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The extension to LWRs of the use of Deep-Burn coated particle fuel envisaged for HTRs has been investigated. TRISO coated fuel particles are used in Fully-Ceramic Microencapsulated (FCM) fuel within a SiC matrix rather than the graphite of HTRs. TRISO particles are well characterized for uranium-fueled HTRs. However, operating conditions of LWRs are different from those of HTRs (temperature, neutron energy spectrum, fast fluence levels, power density). Furthermore, the time scales of transient core behavior during accidents are usually much shorter and thus more severe in LWRs. The PASTA code was updated for analysis of stresses in coated particle FCM fuel. The code extensions enable the automatic use of neutronic data (burnup, fast fluence as a function of irradiation time) obtained using the DRAGON neutronics code. An input option for automatic evaluation of temperature rise during anticipated transients was also added. A new thermal model for FCM was incorporated into the code; so-were updated correlations (for pyrocarbon coating layers) suitable to estimating dimensional changes at the high fluence levels attained in LWR DB fuel. Analyses of the FCM fuel using the updated PASTA code under nominal and accident conditions show: (1) Stress levels in SiC-coatings are low for low fission gas release (FGR) fractions of several percent, as based on data of fission gas diffusion in UO2 kernels. However, the high burnup level of LWR-DB fuel implies that the FGR fraction is more likely to be in the range of 50-100%, similar to Inert Matrix Fuels (IMFs). For this range the predicted stresses and failure fractions of the SiC coating are high for the reference particle design (500 {micro}mm kernel diameter, 100 {micro}mm buffer, 35 {micro}mm IPyC, 35 {micro}mm SiC, 40 {micro}mm OPyC). A conservative case, assuming 100% FGR, 900K fuel temperature and 705 MWd/kg (77% FIMA) fuel burnup, results in a 8.0 x 10−2 failure probability. For a 'best-estimate' FGR fraction of 50% and a more modest burnup target level of 500 MWd/kg, the failure probability drops below 2.0 x 10−5, the typical performance of TRISO fuel made under the German HTR research program. An optimization study on particle design shows improved performance if the buffer size is increased from 100 to 120 {micro}mm while reducing the OPyC layer. The presence of the latter layer does not provide much benefit at high burnup levels (and fast fluence levels). Normally the shrinkage of the OPyC would result in a beneficial compressive force on the SiC coating. However, at high fluence levels the shrinkage is expected to turn into swelling, resulting in the opposite effect. However, this situation is different when the SiC-matrix, in which the particles are embedded, is also considered: the OPyC swelling can result in a beneficial compressive force on the SiC coating since outward displacement of the OPyC outer surface is inhibited by the presence of the also-swelling SiC matrix. Taking some credit for this effect by adopting a 5 {micro}mm SiC-matrix layer, the optimized particle (100 {micro}mm buffer and 10 {micro}mm OPyC), gives a failure probability of 1.9 x 10−4 for conservative conditions. During a LOCA transient, assuming core re-flood in 30 seconds, the temperature of the coated particle can be expected to be about 200K higher than nominal temperature (900K). For this event the particle failure fraction for a conservative case is 1.0 x 10−2, for the optimized particle design. For a FGR-fraction of 50% this value reduces to 6.4 x 10−4.
The current focus of the Deep Burn Project is on once-through burning of transuranics (TRU) in light-water reactors (LWRs). The fuel form is called Fully-Ceramic Micro-encapsulated (FCM) fuel, a concept that borrows the tri-isotropic (TRISO) fuel particle design from high-temperature reactor technology. In the Deep Burn LWR (DB-LWR) concept, these fuel particles are pressed into compacts using SiC matrix material and loaded into fuel pins for use in conventional LWRs. The TRU loading comes from the spent fuel of a conventional LWR after 5 years of cooling. Unit cell and assembly calculations have been performed using the DRAGON-4 code to assess the physics attributes of TRU-only FCM fuel in an LWR lattice. Depletion calculations assuming an infinite lattice condition were performed with calculations of various reactivity coefficients performed at each step. Unit cells and assemblies containing typical UO2 and mixed oxide (MOX) fuel were analyzed in the same way to provide a baseline against which to compare the TRU-only FCM fuel. Then, assembly calculations were performed evaluating the performance of heterogeneous arrangements of TRU-only FCM fuel pins along with UO2 pins.
The current focus of the Deep Burn Project is on once-through burning of transuranice (TRU) in light water reactors (LWRs). The fuel form is called Fully-Ceramic Micro-encapsulated (FCM) fuel, a concept that borrows the tri-isotropic (TRISO) fuel particle design from high-temperature reactor technology. In the Deep Burn LWR (DB-LWR) concept, these fuel particles would be pressed into compacts using SiC matrix material and loaded into fuel pins for use in conventional LWRs. The TRU loading comes from the spent fuel of a conventional LWR after 5 years of cooling. Unit cell calculations have been performed using the DRAGON-4 code in order assess the physics attributes of TRU-only FCM fuel in an LWR lattice. Depletion calculations assuming an infinite lattice condition were performed with calculations of various reactivity coefficients performed at each step. Unit cells containing typical UO2 and MOX fuel were analyzed in the same way to provide a baseline against which to compare the TRU-only FCM fuel. Loading of TRU-only FCM fuel into a pin without significant quantities of uranium challenges the design from the standpoint of several key reactivity parameters, particularly void reactivity, and to some degree, the Doppler coefficient. These unit cells, while providing an indication of how a whole core of similar fuel would behave, also provide information of how individual pins of TRU-only FCM fuel would influence the reactivity behavior of a heterogeneous assembly. If these FCM fuel pins are included in a heterogeneous assembly with LEU fuel pins, the overall reactivity behavior would be dominated by the uranium pins while attractive TRU destruction performance of the TRU-only FCM fuel pins may be preserved. A configuration such as this would be similar to CONFU assemblies analyzed in previous studies. Analogous to the plutonium content limits imposed on MOX fuel, some amount of TRU-only FCM pins in an otherwise-uranium fuel assembly may give acceptable reactivity performance. Assembly calculations will be performed in future work to explore the design options for heterogeneous assemblies of this type and their impact on reactivity coefficients.
The charm of Mathematical Physics resides in the conceptual difficulty of understanding why the language of Mathematics is so appropriate to formulate the laws of Physics and to make precise predictions. Citing Eugene Wigner, this “unreasonable appropriateness of Mathematics in the Natural Sciences” emerged soon at the beginning of the scientific thought and was splendidly depicted by the words of Galileo: “The grand book, the Universe, is written in the language of Mathematics.” In this marriage, what Bertrand Russell called the supreme beauty, cold and austere, of Mathematics complements the supreme beauty, warm and engaging, of Physics. This book, which consists of nine articles, gives a flavor of these beauties and covers an ample range of mathematical subjects that play a relevant role in the study of physics and engineering. This range includes the study of free probability measures associated with p-adic number fields, non-commutative measures of quantum discord, non-linear Schrödinger equation analysis, spectral operators related to holomorphic extensions of series expansions, Gibbs phenomenon, deformed wave equation analysis, and optimization methods in the numerical study of material properties.
Highly innovative nuclear reactor technologies have the potential to meet the global energy demand while reducing carbon emissions. Generation IV reactors, with advances in safety, reliability, sustainability and economic benefits, are currently being investigated. The high-temperature gas-cooled reactor (HTGR), moderated by graphite and cooled by helium, has the highest technology readiness level compared to the other Generation IV reactor designs.Conventional HTGR fuel consists of TRistructural ISOtropic (TRISO) coated fuel particles embedded in a graphite matrix. Several historic HTGRs fueled with conventional fuel have been constructed and operated, including the Peach Bottom Unit No.1 reactor operated in Pennsylvania and the Fort St. Vrain reactor that was operated in Colorado.The FCM fuel consists of TRistructural ISOtropic (TRISO) coated fuel particles embedded in a silicon carbide (SiC) matrix. Compared to the conventional HTGR fuel, the FCM fuel could potentially enhance the safety of the reactor due to the numerous advantages provided by the SiC matrix. The FCM fuel features enhanced ability to retain fission products. The FCM fuel exhibits a greater stability under irradiation and less swelling after irradiation. Moreover, the FCM fuel has better mechanical characteristics and would be less sensitive to physical disturbances. The FCM fuel has higher oxidation resistance and would suffer less damage in air-ingress accidents. The SiC matrix may also increase the proliferation resistance of the FCM fuel.However, due to the replacement of the graphite matrix in the conventional HTGR fuel, the FCM fuel hardens the neutron spectrum in the reactor core. This may further cause economic penalties of an FCM-fueled HTGR as well as a higher fuel temperature which jeopardizes the core safety.This dissertation proved the viability of FCM-fueled HTGRs by answering the following six questions based on analysis of experimental data as well as neutronics and thermal-hydraulics numerical calculations:(1) What are the key changes in fuel cycle performance and fuel cost of HTGRs with the FCM fuel?(2) What is the potential impact of the FCM fuel on reactor performance and safety characteristics of HTGRs?(3) How does the FCM fuel impact anticipated transients and design-basis accidents?(4) What are the most important parameters for each of the design-basis accidents and their sensitivities to the maximum fuel temperature?(5) What is the kinetics of the annealing process of neutron-irradiated SiC?(6) Does the irradiation defect annealing process of SiC significantly impact fuel temperature during design-basis accidents?The reference HTGR core configuration considered was the General Atomics designed 350-MWt prismatic mHTGR which has a prismatic block configuration similar to the Fort St. Vrain reactor.In this dissertation, I identified three FCM fuel options which are able to maintain the fuel cycle length of the reference core. However, because of the higher natural resource requirement, the FCM fuel cycle cost could be up to 74% more expensive than the conventional HTGR fuel. The impact of the FCM fuel on the other parameters which are important to the core safety, including decay power, reactivity temperature coefficients and control rod worth, is minor. I investigated three typical design-basis accidents of the HTGRs, including the pressurized loss of forced cooling accident, the depressurized loss of forced cooling accident and the control rod withdrawal accident. The maximum fuel temperature of an FCM-fuel core could be up to 65 K higher than that of the reference core during normal operating conditions, and the peak maximum fuel temperature of an FCM-fuel core could be up to 55 K higher than that of the reference core during those design-basis accidents. I also studied the sensitivity of the maximum fuel temperature to various parameters of interest during different operating conditions and identified the steady-state power distribution to have the largest impact on the peak maximum fuel temperature during the design-basis accidents. By analyzing acquired experimental data, I elucidated information on the kinetics of the SiC annealing process. I further estimated the maximum possible impact of the SiC annealing process on the maximum fuel temperature of FCM-fueled HTGRs during design-basis accidents based on conservative assumptions. The SiC annealing process would at most increase the peak maximum fuel temperature of an FCM-fueled HTGR by 40 K.According to the calculations conducted, the increase of the maximum fuel temperature caused by the use of the FCM fuel in HTGRs would not exceed 100 K which is minor compared to the maximum fuel temperature of around 1200 K in the reference core during normal operating conditions. Therefore, the use of the FCM fuel in HTGRs is viable.Additionally, by comparing calculation results with experimental data, I demonstrated the validity of the system analysis code RELAP5-3D to conduct thermal-hydraulics calculations of transients in HTGRs.
Materials in a nuclear environment are exposed to extreme conditions of radiation, temperature and/or corrosion, and in many cases the combination of these makes the material behavior very different from conventional materials. This is evident for the four major technological challenges the nuclear technology domain is facing currently: (i) long-term operation of existing Generation II nuclear power plants, (ii) the design of the next generation reactors (Generation IV), (iii) the construction of the ITER fusion reactor in Cadarache (France), (iv) and the intermediate and final disposal of nuclear waste. In order to address these challenges, engineers and designers need to know the properties of a wide variety of materials under these conditions and to understand the underlying processes affecting changes in their behavior, in order to assess their performance and to determine the limits of operation. Comprehensive Nuclear Materials, Second Edition, Seven Volume Set provides broad ranging, validated summaries of all the major topics in the field of nuclear material research for fission as well as fusion reactor systems. Attention is given to the fundamental scientific aspects of nuclear materials: fuel and structural materials for fission reactors, waste materials, and materials for fusion reactors. The articles are written at a level that allows undergraduate students to understand the material, while providing active researchers with a ready reference resource of information. Most of the chapters from the first Edition have been revised and updated and a significant number of new topics are covered in completely new material. During the ten years between the two editions, the challenge for applications of nuclear materials has been significantly impacted by world events, public awareness, and technological innovation. Materials play a key role as enablers of new technologies, and we trust that this new edition of Comprehensive Nuclear Materials has captured the key recent developments. Critically reviews the major classes and functions of materials, supporting the selection, assessment, validation and engineering of materials in extreme nuclear environments Comprehensive resource for up-to-date and authoritative information which is not always available elsewhere, even in journals Provides an in-depth treatment of materials modeling and simulation, with a specific focus on nuclear issues Serves as an excellent entry point for students and researchers new to the field