Hydrogen produces no harmful by-products upon combustion, but it is highly flammable gas over a concentration of 4%2in the air. In order to use hydrogen gas safely, therefore, the hydrogen safety sensor is required wherever using the hydrogen gas. Conventionally, Palladium (I'd) metal has long been used for the safety sensors because of its high hydrogen sensitivity and selectivity to other gases. In this study, we demonstrated the hydrogen sensing using I'd nanowire array as a proto-type sensor. Especially we focused on fabricating a proto-type hydrogen safety sensor and evaluating the sensing performance of the sensor.

In France, the steel transportation network for natural gas is connected to the distribution network which operates at lower pressure. This one (total length of 165 000 km) is mainly made of polymer pipes like polyethylene. With the introduction of hydrogen in mixture with natural gas and finally the transport of pure hydrogen, the key challenge is the high level of permeability that is to say the flow rate of hydrogen through polymer infrastructures (pipes or components like connecting parts). This high flow rate of hydrogen has to be taken into account for safety and economic requirements. Long-term behaviour must be carefully assessed: permeation/diffusion properties, thermo-mechanical behaviour and ageing. It is important to characterize the existing distribution network and to propose more innovative materials than polyethylene that could meet the targets for future hydrogen distribution applications. The aim of this project was to develop and assess material solutions to cope with today problems in term of high flow rate of hydrogen and ageing under a hydrogen environment. Polyethylene is considered as a reference material since it is used today in natural gas distribution pipes. Test benches and protocols for testing materials in term of mechanical and barrier properties were first developed. On the other hand, technical polymers (multi-layers, other thermoplastics, polymer blends...) have been proposed and studied to improve gas-barrier performances compared to polyethylene. Step by step, permeation and basic mechanical tests have been performed and then more specific characterisations have been done (for long-term ageing under various conditions) in order to choose one or several materials that could meet the specifications required by hydrogen distribution. The design of a pipe prototype was also carried out at the end the project and an economic study was performed for the different potential solutions.

In ferritic steels, especially those of higher tensile strength, Hydrogen-Induced Stress Corrosion Cracking (HISCC) can lead to sudden component failure and is thus a safety risk. The interaction of the steel with the diffusing hydrogen leads to changes in the material's properties that can be detected with micromagnetic testing methods. The experiments and measurements described where carried out on tube specimens with martensitic microstructure (steel grade X 20 Cr 13) in order to generally evaluate the potential of micromagnetic testing methods for the early recognition of HISCC.

The materials sensitivity to hydrogen is studied and measured in this work using the disk pressure testing, whose principle is the comparison of the rupture parameters obtained with metallic membranes tested similarly under helium and hydrogen Such technique allows various studies and reveals parameters that remain not significant with less sensitive methods This work presents an overview of numerous experimental results concerning the influence of various factors (material and gas composition, mechanical and heat treatments, type of microstructure.) on the hydrogen embrittlement of ferrous and nonferrous alloys There are shown synergies between such factors, related to physical and metallurgical phenomena and we give some practical considerations, which can be useful for the evaluation of the safety offered by different materials in contact with hydrogen and for searching ways to improve their behavior

Detection of hydrogen gas is important for safety reasons. To obtain improved hydrogen sensing performances for miniaturized sensors, copper doping in zinc oxide micro- and nanostructures were investigated. Samples were grown by hydrothermal technique at relatively low temperature and studied by X-ray diffraction, micro- Raman, SEM and sensorial techniques. It is found evidence on the improvement of the sensorial properties due to copper-doping in zinc oxide rods-like structures.

There appears a level of consternation swirling about of late that is rooted in varying interpretations by Authorities Having Jurisdiction (AHJ) such as building inspectors, electrical inspectors and so on regarding international building codes now that they have been adopted over national codes in many US jurisdictions. The intention of this paper is to identify the international codes covering hydrogen evolution in stationary battery strings and compare them with national codes, IEEE practices, Telephone company best practices and practical experience. Conclusions to be drawn will identify perhaps a need for soundly reasoned input to the next international code cycle and a reiteration of best practices for stationary battery installations. First and foremost, the telecommunications and data center industries have an excellent reputation for safety and that includes its handling of hydrogen evolved from battery cells. In more than a century of operation of greater than a hundred thousand battery installations nationally, one could count on his or her fingers the number of hydrogen related explosions that caused damage to a facility and none of those resulted in injury. Even battery jar explosions are quite rare. In part, many of the issues at hand are related to the wide deployment of Valve Regulated lead Acid batteries (VRLA) because these cells typically outgas only about 5%2of hydrogen volumes as their vented (AKA flooded) counterparts. As written, however, the codes specify that ventilation must limit hydrogen accumulations that might result during worst case conditions, typically an overcharge condition or thermal runaway state when little or no gas recombination is occurring. This requirement causes grief in some instances because in the case of continuous ventilation it flies in the face of energy conservation. To provide ventilation for the worst case battery condition is effective only in unconditioned spaces. However, if the area being ventilated is conditioned space, potentially large volumes of expensively cooled air are being pushed outdoors, thus raising the cooling cost and the carbon footprint for the facility. An exaggerated model of the problem is seen in the shops and stores in Disney World where customer sales floors are heavily air conditioned but the doors are either wide open or there are no doors at all. The scheme works well for tourist impulse buying but from an energy viewpoint it's wasteful. Another approach is the use of an exhaust fan or purge ventilation, under the control of hydrogen sensors; but experience has shown that most such installations are problematic due to wide variance in sensor product quality, miscalibration or delayed calibration and prolific installation errors. Nothing in the fire codes, nor IEEE 450 and IEEE 1187, the industry standard for Vented (also called 'flooded') cells and Valve Regulated Lead Acid, (VRLA) cells require hydrogen detectors, however many AHJs insist upon them. As a practical matter, natural 'pockets' often form in crowded ceiling spaces and hydrogen will rise towards and accumulate in those pockets. The stratification principle is the same whether the space is in a telecommunications facility accumulating hydrogen or a coal mine accumulating pockets of methane. About the only difference is that in a coal mine, a serious explosion generally is a result of two or more sequential explosions. Usually the first explosion is a pocket of methane and a collateral effect of that event is to push a blast wave through the mine shafts blowing up billowing clouds of coal dust which in turn becomes a secondary, usually more powerful explosion or series of them. In either case, whether the side is coming off a cabinet, the roof is coming off a battery room or a mine shaft is blowing apart, the triggering event was an ignition source finding a pocket of gas that had reached its lower explosive limit. Accordingly, the overall site design must address sufficient airflow to prevent the formation of stratification pockets of hydrogen. Until recently, three model building codes were adopted across the US as is shown on Map 1. The Uniform Building Code (UBC) was adopted over most of the western US, the National Building Code (NBC) covered the northeast and the Standard Building Code (SBC) covered the southeast. In some jurisdictions, a mix and match of codes were adopted by local AHJs within the state.

According to leading automobile manufacturers, hydrogen vehicles will be commercially available within the next few years. Up to now, a number of pre-production models have covered millions of test kilometres and proven to be sufficiently reliable for market launch. Nevertheless, there are still some reservations with respect to safety. The concerns are nourished by the fact that the physical properties of hydrogen differ significantly from the properties of conventional fuels like gasoline and diesel. Thus, the development of hydrogen vehicles requires a radical rethinking of the fuel system. In this context the question arises, which system components should be chosen and where they should be positioned in order to minimise the overall risk. The answer to this question can be given with the help of a quantitative risk analysis (QRA). The risk associated with the interrelated system components depends on a set of non-linear equations and thus requires non-linear numerical approaches. One such non-linear approach is the gradient descent method. Using this method, the safety of an automobile hydrogen system was optimised. The following article summarises the basic approach and the outcomes of the optimisation study.

One still unsolved problem for the use of hydrogen as dean fuel is the safe and efficient storage of hydrogen. Currently cryo tanks, gas cylinders or metal hydrides are used. Important parameters for a hydrogen storage system ate weight and volume density, cost and safety. Recent publications [1-3] claimed that large amounts of hydrogen can be stored reversibly in carbon nanotubes from the gas phase. Similar to a gas phase experiment where the storage material absorbs hydrogen as a function of pressure the hydrogen absorption in a electrochemical system is controlled by the potential. We report results of experiments with carbon nanotubes charged reversibly with hydrogen. The density of hydrogen per weight exceeds the storage density of metal hydrides. Samples with different degrees of purity are compared.

Plasma wall interactions studies are of primary importance for increasing the life time of the first wall in fusion devices. In ITER, the divertor target plates will receive on a small surface a significant part of the power during operation, and carbon materials will be used. Although carbon has several advantages than the materials used at other places of the plasma chamber (W and Be), they undergo chemical reactions with hydrogen and its isotopes used as fuel for the fusion reaction. Under ITER operating conditions, the high temperature of the wall will promote diffusion and recombination of atomic hydrogen, withholding the fuel. Moreover, carbon atoms produced by erosion may be deposited at other locations, causing further increase of the hydrogen inventory in the vessel, and encountering several subsequent major safety issues. In our experiment, carbon dust formation and growth are studied in a radiofrequency discharge. Dust particles sediment into the cathode sheath using carbon originating either from a graphite cathode in pure argon plasmas or from C2H2 mixed with argon in case where a stainless steel cathode is used. In this contribution, we present a characterization of carbon dust particles under various plasma conditions (pressure, RF power, C2H2 percentage). Dust growth is studied in situ using FTIR spectroscopy, whereas the structural properties of the dust particles are studied ex situ using TEM, SEM, and FTIR.