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rod pipe container. Determining an upper fuel assembly enrichment limit for the Traveller is difficult due

to the complexity of the safety analysis, which covers numerous fuel designs and three versions of the

package. Subcritical margin is relatively insensitive to package array size due to the use of Boral plates

and polyethylene moderator blocks, which limit neutronic interaction between packages. The Traveller

standard version could support transportation of 5.5 to 6.5 wt% 235U (assembly average) PWR fuel

and polyethylene moderator blocks, which limit neutronic interaction between packages. 

The Traveller standard version could support transportation of 5.5 to 6.5 wt% 235U (assembly average) PWR fuel

assemblies for some fuel designs through a combination of transportation array size limits and safety

analysis margin harvesting. In addition, maximum enrichment can be increased by crediting minimum

integral poisons in the fuel assembly, similar to the TN-B1 BWR assembly package. Numerous critical

The CHT-OP-TU package can be configured to transport up to 18 wt% UO2 powder and up to 16.5 wt%

UO2 pellets through a combination of oxide vessel diameter and package array size. Numerous critical

experiment candidates are available for validation of 5 to 16.5 wt% 235U CHT-OP-TU models.

The Versa-Pac package is currently licensed to transport U materials enriched up to 100% 235U with a

235U content maximum allowed mass determined by enrichment bin and packaging type. Because the

Versa-Pac is already licensed to transport HALEU and has mass limits that are a function of enrichment,

using a combination of package array size and gadolinia rod credit. Subcritical margin is highly sensitive

to package array size in the un-poisoned TN-B1. Numerous critical experiment candidates were

identified for validation of 5 to 8 wt% 235U TN-B1 models.

The DN-30 package can support transportation of UF6 up to 9.5 wt% by reducing transportation array size

from unlimited (5 wt% 235U) to 2 packages (9.5 wt% 235U). These results are based on retaining the 10 CFR 71.55(b) exemption from the assumption of water leakage into the containment system. Because the

limiting accident conditions do not include water in-leakage, the neutron energy spectrum of the DN-30 is

harder than other evaluated packages and only a few critical experiments were identified with a similarity

index (ck) of 0.8 or higher. Discussion of methods for validation penalty assessment is provided in the

DN-30 analysis.

from unlimited (5 wt% 235U) to 2 packages (9.5 wt% 235U). These results are based on retaining the 10 CFR 71.55(b) exemption from the assumption of water leakage into the containment system. Because the limiting accident conditions do not include water in-leakage, the neutron energy spectrum of the DN-30 is harder than other evaluated packages and only a few critical experiments were identified with a similarity index (ck) of 0.8 or higher. Discussion of methods for validation penalty assessment is provided in the DN-30 analysis.

Table 31. Package array criticality summary.

Package Fuel form Enrichment

|Package|Fuel form|Enrichment (wt.% 235U)|HAC array size| Note |

|-|-|-|-|-|

|Traveller|PWR FA1|5|Varies| Current limit. |

1PWR FA = PWR fuel assembly, one per package, assembly average enrichment

2BWR FA = BWR fuel assemblies, two per package, assembly average enrichment

## Acknowledgements

Support for this work was provided by the NRC Office of Nuclear Regulatory Research and the Office of Nuclear Material Safety and Safeguards. The authors would like to thank many ORNL staff members for their feedback on the contents and presentation in this report.