Need For A Relook Into The Thermal Test Criteria Fortype B Package For Transport Of Radioactive Materials

Based on statistical data, hazardous materials (hazmat) transport accidents result in releases(78%), followed by fires (28%), explosions (14%) and gas clouds (6%) which includes subsequent hazard after release. On the other hand, during transport of radioactive materials (RAM), packages withstood accident impacts without any significant release. Though RAM transport constitutes a small fraction (<2%) of overall hazmat transport, it needs highest level of safety because of its nature, contamination potential, media attention, public perception, etc. Accordingly, stringent safety protocols are followed since beginning and being improved continually based on experiences gained and new/additional research studies. This paper focuses on the need for revising the thermal test criteria of IAEA’s SSR-6 (2018). During accident, different fire scenarios may be encountered such as cellulosic fire from solid combustibles of vehicle or pool fire from leaking petroleum tanker or exposed to radiant heat flux from the adjacent fire plume, etc. Because of significant increase in transport of gasoline, diesel, petrochemicals, etc., worst accident involves hydrocarbon fire which can grow rapidly to engulf package. Accidental hydrocarbon fire is characterized by smoke/sooty flame and radiative power varies with concentration of CO2,moisture, soot particles, etc. in the fire plume whose characteristics depends on fuel type, the shape & size of pool, atmospheric condition, etc. Literature data on pool fire of various hydrocarbon fuels have been analyzed with focus on large pool fires. It indicates that the flame temperature of majority of hydrocarbon fuel fire will be >1000 ºC whereas fire plume temperature is expected to be >900 ºC which is higher than the minimum 800 ºC stated in regulatory thermal test. In case of open pool fire test, hydrocarbon fuel, pool size required for full engulfment can be selected but flame emissivity (>0.9) and specimen’s surface absorptivity (0.8) cannot be maintained during actual test. These conditions can only be used for thermal qualification by analysis. Thus, it is imperative to revise the thermal test criteria. This paper will highlight the need for separately specifying regulatory test conditions for thermal qualification by analysis and actual pool fire tests along with proposed thermal test conditions for both categories.