Overview of First Results on the H2 Distribution Test at the Large Scale HDR-Facility

Abstract

On the basis of the past experiences gained both with respect to experimental and computational aspects, a complete, major test group, Ell, was designed and performed in the context of HDR-Safety Program Phase III (1988-1992) in the summer of 1989. This test series consisted of eight different experiments covering all aspects of H -distribution and mitigation features such as: small and large LOCA controlled containment atmosphere conditions, axially different injection positions, multiple injections of gas mixtures (He/H: 85/15% vol plus 60/40% vol) multiple steam injections into different compartments, internal and external spray (on top of dome) initiations, boiling sump simulation, "dry" energy addition and venting measures at three different axial positions. Special attention was given to the completeness accuracy and reliability of instrumentation especially with respect to local H2-concentrations and steam/air concentrations. 45 H2-sensors were applied throughout the facility with the same number of steam/air concentration sensors, and thermocouples in their immediate vicinity. In addition, velocities and structural temperatures were measured inside the containment as well as throughout the annular gap between steel shell and secondary concrete. The paper outlines all major facility features used during the individual experiments and presents the detailed experimental procedures and results as performed for tests Ell.2 and Ell.4. Experimental results of test Ell.2 will be used to demonstrate the major findings and the most important effects by mitigating measures on the containment atmosphere, expecially the H2-concentration throughout the facility. The results will be shown both in the format of time histories of the important quantities as well as by virtue of axial profiles with time as parameter. The institutions and computer codes which participate in the PHDR-Benchmark Exercise on Ell. 2 and Ell. 4 will be identified. Test Ell.2 has been recently chosen for the open post-test OECD-International Standard Problem No. 29 on hydrogen distribution.