The contribution by the Heiss Dampf Reaktor Safety Program, phase III, to the German containment hydrogen research activities were twofold:

1. to confirm the findings of the experiments in the Battelle Model Containment (BMC) in volumes of typically ~100 m3 by similar ones at a larger scale with a total volume of 500 m3

2. to broaden the database for assessing the emerging modeling strategy for larger scales toward more realistic subcompartment sizes.

To supplement the results obtained in the BMC in a proper, controlled manner for additional model development and computer code verification, a total of seven experiments was performed, and the following positions for hydrogen ignition were examined:

test group E12.1: hydrogen deflagration in a vertically oriented subcompartment

test group E12.2: ignition close to the vent

test group E12.3: accelerated jet ignition in a horizontal direction.

The maximum peak pressure occurred for E12.3.3 at 1.8 bars under typical accelerated jet ignition conditions for 12 vol% initial H2 concentration. Because of larger vent openings, maximum peak pressures were generally lower than observed in BMC tests, whereas maximum temperatures were substantially higher, reaching 1000°C and above. A few comparisons between data and code results from CONTAIN, RALOC-HYDCOM, and CONTAIN/BASSIM computations are shown, indicating the need for further improvements.