ASN Report 2017

316 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 11  - Transport of radioactive substances The first three tests (drop, penetration and fire test) must be performed in turn on the same package specimen. They must be performed in the most penalising configuration (package orientation, outside temperature, position of content, etc.). The type B packagemodels 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 travel. To obtain this approval, the designer of the package model must demonstrate the ability to withstand the above-mentioned tests in the safety file. 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 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 fromnatural uranium), enriched (i.e. with an isotopic composition enriched in uranium-235), and 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 prescriptions for packages of UF 6 . They must meet the requirements of standard ISO 7195, which governs the design, manufacture and utilisation of packages. These packages are also subject to three tests: ཛྷ ཛྷ a free-drop test of between 0.3 and 1.2 metres (depending on the mass of the package) onto an unyielding target; ཛྷ ཛྷ a thermal test, with an 800°C fire for 30 minutes; ཛྷ ཛྷ a hydrostatic resistance test at 27.6 bar. Packages containing enriched, and therefore fissile UF 6 , are also subject to the prescriptions previously presented (see point 2.3.3). The UF 6 is transported in type 48Y or 30B metal cylinders. In the case of enriched UF 6 , this cylinder is transported with 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 package models are designed for the transport of highly radioactive substances by air. In France there is no approval for 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 around shipments of radioactive substances must be a constant concern. The public and non-specialisedworkers must not be exposed to a dose exceeding 1 millisievert (mSv) per year. However, this limit is not intended to be an authorisation to expose the public to up to 1mSv. 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 radiation at the surface of the package must not exceed 2mSv/h. This limit may be raised to 10 mSv/h in “exclusive use” 3 conditions, because the consignor or consignee can then issue instructions to restrict activities in the vicinity of the package. In any case, the radiation should not exceed 2 mSv/h in contact with the vehicle and should be less than 0.1 mSv/h at a distance of 2 metres from the vehicle. Assuming that radiation at the surface of a transport vehicle reaches the limit of 0.1 mSv/h at 2 metres, a person would have to spend 10 consecutive hours at a distance of 2m 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 linked to exposure to 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 principle): for example, lead-lined trolleys could bemade available to handling staff to reduce their exposure. This evaluation also makes it possible to decide on whether to implement dosimetry to measure the dose received by the workers, if it is anticipated that this risk could exceed 1 mSv/ year. Finally, all the transport stakeholders must be trained in the risks linked to radiation, so that they are conscious of the nature of the risks, as well as how to protect themselves and how to protect others. The workers involved in the transport of radioactive substances are also subject to the provisions of the Labour Code concerning protection against ionising radiation. 3 . 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. TABLE 2: Breakdown of transported packages by type TYPE OF PACKAGE APPROXIMATE SHARE OF PACKAGES TRANSPORTED ANNUALLY Packages approved by ASN Type B packages, packages containing fissile materials and packages containing UF 6 2% Packages not requiring approval by ASN Type A packages not containing fissile radioactive substances 32% Industrial packages not containing fissile radioactive substances 8% Excepted packages 58%