Reactor Operation Period Research Articles

A coupled faradaic/electrostatic boosting strategy for decolorization of a refractory dye inside a dually-biased photoelectrochemical reactor: Time and energy saving

A green sustainable strategy for environmental remediation and treatment of dye-polluted water is the application/development of effective photoelectrochemical (PEC) reactors. Despite some recent progress in PEC systems, achieving a complete decolorization is still a challenging issue and often requires a long period of reactor operation. Herein, the authors address this interesting time/energy-related problem, demonstrating how without consuming extra electricity/chemicals, fabricating complex photoelectrodes, or changing the pH of medium, one can effortlessly promote the activity of a PEC reactor just by its coupling to a non-faradaic bias source. By applying this novel dually biased (faradaic/electrostatic) boosting strategy, we reveal that decolorization of methyl orange (a refractory dye pollutant) is significantly improved and the decolorization time (thereby energy consumption) is reduced by almost half in comparison to that of a conventional PEC reactor–operating under a single-bias (faradaic) condition. The reactor activity and its photoelectrochemical response are finally discussed in detail in terms of applied potential biases, semiconductor's band bending, open-circuit-potential displacement, electrostatic interaction and electrosorption of dye pollutant.

T production using a high-temperature gas-cooled reactor for the DEMO fusion reactor: Li rod structure for the initial irradiation test

This work proposes tritium (T) production using a high-temperature gas-cooled reactor (HTGR) and studies it for the initial T inventory in a demonstration fusion reactor and a prior engineering test with T handling. At this stage, the aim is to investigate the compatibility between electricity and T production, which makes the stable confinement of T in the Li-loading rods during the HTGR operation period a crucial issue. The total T outflow into the helium gas during the reactor operation period was attempted to be reduced using Zr spheres with Ni coating as a T absorption material to avoid an increase in the inner T pressure. The basic hydrogen absorption properties of the Zr spheres with Ni coating, which coexist in an environment with Al2O3 and/or LiAlO2 oxides, were measured. The structures of the Li-loading rod for a typical commercial HTGR and irradiation test were studied using the obtained data. In addition, an outline of the irradiation test is reported.

Biogas upgrading in a pilot-scale trickle bed reactor – Long-term biological methanation under real application conditions

The biological methanation of H2 and CO2 in trickle bed reactors is one promising energy conversion technology for energy storage, but experiences at pilot-scale under real application conditions are still rare. Therefore, a trickle bed reactor with a reaction volume of 0.8 m3 was constructed and installed in a wastewater treatment plant to upgrade raw biogas from the local digester. The biogas H2S concentration of about200 ppm was reduced by half, but an artificial sulfur source was required to completely satisfy the sulfur demand of the methanogens. Increasing the ammonium concentration to > 400 mg/L was the most successful pH control strategy, enabling stable long-term biogas upgrading at a CH4 production of 6.1 m3/(m3RV·d) with synthetic natural gas quality (CH4 > 98%). The results of this study with a reactor operation period of nearly 450 days, including two shutdowns, represents an important step towards the necessary full-scale integration.

Investigating the in-core 60Co production assembly for open pool type reactor

Abstract Production of high specific 60Co activity in nuclear research reactor needs long time of irradiation to reach the proper consumer demands. Cobalt device is a fixed experiment inside the core of the second research reactor (ETRR-2) that designed for production of 60Co with activity of 50,000 Ci. Cobalt device is assembly of 16 pins of aluminum cans that filling with the cobalt foils. Utilizing the programs that depend on the Monte Carlo method to estimate 60Co activity is the objective of this study. MCNP6, KENO-VI, and MAVRIC codes would be used to evaluate the time that the cobalt device has been spent inside the reactor core for reaching the proper 60Co activity considering the continuous irradiation as well as the discrete irradiation. The calculations show that nearly one year of continuous neutron irradiation is sufficient for reaching the required activity. In case of discrete irradiation, the time required for reaching the required activity would be more than a year depending on the reactor operation period.

Effect of Mixing Ratios in a Batch Reactor for Biological Hydrogen Production

This study was to evaluate the cause on the production of bio-hydrogen utilizing Distillery Spent Wash (DSW) and starch mixed wastewater in various mixing ratios under dark fermentation conditions with varying Hydraulic Retention Time in a batch reactor. The pH was kept constantly at 5.5 throughout the study. Thus the hydrogen production investigated in the batch reactor for following Hydraulic Retention Time 24h, 16h, 12h and 8h, the results revealed an extended and steady period of reactor operation with hydrogen percent in the biogas and hinders the methane production. The perfect mixing ratios and Hydraulic Retention Time were seen to be 50:50 (DSW: Starch wastewater) and 16h to 12h HRT with contrasting cumulative hydrogen yields of 3256.5ml and 2674.3ml with specific maximum production of hydrogen rate 468ml/L/d as well as 236.64ml/L/d with the best biomass improvement combination of 4.7g/l and 4.5g/l. The maximum Chemical Oxygen Demand removal rates of 68 and 50 percentage for the optimum HRT of 16h and 12h.

Neutronic analysis of thorium MOX fuel blocks with different driver fuels in advanced block-type HTRs

The use of thorium-based fuels is an attractive option to achieve high burnup level and relatively longer reactor operation period. This also includes some other potential advantages, such as, low proliferation risk and high conversion ratio, etc. It is interesting to utilize thorium-based fuels in advanced high temperature reactors (AHTRs), because they are a better choice for their high burnup limit and inherently-safe HTRs with a low-pressure operation condition. The neutronic performance of thorium MOX fuel blocks, including infinite multiplication factor, conversion ratio, discharge burnup and the neutron spectra in AHTRs, has been investigated by the DRAGON V4 code for four different driver fuels, U-233, reactor-grade plutonium (RGrPu), weapon-grade plutonium (WGrPu) and weapon-grade uranium (WGrU). Based on a typical fuel block of AHTRs, the influence of varying heavy metal loading and effective enrichment on the neutronic performance of the four fuel blocks is firstly investigated. The heavy metal loading of 5 kg and effective enrichment of 12% are selected for the neutronic comparisons. The further comparisons of the four thorium fuels with different driver fuels show that the Th/RGrPu and Th/WGrPu fuel blocks have intermediate neutron spectra, while Th/U233 and Th/WGrU fuel blocks have thermal neutron spectra. The Th/U233 fuel achieves the highest infinite multiplication factor at beginning of life because of its high thermal η value. Th/RGrPu fuel achieves the highest conversion ratio and the highest discharge burnup.

Simultaneous catalytic reduction of N2O and NOx for tertiary N2O abatement technology: A field study in a nitric acid production plant

To investigate the feasibility of the simultaneous abatement of N2O and NOx in a single reactor, this field study was performed in a nitric acid production plant. An Fe/BEA powder catalyst prepared by Fe ion‐exchange with steam‐treated BEA zeolite was extruded in pellets and honeycombs. In the simultaneous reduction of N2O and NOx, the pellet‐ and honeycomb‐type catalysts showed more than a 90% and 95% conversion of N2O and NOx, respectively, at a reaction temperature between 350 °C and 380 °C which is typical for the DeNOx process. The catalytic performance of the pellets and honeycombs was also stable during the reactor operation period. With higher N2O and NOx conversions of over 90%, NH3 concentration in exhaust gas streams can be reduced to satisfy domestic regulations for air pollutant emissions. Accordingly, it is suggested that the simultaneous reduction of N2O and NOx in a single reactor with the Fe/BEA catalyst may be a reasonable option for a tertiary abatement technology for nitric acid production plants.Novelty or Significance: The simultaneous catalytic reduction of N2O and NOx in a tail gas from a nitric acid production plant was investigated with Fe/BEA catalysts prepared by Fe ion‐exchange with steam‐treated BEA zeolite. Pellet‐ and honeycomb‐type catalysts were applied to abatement using NH3 as the reducing agent. Over 90% of N2O and NOx from the nitric acid production process was simultaneously removed from a single reactor at a reaction temperature between 350 °C and 380 °C. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 451–456, 2019

Impact of High-Nitrogen Leachate on Microfauna of Aerobic Granular Sludge.

The microfauna communities present in aerobic granular sludge reactors (e.g., granule sludge batch reactor or GSBR) that are used to treat landfill leachate were studied to determine which taxons are useful as process performance indicators. Communities were analyzed during four periods: a stable reactor operation period at a temperature of 29 °C, a transitional period of biomass adaptation at a temperature of 25 °C, an additional period of stable reactor operation at 25 °C, and at 25 °C after a period of lowered dissolved oxygen concentration. The results indicate that Vorticella infusionum and telotrochs were the taxons most sensitive to environmental changes in the GSBR, showing potential as biological indicators of ammonium overload and process destabilisation. Other taxons had similar abundance, despite changing environmental conditions in the bioreactor.

Development of Technology for Detachment of Calandria Tube Rolled Joint of Pressurised Heavy Water Reactors

Coolant channel assembly of PHWRs consisting mainly of pressure tube and calandria tube undergoes sag due to irradiation enhanced creep during its life time. Typical service life of the pressure tube is limited to about 15 full power years due to such ageing related degradation. On account of the degradation the pressure tube needs replacement more than twice during the licensed period of reactor operation. As the sag in the calandria tube is also excessive, it has to be replaced to facilitate installation of new and straight pressure tube during retubing and to avoid interference of sagged calandria tube with horizontal reactivity devices. The calandria tube and the tube sheet are joined by sandwich type rolled joints. For detaching the joint an improved technique has been developed that helps to detach the joint without affecting the groove geometry and integrity of the tube sheet. The system works on the principle of fast thermal cycle of heating and cooling of the insert and calandria tube in the rolled joint region while applying axial load to the calandria tube. Though rolled joint detachment by induction heating technique has been in use in CANDU reactors for removal of pressure tubes and calandria tubes, the present design incorporates a liquid nitrogen for faster cooling and simultaneous application of load with a gripping module for detachment and removal of calandria tube and the insert from the tube sheet of end shield in shorter time. This paper describes the methodology of rolled joint detachment, challenges involved in the design, features of the detachment system, findings of experimental trials and observations.

Thorium Fuel Utilization Analysis on Small Long Life Reactor for Different Coolant Types

A small power reactor and long operation which can be deployed for less population and remote area has been proposed by the IAEA as a small and medium reactor (SMR) program. Beside uranium utilization, it can be used also thorium fuel resources for SMR as a part of optimalization of nuclear fuel as a “partner” fuel with uranium fuel. A small long-life reactor based on thorium fuel cycle for several reactor coolant types and several power output has been evaluated in the present study for 10 years period of reactor operation. Several key parameters are used to evaluate its effect to the reactor performances such as reactor criticality, excess reactivity, reactor burnup achievement and power density profile. Water-cooled types give higher criticality than liquid metal coolants. Liquid metal coolant for fast reactor system gives less criticality especially at beginning of cycle (BOC), which shows liquid metal coolant system obtains almost stable criticality condition. Liquid metal coolants are relatively less excess reactivity to maintain longer reactor operation than water coolants. In addition, liquid metal coolant gives higher achievable burnup than water coolant types as well as higher power density for liquid metal coolants.

Evaluation of isotopic composition of fast reactor core in closed nuclear fuel cycle

The strategy of the development of nuclear power in Russia provides for use of fast power reactors in closed nuclear fuel cycle. The PRORYV (i.e. «Breakthrough» in Russian) project is currently under development. Within the framework of this project, fast reactors BN-1200 and BREST-OD-300 should be built to, inter alia, demonstrate possibility of the closed nuclear fuel cycle technologies with plutonium as a main source of energy. Russia has a large inventory of plutonium which was accumulated in the result of reprocessing of spent fuel of thermal power reactors and conversion of nuclear weapons. This kind of plutonium will be used for development of initial fuel assemblies for fast reactors. The closed nuclear fuel cycle concept of the PRORYV assumes self-supplied mode of operation with fuel regeneration by neutron capture reaction in non-enriched uranium, which is used as a raw material. Operating modes of reactors and its characteristics should be chosen so as to provide the self-sufficient mode by using of fissile isotopes while refueling by depleted uranium and to support this state during the entire period of reactor operation. Thus, the actual issue is modeling fuel handling processes. To solve these problems, the code REPRORYV (Recycle for PRORYV) has been developed. It simulates nuclide streams in non-reactor stages of the closed fuel cycle. At the same time various verified codes can be used to evaluate in-core characteristics of a reactor. By using this approach various options for nuclide streams and assess the impact of different plutonium content in the fuel, fuel processing conditions, losses during fuel processing, as well as the impact of initial uncertainties on neutron-physical characteristics of reactor are considered in this study.

Tritium permeation behavior through pyrolytic carbon in tritium production using high-temperature gas-cooled reactor for fusion reactors

Under tritium production method using a high-temperature gas-cooled reactor loaded Li compound, Li compound has to be coated by ceramic materials in order to suppress the spreading of tritium to the whole reactor. Pyrolytic carbon (PyC) is a candidate of the coating material because of its high resistance for gas permeation. In this study, hydrogen permeation experiments using a PyC-coated isotropic graphite tube were conducted and hydrogen diffusivity, solubility and permeability were evaluated. Tritium permeation behavior through PyC-coated Li compound particles was simulated by using obtained data. Hydrogen permeation flux through PyC in a steady state is proportional to the hydrogen pressure and is larger than that through Al2O3 which is also candidate coating material. However, total tritium leak within the supposed reactor operation period through the PyC-coated Li compound particles is lower than that through the Al2O3-coated ones because the hydrogen absorption capacity in PyC is considerably larger than that in Al2O3.

Effects of Al2O3 nanoparticles deposition on critical heat flux of R-123 in flow boiling heat transfer

Abstract In this study, R-123 flow boiling experiments were carried out to investigate the effects of nanoparticle deposition on heater surfaces on flow critical heat flux (CHF) and boiling heat transfer. It is known that CHF enhancement by nanoparticles results from porous structures that are very similar to layers of Chalk River unidentified deposit formed on nuclear fuel rod surfaces during the reactor operation period. Although previous studies have investigated the surface effects through surface modifications, most studies are limited to pool boiling conditions, and therefore, the effects of porous surfaces on flow boiling heat transfer are still unclear. In addition, there have been only few reports on suppression of wetting for decoupled approaches of reasoning. In this study, bare and Al 2 O 3 nanoparticle-coated surfaces were prepared for the study experiments. The CHF of each surface was measured with different mass fluxes of 1,600 kg/m 2 s, 1,800 kg/m 2 s, 2,100 kg/m 2 s, 2,400 kg/m 2 s, and 2,600 kg/m 2 s. The nanoparticle-coated tube showed CHF enhancement up to 17% at a mass flux of 2,400 kg/m 2 s compared with the bare tube. The factors for CHF enhancement are related to the enhanced rewetting process derived from capillary action through porous structures built-up by nanoparticles while suppressing relative wettability effects between two sample surfaces as a highly wettable R-123 refrigerant was used as a working fluid.

Direct, rapid and sustainable vermicomposting of the leaf litter of neem (Azadirachta indica).

The recently developed concept of high rate vermicomposting was successfully used to enable direct vermicomoposting of neem leaves-without any pre-composting or cow dung supplementation as previously reported processes had necessitated. All the three epigeic species of earthworms that were explored, Eudrilus eugeniae, Eisenia fetida and Perionyx excavatus, provided efficient vermicast production with no mortality, persistent gain in body mass and good fecundity over the 16 months long period of reactor operation. In this period, all reactors were pulse-fed at the solid retention time of 20 days and were operated in the pseudo discretized continuous operation protocol developed earlier by the authors. With this, it was possible to almost completely dampen the influence of natural biodegradation of the feed or grazing by the earthworm born in the vermireactors. The findings, thus, conclusively prove that, all-through, the brisk vermicomposting was caused almost entirely by the action of the 'parent' earthworms on fresh feed.

THE INVESTIGATION OF BURNUP CHARACTERISTICS USING THE SERPENT MONTE CARLO CODE FOR A SODIUM COOLED FAST REACTOR

In this research, we investigated the burnup characteristics and the conversion of fertile 232Th into fissile 233U in the core of a Sodium-Cooled Fast Reactor (SFR). The SFR fuel assemblies were designed for burning 232Th fuel (fuel pin 1) and 233U fuel (fuel pin 2) and include mixed minor actinide compositions. Monte Carlo simulations were performed using Serpent Code1.1.19 to compare with CRAM (Chebyshev Rational Approximation Method) and TTA (Transmutation Trajectory Analysis) method in the burnup calculation mode. The total heating power generated in the system was assumed to be 2000 MWth. During the reactor operation period of 600 days, the effective multiplication factor (keff) was between 0.964 and 0.954 and peaking factor is 1.88867.

Burnup calculations using serpent code in accelerator driven thorium reactors

Abstract In this study, burnup calculations have been performed for a sodium cooled Accelerator Driven Thorium Reactor (ADTR) using the Serpent 1.1.16 Monte Carlo code. The ADTR has been designed for burning minor actinides, mixed 232Th and mixed 233U fuels. A solid Pb-Bi spallation target in the center of the core is used and sodium as coolant. The system is designed for a heating power of 2000 MW and for an operation time of 600 days. For burnup calculations the Advanced Matrix Exponential Method CRAM (Chebyshev Rational Approximation Method) and different nuclear data libraries (ENDF7, JEF2.2, JEFF3.1.1) were used. The effective multiplication factor change from 0.93 to 0.97 for different nuclear data libraries during the reactor operation period.

Simultaneous removal of phenol and nitrate in an anoxic fluidized bed reactor

The general purpose of this study was to characterize a biological treatment system for phenol removal in an anoxic fluidized bed reactor (AFBR) that employed nitrate as the final electron acceptor. The average influent phenol concentrations in the study were 52, 107, 201, 335, and 518 mg/L so that phenol was not detected in the effluent for influent concentrations up to 335 mg/L. The removal efficiency dropped to 70% when the AFBR was operated with influent phenol concentrations above 500 mg/L. The ratio of carbon (derived solely from phenol) to nitrate (N-NO3) was approximately 1. Hence, the average influent N-NO3 concentrations in the study were 45, 79, 157, 260, and 362 mg/L, with corresponding nitrogen removal efficiencies of 94%, 89%, 86%, 79%, and 51%. Nitrite accumulation was not observed because the average effluent N-NO3 concentration during the entire reactor operation period was 1.5 mg/L.

Novel FGBAC reactor for controlling the leakage of microfauna in drinking water treatment

In order to reduce the microfauna leakage risk from a granular biological activated carbon (GBAC) reactor which employs granular activated carbon (GAC) as adsorption media in drinking water advanced treatment, a novel fiber and granular biological activated carbon (FGBAC) reactor which employs both GAC and activated carbon fiber (ACF) as adsorption media, was developed. The results showed that the species composition of microfauna leaking from FGBAC reactor is almost similar to that leaking from GBAC reactor, however the densities of microfauna leaking from FGBAC reactor is reduced by 26%–81% compared to those leaking from GBAC reactor. In addition, compared to GBAC reactor, FGBAC reactor can increase the removal efficiencies of chemical oxygen demand (COD) and turbidity by 7% and 10%, respectively, during the stable operation period of reactor.

Linking Community Profiles, Gene Expression and N-Removal in Anammox Bioreactors Treating Municipal Anaerobic Digestion Reject Water

Anaerobic ammonium oxidation (anammox) requires 60% less oxygen and no external organic carbon compared to conventional biological nitrogen removal (BNR). Nevertheless, full-scale installations of anammox are uncommon, primarily owing to the lack of well-established process monitoring and control strategies that result in stable anammox reactor performance. The overarching goal of this study was to develop and apply molecular biomarkers that link microbial community structure and activity to anammox process performance in a bioreactor fed with actual anaerobic digestion centrate from a full-scale operational wastewater treatment facility. Over long-term operation, Candidatus "Brocadia sp. 40" emerged as the dominant anammox population present in the reactor. There was good correspondence between reactor nitrogen removal performance and anammox bacterial concentrations. During the period of reactor operation, there was also a marked shift in biomass morphology from discrete cells to granular aggregates, which was paralleled by a shift also to more stable nitrogen removal and the succession and establishment of bacteria related to the Chlorobi/Bacteroidetes superfamily. Based on batch assays, hydrazine oxidoreductase (hzo) expression and concentrations of the 16S-23S rRNA intergenic spacer region (ISR) were good quantitative biomarkers of oxygen- and nitrite-mediated inhibition. When applied to a continuous anammox reactor, both molecular biomarkers show promise as monitoring tools for "predicting" reactor performance.

Using recurrent neural networks for estimation of minor actinides’ transmutation in a high power density fusion reactor

In this paper, recurrent neural networks (RNNs) were presented for the computation of minor actinides’ transmutation with reactor’s operation period. The results of the RNNs implemented for the computation of the change in the atomic density of minor actinides ( 237Np, 241Am, 242Cm, 238Pu, 239Pu) and the results available in the literature obtained by using Scale 4.3 ( Übeyli, 2004) were compared. The results brought out that the proposed RNNs could provide an accurate computation of the atomic densities of minor actinides of the hybrid reactor with respect to operation period of reactor.