Influence of initial pressure in hydrogen/air flame acceleration during severe accident in Nuclear Power Plant

Flame acceleration (FA) and explosion of hydrogen/air mixtures remain key issues for severe accident management in nuclear power plants. Empirical criteria were developed in the early 2000s by Dorofeev and colleagues, providing effective tools to discern possible FA or DDT (Deflagration-toDetonation Transition) scenarios. A large experimental database, composed mainly of middle-scale experiments in obstacle-laden ducts at atmospheric pressure condition, has been used to validate these criteria.

Prevention of hydrogen accumulation inside the vacuum vessel pressure suppression system of the ITER facility by means of passive auto-catalytic recombiners

Hydrogen safety is a relevant topic for both nuclear fission and fusion power plants. Hydrogen generated in the course of a severe accident may endanger the integrity of safety barriers and may result in radioactive releases. In the case of the ITER fusion facility, accident scenarios with water ingress consider the release of hydrogen into the suppression tank (ST) of the vacuum vessel pressure suppression system (VVPSS). Under the assumption of additional air ingress, the formation of flammable gas mixtures may lead to explosions and safety component failure.

Characterising the performance of hydrogen sensitive coatings for nuclear safety applications

The detection of hydrogen gas is essential in ensuring the safety of nuclear plants. However, events at Fukushima Daiichi NPP highlighted the vulnerability of conventional detection systems to extreme events, where power may be lost. Herein, chemochromic hydrogen sensors have been fabricated using transition metal oxide thin films, sensitised with a palladium catalyst, to provide passive hydrogen detection systems that would be resilient to any plant power failures.

Humidity tolerant hydrogen-oxygen recombination catalysts for hydrogen safety applications

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.

RBD-fast based sensitivity and uncertainty analysis on a computational hydrogen recombiner test case

Deflagration-to-Detonation Transition Ratio (DDTR) is an important parameter in measuring the hazard of hydrogen detonation at given thermodynamic conditions. It’s among the major tasks to evaluate DDTR in the study of hydrogen safety in a nuclear containment. With CFD tools, detailed distribution of thermodynamic parameters at each instant can be simulated with considerable reliability. Then DDTR can be estimated using related CFD output. Forstochastic or epistemic reasons, uncertainty always exists in input parameters during computations.

Response time measurement of hydrogen sensors

The efficiency of gas sensor application for facilitating the safe use of hydrogen depends considerably on the sensor response to a change in hydrogen concentration. Therefore, the response time has been measured for five different-type commercially available hydrogen sensors. Experiments showed that all these sensors surpass the ISO 26142 standard; for the response times t90 values of 2 s to 16 s were estimated. Results can be fitted with an exponential or sigmoidal function.

Test methodologies for hydrogen sensor performance assessment: chamber vs. flow-through test apparatus

Certification of hydrogen sensors to standards often prescribes using large-volume test chambers [1, 2]. However, feedback from stakeholders such as sensor manufacturers and end-users indicate that chamber test methods are often viewed as too slow and expensive for routine assessment. Flow through test methods potentially are an efficient, cost-effective alternative for sensor performance assessment. A large number of sensors can be simultaneously tested, in series or in parallel, with an appropriate flow through test fixture.

A study on the effectivity of hydrogen leakage detection for hydrogen fuel cell

Unlike four-wheel fuel-cell vehicles, fuel-cell motorcycles have little semi-closure space corresponding to the engine compartment of four-wheel fuel-cell vehicles. Furthermore, motorcycles may fall while parked or running. We conducted hydrogen concentration measurement and ignition tests to evaluate the feasibility of detecting leaks when hydrogen gas leaked from a fuel-cell motorcycle, as well as the risk of ignition.

Application of the validated 3D multiphase-multicomponent CFD model to an accidental liquid hydrogen release scenario in a liquefication plant

Hydrogen-air mixtures are flammable in a wide range of compositions and have a low ignition energy, compared to gaseous hydrocarbons. Due to its low density, high buoyancy, and diffusivity the mixing is strongly enhanced, which supports distribution into large volumes if accidentally released. Economically valuable discontinuous transportation over large distances is only expected using liquid hydrogen (LH2). Releases of LH2, at its low temperature (20.3 K at 0.1 MPa), have additional hazards besides the combustible character of gaseous hydrogen (GH2).

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