Calculation of energy transfer rates into structures for the HDR containment experiments

The HDR containment experiments have greatly expanded the data base of energy transfer to structure within large, complex geometry volumes. In terms of linear dimensions, the HDR facility is close to full scale, the linear scaling ratio being ∼1.6. However, due to its unique elongated shape the severity of test conditions where enhanced. Consequently in several domains the test data now brackets the accidental containment conditions computed in the containment design and licensing process. Energy transfer rates where measured at 11 locations covering a wide range of post-accident conditions. The six tests which have already been performed have thus increased the data base severalfold and the program is continuing. This paper will confine itself to experiment and computational model comparisons and to the conclusions to be drawn from them. The experimental and calculated pressure values are superimposed on a set of parametric curves representing fractional energy absorption into structures up to the time of peak pressure. The adiabatic case forms the bounding envelope of pressures. It is shown in the figure that for the two earlier large scale experiments, namely the CVTR and Battelle-Frankfurt test series fractional energy absorption up to the time of peak pressure was ∼ 20-25%. A number of calculated pressures for actual containments obtained from various design documents are also shown. The calculated fractional energy absorption is seen to be lower, falling in the range of ∼ 15-20%. This reflects the various 'conservatisms' that afflict design calculations and the plotted points should not be confused with best-estimate values. Fractional energy absorption is seen to range from ∼ 35 to 45%. This high energy absorption range increases the significance of the HDR data for two reasons: it enhances the importance of the transferred energy component. The HDR thus provide a severe test for measuring the adequacy of energy transfer modeling; and it moves the data base in the direction that envelopes most structural energy absorption rates under actual accident conditions