A Fire Test Stand for Thermal Testing of Extra-Large Packages

Abstract Packages for the transport of high-level radioactive materials are designed to withstand severe accidents. These packages must adhere to the specification-based criteria of the International Transport Regulations of the International Atomic Energy Agency (IAEA). To ensure compliance with these requirements, specific mechanical and thermal tests need to be addressed with respect to the package type. Typically, the Regulations prescribe mechanical tests followed by a thermal test as part of a cumulative test scenario. The thermal test is specified by the exposure of a test specimen for a period of 30 minutes to a thermal environment that provides a heat flux equivalent to that of a hydrocarbon fuel-air fire with an average fire temperature of at least 800 °C fully flame engulfing the test specimen. The Federal Institute for Materials Research and Testing (BAM) operates various test facilities for this purpose at their test site (TTS) near Berlin in Germany. Thermal tests for large packages are carried out in an established fire test stand that can be adapted by the test-setup to the geometric boundary conditions of a test specimen. This fire test stand is built for test specimens with masses up to 200,000 kg and geometric dimensions relating to large transport packages including their impact limiters. The test specimen is usually placed on a water-cooled support frame in the middle of the test-stand. The fire is realized by burning propane gas which is released in liquid state from an array of gas nozzles arranged in the form of a burner ring surrounding the test specimen. For particularly extra-large test specimens, two burner rings are used on top of each other and at different heights in order to firstly achieve full fire engulfment with a significantly larger volume of fire and secondly to achieve the required heat output. In advance of a regular thermal test BAM usually performs so-called fire reference tests to determine the test conditions for compliance with the IAEA requirements. These tests are performed using a generic package which corresponds to the external geometric dimensions of the test specimen used later in the approval test. Then, this reference package is exposed to a fire under defined test parameters whereas the corresponding heat input determined from the temperature changes measured is regarded as main criterion for proofing compliance with the IAEA criteria. The paper shows the experimental proof of the suitability of BAM’s fire test stand for thermal testing of extra-large packages. The heat input and fire temperatures fully meet the IAEA criteria but can also be set significantly higher for e.g. extra-regulatory testing.