Thermal Testing of Type B Packages in Furnaces per ASTM Standard Practice E 2230

In the United States, the requirements for the Hypothetical Accident Conditions (HAC) Thermal Test are presented in 10 CFR 71.73 (c)(4) and state: Exposure of the specimen fully engulfed, except for a simple support system, in a hydrocarbon fuel/air fire of sufficient extent, and in sufficiently quiescent ambient conditions, to provide an average emissivity coefficient of at least 0.9, with an average flame temperature of at least 800°C (1475°F) for a period of 30 minutes, or any other thermal test that provides the equivalent total heat input to the package and which provides a time averaged environmental temperature of 800°C. The fuel source must extend horizontally at least 1 m (40 in), but may not extend more than 3 m (10 ft), beyond any external surface of the specimen, and the specimen must be positioned 1 m (40 in) above the surface of the fuel source. For purposes of calculation, the surface absorptivity coefficient must be either that value which the package may be expected to possess if exposed to the fire specified or 0.8, whichever is greater; and the convective coefficient must be that value which may be demonstrated to exist if the package were exposed to the fire specified. Artificial cooling may not be applied after cessation of external heat input, and any combustion of materials of construction, must be allowed to proceed until it terminates naturally. This regulatory wording was first introduced in the 1996 version of 10 CFR 71. Before that, the thermal test outlined in 10 CFR 71 was very difficult to interpret. It was not clear that a method other than an actual pool fire (such as a furnace tests) could be used when actual physical tests were being performed. The added wording in the 1996 version answered some questions, including the use of means other then a pool fire; however, it, too, had clauses which remained open to interpretation. Some limited guidance could be found in U.S. Nuclear Regulatory Commission (NRC) Guides, and in the international regulations, but a comprehensive set of guidelines regarding the performance of 10 CFR 71 thermal tests did not exist. In 1997 Jorman Koski, then of Sandia National Laboratories, initiated the formation of the ASTM E05.13 Subcommittee on Large Scale Fire Tests under the E05 Committee on Fire Standards. Experts in the field of thermal testing of Type B shipping packages were invited to join the subcommittee based on their experience and general participation in the development of these types of tests. This subcommittee undertook the task of authoring an ASTM Standard Practice that would detail recommended practices for performing the thermal tests outlined in the NRC’s 10 CFR 71. Legitimacy of the ASTM Standard was ensured by the presence and participation of a representative of the U.S. NRC. The result of this undertaking was the publication of ASTM E2230, entitled Standard Practice for Thermal Qualification of Type B Packages for Radioactive Material in 2002.