass in a wetter lattice. Practical issues and constraints for the high burnup fuel include neutronic reactivity control, heat transfer margin, and fission gas release. Overall the IXAF design appears to be the most promising approach to realization of high burnup fuel. High-burnup spent fuel characteristics are compared to the reference spent fuel of 33 MWd/kg, representative of most of the spent fuel inventory. Although an increase of decay power and radioactivity per unit mass of initial heavy metal is immediately observed, the heat load (integration of decay power over time) per unit electricity generation decreases as the fuel discharge burnup increases. The magnitude of changes depends on the time after discharge. For the same electricity production, not only the mass and volume of the spent fuel are reduced, but also, to a lesser extent, the total heat load of the spent fuel. Since the heat load in the first several hundred years roughly determines the capital cost of the repository, a high burnup strategy coupled with adequate cooling time, may provide a cost-reduction approach to the repository. High burnup is beneficial to enhancing the proliferation resistance. The plutonium vector in the high-burnup spent fuel is degraded, hence less attractive for weapons. For example, the ratio of Pu-238 to Pu-239 increases with burnup to the 2.5 power. However, the economic benefits are uncertain. Under the current economic conditions, the PWR fuel burnup appears to have a shallow optimum discharge burnup between 50 and 80 MWd/kg. The actual minimum is influenced by the financing costs as well as the cost of refueling shutdowns. Since the fuel cycle back-end benefits will accrue to the federal government, the current economic framework, such as the waste fee based on the electricity produced rather than volume or actinide content, does not create an incentive for utilities to increase burnup. Different schemes exist for fuel management of high burnup PWR cores. For the conventional core design, a generalized enrichment-burnup correlation (applicable between 3 w/o and 20 w/o) was produced based on CASMO/SIMULATE PWR core calculations. Among retrofit cores, increasing the number of fuel batches is preferred over increasing the cycle length due to nuclear fuel cycle economic imperatives. For future core designs, a higher power-density core is a very attractive option to cut down the busbar cost. The IXAF concept possesses key design characteristics that provide the necessary thermal margins at high core power densities. In this regard, the IXAF fuel deserves further investigation to fully exploit its high burnup capability.
Author: Yoshiaki Oka Publisher: Springer Science & Business Media ISBN: 1441960341 Category : Technology & Engineering Languages : en Pages : 664
Book Description
Super Light Water Reactors and Super Fast Reactors provides an overview of the design and analysis of nuclear power reactors. Readers will gain the understanding of the conceptual design elements and specific analysis methods of supercritical-pressure light water cooled reactors. Nuclear fuel, reactor core, plant control, plant stand-up and stability are among the topics discussed, in addition to safety system and safety analysis parameters. Providing the fundamentals of reactor design criteria and analysis, this volume is a useful reference to engineers, industry professionals, and graduate students involved with nuclear engineering and energy technology.
Author: Mujid S. Kazimi Publisher: ISBN: Category : Languages : en Pages :
Book Description
The use of internally and externally cooled annular fule rods for high power density Pressurized Water Reactors is assessed. The assessment included steady state and transient thermal conditions, neutronic and fuel management requirements, mechanical vibration issues, fuel performance issues, fuel fabrication methods and econmic assessment. The investigation was donducted by a team from MIT, Westinghouse, Gamma Engineering, Framatome ANP, and AECL. The analyses led to the conclusion that raising the power density by 50% may be possible with this advanced fuel. Even at the 150% power level, the fuel temperature would be a few hundred degrees lower than the current fuel temperatre. Significant economic and safety advantages can be obtained by using this fuel in new reactors. Switching to this type of fuel for existing reactors would yield safety advantages, but the economic return is dependent on the duration of plant shutdown to accommodate higher power production. The main feasiblity issue for the high power performance appears to be the potential for uneven splitting of heat flux between the inner and outer fuel surfaces due to premature closure of the outer fuel-cladding gap. This could be overcome by using a very narrow gap for the inner fuel surface and/or the spraying of a crushable zirconium oxide film at the fuel pellet outer surface. An alternative fuel manufacturing approach using vobropacking was also investigated but appears to yield lower than desirable fuel density.
Author: Dandong Feng (Ph. D.)
Author: Dandong Feng (Ph. D.)
Author: David Michael Carpenter
Author: International Atomic Energy Agency
Author: Nathan Christopher Andrews
Author: W. D. Fowler
Author: A. P. Bray
Author: Jun Wang
Author: Zhiwen Xu
Author: Yoshiaki Oka
Author: Mujid S. Kazimi