The Radioactive Material (Road Transport) (Great Britain) Regulations 1996

Regulation 2(1)

SCHEDULE 7 Requirements for packages containing fissile material

1.  Fissile material shall be packaged and shipped in such a manner that subcriticality is maintained under conditions likely to be encountered during normal and accident conditions of transport. The following contingencies shall be considered:

(a) Water leaking into or out of packages;

(b) The loss of efficiency of built-in neutron absorbers or moderators;

(c) Possible rearrangement of the radioactive contents either within the package or as a result of loss from the package;

(d) Reduction of spaces between packages or radioactive contents;

(e) Packages becoming immersed in water or buried in snow; and

(f) Possible effects of temperature changes.

2.  A packaging for fissile material shall be so designed that, if it were subjected to the tests specified in paragraphs 6–11 of Part III of Schedule 15:

(a) Neither the volume nor any spacing on the basis of which nuclear criticality control for the purpose of paragraph 6(a) has been assessed would suffer more than 5% reduction, and the construction of the packaging would prevent the entry of a 10 cm cube; and

(b) Water would not leak into or out of any part of the package unless water in-leakage into or out-leakage from that part, to the optimum foreseeable extent, has been assumed for the purposes of paragraphs 5 and 6; and

(c) The configuration of the radioactive contents and the geometry of the containment system would not be altered so as to increase the neutron multiplication significantly.

3.  For the purposes of this Schedule the following words have the following meanings:

• “undamaged”, in relation to a package, means the condition of the package as it is designed to be presented for transport; and

• “damaged”, in relation to a package, means the evaluated or demonstrated condition of the package if it had been subjected to whichever of the following combination of tests is the more limiting—

  (a)

  the tests specified in paragraphs 6–11 of Part III of Schedule 15 followed by the tests specified in paragraphs 13 to 15 of that Part of that Schedule and completed by the tests specified in paragraphs 18–20 of that Part of that Schedule (the mechanical test of paragraph 14 of that Part of that Schedule shall be that required by paragraph 8 of Schedule 12); or

  (b)

  the tests specified in paragraphs 6–11 of Part III of Schedule 15 followed by the test in paragraph 16 of Part III of Schedule 15.

4.  In determining the subcriticality of individual packages in isolation for the purposes of this Schedule, it shall be assumed that water can leak into or out of all void spaces of the package, including those within the containment system. However, if the design incorporates special features to prevent such leakage of water into or out of certain void spaces, even as a result of human error, absence of leakage may be assumed in respect of those void spaces. Special features shall include the following:

(a) Multiple high standard water barriers, each of which would remain leaktight if the package were damaged; a high degree of quality control in the production and maintenance of packagings; and special tests to demonstrate the closure of each package before shipment; or

(b) Other features given multilateral approval.

5.  The individual package damaged or undamaged shall be subcritical under the conditions specified in paragraphs 3 and 4 taking into account the physical and chemical characteristics including any change in those characteristics which could occur when the package is damaged and with the conditions of moderation and reflection as specified below:

(a) For all material within the containment system: the material arranged in the containment system

(i) in the configuration and moderation that results in maximum neutron multiplication; and

(ii) with close reflection of the containment system by water 20 cm thick (or equivalent) or such greater reflection of the containment system as may additionally be provided by the surrounding material of the packaging; and, in addition

(b) If any part of the material escapes from the containment system: that material arranged in

(i) the configuration and moderation that results in maximum neutron multiplication; and

(ii) with close reflection of that material by water 20 cm thick (or equivalent).

6.  An array of packages shall be subcritical. A number, “N” shall be derived assuming that if packages were stacked together in any arrangement with the stack closely reflected on all sides by water 20 cm thick (or its equivalent) both of the following conditions would be satisfied:

(a) Five times “N” undamaged packages without anything between the packages would be subcritical; and

(b) Two times “N” damaged packages with hydrogenous moderation between packages to the extent which results in the greatest neutron multiplication would be subcritical.

7.  In evaluating the subcriticality of fissile material in its transport configuration, the following shall apply:

(a) The determination of subcriticality for irradiated fissile material may be based on the actual irradiation experience, taking into account significant variations in composition.

(b) For irradiated fissile material of unknown irradiation experience the following assumptions shall be made in determining subcriticality:

(i) If its neutron multiplication decreases with irradiation, the material shall be regarded as unirradiated;

(ii) If its neutron multiplication increases with irradiation, the material shall be regarded as irradiated to the point corresponding to the maximum neutron multiplication; and

(c) For unspecified fissile material, such as residues or scrap, whose fissile composition, mass, concentration, moderation ratio or density is not known or cannot be identified, the assumption shall be made in determining subcriticality that each parameter that is not known has the value which gives the maximum neutron multiplication under credible conditions of transport.