Loss of offsite power (LOOP) accident analysis by integration of deterministic and probabilistic approaches in Bushehr-1 VVER-1000/V446 nuclear power plant

The results of an accident analysis for the loss of offsite power(LOOP)scenario in a reference Bushehr-1 VVER-1000/V446 nuclear power plant(NPP)are presented in this paper.This study attempted to provide a better analysis of LOOP accident management by integrating deterministic and probabilistic approaches.The RELAP5 code was used to investigate the occurrence of specific thermal–hydraulic phenomena.The probabilistic safety assessment of the LOOP accident is presented using the SAPHIRE software.LOOP accident data were extracted from the Bushehr NPP final safety analysis reports and probabilistic safety analysis reports.A deterministic approach was used to reduce the core damage frequency in the probabilistic analysis of LOOP accidents.The probabilistic approach was used to better observe the philosophy of defense in depth and safety margins in the deterministic analysis of the LOOP accident.The results show that the integration of the two approaches in LOOP accident investigations improved accident control.

Breaking Barriers:Selenium and Silicon-Mediated Strategies for Mitigating Abiotic Stress in Plants

Numerous plant species,particularly those that can accumulate selenium(Se)and silicon(Si),benefit from these essential micronutrients.Se and Si accumulation in plants profoundly affects several biochemical reactions in cells.Understanding how plants react to Se/Si enrichment is crucial for ensuring adequate dietary Se/Si intake for humans and animals and increasing plant tolerance to environmental stressors.Several studies have shown that Se/Si-enriched plants are more resistant to salinity,drought,extreme temperatures,UV radiation,and excess metalloids.The interplay between Se/Si in plants is crucial for maintaining growth and development under normal conditions while providing a critical defense mechanism against stressors like heavy metals and drought.Se and Si commonly stimulate antioxidant defense systems in plants exposed to environmental stressors,but the involved mechanisms are complex and not well understood.To ensure the positive effects of Se/Si fortification in plants,it is essential to consider the degree of accumulation,the chemical form of Se/Si used,the method of application,and the likelihood of interaction with other elements.In this review,we will discuss the effects of Se/Si bio-fortification on plants subjected to abiotic stressors.Plant responses to exogenous Se/Si will also be reviewed,emphasizing the influences of Se/Si in the modulation of enzymatic and non-enzymatic antioxidant defense mechanisms under various abiotic stress conditions.

Simulation of hydrogen distribution and effect of Engineering Safety Features (ESFs) on its mitigation in a WWER-1000 containment

In this study, thermal–hydraulic parameters inside the containment of aWWER-1000/v446 nuclear power plant are simulated in a double-ended cold leg accident for short and long times (by using CONTAIN 2.0 and MELCOR 1.8.6 codes), and the effect of the spray system as an engineering safety feature on parameters mitigation is analyzed with the former code. Along with the development of the accident from design basis accident to beyond design basis accident, the Zircaloy–steam reaction becomes the source of in-vessel hydrogen generation. Hydrogen distribution inside the containment is simulated for a long time (using CONTAIN and MELCOR), and the effect of recombiners on its mitigation is analyzed (using MELCOR). Thermal–hydraulic parameters and hydrogen distribution profiles are presented as the outcome of the investigation. By activating the spray system, the peak points of pressure and temperature occur in the short time and remain belowthe maximumdesign values along the accident time. It is also shown that recombiners have a reliable effect on reducing the hydrogen concentration below flame propagation limit in the accident localization area. The parameters predicted by CONTAIN and MELCOR are in good agreement with the final safety analysis report. The noted discrepancies are discussed and explained.

Effects of salt and nitrogen on physiological indices and carbon isotope discrimination of wheat cultivars in the northeast of Iran

In order to study the effects of different levels of salt stress and nitrogen(N) on physiological mechanisms,carbon isotope discrimination(△13C),and yield of two wheat cultivars(cv.),a two-year field experiment was carried out during 2013-2015.The treatments included three levels of salt stress(1.3,5.2,and 10.5 dS m^-1),three levels of N(50,100,and 150 kg N ha-1),and two wheat cultivars,Bam and Toos.Under salt stress,N application(100 and 150 kg N ha^-1) produced a significant effect on both cultivars with respect to physiological traits,i.e.,net photosynthetic rate(Pn),stomatal conductance(gs),chlorophyll index(Cl),Na^+/K^+ ratio as well as the grain yield(GY).The salt-tolerant and-sensitive cultivars exhibited the maximum values of physio-biochemical and yield attributes at 100 and 150 kg N ha-1,respectively.The results of △13C showed a significant difference(P<0.001) between wheat cultivars under the control and salt stress.According to our result,salt-tolerant cultivar Bam seems to be more efficient in terms of higher GY,Pn,gs,Cl,and lower Na^+/K^+ ratio as well as higher △13C as compared with salt-sensitive cultivar Toos,under salt stress.Therefore,a significant positive correlation that observed between △13C and GY,indicated that △13C may be an effective index for indirect selection of yield potential in wheat under irrigation regimes with saline water.

Neutronic design investigation of a liquid injection-based second shutdown system for a typical research reactor using MCNPX

Safety systems, built on state-of-the-art technology, are essential for achieving acceptable levels of plant safety to minimize hazards to the reactor and the general public. The second shutdown system(SSS) as an engineered safety feature and a part of the reactor protection system(RPS) is a means for rapidly shutting down a nuclear reactor, keeping it in a subcritical state and serving as a backup to the first shutdown system(FSS). In this research, one SSS with two types of optimum chamber designs is proposed that take into account the main current characteristic features of the Tehran research reactor with improvements over earlier designs. They are based on a liquid neutron absorber injection that is preferably different, diverse, and independent from the FSS based on the rod drop mechanism. The major design characteristics of this SSS with two different chambers were investigated using MCNPX 2.6.0 code. The performed calculations showed that the designed SSS is a reliable shutdown system, assuring an appropriate shutdown margin and injection time, with no significant effects on the effective delayed neutron fraction while causing minimal variations to the core structure. Further, the reasonable financial cost and the prolongation of the operation cycle are additional advantages of this design.

Calculation of photon attenuation coefficient and dose rate in concrete with the addition of SiO_2 and MnFe_2O_4 nanoparticles using MCNPX code and comparison with experimental results

One of the most important safety features of nuclear facilities is the shielding material used to protect the operating personnel from radiation exposure. The most common materials used in radiation shielding are concretes. In this study, a Monte Carlo N-Particle eXtended code is used to calculate the gamma-ray attenuation coefficients and dose rates for a new concrete material composed of MnFe_2O_4 nanoparticles, which is then compared with the theoretical and experimental results obtained for a SiO_2 nanoparticle concrete material. According to the results, the average relative differences between the simulations and the theoretical and experimental results for the linear attenuation coefficient(l) in the SiO_2 nanoparticle materials are 6.4% and 5.5%, respectively. By increasing the SiO_2 content up to 1.5% and the temperature of MnFe_2O_4 up to 673 K, l is increased for all energies. In addition, the photon dose rate decreases up to 9.2% and3.7% for MnFe_2O_4 and SiO_2 for gamma-ray energies of0.511 and 1.274 MeV, respectively. Therefore, it was concluded that the addition of SiO_2 and MnFe_2O_4 nanoparticles to concrete improves its nuclear properties and could lead to it being more useful in radiation shielding.

Preparation and biodistribution assessment of 68Ga-DKFZ-PSMA-617 for PET prostate cancer imaging

Prostate-specific membrane antigen(PSMA) is a useful target for diagnostic and therapeutic applications,and it is demonstrated that ^(68) Ga in conjugation with DKFZPSMA-617 is better than ^(68)Ga-PSMA-1 in biodistribution data after 1 h,but more preclinical data are still required.In this paper,we presented the additional preclinical data for ^(68)Ga-DKFZ-PSMA-617 and relevant aspects of its production.^(68) Ga was obtained from the SnO_2-based ^(68)Ge/ ^(68) Ga generator.Optimum conditions(p H,temperature,time and ligand concentration) for ^(68)Ga-DKFZPSMA-617 preparation were studied.Radiochemical purity of the radiolabeled compound was determined by HPLC and RTLC.After stability assessments,the complex was intravenously injected into rats.HPLC and ITLC characterizations indicated that the radiopharmaceutical could be prepared with radiochemical purity of [96 % and specific activity of 308.3 TBq/mmol at the optimized conditions(p H of 3.5–4,ligand amount of 2.4 nmol,temperature of90–95 C and reaction time of 10 min).Also,the biodistribution data showed no undesirable uptake in nontarget organs at any interval after injection.In fact,the activity is cleaned from blood and excreted rapidly via the kidneys.Generally,this compound can be considered as a wellestablished PET imaging agent.

Strongly Anchoring Polysulfides by Hierarchical Fe3O4/C3N4 Nanostructures for Advanced Lithium-Sulfur Batteries

Li-S batteries have attracted considerable interest as nextgeneration energy storage devices owing to high energy density and the natural abundance of sulfur.However,the practical applications of Li-S batteries are hampered by the shuttle effect of soluble lithium polysulfides(LPS),which results in low cycle stability.Herein,a functional interlayer has been developed to efficiently regulate the LPS and enhance the sulfur utilization using hierarchical nanostructure of C3 N4(t-C3 N4)embedded with Fe304 nanospheres.t-C3 N4 exhibits high surface area and strong anchoring of LPS,and the Fe3 O4/t-C3 N4 accelerates the anchoring of LPS and improves the electronic pathways.The combination of these materials leads to remarkable battery performance with 400%improvement in a specific capacity and a low capacity decay per cycle of 0.02%at 2 C over 1000 cycles,and stable cycling at 6.4 mg cm-2 for high-sulfur-loading cathode.

Gamma-ray shielding study of light to heavyweight concretes using MCNP-4C code

In this work, linear and mass attenuation coefficients, half and tenth-value layers, effective atomic number and electron density of different types of concretes were determined at 316.51, 468.07, 511, 662, 1173 and 1332 keV using MCNP-4C code and Win XCom programs. The MCNP-4C and Win XCom results agreed well with each other, with differences of \±1.9%. The results agreed with available experimental data, too, with differences of \±6%.The MCNP-4C results showed better agreement with the experimental data than the Win XCom results. Also, it was found that the effective electron density of studied concretes varies in the range of(2.83–3.2) 9 10^(23)electron/g.

Dose evaluation of therapeutic radiolabeled bleomycin complexes based on biodistribution data in wild-type rats:Effect of radionuclides in absorbed dose of different organs

Bleomycins(BLMs), as tumor-seeking antibiotics, have been used for over 20 years in treatment of several types of cancers. Several radioisotopes are used in radiolabeling of BLMs for therapeutic and diagnostic purposes. An important points in developing new radiopharmaceuticals, especially therapeutic agents, is the absorbed dose delivered in critical organs. In this work, absorbed dose to organs after injection of ^(153)Sm-,^(177)Lu- and ^(166)Ho-labeled BLM was investigated by radiation dose assessment resource(RADAR) method based on biodistribution data in wild-type rats. The absorbed dose effect of the radionuclides was evaluated. The maximum absorbed dose for the complexes was observed in the kidneys, liver and lungs. For all the radiolabeled BLMs,bone and red marrow received considerable absorbed dose. Due to the high energy beta particles emitted by ^(166)Ho, higher absorbed dose is observed for ^(166)Ho-BLM in the most organs. The reported data can be useful for the determination of the maximum permissible injected activity of the radiolabeled BLMs in the treatment planning programs.

Seismic hazard assessment of Tehran,Iran with emphasis on near-fault rupture directivity effects

Many destructive earthquakes happened in Tehran, Iran in the last centuries. The existence of active faults like the North Tehran is the main cause of seismicity in this city. According to past investigations, it is estimated that in the scenario of activation of the North Tehran fault, many structures in Tehran will collapse. Therefore, it is necessary to incorporate the near field rupture directivity effects of this fault into the seismic hazard assessment of important sites in Tehran. In this study, using calculations coded in MATLAB, Probabilistic Seismic Hazard Analysis （PSHA） is conducted for an important site in Tehran. Following that, deaggregation technique is performed on PSHA and the contribution of seis- mic scenarios to hazard is obtained in the range of distance and magnitude. After identifying the North Tehran fault as the most hazardous source affecting the site in 10000-year return period, rupture directivity effects of this fault is incorporated into the seismic hazard assessment using Somerville et al. （1997） model with broadband approach and Shahi and Baker （2011） model with narrowband approach. The results show that the narrowband approach caused a 27% increase in the peak of response spectrum in 10000-year return period compared with the conventional PSHA. Therefore, it is necessary to incorporate the near fault rupture directivity effects into the higher levels of seismic hazard assessment attributed to important sites.

A Novel High Performance of GaN-Based HEMT with Two Channel Layers of GaN/InAlGaN

The potential impact of GaN-based high electron mobility transistor (HEMT) with two channel layers of GaN/InAlGaN is reported. Using two-dimensional and two-carrier device simulations, we investigate the device performance focusing on the electrical potential, electron concentration, breakdown voltage and transconductance (gm). Also, the results have been compared with structure of AlGaN/GaN HEMT. Our simulation results reveal that the proposed structure increases electron concentration, breakdown voltage and transconductance;and reduces the leakage current. Also, the mole fraction of aluminum in the InAlGaN has been optimized to create the best performing device.

A High Efficiency Ultrathin CdTe Solar Cell for Nano-Area Applications

Due to limited availability and the rising price of telluride, the biggest challenge in solar Photo-voltaic (PV) is to successfully design and fabricate optimized CdTe solar cells with reducing the cell thickness that show simultaneously high efficiency and current density. A novel structure of ultrathin CdTe solar cells is proposed in this paper that focuses on conversion efficiency. This structure achieved by rotating 90o in the base line structure that suggests high efficiency due to the high current density. The result showed a considerable improvement over the 15% efficiency of the reference solar cell. The proposed structure is quite noteworthy in reducing the amount of material used and associated losses. Under global air mass (AM) 1.5 conditions, an open-circuit voltage (Voc) of 866 mV, a short-circuit current density (Jsc) of 74.84 mA/cm2, and a fill factor (FF) of 48.2% were obtained corresponding to a conversion efficiency of 31.2%.

Strengthening of polysulfone membranes using hybrid mixtures of micro- and nano-scale modifiers

Polysulfone （PSf） membranes were modified by either a new organic modifier （sulfonated poly（ether sulfide sulfone）, SPESS） or a traditional modifier （rice hulk）. These membranes were further reinforced with either multi-walled carbon nanotubes （MWCNTs） or silica nanoparticles. Having a dye rejection of 98.46%, the reinforced membranes increased more than 50% in strength but no change in solution flux was observed. The morphological and roughness studies were conducted using scanning electron microscopy and atomic force microscopy. Moreover, the PSF membranes were also characterized by differential scanning calorimetry. Modifying the membranes with organic modifier or nanofiller increases the glass transition temperature （Tg）. The highest Tg and strength were observed for the PSf-SPESS- MWCNT membrane. SPESS decreases surface roughness but MWCNT increases roughness on the nanoscale. All membranes show a bimodal pore size distribution, whereas the PSf-SPESS-MWCNT membrane exhibits a relatively uniform distribution of macroscopic and microscopic pores.

Nitrapyrin effectiveness in reducing nitrous oxide emissions decreases at low doses of urea in an Andosol

In the tropics,frequent nitrogen(N)fertilization of grazing areas can potentially increase nitrous oxide(N_(2)O)emissions.The application of nitrification inhibitors has been reported as an effective management practice for potentially reducing N loss from the soil-plant system and improving N use efficiency(NUE).The aim of this study was to determine the effect of the co-application of nitrapyrin(a nitrification inhibitor,NI)and urea in a tropical Andosol on the behavior of N and the emissions of N_(2)O from autotrophic and heterotrophic nitrification.A greenhouse experiment was performed using a soil(pH 5.9,organic matter content 78 g kg^(-1),and N 5.6 g kg^(-1))sown with Cynodon nlemfuensis at 60%water-filled pore space to quantify total N_(2)O emissions,N_(2)O derived from fertilizer,soil ammonium(NH_(4)^(+))and nitrate(NO_(3)^(-)),and NUE.The study included treatments that received deionized water only(control,NI).No significant differences were observed in soil NH_(4)^(+)content between the UR and UR+NI treatments,probably because of soil mineralization and NO_(3)^(-)produced by heterotrophic nitrification,which is not effectively inhibited by nitrapyrin.After 56 d,N_(2)O emissions in UR(0.51±0.12 mg N_(2)O-N concluded that the soil organic N mineralization and heterotrophic nitrification are the main processes of NH_(4)^(+)and NO_(3)^(-)production.Additionally,it was found that N_(2)O emissions were partially a consequence of the direct oxidation of the soil's organic N via heterotrophic nitrification coupled to denitrification.Finally,the results suggest that nitrapyrin would likely exert significant mitigation on N_(2)O emissions only if a substantial N surplus exists in soils with high organic matter content.

Nitrification inhibitor nitrapyrin does not affect yield-scaled nitrous oxide emissions in a tropical grassland

Urea is the most common nitrogen(N)fertilizer used in the tropics but it has the risk of high gaseous nitrogen(N)losses.Use of nitrification inhibitor has been suggested as a potential mitigation measure for gaseous N losses in N fertilizer-applied fields.In a field trial on a tropical Andosol pastureland in Costa Rica,gaseous emissions of ammonia(NH_(3))and nitrous oxide(N_(2)O)and grass yield were quantified from plots treated with urea(U;41.7 kg N ha^(-1)application^(-1))and urea plus the nitrification inhibitor nitrapyrin(U+NI;41.7 kg N ha^(-1)application^(-1)and 350 g of nitrapyrin for each 100 kg of N applied)and control plots(without U and NI)over a six-month period(rainy season).Volatilization of NH_(3)(August to November)in U(7.4%±1.3%of N applied)and U+NI(8.1%±0.9%of N applied)were not significantly different(P>0.05).Emissions of N_(2)O in U and U+NI from June to November were significantly different(P<0.05)only in October,when N_(2)O emission in U+NI was higher than that in U.Yield and crude protein production of grass were significantly higher(P<0.05)in U and U+NI than in the control plots,but they were not significantly different between U and U+NI.There was no significant difference in yield-scaled N_(2)O emission between U(0.31±0.10 g N kg^(-1)dry matter)and U+NI(0.47±0.10 g N kg^(-1)dry matter).The results suggest that nitrapyrin is not a viable mitigation option for gaseous N losses under typical N fertilizer application practices of pasturelands at the study site.

Combination of a gamma radiation-based system and the adaptive network-based fuzzy inference system(ANFIS)for calculating the volume fraction in stratified regime of a three-phase flow

Background Understanding the volume fraction of water-oil-gas three-phase flow is of significant importance in oil and gas industry.Purpose The current research attempts to indicate the ability of adaptive network-based fuzzy inference system(ANFIS)to forecast the volume fractions in a water-oil-gas three-phase flow system.Method The current investigation devotes to measure the volume fractions in the stratified three-phase flow,on the basis of a dual-energy metering system consisting of the 152Eu and 137Cs and one NaI detector using ANFIS.The summation of volume fractions is equal to 100%and is also a constant,and this is enough for the ANFIS just to forecast two volume fractions.In the paper,three ANFIS models are employed.The first network is applied to forecast the oil and water volume fractions.The next to forecast the water and gas volume fractions,and the last to forecast the gas and oil volume fractions.For the next step,ANFIS networks are trained based on numerical simulation data from MCNP-X code.Results The accuracy of the nets is evaluated through the calculation of average testing error.The average errors are then compared.The model in which predictions has the most consistency with the numerical simulation results is selected as the most accurate predictor model.Based on the results,the best ANFIS net forecasts the water and gas volume fractions with the mean error of less than 0.8%.Conclusion The proposed methodology indicates that ANFIS can precisely forecast the volume fractions in a water-oil-gas three-phase flow system.