Safety

Hydrogen combustion inside a post-accident nuclear reactor containment may pose a challenge to the containment integrity which could alter the fission-product release source term to the public. Combustion-generated overpressures may be relieved by venting to adjacent compartments through relief panels or existing openings. Thus an improved understanding of the propagation of lean hydrogen deflagrations in inter-connected compartments is essential for the development of appropriate management strategies. GOTHIC is a general purpose lumped parameter thermal-hydraulic code for solving multi-phase compressible flows which is accepted as an industry-standard code for containment safety analyses. Following the Fukushima accident the application of three-dimensional computational fluid dynamics methods to high-fidelity detailed analysis of hydrogen combustion processes has become more widespread. In this study a recently developed large-eddy-simulation (LES) capability is applied to the prediction of lean premixed hydrogen deflagrations in large-scale vented vessels of various configurations. The LES predictions are compared with GOTHIC predictions and experimental data obtained from the large-scale vented combustion test facility at the Canadian Nuclear Laboratories. The LES methodology makes use of a flamelet- or a progress-variable-based combustion model. An empirical burning velocity model is combined with an advanced finite-volume framework and a mesh-independent subfilter-scale model. Descriptions of the LES and GOTHIC modelling approaches used to simulate the hydrogen reactive flows in the vented vessels along with the experimental data sets are given. The potential and limitations of the lumped parameter and LES approaches for accurately describing lean premixed hydrogen deflagrations in vented vessels are discussed.

Adopting proton exchange membrane fuel cells fuelled by hydrogen presents a promising solution for the shipping industry’s deep decarbonisation. However the potential safety risks associated with hydrogen leakage pose a significant challenge to the development of hydrogen-powered ships. This study examines the safe design principles and leakage risks of the hydrogen gas supply system of China’s first newbuilt hydrogen-powered ship. This study utilises the computational fluid dynamics tool FLACS to analyse the hydrogen dispersion behaviour and concentration distributions in the hydrogen fuel cell room based on the ship’s parameters. This study predicts the flammable gas cloud and time points when gas monitoring points first reach the hydrogen volume concentrations of 0.8% and 1.6% in various leakage scenarios including four different diameters (1 3 5 and 10 mm) and five different directions. This study’s findings indicate that smaller hydrogen pipeline diameters contribute to increased hydrogen safety. Specifically in the hydrogen fuel cell room a single-point leakage in a hydrogen pipeline with an inner diameter not exceeding 3 mm eliminates the possibility of flammable gas cloud explosions. Following a 10 mm leakage diameter the hydrogen concentration in nearly all room positions reaches 4.0% within 6 s of leakage. While the leakage diameter does not impact the location of the monitoring point that first activates the hydrogen leak alarm and triggers an emergency hydrogen supply shutdown the presence of obstructions near hydrogen detectors and the leakage direction can affect it. These insights provide guidance on the optimal locations for hydrogen detectors in the fuel cell room and the pipeline diameters on hydrogen gas supply systems which can facilitate the safe design of hydrogen-powered ships.

There is growing interest in utilizing existing infrastructure for storage and distribution of hydrogen. Gaseous hydrogen for example could be added to natural gas in the short-term whereas entire systems can be converted to transmission and distribution networks for hydrogen. Many active programs around the world are exploring the safety and feasibility of adding hydrogen to these networks. Concerns have been raised about the structural integrity of materials in these systems when exposed to hydrogen. In general the effects of hydrogen on these materials are grossly misunderstood. Hydrogen unequivocally degrades fatigue and fracture resistance of structural steels in these systems even for low hydrogen partial pressure (-l bar). In most systems however hydrogen effects will not be apparent because the stresses in these systems remain very low. Another misunderstanding results from the kinetics of the hydrogen  effects:  hydrogen  degrades   fatigue  and  fracture  properties  immediately  upon  exposure  to gaseous hydrogen and those effects disappear when the hydrogen environment is removed even after prolonged exposure. There is also a misperception that materials selection can mitigate hydrogen effects. While some classes of materials perform better in hydrogen environments than other classes for most practical   circumstances  the  range  of  response  for  a  given  class  of  material  in  gaseous  hydrogen environments is rather narrow. These observations can be systematically characterized by considering the  intersection  of  materials  environmental  and  mechanical  variables   associated  with  the  service application. Indeed any safety assessment of a hydrogen pressure system must quantitatively consider these aspects. In this report we quantitatively evaluate the importance of the materials environmental and mechanical variables in the context of hydrogen additions to natural gas piping and pipeline systems with  the  aim  of  providing  an  informed   perspective  on  parameters relevant for assessing  structural integrity of natural gas systems in the presence of gaseous hydrogen.

The increasing demand for renewable energy storage may position hydrogen as one of the major players in the future energy system. However to introduce such technology high level of safety must be offered. In particular for the accident scenarios with combustion or explosion of the unintendedly released hydrogen in partially or fully confined volumes such as e.g. road tunnel the effective countermeasures preventing or reducing the risk of equipment damages and person injuries should be established. A mitigation strategy could be the use of existing fire suppression system which can inject water as a spray. The shock waves resulted from hydrogen explosion could be weakened by the water droplets met on the shock path. In the presented work an attenuation effect of water droplets presence on the strength of the passing shock was studied. The analysis of the different attenuation mechanisms was performed and estimation of the effect of spray parameters such as droplet size and spray density on the shock wave was carried out. For the quantitative evaluation of the attenuation potential a numerical model for the COM3D combustion code was developed. The novel model for the droplet behavior accounting for the realistic correlations for the fluid (water) particle drag force linked with the corresponding droplet breakup model describing droplet atomization is presented. The model was validated against literature experimental data and was used for the blind simulations of the hydrogen test facility in KIT.

One of China’s ambitious hydrogen strategies over the past few years has been to promote fuel cells. A number of hydrogen refueling stations (HRSs) are currently being built in China to refuel hydrogen-powered automobiles. In this context it is crucial to assess the dangers of hydrogen leaking in HRSs. The present work simulated the liquid hydrogen (LH2) leakage with the goal of undertaking an extensive consequence evaluation of the LH2 leakage on an LH2 refueling station (LHRS). Furthermore the utilization of an air curtain to prevent the diffusion of the LH2 leakage is proposed and the defending effect is studied accordingly. The results reveal that the Richardson number effectively explained the variation of plume morphology. Furthermore different facilities have great influence on the gas cloud diffusion trajectory with the consideration of different leakage directions. The air curtain shows satisfactory prevention of the diffusion of the hydrogen plume. Studies show that with the increase in air volume (equivalent to wind speed) and the narrowing of the air curtain width (other factors remain unchanged) the maximum flammable distance of hydrogen was shortened.

Hydrogen sensors especially those operating at high temperatures are essential tools for the emerging hydrogen economy. Monitoring hydrogen under process conditions to control the reactions for detecting confined species is crucial to the safe widespread use and public acceptance of hydrogen as fuel. Hydrogen sensors must have a sensitivity ranging from traces of hydrogen (parts per million (ppm)) up to levels near the lower explosive limit (LEL = 4% H2 in the air) for safety reasons. Furthermore they need to operate in cryogenic ambient and high-temperature environments. Herein emphasis is given to hydrogen sensors based on solid oxide electrolytes (operating at high temperatures) in particular oxygen ion and proton conductors. The review is devoted to potentiometric amperometric and combined amperometric-potentiometric hydrogen sensors. Experimental results already reported in the international literature are presented and analyzed to reveal the configuration principle of operation and the applied solid electrolytes and electrodes of the high-temperature hydrogen sensors. Additionally an amperometric sensor able to detect hydrogen and steam in atmospheric air through a two-stage procedure is presented and thoroughly discussed. The discussion reveals that high-temperature hydrogen sensors face different challenges in terms of the electrodes and solid electrolytes to be used depending on the operating principle of each sensor type.

Hydrogen cars are expected to play an important role in a decarbonised clean-transport future. Safety issues arise though in tunnels due to the possibility of accidental release and accumulation of hydrogen. This Computational Fluid Dynamics (CFD) study focuses on the effect of tunnel inclination and ventilation on hydrogen dispersion. A horseshoe shaped tunnel of 200 m length is considered in all seventeen cases examined. In most cases hydrogen is released from the bottom of a car placed at the center of the tunnel. Various inclinations in-tunnel wind speeds and fuel tank Pressure Relief Device (PRD) diameters were considered in order to assess their influence on safety. It was found that even if the long-term influence of the inclination is positive there is no systematic effect at initial stages nor at the most dangerous ‘nearly-stoichiometric’ cloud volumes (25% - 35% v/v). Adverse effects may also exist like the occasionally higher flammable cloud (4% - 75% v/v). Regarding ventilation it was found that even low wind speeds (e.g. 1 m/s) can reduce the flammable cloud by several times. However no significant effect on the total nearly-stoichiometric volumes was found for most of the cases examined. Ventilation can also cause adverse effects as for example at mid-term of the release duration in some cases. Concerning the PRD diameter a reduction from 4 mm to 2 mm resulted in about five times smaller maximum of the nearly-stoichiometric cloud volume. In addition the effect of release orientation on hydrogen cloud was examined and it was found that the downwards direction presents drawbacks compared to the backwards and upwards release directions.

This paper discusses the optimal control of pressure using the zero-gradient control (ZGC) approach. It is applied for the first time in the study to control the optimal pressure of hydrogen natural gas mixture in an inclined pipeline. The solution to the flow problem is first validated with existing results using the Taylor series approximation regression analysis and the Runge-Kutta method combined. The optimal pressure is then determined using ZGC where the optimal set points are calculated without having to solve the non-linear system of equations associated with the standard optimization problem. It is shown that the mass ratio is the more effective parameter compared to the initial pressure in controlling the maximum variation of pressure in a gas pipeline.

There is worldwide interest in transporting hydrogen using both new pipelines and pipelines converted from natural gas service. Laboratory tests investigating the effect of hydrogen on the mechanical properties of pipeline steels have shown that even low partial pressures of hydrogen can substantially reduce properties such as reduction in area and fracture toughness and increase fatigue crack growth rates. However qualitative arguments suggest that the effects on pipelines may not be as severe as predicted from the small scale tests. If the trends seen in laboratory tests do occur in service there are implications for the assessment of damage such as volumetric corrosion dents and mechanical interference. Most pipeline damage assessment methods are semi-empirical and have been calibrated with data from full scale tests that did not involve hydrogen. Hence the European Pipeline Research Group (EPRG) commissioned a study to investigate damage assessment methods in the presence of hydrogen. Two example pipeline designs were considered both were assessed assuming a modern high performance material and an older material. From these analyses the numerical results show that the high toughness material will tolerate damage even if the properties are degraded by hydrogen exposure. However low toughness materials may not be able to tolerate some types of severe damage. If the predictions are realistic operators may have to repair more damage or reduce operating pressures. Furthermore damage involving cracking may not Page 2 of 22 satisfy the ASME B31.12 requirements for preventing time dependent crack growth. Further work is required to determine if the effects predicted using small scale laboratory test data will occur in practice.

Hydrogen has a high risk of ignition owing to its extremely low ignition energy and wide range of flammability. Therefore acquiring parameters relating to safe usage is of particular interest. The ignition of hydrogen generates combustion processes such as detonation and deflagration which may produce a blast wave. The severity of injuries sustained from a blast wave is determined by its strength. To reduce the physical hazards caused by explosion there is a need for some concepts for attenuating explosions and blast waves. In the present study we used water droplets as a material to reduce the blast wave strength. Numerical analysis of the interaction between blast waves and water droplets in a shock tube was conducted to understand the mitigation mechanism of blast wave. In this report we numerically modelled the experiment conducted by Mataradze et al. [1] to understand the main factor of blast mitigation by water droplets. In order to quantitatively clarify the mitigation effect of water droplets on the blast wave especially by quasi-steady drag here we conducted parameter studies on water droplet sprayed region. From this calculation it was suggested that the location of water droplet sprayed layer did not affect the blast mitigation effect at far side of the high explosives.

Unexpected hydrogen leakage may occur in the production storage transportation and utilization of hydrogen. The lower flammability limit (LFL) for the hydrogen is 4% in air. The combustion and explosion of hydrogen-air mixture poses potential hazards to personnel and property. In this study unintended release of hydrogen from a hydrogen fuel cell forklift vehicle inside a enclosed warehouse is simulated by fireFoam which is an LES Navier-Stokes CFD solver. The simulation results are verified by experimental data. The variation of hydrogen concentration with time and the isosurface of hydrogen concentration of 4% vol. are given. Furthermore the leakage of hydrogen from a storage tanks in a hydrogen refueling station is simulated and the evolution of the isosurface of hydrogen concentration of 4% vol. is given which provides a quantitative guidence for determination the hazardous area after the leakage of hydrogen.

In 2021 only 6 hydrogen fuelling station have been built in Italy of which 3 are not operational and only 1 is open to the public while the rest are built in private or industrial areas. While fuelling station which store more than 5000 kg of hydrogen are subjected to the “Seveso Directive” the permitting procedure for refuelling station which store less than the threshold is supervised by the fire brigade command of the province where the station is built. Recently in the effort to easy the permitting procedure to establish new stations a Ministerial Decree was published in the official gazette of the Italian Republic which lists minimum safety features and safety distances that if respected guarantee the approval by the authority. Nevertheless the imposed distances are such that the land required to build the station constitute a barrier rather than a facilitation. Exploiting the possibility introduced by the Decree to calculate safety distances following a Fire Safety Engineering approach a method is proposed for calculation of safety distances. The present paper presents the Italian regulation and describes an approach to calculate the safety distances including an example applied on the dispenser.

Determination of the behaviour of hydrogen when leaking from pipework on gas distribution assets is essential in assessing the comparative risk associated with using pure hydrogen in place of natural gas in existing assets. Experimental work considering the behaviour of gaseous hydrogen when released in large volumes from gas distribution pipework at pressures of up to 7 barg through holes of up to 200mm in diameter in both buried and unburied scenarios is currently underway. The present paper presents and briefly discusses the results from a set of ignited 20mm diameter releases of hydrogen at pressures up to 7 barg vertically upwards from a pipe in an open excavation. Gaseous releases which find a direct route to atmosphere have the potential to create significant volumes of flammable gas and subsequently significant fires in the case of ignition. It is important to understand both the dispersion distances and thermal hazard field to be able to understand the comparative risk posed when compared to natural gas releases in similar situations. Results of current work completed to date are presented alongside comparisons with known properties of natural gas releases and the potential implications to the comparative risk of hydrogen network operation. The work has been conducted at the DNV GL Spadeadam Testing and Research Centre UK as part of the UK Gas Distribution Networks and Ofgem National Innovation Competition funded H21 project.

Efficient storage of hydrogen is crucial for the success of hydrogen energy markets (early markets as well as transportation market). Hydrogen can be stored either as a compressed gas a refrigerated liquefied gas a cryo-compressed gas or in hydrides. This paper gives an overview of hydrogen storage technologies and details the specific issues and constraints related to the materials behaviour in hydrogen and conditions representative of hydrogen energy uses. It is indeed essential for the development of applications requiring long-term performance to have good understanding of long-term behaviour of the materials of the storage device and its components under operational loads.

The higher rate of component failure and downtime during initial operation in hydrogen stations is not well understood. The National Renewable Energy Laboratory (NREL) has been collecting failed components from retail and research hydrogen fuelling stations in California and Colorado and analyzing them using an optical zoom and scanning electron microscope. The results show stainless steel metal particulate contamination. While it is difficult to definitively know the origin of the contaminants a possible source of the metal particulates is improper tube cleaning practices. To understand the impact of different cleaning procedures NREL performed an experiment to quantify the particulates introduced from newly cut tubes. The process of tube cutting threading and bevelling which is performed most often during station fabrication is shown to introduce metal contaminants and thus is an area that could benefit from improved cleaning practices. This paper shows how these particulates can be reduced which could prevent station downtime and costly repair. These results are from the initial phase of a project in which NREL intends to further investigate the sources of particulate contamination in hydrogen stations.

All vehicular high-pressure hydrogen tanks are equipped with thermally-activated pressure relief devices (TPRDs) required by Global Technical Regulation. This safety device significantly reduces the risk of tank catastrophic rupture by venting the hydrogen pressure outside. However the released flammable hydrogen raises additional safety problems. Japan Automobile Research Institute has demonstrated that in the vehicle fire event once the TPRD opens the hydrogen fires will engulf the whole vehicle making it difficult for the drivers and passenger to evacuate from the vehicle. This paper designs a new safety system to solve the evacuation problem. The safety system includes a rotatable pressure relief device with a motor a sensory system that consists of infrared sensors ultrasonic radar and temperature sensors a central control unit and an alarm device. The new design of the pressure relief device allows the system actively adjusting the release direction towards void open space outside the vehicle to minimize the risks of hydrogen fires. The infrared sensors located at the roof of the vehicles collect info inside the vehicle and the ultrasonic radar detect the region outside the vehicle. Temperature sensors tell when to trigger the alarm and set the motor in standby mode and the central control unit determines where to rotate based on the info from the infrared sensors and ultrasonic radars. A control strategy is also proposed to operate the safety system in an appropriate way. The cost-benefit analysis show that the new safety system can significantly reduce the risks of intended hydrogen releases from onboard pressure relief devices with total cost increases by less than 1% of the vehicle cost making it a good cost-effective engineering solution.

The authors presented a basic mathematical model for estimating peak overpressure attained in vented explosions of hydrogen in a previous study (Sinha et al. [1]). The model focussed on idealized cases of hydrogen and was not applicable for realistic accidental scenarios like presence of obstacles initial turbulent mixture etc. In the present study the underlying framework of the model is reformulated to overcome these limitations. The flame shape computations are simplified. A more accurate and simpler formulation for venting is also introduced. Further by using simplifying assumptions and algebraic manipulations the detailed model consisting of several equations is reduced to a single equation with only four parameters. Two of these parameters depend only on fuel properties and a standard table provided in the Appendix can be used. Therefore to compute the overpressure only the two parameters based on enclosure geometry need to be evaluated. This greatly simplifies the model and calculation effort. Also since the focus of previous investigation was hydrogen properties of hydrocarbon fuels which are much more widely used were not accounted for. The present model also accounts for thermo-physical properties of hydrocarbons and provides table for fuel parameters to be used in the final equation for propane and methane. The model is also improved by addition of different sub-models to account for various realistic accidental scenarios. Moreover no adjustable parameters are used; the same equation is used for all conditions and all gases. Predictions from this simplified model are compared with experimentally measured values of overpressure for hydrogen and hydrocarbons and found to be in good agreement. First the results from experiments focussing on idealized conditions of uniformly mixed fuel in an empty enclosure under quiescent conditions are considered. Further the model applicability is also tested for realistic conditions of accidental explosion consisting of obstacles inside the enclosure non-uniform fuel distribution initial turbulent mixture etc. For all the cases tested the new simple model is found to produce reasonably good predictions.

According to the Global technical regulation on hydrogen and fuel cell vehicles (FCV) fuel cell discharge system at the vehicle exhaust system`s point of discharge the hydrogen concentration level shall not exceed 4 % average by volume during any moving three-second time interval during normal operation including start-up and shut down [1]. FC stack need to washout by the concentrated hydrogen as the purge gas and how to exhaust gas without exceeding 4 % is the most concerns. Also how to measure hydrogen pulse of millisecond in exhaust is also the rising up issue. In this paper model of FCV hydrogen discharge system was composed and variety of simple experiments were carried out to control the H2 concentration and release. In the case which the semiconductor sensor with porous material (average size less than quench distance) were applied to check H2 concentration the short pulse of high concentration of H2 in millisecond was hard to find. In this experiment the simple exhaust gas model H2/N2 flow was used instead of Air/H2. In the exhaust gas test experiment was conducted under the atmospheric condition in room temperature with small pressure difference and the fast solenoid valve to create quick hydrogen control. Most of the experiments except the turbulent flow experiments laminar flow is expected to be dominated when steady state condition is satisfied but the most result discussed here is the measurement of H2 concentration during the start point at the time of discharge within seconds. The results showed when H2 was added to N2 flow the boundary layer between N2 and H2 contained the high concentration of H2 at the initial wave front and decrease to reach steady state. This H2 pulse is typical in the FCV exhaust gas and topics of this paper.

Catalytic hydrogen-oxygen recombination is a non-traditional method to limit hydrogen accumulation and prevent combustion in the hydrogen industry. Outside of conventional use in the nuclear power industry this hydrogen safety technology can be applied when traditional hydrogen mitigation methods (i.e. active and natural ventilation) are not appropriate or when a back-up system is required. In many of these cases it is desirable for hydrogen to be removed without the use of power or other services which makes catalytic hydrogen recombination attractive. Instances where catalytic recombination of hydrogen can be utilized as a stand-alone or back-up measure to prevent hydrogen accumulation include radioactive waste storage (hydrogen generated from water radiolysis or material corrosion) battery rooms hydrogen-cooled generators hydrogen equipment enclosures etc.<br/>Water tolerant hydrogen-oxygen recombiner catalysts for non-nuclear applications have been developed at Canadian Nuclear Laboratories (CNL) through a program in which catalyst materials were selected prepared and initially tested in a spinning-basket type reactor to benchmark the catalyst’s performance with respect to hydrogen recombination in dry and humid conditions. Catalysts demonstrating high activity for hydrogen recombination were then selected and tested in trickle-bed and gas phase recombiner systems to determine their performance in more typical deployment conditions. Future plans include testing of selected catalysts after exposure to specific poisons to determine the catalysts’ tolerance for such poisons.

The paper describes a lumped-parameter model for vented deflagrations of localised and layered fuel air mixtures. Theoretical model background is described to allow insight into the model development with focus on lean mixtures and overpressures significantly below 0.1 MPa for protection of low strength equipment and buildings. Phenomena leading to combustion augmentation was accounted based on conclusions of recent CFD studies. Technique to treat layered mixtures with concentration gradient is demonstrated. The model is validated against 25 vented deflagration experiments with lean non-uniform and layered hydrogen-air mixtures performed in Health and Safety Laboratory (UK) and Karlsruhe Institute of Technology (Germany).

Liquid hydrogen (LH2) compared to compressed gaseous hydrogen offers advantages for large-scale transport and storage of hydrogen with higher densities. Although the gas industry has good experience with LH2 only little experience is available for the new applications of LH2 as an energy carrier. Therefore the European FCH JU funded project PRESLHY conducted pre-normative research for the safe use of cryogenic LH2 in non-industrial settings. The central research consisted of a broad experimental program combined with analytical work modelling and simulations belonging to the three key phenomena of the accident chain: release and mixing ignition and combustion. The presented results improve the general understanding of the behavior of LH2 in accidents and provide some design guidelines and engineering tools for safer use of LH2. Recommendations for improvement of current international standards are derived.

High-strength steels with yield strength of 960 MPa are susceptible to hydrogen-assisted cracking (HAC) during welding processing. In the present paper the implant test is used to study HAC in a quenched and tempered steel S960QL and a high-strength steel produced by thermo-mechanical controlled process S960MC. Welding is performed using the gas-metal arc welding process. Furthermore diffusible hydrogen concentration (H_D) in arc weld metal is determined. Based on the implant test results lower critical stress (LCS) for complete fracture critical implant stress (σ_krit) for crack initiation and embrittlement index (EI) are determined. At HD of 1.66 ml/100 g LCS is 605 MPa and 817 MPa for S960QL and S960MC respectively. EI is 0.30 and 0.46 for S960QL and S960MC respectively. Fracture surfaces of S960QL show higher degradation with reduced deformation. Both higher EI of S960MC and fractography show better resistance to HAC in the HAZ of S960MC compared to S960QL.

Purpose- To present an overview of the research and development carried out in a European funded framework 7 (FP7) project called SafeHPower for the implementation of neutron radiography to inspect fatigue cracks in vehicle and storage hydrogen fuel tanks. Project background– Hydrogen (H2) is the most promising replacement fuel for road transport due to its abundance efficiency low carbon footprint and the absence of harmful emissions. For the mass market of hydrogen to take off the safety issue surrounding the vehicle and storage hydrogen tanks needs to be addressed. The problem is the residual and additional stresses experienced by the tanks during the continuous cyclic loading between ambient and storage pressure which can result in the development of fatigue cracks. Steel tanks used as storage containers at service stations and depots and/or the composite tanks lined with steel are known to suffer from hydrogen embrittlement (HE). Another issue is the explosive nature of hydrogen (when it is present in the 18-59% range) where it is mixed with oxygen which can lead to catastrophic consequences including loss of life. Monitoring systems that currently exist in the market impose visual examination tests pressure tests and hydrostatic tests after the tank installation [1] [2]. Three inspection systems have been developed under this project to provide continuous monitoring solutions. Approach and scope- One of the inspection systems based on the neutron radiography (NR) technology that was developed in different phases with the application of varied strategies has been presented here. Monte Carlo (MCNP) simulation results to design and develop a bespoke collimator have been presented. A limitation of using an inertial electrostatic Deuterium-Tritium (D-T) pulsed neutron generator for fast neutron radiography has been discussed. Radiographs from the hydrogen tank samples obtained using thermal neutrons from a spallation neutron source at ISIS Rutherford laboratory UK have been presented. Furthermore radiograph obtained using thermal neutrons from a portable D-T neutron generator has been presented. In conclusion a proof in principle has been made to show that the defects in the hydrogen fuel tank can be detected using thermal neutron radiography.

Hydrogen is one of the most suitable candidates in replacing fossil fuels. However storage issues due to its very low density under ambient conditions are encountered in many applications. The liquefaction process can overcome such issues by increasing hydrogen’s density and thus enhancing its storage capacity. A boiling liquid expanding vapour explosion (BLEVE) is a phenomenon in liquefied gas storage systems. It is a physical explosion that might occur after the catastrophic rupture of a vessel containing a liquid with a temperature above its boiling point at atmospheric pressure. Even though it is an atypical accident scenario (low probability) it should be always considered due to its high yield consequences. For all the above-mentioned reasons the BLEVE phenomenon for liquid hydrogen (LH2) vessels was studied using the CFD methodology. Firstly the CFD model was validated against a well-documented CO2 BLEVE experiment. Secondly hydrogen BLEVE cases were simulated based on tests that were conducted in the 1990s on LH2 tanks designed for automotive purposes. The parametric CFD analysis examined different filling degrees initial pressures and temperatures of the tank content with the aim of comprehending to what extent the initial conditions influence the blast wave. Good agreement was shown between the simulation outcomes and the LH2 bursting scenario tests results.

Hydrogen fuel cell vehicle (HFCV) technology poses great promise as an alternative to significantly reduce the environmental impact of the transport sector’s emissions. However hydrogen fuel cell technology is relatively new therefore confirmation of the reliability and safety analysis is still required particularly for fire scenarios within confined spaces such as tunnels. This study applied the computational fluid dynamics (CFD) simulations in conjunction with probabilistic calculation methods to determine the associated thermal risk of a hydrogen jet fire in a tunnel and its dependency on scenarios with different tunnel slopes longitudinal and transverse ventilation velocities and fire positions. A large-scale model of 102 m in which the effects of outlined parameter variations on the severity of the fire incident were analysed. It is found that both tunnel ventilation techniques and slope were critical for the effective ejection of accumulated heat. With ventilation playing a primary role in the ejection of heat and gas and slope ensuring the stability of the ejected heat probabilities of thermal burns were found to be reduced by up to approximately 35% with a strong suggestion of critical combinations to further reduce the dangers of hydrogen tunnel fires.