Geo-Scientific Evidence to Support the I1 Isolation Function Related to Human Actions, As Part of the Safety and Feasibility Case 1 (SFC1)
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EXTERNAL REPORT SCK•CEN-ER-186 12/MDC/P-39 Geo-scientific evidence to support the I1 isolation function related to human actions, as part of the Safety and Feasibility Case 1 (SFC1) Mieke De Craen, Koen Beerten, Matej Gedeon and Katrijn Vandersteen SCK•CEN Contract: CO-90-08-2214-00 NIRAS/ONDRAF contract: CCHO 2009-0940000 Research Plan Geosynthesis July, 2012 SCK•CEN RDD & PAS Boeretang 200 BE-2400 Mol Belgium EXTERNAL REPORT OF THE BELGIAN NUCLEAR RESEARCH CENTRE SCK•CEN-ER-186 12/MDC/P-39 Geo-scientific evidence to support the I1 isolation function related to human actions, as part of the Safety and Feasibility Case 1 (SFC1) Mieke De Craen, Koen Beerten, Matej Gedeon and Katrijn Vandersteen SCK•CEN Contract: CO-90-08-2214-00 NIRAS/ONDRAF contract: CCHO 2009-0940000 Research Plan Geosynthesis July, 2012 Status: Unclassified ISSN 1782-2335 SCK•CEN Boeretang 200 BE-2400 Mol Belgium © SCK•CEN Studiecentrum voor Kernenergie Centre d’étude de l’énergie Nucléaire Boeretang 200 BE-2400 Mol Belgium Phone +32 14 33 21 11 Fax +32 14 31 50 21 http://www.sckcen.be Contact: Knowledge Centre [email protected] COPYRIGHT RULES All property rights and copyright are reserved to SCK•CEN. 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SCK•CEN, Studiecentrum voor Kernenergie/Centre d'Etude de l'Energie Nucléaire Stichting van Openbaar Nut – Fondation d'Utilité Publique ‐ Foundation of Public Utility Registered Office: Avenue Herrmann Debroux 40 – BE‐1160 BRUSSEL Operational Office: Boeretang 200 – BE‐2400 MOL Table of Contents 1 Introduction ......................................................................................................................... 7 2 Safety functions and the development of safety statements .............................................. 10 3 The safety function 'Isolation' (I) ...................................................................................... 11 4 Geo-scientific evidence to support the safety statement on 'reducing the likelihood of inadvertent human intrusion and human actions, and its possible consequences' (I1) ..... 12 4.1 The thickness of the overlying rock mass .......................................................... 14 4.1.1 Current thickness of the rock mass overlying the Boom Clay ........................... 14 4.1.2 Long-term evolution of the thickness of the overlying rock mass ..................... 16 4.1.3 Main conclusions on the thickness of the overlying rock mass ......................... 18 4.2 Natural resources in the Campine and associated human actions...................... 19 4.2.1 Natural water resources ...................................................................................... 20 4.2.2 Natural mineral resources ................................................................................... 26 4.2.3 Natural energy resources .................................................................................... 31 4.2.4 Use of deep geological layers ............................................................................. 42 4.2.5 Concessions and conflict of use ......................................................................... 50 4.2.6 Main conclusions on the natural resources in the Campine ............................... 51 4.3 Consequences of human actions in the Campine ............................................... 53 4.3.1 Possible consequences of exploitation of natural water resources ..................... 53 4.3.2 Possible consequences of exploitation of natural mineral resources ................. 56 4.3.3 Possible consequences of exploration and exploitation of natural energy resources ............................................................................................................ 56 4.3.4 Possible consequences of exploration and use of deep geological layers for gas storage ................................................................................................................ 58 4.3.5 Borehole drilling as most important type of inadvertent human intrusion ........ 59 4.3.6 Main conclusions on the possible consequences of human actions in the Campine ............................................................................................................. 68 5 References ......................................................................................................................... 69 5 1 Introduction The general safety objective of disposal as the final step of radioactive waste management is to protect human health and the environment, now and in the future, without imposing undue burdens on future generations. The generally adopted strategy for disposal to achieve this objective is to concentrate and confine the waste and to isolate it from man and the environment (IAEA, 2006). A safety case is a collection of arguments and evidence that demonstrates that a particular facility, part of a facility or an activity on a site is safe. Safety assessment is the process of using appropriate methods to analyse systematically the risk associated with the facility, and the ability of the site and the design of the facility to meet safety requirements (IAEA, 2011). The safety assessment methodology for geological disposal of radioactive waste is implemented through different safety functions (ONDRAF/NIRAS, 2009 a-b-c), i.e. functions that the disposal system should fulfil to achieve its general safety objective of providing long- term safety through concentration and confinement strategy. ONDRAF/NIRAS considers three main safety functions: engineered containment (C) preventing the dispersion of contaminants from the waste form as long as required, delay and attenuation of the releases (R) in order to retain the contaminants within the disposal system for as long as required, and isolation (I) of the waste from humans and the biosphere for as long as required. These three main safety functions are furthermore divided in several sub-functions, and for each of them, a set of safety statements is developed. The isolation function I is determined by the geological environment, the occurrence of natural resources and associated possibility of human intrusions, the long-term geodynamic evolution of the geological system, and climate evolution. The sub-function I1 “Reduction of the likelihood of inadvertent human intrusion and of its possible consequences” is related to human actions, while the sub-function I2 “Ensuring stable conditions for the disposed waste and the system components” relies on the geological environment and its long-term evolution. In this report, we will focus on the geoscientific evidence to support the safety sub-function 'I1', i.e. 'reducing the likelihood of inadvertent human intrusion and of its possible consequences'. There are many national and international references which describe the study of human impacts on repositories of radioactive waste (Bailey et al., 2011). The terms used for those impacts vary widely, e.g. human events, intrusion events, future human actions, human intrusion, inadvertent actions, etc. Some of them are similar and some are slightly different in their meaning. Unfortunately, the IAEA glossary does not provide definitions for human action, human intrusion, inadvertent action or other related terms (IAEA, 2007). Therefore, Baileys et al. (2011) gave an overview of several definitions. Based on these, the following definitions are used here: ‘Human actions’ is a general term that encompasses those actions that can influence the surface as well as the underground environment of the disposal system, e.g. alteration of the groundwater flow regime (Baileys et al., 2011) and those that can potentially alter the barriers or/and safety functions of the disposal system .’Human intrusion’ is a special case of human actions treated separately in safety assessment (ICRP 1998, NEA, 1995). A human intrusion affects the integrity of the disposal facility with direct disturbance and can potentially give 7 rise to radiological consequences (IAEA, 2011). A typical example is the drilling of a borehole through the waste emplacement area. By definition, an intrusion event bypasses the isolation function, and consequently could jeopardise other passive safety functions. In some extreme cases, it could even bring the waste in direct contact with the intruder and the nearby population if the waste material is brought to the surface. Only ‘inadvertent’ human intrusions are considered in geological safety assessment where either the repository or its barrier system are accidentally penetrated or their performance impaired, because the repository location is unknown, its purpose forgotten, or the consequences of the actions are unknown (NEA, 1995; ICRP, 1998). Deliberate intrusion into a repository are of the responsibility of the intruder and it is inherently impossible to limit their probability or their consequences. The elevated exposures from human intrusion is an inescapable consequence of the decision to concentrate waste in a discrete disposal facility rather than diluting or dispersing it (ICRP, 1998). The Boom Clay at the Mol-site is considered as