Feedback from IAEA TRANSSC Working Group and Technical Expert Group on Criticality

One of IAEA's missions is to establish model regulations for the safe transport of radioactive material by all modes. The transport Regulations (SSR-6) are important for all stakeholders in transport including governments, regulators, operators of nuclear facilities, carriers, producers of radiation sources, cargo-handlers and the public. This mission for the evolution of SSR-6 is performed by the TRANsport Safety Standards Committee (TRANSSC). Four TRANSSC Technical Expert Groups (TTEG) are being established to deal with four subject areas for the Committee. The Criticality TTEG is one of them. The Criticality Working Group (CWG) already established at TRANSSC n°34 in July 2017 is the first WG under this TTEG. In the past, the CWG has met for two days, just before the TRANSSC meetings.The discussions during the past CWG meetings include the following topics:•Proposals on criticality safety for evolution of the Regulations or the Advisory Material SSG-26. Some of these issues are the resolution of an inconsistency between SSR-6 and the IMDG code for sea transport of large freight containers, a solution under development for the transport of empty washed UF6 cylinders;•Justification for the provisions of the Regulations. In support of a future Technical Basis Document development, the CWG has collected some consensus explanations related to provisions that have been questioned (for example, high-speed air accidents, 10 cm minimum external package dimensions and 10 cm cube entry, intent of confinement system, etc).•The interpretation of the Regulations. Examples include nuclear data at temperatures other than room temperature (including those at very low temperatures), \"exclusive use\" of large freight containers and conveyances, criticality safety at less severe test conditions than maximum (fire and others), etc.The first part of this paper aims to summarize the CWG exchanges about the three previous topics.The second part of this paper aims to present a questionnaire which is designed to share technical basis information, to learn about current use of SSR-6 and to encourage proposals for improvements. The final purpose is to compile the questionnaires to support future use and development of the SSR-6, SSG-26 and Technical Basis Document.