A Possible Alternative to the Water Immersion Test for Type-B Fissile Material Packages·

U.S. transportation regulations (10 CFR 71) require that a Type B package certified for the transport of fissile material be capable of withstanding a series of tests that demonstrate package integrity under hypothetical accident conditions (HAC). These tests, which are similar to those specified in IAEA regulations, include a sequence consisting of (1) a 9-m (30-ft.) free drop onto an unyielding surface, (2) a 1-m (40-in.) free drop onto a mild steel puncture bar, (3) an exposure to a 30-minute fire of at least 800°C, and (4) an 8-hour immersion in 0.9 m (3ft.) of water. The first three tests are required for all Type B packages. The water immersion test is needed only for fissile material packages, and then only if water inleakage is not assumed in the criticality analysis. (Regulations generally require one package remain subcritical with water inleakage, although exceptions provided in §71.55(c) can be approved. On the other hand, if the shipment contains. an array of packages, the applicant has more flexibility to demonstrate that water inleakage need not be considered for all packages, based on their performance under HAC.) For many packages, especially those that are small and relatively inexpensive, the method used to demonstrate that these requirements are satisfied is typically to perform the actual tests specified in the regulation on a sample package. Development of a testing plan and execution of the tests represent a considerable effort, and any changes in the package design or specifications implemented after such tests can have significant impact in the certification process. Because the water immersion test discussed above is not required for all Type B packages, it may not be part of the original test sequence. If at a later date a need is seen to qualify that package for fissile material, or if the criticality analysis without water inleakage is deemed inadequate, a repetition of the testing program would be a very undesirable course of action. This paper presents a possible alternative to conducting such a test. This alternative would be especially attractive in the case where the water immersion requirement arises...