This work investigated material corrosion by nuclear reactor coolants, including pressurized water reactor (PWR) coolant, boiling water reactor (BWR) coolant, high-temperature steam, lead-bismuth eutectic (LBE), and molten salt. Novel cladding materials for accident tolerant fuel (ATF) and additive manufacture (AM) Ni-based alloy were studied in water coolants. Similarly, the ATF material and Ni-based alloys were also examined under high-temperature steam to understand the corrosion behavior in beyond design basis accident (BDBA) scenarios. In addition to isothermal corrosion, stress corrosion cracking (SCC) and oxide layer in situ measurements were also conducted. Unlike conventional studies in liquid LBE that focused on Fe-based alloys, the present studies also investigated Ni-based alloys to explore the Ni content effects on the corrosion by LBE at high temperatures under saturated oxygen conditions. In molten salt environments, the corrosion behaviors of both Ni-based and Fe-based alloys were investigated. This study developed a redox potential range for mitigating corrosion by using a redox couple of UF4 /UF3 and a novel approach of potential measurements against F2/ F- potential experimentally. / Doctor of Philosophy / This work focuses on material degradation in harsh and extreme nuclear environments, including light water reactors and advanced reactors such as molten salt and liquid metal coolant reactors. Given the renewed interest in advanced nuclear reactors as a resource of clean energy, advanced material development, including structural, fuel, and coolant materials, has become a significant and trending research area. Based on our past experiences, we have seen the detrimental effects of material failure due to corrosion. Systems are inherently safe in the absence of material degradation. Nevertheless, this is an idealistic thought, as corrosion is inevitable. Therefore, this research focuses on corrosion mitigation, as absolute material preservation is impossible. This work includes corrosion studies in aqueous environments in light water reactors and advanced nuclear reactors under normal operation and extreme conditions such as accident environments. Much of this work provides insights into material corrosion behavior and mitigation that helps nuclear reactor operators ensure safe operations. Commercially available alloys such as SS316, Hast. X and Hast. N were examined in primary water, molten salt, high-temperature steam, and liquid bismuth environment and model Fe-Cr-Si alloys were investigated in water and steam to compare the corrosion mechanisms.

This study concerns a neutronic and transient thermal study of the first wall and blanket region of a typical controlled thermonuclear reactor (CTR). Previous studies assumed a neutron wall loading of 1 ~ 5 MW/m², and usually an infinite slab for a blanket region in calculating the transient thermal behavior following a major plasma disruption (MPD). Besides, neutrons with a kinetic energy of 14 MeV were usually assumed by ignoring the energy distribution of fusion neutrons. Furthermore, the cross-sections of the interaction between the incident neutron and the first wall were neglected by assuming that all these 14 MeV neutrons were absorbed by the first wall. This study made use of a more accurate model involving a canister design and considered both the incident neutron and secondary gamma heating in calculating the volumetric heat source rate. With these modifications, the average value of the volumetric heat source rate was calculated to be 0.05 MW/m³ ~ 0.5 MW /m³. The disruption times used in this analysis were assumed to be 24 ms and 10 ms. For each case, a constant velocity model and a Gaussian velocity model were assumed for the surface heat flux impinging on the first wall after an MPD with emphasis on the constant velocity model. Neutronic studies including a Diffusion Test Model (DTM), a 23-group cross-section library, and a 37-group neutron and 21-group gamma library from ORNL used in conjunction with the ANISN Code, provided different volumetric heat source rates which were used to do a thermal analysis for the blanket at the steady state. With these volumetric heat source rates obtained, a heat conduction code HEATING5 was run for the steady state temperature distribution. Results show that the average temperature for the first wall and the blanket are ~160°C and ~200°C, respectively. This steady state temperature distribution remained almost the same no matter whether DTM, 23G or 37N-21G cross-section sets were used, since the difference in the volumetric heat source rates generated were so small they did not change the temperature distribution significantly. With the steady state temperature distribution as an initial condition, HEATING5 was run again for the transient thermal study which included the surface heat flux due to the disruption, together with a volumetric heat source rate resulting from the eddy currents induced in the wall following an MPD. Results show that there is a possibility of melting portions of the first wall if the disruption time of 10 ms is used, while no melting is possible for the 24 ms case; however, a maximum transient temperature of ~1000°C on the first wall does occur. With respect to the temperatures in the blanket region, they remained the same as they were before an MPD. The transient took place so rapidly that the effects were mostly on the first wall. For the case of 24 ms, the average number of abortions allowed for failure of the first wall was 200 thermal cycles. / Ph. D.

In the first part of this work, instability is correctly predicted for a Rijke tube with a new two-term acoustic forcing term derived from a one-dimensional flame dynamics model. The new two-term acoustic forcing term, which is comprised of the summation of chemical heat release rate and heat transfer due to convection, correctly predicts instability where older models of acoustic forcing based solely on chemical heat release rate incorrectly predicted stability. This stability analysis correctly predicts the inlet conditions of the instability in addition to the frequency of instability. In the second part of this work, networks of dynamic well-stirred reactors are used to model qualitative behavior observed in turbulent combustion. First a model of dynamic well-stirred reactor is derived, and then several reactors are coupled together by recirculation. The dynamics of the various models are computed and assessed. The models exhibit interesting behavior that has been viewed experimentally including hysteresis and peaking in the dynamic response. / Master of Science

The selection of the form of spent nuclear fuel disposition, currently under debate, will precipitate an immediate requirement for spent-fuel transport regardless of the disposition alternative chosen. In this study, a constrained transportation model of the spent fuel cask scheduling problem is formulated with the objective of determining the minimum number of casks required to meet a fixed transport schedule. An iterative search procedure is employed to determine schedules which minimize cask idle time for each required spent fuel cask. The formulated model and the iterative search procedure are applied to a reference case to demonstrate their utility. An economic analysis of the results was performed to compare the truck and rail transport modes. Results indicate a substantial savings when rail transport is employed. An economic comparison of the cask lease and cask purchase options indicates that cask purchase is preferable for the 23-year planning horizon. / Master of Science

The purpose of this study is to determine the constituents of value in spent nuclear fuel and integrate these results into an economic time dependent model of a spent fuel assembly. The value of the constituents in the spent fuel is balanced against the cost of the various nuclear fuel cycle services. BWR and PWR-UO₂/MOX spent fuel assemblies are modeled at 5 different burnups. The recycle modes that are examined are uranium recycle with and without fission product sales and uranium and plutonium recycle with and without fission product sales. UO₂ and MOX spent fuel assemblies discharged from a nuclear reactor from 1977 to 1990 are modeled for a period of 19 years. Four key results of this study are: (1) a re-examination of the value of recycling materials other than uranium and plutonium, namely cesium-137, 134, rhodium, palladium and xenon is justified; (2) the magnitude of the net profits obtainable from the recycling of spent nuclear fuel are tied primarily to burnup and the decision to sell fission products; (3) for fission product recycle, any burnup yields a net positive value with the greater values being at high burnups; and (4) under only spent uranium and plutonium recycle, it is marginally profitable or unprofitable to recycle spent nuclear fuel. The utilization of cesium-137, 134 in the treatment of municipal sludge can reduce the importation of oil by 47.92 million U.S. barrels annually for the United States. / Master of Science

No / In this paper, a model of catalytic naphtha reforming process of commercial catalytic reforming unit of Kaduna Refining & Petrochemical Company (KRPC) is adopted and simulated using the gPROMS software, an equation-oriented modelling software. The kinetic and thermodynamic parameters and properties were obtained from literature. The model was used to monitor the behaviour of the temperature and concentrations of parafins, naphthenes and aromatics with respect to the changing heights of the reactors. A comprehensive sensitivity analysis of the product quality (Aromatics) and product yield, reformate, lighter gases and hydrogen yields is performed by varying the operating conditions of the reaction and the following conclusions were made. It was found that the production of aromatics, hydrogen yield, lighter gases and coke on catalyst increase with increasing temperature of the reaction while the reformate yield decreases with the increasing temperature and vice versa. The aromatics, hydrogen yield, coke on catalyst and lighter gases decrease with increasing pressure while the reformate yield decreases with decreasing pressure and vice versa. Hydrogen-hydrocarbon ratio (HHR) affects the product quality slightly by increasing the reformate and hydrogen yield and decreasing the aromatics slightly as well decreasing the coke on catalyst.

Yes / Polypropylene is one type of plastic that is widely used in our everyday life. This study focuses on the identification and justification of the optimum process parameters for polypropylene production in a novel pilot plant based fluidized bed reactor. This first-of-its-kind statistical modeling with experimental validation for the process parameters of polypropylene production was conducted by applying ANNOVA (Analysis of variance) method to Response Surface Methodology (RSM). Three important process variables i.e., reaction temperature, system pressure and hydrogen percentage were considered as the important input factors for the polypropylene production in the analysis performed. In order to examine the effect of process parameters and their interactions, the ANOVA method was utilized among a range of other statistical diagnostic tools such as the correlation between actual and predicted values, the residuals and predicted response, outlier t plot, 3D response surface and contour analysis plots. The statistical analysis showed that the proposed quadratic model had a good fit with the experimental results. At optimum conditions with temperature of 75 °C, system pressure of 25 bar and hydrogen percentage of 2%, the highest polypropylene production obtained is 5.82% per pass. Hence it is concluded that the developed experimental design and proposed model can be successfully employed with over a 95% confidence level for optimum polypropylene production in a fluidized bed catalytic reactor (FBCR).

Water pollution is one of many environmental problems that currently exists and inadequate treatment of industrial wastewater is contributing to further pollution. SpinChem AB's Rotating Bed Reactor (RBR) technology offers the possibility of water treatment by carrying out reactions between a solution and a solid phase. To move further in the field of large scale water treatment, SpinChem AB developed a prototype of a mobile reactor, i.e. a raft, carrying the RBR technology. The prototype proved that a mobile reactor can greatly reduce the process time for larger water volumes compared to a stationary RBR. The aim of this thesis is to develop the next version of the mobile reactor, with increased operational stability and autonomous driving (autopilot) as main goals. This work covers all parts in the development of the new mobile reactor which involves design, simulation, construction, electronics, software implementations and testing. The presented mobile reactor is a twin hull surface vehicle with the possibility of using two RBRs for water treatment. The steering is based on differential motor thrust and the autonomous driving was achieved using sensor data from a GPS, magnetometer and accelerometer, together with a proportional-integral-derivative (PID) type control system. The autopilot was put to the test on two different travel routes with a P and PI controller. The mobile reactor successfully followed the given routes, thus verifying that the developed mobile reactor can be used for future autonomous large scale water treatment.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-03-03T13:47:59Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) PDF - Jéssyca de Freitas Lima.pdf: 2404063 bytes, checksum: 1bc2b053016876aef2b6f46044945849 (MD5) / Made available in DSpace on 2016-03-03T13:47:59Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) PDF - Jéssyca de Freitas Lima.pdf: 2404063 bytes, checksum: 1bc2b053016876aef2b6f46044945849 (MD5) Previous issue date: 2015-02-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The process that occurs in anaerobic reactors called sulfetogênese is a process considered undesirable due to various problems he carries with the production of sulfides, causing: harsh odors, corrosion, toxicity and decreased concentrations of methane in the biogas. The present research aimed to develop processes to reduce the concentration of sulfides present in the effluent of anaerobic reactors in wastewater treatment. The experimental investigation was divided into two phases. In the first two Upflow Anaerobic reactors were used Sludge Blanket – UASB, one with low concentration of oxygen in the sludge blanket (UASB – O 2 ) and another with a UASB features without modification to be compared (UASB – control). In the second phase we used a Hybrid anaerobic reactor (RAH): composed of two overlapping UASB reactor ballasts at the bottom and an anaerobic filter at the top. When analyzing the results of the UASBs reactors, it was possible to identify that the addition of oxygen resulted in oxidation of the sulfide produced in the UASB reactor sulphate obtaining a final concentration in the effluent of 12.09± 3.22 mg S-SO 4 2 .L -1 -2 .L -1 and 2.54±1.92 mg S-S , inhibiting the stench and various problems related to the formation of sulfide on anaerobic reactors. The UASB – control, produced an effluent with a concentration of 13.20±8.65 mg S-S -2 .L -1 and 1.57±0.68 mg S-SO 4 -2 .L -1 by following the principles of an anaerobic reactor, when comparing with the other reactor. With the results obtained from the RAH was possible to assess that at the bottom (UASB) the sulfetogênese effectively occurred, reducing the sulfate contained in wastewater in sulphide and subsequently forming the hydrogen sulfide (H 2 S). At the top (filter) the oxidation of sulfide formed the elemental sulphur and sulphate, inhibiting so the stench of anaerobic reactors. / O processo que ocorre em reatores anaeróbios denominado de sulfetogênese é um processo considerado indesejável devido aos vários problemas que ele acarreta com a produção de sulfetos, causando: odores agressivos, corrosão, toxicidade e diminuição da concentração de metano no biogás. A presente pesquisa objetivou desenvolver processos para reduzir a concentração de sulfetos presente no efluente de reatores anaeróbios, no tratamento de águas residuárias. A investigação experimental foi dividida em duas fases. Na primeira foram utilizados dois reatores Upflow Anaerobic Sludge Blanket – UASB, um com baixa concentração de oxigênio na manta de lodo (UASB – O 2 ) e outro com características de um UASB sem modificações para serem comparados (UASB - Controle). Na segunda fase foi utilizado um Reator Anaeróbio Híbrido (RAH): composto por dois reatores sobrepostos, um reator UASB na parte inferior e um filtro anaeróbio na parte superior. Ao se analisar os resultados dos reatores UASBs, foi possível identificar que a adição de oxigênio resultou na oxidação do sulfeto produzido no reator UASB a sulfato obtendo uma concentração final no efluente de 12,09±3,22 mg S-SO 4 2- .L -1 e 2,54±1,92 mg S-S 2- .L -1 , inibindo o mau cheiro e diversos problemas relacionados com a formação de sulfeto em reatores anaeróbios. O UASB – Controle, produziu um efluente com uma concentração de 13,20±8,65 mg SS 2- .L -1 e 1,57±0,68 mg S-SO 4 2- .L -1 seguindo assim os princípios de um reator anaeróbio, ao comparar com o outro reator. Com os resultados obtidos do RAH foi possível avaliar que na parte inferior (UASB) a sulfetogênese ocorreu de forma efetiva, reduzindo o sulfato contido na água residuária a sulfeto e posteriormente formando o sulfeto de hidrogênio (H 2 S). Na parte superior (Filtro) ocorreu a oxidação do sulfeto formado à enxofre elementar e a sulfato, inibindo assim o mau cheiro de reatores anaeróbio.

Continuous flow reaction using micro-reactors is a valued technology due to its excellent mass and heat transfer performance, reduced reactor volume, handling capacity of hazardous reactions, and many other process intensifications. These intensifications opportunities interest the fine chemicals, pharmaceuticals producers and other multiphase reaction users who currently use batch processes or already use continuous flow. In this thesis, elements of passive and active mixing are investigated for the application of immiscible liquid-liquid systems. In the first study, the effects of geometrical arrangements of a residence time between mixing units on the interphase mass transfer rates are evaluated with four different immiscible liquid-liquid systems. A presentation of an algorithm for the optimal selection of a reactor and its operating conditions is given in order to enable easy and improved use of one’s micro-reactor. In the second study, the impact of a secondary pulse flow on interphase mass transfer is investigated. A coil without internal baffles is used as the oscillatory-flow coil reactor with a continuous active mixing source. The best application for the reactor is determined using a comparison to other complementary continuous flow platforms in the toolbox approach. The novel advancements presented here will help lead new molecular discoveries and connect the laboratory science scale to the process engineering production scale.