• Corrosion Science and Technology
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• v.13 no.2
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• pp.56-61
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• 2014

The purpose of this work is to investigate the effect of dissolved hydrogen concentration on crud deposition onto the fuel cladding surface in the simulated primary environments of a pressurized water reactor. Crud deposition tests were conducted in the dissolved hydrogen concentration range of 5~70 cc/kg at $325^{\circ}C$ for 14 days. Needle-shaped NiO deposits were formed in the hydrogen range of 5~25 cc/kg, while polygonal nickel ferrite deposits were observed at a hydrogen concentration above 35 cc/kg. However, the dissolved hydrogen content seems to have little effect on the amount of crud deposits.

• Journal of Microbiology and Biotechnology
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• v.24 no.11
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• pp.1542-1550
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• 2014

Co-digesting molasses wastewater and sewage sludge was evaluated for hydrogen production by response surface methodology (RSM). Batch experiments in accordance with various dilution ratios (40- to 5-fold) and waste mixing composition ratios (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100, on a volume basis) were conducted. Volatile solid (VS) concentration strongly affected the hydrogen production rate and yield compared with the waste mixing ratio. The specific hydrogen production rate was predicted to be optimal when the VS concentration ranged from 10 to 12 g/l at all the mixing ratios of molasses wastewater and sewage sludge. A hydrogen yield of over 50 ml $H_2/gVS_{removed}$ was obtained from mixed waste of 10% sewage sludge and 10 g/l VS (about 10-fold dilution ratio). The optimal chemical oxygen demand/total nitrogen ratio for co-digesting molasses wastewater and sewage sludge was between 250 and 300 with a hydrogen yield above 20 ml $H_2/gVS_{removed}$.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3286-3297
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• 2021

The released hydrogen can be ignited even with weak ignition sources. This emphasizes the importance of the hydrogen flammability evaluation to prevent catastrophic failure in hydrogen related facilities including a nuclear power plant. Historically numerous attempts have been made to determine the flammability limit of hydrogen mixtures including several diluents. However, no analytical model has been developed to accurately predict the limit concentration for mixtures containing radiating gases. In this study, the effect of H₂O and CO₂ on flammability limit was investigated through a numerical simulation of lean limit hydrogen flames. The previous flammability limit model was improved based on the mechanistic investigation, with which the amount of indirect radiation heat loss could be estimated by the optically thin approximation. As a result, the sharp increase in limit concentration by H₂O could be explained by high thermal diffusivity and radiation rate. Despite the high radiation rate, however, CO₂ with the lower thermal diffusivity than the threshold cannot produce a noticeable increase in heat loss and ultimately limit concentration. We concluded that the proposed mechanistic analysis successfully explained the experimental results even including radiating gases. The accuracy of the improved model was verified through several flammability experiments for H₂-air-diluent.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.2
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• pp.205-214
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• 2021

Currently, the interim storage pools of spent fuels in South Korea are expected to become saturated from 2024. It is required to prepare an operation plan of a domestic dry storage facility during a long-term period, with the researches on safety evaluation methods. This study modified the FRAPCON code to predict the spent fuel integrity evaluation such as the axial cladding temperature, the hoop stress and hydrogen distribution in dry storage. The cladding temperature in dry storage was calculated using the COBRA-SFS code with the burnup information which was calculated using the FRAPCON code. The hoop stress was calculated using the ideal gas equation with spent fuel information such as rod internal pressure. Numerical analysis method was used to calculate the degree of hydrogen diffusion according to the hydrogen concentration and temperature distribution during a dry storage period. Before 50 years of dry storage, the cladding temperature and hoop stress decreased rapidly. However, after 50 years, they decreased gradually and the cladding temperature was below 400 K. The initial temperature distribution and hydrogen concentration showed a parabolic line, but hydrogen was transferred by the hydrogen concentration and temperature gradient over time.

• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.425-428
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• 2012

This paper presents the fabrication and characterization of graphene based hydrogen sensors. Graphene was synthesized by annealing process of Ni/3C-SiC thin films. Graphene was transferred onto oxidized Si substrates for fabrication of chemiresistive type hydrogen sensors. Au electrode on the graphene shows ohmic contact and the resistance is changed with hydrogen concentration. Nanoparticle catalysts of Pd and Pt were decorated. Response factor and response (recovery) time of hydrogen sensors based on the graphene are improved with catalysts. The response factors of pure graphene, Pt and Pd doped graphenes are 0.28, 0.6 and 1.26, respectively, at 50 ppm hydrogen concentration.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.663-668
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• 1996

A two-dimensional continuum model for the prediction of the hydrogen mixing phenomena in the containment compartment under the severe accident conditions is developed. The model could predict well the distribution of time-dependent hydrogen concentration for selected HEDL Experiment. For a simulation of these experiments, the hydrogen is mixed uniform over the test compartment. To predict the extent of non-uniform distribution, the dominant factors such as the geometrical shape of obstacle and velocity of source injection in mixing phenomena are investigated. If the obstacle disturbing the flow of gas mixture exists in the compartment, the uniform distribution of hydrogen may be not guaranteed. The convective circulation of gas flow is separately formed up and down of the obstacle position, which makes a difference of hydrogen concentration between the upper and lower region of the compartment. The recirculation flow must have a considerable mass flow rate relative to velocity of the source injection to sustain the well-mixed conditions of hydrogen.

• KSBB Journal
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• v.6 no.4
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• pp.351-361
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• 1991

This study is on the investigation of hydrogen production and substrate removal by photosynthetic bacteria. After using of Rhodospillum rubrum KS-301 and IFO 3986, which are photosynthetic bacteria as strains, R. rubrum KS-301 was turned out a better strain. And result of experiment in which glucose and sodium lactate, components of wastewater, were used limiting substrates, showed that the productivity of hydrogen was indifferent with the kind of substrates. In batch experiments using free cells and immobilized whole cells, the decrease in hydrogen productivity was observed in the latter case. From the results of these experiments, specific growth rate of cells, specific utilization rate of glucose, and specific production rate of hydrogen were calculated. And each rate was expressed in the form of Monod equation of which parameters were estimated. Also the optimum condition of hydrogen production for free cells was $30^{\circ}C$, pH 7, and 12,000 Lux, and the optimum immobilized condition was as follows: initial immobilized cell concentration 1.0g/L, sodium alginate concentration 2% and light intensity 12,000 Lux.

• Journal of the Korean Institute of Gas
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• v.11 no.4
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• pp.41-46
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• 2007

The residential fuel cell system was modeled as a box-shaped chamber with vent openings, filled with various components such as reformer, desulfurizer, fuel cell stack and humidifier. When the vent openings are 1% of the total surface and hydrogen leakage 1%, hydrogen concentration is around 0.1% higher than the other regions from leak points in the chamber at 30 seconds and hydrogen concentration is increased from 0.3% to 0.7% in the upper region of the system after 200 seconds. When the vent openings are 1% of the total surface and hydrogen leakage 1%, 3%, 5%, the steady state result of CFD, 5% of hydrogen leakage is reached the lowest ignition limit in the system. When the vent openings are 2% of the total surface and hydrogen leakage 1%, hydrogen concentration is increased in the bottom of the system for 60 seconds. After 250 seconds, hydrogen concentration is reached the steady state in the system. As the vent opening of the total surface increased from 1% to 2%, averaged hydrogen mole fraction is under 1% in the system, however, upper regions of the system from the hydrogen leakage points are shown over 1% of hydrogen mole fraction.

• KSBB Journal
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• v.20 no.6
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• pp.447-452
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• 2005

The hydrogen production using immobilized cellsl was conducted using fruit wastewaters at various culture conditions. Three kinds of fruit wastewaters, melon, watermelon and pear were used. Sodium alginate was used as immobilization material. Among them, concentration of reducing sugar which was one of the main components in fruit was the highest at watermelon wastewater, and also hydrogen production was the highest as 2319.2 mL/L in it. Although hydrogen production was not much changed according to sodium alginate concentration, its production was the most at 3%(w/v). As bead size as small, hydrogen production was higher. With inspection of interior, it confirmed that the cell grew well in bead. But the addition of amino acids using as agent for metabolite production had almost no affected on hydrogen productivity. The effective range of $FeSO_4$ addition on hydrogen production were up to 1.2 g/L, and above the concentration, it inhibited the productivity. Organic acids produced during watermelon fermentation were mainly lactic acid, butyric acid, abd acetic acid; and a little of propionic acid.

• International Journal of Industrial Entomology and Biomaterials
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• v.38 no.1
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• pp.14-17
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• 2019

Oral gargling solution has been used for the control of halitosis. The purpose of this study was to compare the level of hydrogen sulphide concentration between silk oral gargling solution and commercially available oral gargling solution. Total 21 volunteers were included in this study. The relative level of hydrogen sulphide concentration was calculated to the baseline level. In terms of the primary endpoint of the trial, relative level of hydrogen sulphide concentration was $50.84{\pm}33.19%$ with silk group, versus $71.07{\pm}21.83%$ with Listerine group ($P_{non-inferiority}=0.003$). In conclusion, the results of oral gargling with a silk protein for healthy individual were non-inferior to oral gargling with Listerine for hydrogen sulphide concentration reduction.