Near Surface Disposal of Radioactive Waste: Safety Requirements (Safety Standards Series No WS-R-1) and Safety Assessment for Near Surface Disposal of Radioactive Waste:Safety Guide (Safety Standards Series No WS-G-1.1)

Abstract

Near Surface Disposal of Radioactive Waste: Safety Requirements (Safety Standards Series No WS-R-1) IAEA Vienna: International Atomic Energy Agency ISBN: 92-0-101099-0Safety Assessment for Near Surface Disposal of Radioactive Waste: Safety Guide (Safety Standards Series No WS-G-1.1) IAEA Vienna: International Atomic Energy Agency ISBN: 92-0-101299-3These two complementary documents have been issued as part ofthe IAEA's RADWASS programme. The Safety Requirements publication sets out basic safety requirements for the disposal of radioactive wastes in near surface repositories. The Safety Guide addresses the safety assessment for near surface disposal of radioactive waste and provides recommendations on how to meet the requirements set out in WS-R-1.The scope of the Safety Requirements covers a wide range of repository designs, from above-ground structures to rock caverns at a few tens of metres depth. Such repositories are generally targeted at wastes containing short-lived radionuclides and low concentrations of long-lived radionuclides. The document is primarily aimed at new facilities, although the document suggests that it can be used in the review of existing and former repositories.The document states that radiation protection requirements for the operational phase need to take due account of the Basic Safety Standards. For post-closure, criteria should be in terms of dose, risk or both. For modes of repository evolution judged to be likely, projections of dose or risks should not exceed some appropriate fraction of the 1 mSv/y dose limit, or its risk equivalent. For unlikely events, it is suggested that the regulatory body should decide whether the outcome should be compared with the risk constraint, or whether dose and probability of occurrence should be disaggregated.In setting out organisational requirements, the document identifies what should be the roles of the waste generator, the repository operator and regulators, together with their interfaces.The document goes on to address requirements for waste acceptance, and repository siting, design, construction, operation and closure of the repository and post-closure phase. It states that as far as practicable, the safety of a closed repository shall not rely on institutional controls that necessitate continuing active measures.This Safety Guide concentrates on post-closure safety assessments; it is the behaviour of the repository over long periods which distinguishes repository assessments from the operational assessments as carried out for other types of waste management facilities.The guide discusses the various uses of safety assessments, from establishing feasibility at an early stage, siting, establishing waste acceptance criteria, support licence applications and helping to design environmental monitoring programmes. The importance of an iterative approach is stressed.The main part of the guide sets out the basic approach to repository safety assessments. It discusses data collection programmes and the development of conceptual and mathematical models, including the handling of features, events and processes (FEPS) and scenarios. The important aspects of sensitivity analyses and uncertainty and how they link are described.Finally, confidence-building measures are discussed. Methods of model verification, calibration and validation are described, as well as the potential uses of natural analogues and the peer review of results.These two documents provide a good introduction to the requirements for near surface repositories and a guide to safety assessments. They should be equally useful as an introduction to those new to this complex area, and as a reference for those with more experience.