Open Access

A new hydrogen-based test rig is being developed for a feasibility study on the use of hydrogen as an energy source for thermal testing in accordance with the IAEA SSR-6 guidelines for transport packages containing radioactive materials. The test rig will be capable of combusting hydrogen for a wide range of different burner geometries, mass flows and if necessary hydrogen blends. As this type of fire test according to the IAEA boundary conditions (SSR-6 & SSG-26) does not yet exist, a large number of preliminary investigations, safety assessments and calculations must be carried out in order to develop a viable concept for hydrogen fires.

In this presentation we present a new hydrogen-based test rig for an ongoing feasibility study of using hydrogen as an energy source for the thermal testing of transport packages containing radioactive materials. The test rig will be capable of combusting hydrogen for a wide range of different burner geometries, mass flows and if necessary hydrogen blends. As this type of fire test according to the IAEA boundary conditions does not yet exist, a large number of preliminary investigations, safety assessments and calculations must be carried out in order to develop a viable concept for hydrogen fires. In the first step of the feasibility study, the temperature, structure, and radiation of various hydrogen flames are surveyed. In future works, the results will make it possible to design burner frames that are suitable for fire reference tests in order to make comparisons with pool and propane fires used in assessment procedures today. In parallel comparative numerical simulations are conducted to model the thermal behaviour of hydrogen flames using the software package Ansys®. On the one hand, the numerical simulations support the experiments by providing an overview of numerous parameters and the measuring range; on the other hand, they will help with the design of the burner frame in future work. This paper gives an overview in the design and capabilities of the test rig. Furthermore, the results of the parameter studies show that burner geometry and mass flow provide a significant design margin for the thermal shape of the hydrogen flames. In addition, the results of the initial numerical calculations will be used to determine the necessary sensors, the positions, and their operating range. Only the optimal interaction allows a controlled system that permits user-defined hydrogen fires.

In this paper we present an update of the hydrogen based test rig for an ongoing feasibility study of using hydrogen as an energy source for the thermal testing of transport packages containing radioactive materials [ The test rig is capable of combusting hydrogen for a wide range of different burner geometries, mass flows , hydrogen blends and single jet flame operation s as well as a full array of burners for thermal testing can be set up. As this type of fire test according to the IAEA boundary conditions does not yet exist, a large number of preliminary investigations, safety assessments and simulations must be carried out in order to develop a viable concept for hydrogen fires. In a first step of the feasibility study, the temperature , structure, and radiative behavior of hydrogen jet flames must be surveyed. The simulation with a single hydrogen flame was investigated in a previous work. In the next step the results are used to study the interaction and structural behavior of multiple jet flames in proximity with varying nozzle distances. With the test rig completed, it will be possible in future works to design burner frames suitable for fire reference tests to make comparisons with pool and propane fires used in assessment procedure today. Thus, preliminary comparative numerical simulations are conducted to model the behavior of overlapping hydrogen jet flames using the software package Ansys®. This paper gives an overview on the current state and design of the test rig. Furthermore, the results of the simulations show that nozzle geometry, mas s flow and nozzle distance provide significant design margin for designing a test fire capable of fully engulfing a specimen.

Packages for the transport of spent nuclear fuel and high-level radioactive waste must demonstrate their integrity under severe accident conditions to comply with the international transport regulations defined in International Atomic Energy Agency SSR-6. A key component of the approval procedure is the thermal fire test, which requires a fully engulfing 800 °C fire over a duration of 30 minutes. At the Federal Institute of Materials Research and Testing (BAM), such tests are currently conducted using propane gas fires. However, in the context of climate policy objectives, resource availability, and rising costs of fossil fuels, alternative and more sustainable energy sources for fire testing are being investigated. Hydrogen represents a promising candidate due to its carbon-free combustion and alignment with BAM’s hydrogen strategy. Nevertheless, hydrogen flames exhibit fundamentally different physical and thermal characteristics compared to hydrocarbon flames, most notably a significantly lower radiative emissivity caused by the absence of soot formation. This reduced radiative heat transfer poses a challenge for replicating the boundary conditions required by SSR-6. One potential mitigation strategy is the use of hydrogen–methane blends, where methane serves as a carbon source to enhance flame emissivity while maintaining the possibility of a sustainable fuel pathway. This paper presents an experimental investigation of hydrogen–methane jet flames with respect to their suitability for thermal fire testing of radioactive material transport packages. A modular experimental test rig was developed and installed at the BAM Test Site for Technical Safety, enabling controlled variation of burner geometry, thermal power, and fuel composition. A Design of Experiments approach based on a Central Composite Design was applied to systematically explore the three-dimensional parameter space. Flame geometry, radiative heat flux, and characteristic flame temperatures were evaluated using thermographic imaging, Gardon gauges, and thermocouples. The results demonstrate that increasing the methane fraction significantly enhances flame radiation and geometry, while pure hydrogen flames exhibit higher average temperatures but substantially lower radiative heat flux. Quadratic response surface models reveal clear dependencies of flame characteristics on power, nozzle cross section, and methane ratio. Overall, the study confirms that hydrogen–methane blends are a viable option for tailoring flame properties toward the requirements of regulatory fire testing and provides a foundation for the design of future fully engulfing hydrogen-based fire test setups .