Section 71.55 - General requirements for fissile material packages(a) A package used for the shipment of fissile material must be designed and constructed in accordance with §§ 71.41 through 71.47 . When required by the total amount of radioactive material, a package used for the shipment of fissile material must also be designed and constructed in accordance with § 71.51 .(b) Except as provided in paragraph (c) or (g) of this section, a package used for the shipment of fissile material must be so designed and constructed and its contents so limited that it would be subcritical if water were to leak into the containment system, or liquid contents were to leak out of the containment system so that, under the following conditions, maximum reactivity of the fissile material would be attained:(1) The most reactive credible configuration consistent with the chemical and physical form of the material;(2) Moderation by water to the most reactive credible extent; and(3) Close full reflection of the containment system by water on all sides, or such greater reflection of the containment system as may additionally be provided by the surrounding material of the packaging.(c) The Commission may approve exceptions to the requirements of paragraph (b) of this section if the package incorporates special design features that ensure that no single packaging error would permit leakage, and if appropriate measures are taken before each shipment to ensure that the containment system does not leak.(d) A package used for the shipment of fissile material must be so designed and constructed and its contents so limited that under the tests specified in § 71.71 ("Normal conditions of transport")-(1) The contents would be subcritical;(2) The geometric form of the package contents would not be substantially altered;(3) There would be no leakage of water into the containment system unless, in the evaluation of undamaged packages under § 71.59(a)(1) , it has been assumed that moderation is present to such an extent as to cause maximum reactivity consistent with the chemical and physical form of the material; and(4) There will be no substantial reduction in the effectiveness of the packaging, including: (i) No more than 5 percent reduction in the total effective volume of the packaging on which nuclear safety is assessed;(ii) No more than 5 percent reduction in the effective spacing between the fissile contents and the outer surface of the packaging; and(iii) No occurrence of an aperture in the outer surface of the packaging large enough to permit the entry of a 10 cm (4 in) cube.(e) A package used for the shipment of fissile material must be so designed and constructed and its contents so limited that under the tests specified in § 71.73 ("Hypothetical accident conditions"), the package would be subcritical. For this determination, it must be assumed that: (1) The fissile material is in the most reactive credible configuration consistent with the damaged condition of the package and the chemical and physical form of the contents;(2) Water moderation occurs to the most reactive credible extent consistent with the damaged condition of the package and the chemical and physical form of the contents; and(3) There is full reflection by water on all sides, as close as is consistent with the damaged condition of the package.(f) For fissile material package designs to be transported by air: (1) The package must be designed and constructed, and its contents limited so that it would be subcritical, assuming reflection by 20 cm (7.9 in) of water but no water inleakage, when subjected to sequential application of:(i) The free drop test in § 71.73(c)(1) ;(ii) The crush test in § 71.73(c)(2) ;(iii) A puncture test, for packages of 250 kg or more, consisting of a free drop of the specimen through a distance of 3 m (120 in) in a position for which maximum damage is expected at the conclusion of the test sequence, onto the upper end of a solid, vertical, cylindrical, mild steel probe mounted on an essentially unyielding, horizontal surface. The probe must be 20 cm (7.9 in) in diameter, with the striking end forming the frustum of a right circular cone with the dimensions of 30 cm height, 2.5 cm top diameter, and a top edge rounded to a radius of not more than 6 mm (0.25 in). For packages less than 250 kg, the puncture test must be the same, except that a 250 kg probe must be dropped onto the specimen which must be placed on the surface; and(iv) The thermal test in § 71.73(c)(4) , except that the duration of the test must be 60 minutes.(2) The package must be designed and constructed, and its contents limited, so that it would be subcritical, assuming reflection by 20 cm (7.9 in) of water but no water inleakage, when subjected to an impact on an unyielding surface at a velocity of 90 m/s normal to the surface, at such orientation so as to result in maximum damage. A separate, undamaged specimen can be used for this evaluation.(3) Allowance may not be made for the special design features in paragraph (c) of this section, unless water leakage into or out of void spaces is prevented following application of the tests in paragraphs (f)(1) and (f)(2) of this section, and subsequent application of the immersion test in § 71.73(c)(5) .(g) Packages containing uranium hexafluoride only are excepted from the requirements of paragraph (b) of this section provided that:(1) Following the tests specified in § 71.73 ("Hypothetical accident conditions"), there is no physical contact between the valve body and any other component of the packaging, other than at its original point of attachment, and the valve remains leak tight;(2) There is an adequate quality control in the manufacture, maintenance, and repair of packagings;(3) Each package is tested to demonstrate closure before each shipment; and(4) The uranium is enriched to not more than 5 weight percent uranium-235.60 FR 50264, Sept. 28, 1995; 61 FR 28724, June 6, 1996, as amended at 69 FR 3794 , Jan. 26, 2004