COMPETENT AUTHORITY APPROVED FISSILE EXCEPTIONS ONE REGULATOR’S VIEW

The IAEA transport regulations contain criteria for excepting packages containing enriched uranium and/or plutonium from the requirements pertaining to fissile material. Many of these fissile exception criteria were designed to ensure a subcritical k∞ so that criticality safety was ensured regardless of packaging and without the need to control accumulations of packages or material. Concerns were raised over the adequacy of some of these criteria, in particular over the continued adherence to a criterion under accident (or even normal) conditions of transport. Material might initially meet a criterion, however, following an impact or fire the disposition of the fissile isotopes could change leading to the criteria not being met and consequently it may no longer be possible to guarantee criticality safety. With the introduction of TS-R-1 in 1996 a limit on the total mass of fissile material in a consignment was imposed on top of some of the fissile exception criteria in order to address these concerns. The fissile exception criteria have been under review for some time and one aim has been how to exempt materials containing fissile isotopes mixed with much larger quantities of non-fissile material and which do not pose a realistic criticality hazard. One provision in the proposed new fissile exceptions is for a material to be approved by the Competent Authority as fissile excepted and therefore posing no criticality safety concern. Such an approval would be given only following the successful assessment of a safety case justifying that material would remain subcritical under normal and accident conditions. This paper gives a view of the type of material that might be approved under this scheme, the criteria against which an application for approval may be assessed and the type of arguments that an applicant would be expected to present. This paper is the personal view of the author and does not represent UK Competent Authority policy.