ASN Report 2020

The type B package models and those containing fissile substances must be approved by ASN or, in certain cases, by a competent foreign authority, before they can be allowed to be shipped. To obtain this approval, the designer of the package model must demonstrate the ability to withstand the above-mentioned tests in the safety case. This demonstration is usually provided by means of tests on a reduced-scale mock-up representing the package and by numerical calculations (to simulate the mechanical and thermal behaviour, or to evaluate the criticality risk). 2.3.4 Packages containing uranium hexafluoride UF 6 is used in the “fuel cycle”. This is the form in which the uranium is enriched. UF 6 can thus be natural ( i.e. formed from natural uranium), enriched (i.e. with an isotopic composition enriched in uranium-235), or depleted. Apart from the dangers arising from its radioactivity, or even its fissile nature, UF 6 also presents a significant chemical risk. The regulations thus set out particular requirements for packages of UF 6 . They must meet the requirements of standard ISO 7195 (see box previous page), which governs the design, manufacture and utilisation of packages. These packages are also subject to three tests: ∙ a free-fall test of between 0.3 and 1.2 m (depending on the weight of the package) onto an unyielding target; ∙ a thermal test, with an 800°C fire for 30 minutes; ∙ a hydrostatic resistance test at 27.6 bar. Packages containing enriched UF 6 , which is a fissile substance, are also subject to the requirements previously presented (see point 2.3.3). The UF 6 is transported in type 48Y or 30C metal cylinders. In the case of enriched UF 6 , this cylinder is transported within a protective shell, which provides the necessary protection for withstanding the tests applicable to packages containing fissile materials. The package models containing UF 6 must also be approved by ASN or a competent foreign authority, before they can be allowed to travel. 2.3.5 Type C packages Type C packages are designed for the transport of highly radioactive substances by air. In France there are no approved type C packages for civil uses. 2.4  The requirements guaranteeing the reliability of the transport operations 2.4.1 Radiation protection of workers and the public The radiation protection of workers and the public during shipments of radioactive substances must always be born in mind. The public and non-classified workers must not be exposed to a dose greater than 1 millisievert per year (mSv/year). However, this limit is not intended to be an authorisation to expose the public to up to 1 mSv. Moreover, the justification and optimisation principles applicable to all nuclear activities also apply to the transport of radioactive substances (see chapter 2). Radiation protection is the subject of specific requirements in the regulations applicable to the transport of radioactive substances. Thus, for transport by road, the regulations stipulate that the dose rate at the surface of the package must not exceed 2 millisieverts 1. Exclusive use corresponds to cases in which the vehicle is used by a single consignor. This consignor may then give specific instructions for all the transport operations. 2. The ALARA (As Low As Reasonably Achievable) principle appeared for the first time in Publication 26 from the International Commission on Radiological Protection (ICRP) in 1977. It was the end-result of a study of the radiation protection optimisation principle. per hour (mSv/hour). This limit may be raised to 10 mSv/h in “exclusive use (1) ” conditions, because the consignor or consignee can then issue instructions to restrict activities in the vicinity of the package. In any case, the dose rate must not exceed 2 mSv/h in contact with the vehicle and must be less than 0.1 mSv/h at a distance of 2 m from the vehicle. Assuming that a transport vehicle reaches the limit of 0.1 mSv/h at 2 m, a person would have to spend 10 consecutive hours at a distance of 2 m from the vehicle for the dose received to reach the annual public exposure limit. These limits are supplemented by requirements relative to the organisation of radiation protection within companies. The companies working in transport operations are required to implement a radiological protection programme, comprising the steps taken to protect the workers and the public from the risks arising from ionising radiation. This programme is more specifically based on a forecast evaluation of the doses to which the workers and the public are exposed. According to the results of this evaluation, optimisation measures must be taken to ensure that these doses are As Low as Reasonably Achievable (ALARA (2) principle): for example, lead-lined trolleys could be made available to handling staff to reduce their exposure. This evaluation also Prevention of risks of exposure to ionising radiation The joint ASN and Ministry for Labour instruction DGT/ASN/2018/229 of 2 October 2018, concerning the prevention of risks of exposure to ionising radiation, extends the scope of application of the notion of “zoning”, which aims to limit worker and public exposure, to the transfer of radioactive substances within a facility, its annexes or worksites. Thus, the phases of package loading or unloading on a conveyance, modification of a shipment, transhipment or temporary parking within the perimeter of a facility or its annexes can lead to the creation of a “monitored” or “controlled” zone, depending on the characteristics of the packages carried. In addition, specific actions are provided for in the Order of 23 October 2020 regarding measurements taken for the assessment of risks and checks on the effectiveness of the prevention means put into place for the protection of workers against the risks from ionising radiation. It requires, among others, that the periodic checks on vehicles used to carry radioactive substances are performed or supervised by the Radiation Protection Advisor. Whereas the first check is carried out before a vehicle is used for carriage of radioactive substances, to ensure the radiological cleanness of the vehicle, the subsequent checks are carried out to ensure that there is no contamination of the vehicle. These checks are performed at a frequency defined by the employer, taking account of the frequency of shipments and their radiological implications, as well as after each transport operation for which a contamination risk has been identified. In any case, the time between two checks shall not exceed three months. 272 ASN Report on the state of nuclear safety and radiation protection in France in 2020 09 – TRANSPORT OF RADIOACTIVE SUBSTANCES