Thermal integrity tests of a shipping package using a slice model and a half-scale model

KORAD-B/II shipping packages, developed by the Korea Radioactive Waste Agency (KORAD), are used to transport C4 concrete packages, which are temporarily stored in the HANUL nuclear power plant. These packages must therefore meet the requirements of the Korea Nuclear Safety Security Commission Act 2017-56, the IAEA Safety Standard Series No. SSR-6, and US 10 CFR Part 71. The regulatory guidelines classify a KORAD-B/II shipping package as a Type B package, and state that this type of package must be able to withstand a temperature of 800 °C for a period of 30 min. It is desirable to use a full-scale model of a shipping package when performing tests to evaluate its integrity. However, performing a test using a full-scale model is costly. Therefore, to evaluate the thermal integrity of a KORAD-B/II shipping package, thermal tests were conducted using a slice model. For comparison, a thermal test was also carried out using a half-scale model. In the first thermal test using the slice model, the maximum surface temperature of the cask body was higher than the permitted maximum temperature limit because of incomplete combustion. In the second thermal test using the slice model and in the thermal test using the half-scale model, the maximum temperature of the cask body was lower than the permitted maximum temperature limit, thus proving that the thermal integrity of the KORAD-B/II shipping package could be maintained. The temperature results of the thermal test using the slice model were higher than those of the thermal test using the half-scale model. The effect of flame on a single-layer shipping package without neutron shielding, such as the KORAD-B/II shipping package, appears to be influenced more by a reduction in time rather than in size.