Loew, Simon

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Editors MessageNuclear waste disposal in Switzerland: science, politics and uncertaintySimon Loew, Associate EditorIn Switzerland, radioactive waste arises from elec-tricity produced by five nuclear power plants and from theuse of radioactive materials in the fields of medicine,industry and research. The waste is grouped into threecategories: High-level waste (HLW) including spent fuel,Long-lived intermediate-level waste (LILW), and Low-and intermediate-level waste (L/ILW). It is foreseen that amaximum of 100,000 m3 of conditioned and packagedradioactive waste will arise in Switzerland over a periodof 40 years. Based on current knowledge, geologicaldisposal is the only method for isolating radioactivewaste, which fulfils the requirement for long-term safety.Two different types of geologic repositories are foreseenin Switzerland: a deep repository at a depth between 400and 1,000 m in the flat alpine foreland for HLW/LILW(accessed through vertical shafts or a ramp), and an in-termediate-depth repository in the alpine belt for L/ILW(accessed through a horizontal tunnel). Recently it hasbeen proposed that these repositories shall be built asmonitored geological disposal facilities, where the back-filling of access tunnels is delayed for several decades.The behaviour of the safety barriers shall be monitoredthrough long-term experiments in a so-called pilot facil-ity, which is situated just beside the sealed main disposalarea.The federal government and its experts have estab-lished legal and political procedures and protection ob-jectives for these repositories. The Swiss Federal NuclearSafety Inspectorate HSK has published the official re-quirements for geological disposal in the year 1993 (R 21guideline). The provisions in this guideline apply to allmethods of geological disposal in Switzerland and to allcategories of radioactive waste intended for disposal.They relate exclusively to long-term safety followingclosure of a repository. The overall objective of geolog-ical disposal is to protect human health and the environ-ment permanently against radiation from the wastes. Thetwo most important Swiss protection objectives are asfollows:Protection objective 1The release of radionuclides from a sealed repository,subject to the processes and events that may reasonablybe expected to occur during its lifetime, shall at no timegive rise to individual doses that exceed 0.1 mSv/year.Protection objective 2The individual radiological risk of a fatality arising from asealed repository, subsequent to processes and events notconsidered under protection objective 1, shall at no timeexceed one in a million/year.These objectives recognize humans as being radiation-sensitive organisms and thus, released radiation into thepopulation must not exceed a fraction of the dose nor-mally received from natural background radiation. If thehuman population is rigorously protected from radiationexposure, it is assumed that other living organisms willlikewise be protected. These objectives are integral to theprotection of our natural environment and are not limitedto any specific time limits. In the licensing procedure,the applicant (the Swiss nuclear waste producers) mustdemonstrate by means of a safety analysis that its pro-posal fulfils these requirements. Because of the integralnature of these objectives, the corresponding safetyanalyses must be based on model calculations incorpo-rating the full complexity inherent in these systems.Two strongly different aspects of these protection ob-jectives will be briefly discussed. The first relates to themismatch between the know-how of scientists involved inassessing these objectives for a given nuclear waste siteand the knowledge of the local population living near thesite. The second aspect deals with the challenges theseobjectives pose to the specialists and safety authoritiesinvolved.In Switzerland (as elsewhere), the site investigationand safety assessment technologies developed during thelast 20 years have reached a very high scientific andtechnical level (greatly exceeding that used to evaluatemunicipal and chemical waste disposal sites). Even formost professional engineers and geologist, who are notReceived: 5 March 2004 / Accepted: 5 March 2004Published online: 26 March 2004 Springer-Verlag 2004S. Loew ())Federal Institute of Technology ETH,Engineering Geology,8093 Zurich, Switzerlande-mail: loew@erdw.ethz.chHydrogeology Journal (2004) 12:121–122 DOI 10.1007/s10040-004-0337-1necessarily trained in the nuclear waste disposal field, it isvery difficult to evaluate the results from the corre-sponding safety analyses. This has lead to the call formore specific, and if possible, directly measurable siteevaluation criteria.During the many years of democratic political argu-ments about potential sites for L/ILW and HLW inSwitzerland, such site evaluation criteria have beenagreed upon formally (although they have not beenwritten into nuclear waste disposal regulations). Theydepend on the stage/progress of investigation at a givensite and the type of waste/repository called for. In theSwiss HLM/LILW repository program, a potential hostrock (Opalinus Clay) and disposal region (ZrcherWeinland) has recently been identified after 20 years ofsite evaluation and field investigation work. Key criteriaevaluated during the site selection process include theisolation capacity of the host rock, seismic and geody-namic stability, fault pattern, depth and volume of hostrock, groundwater flow properties, and explorability. Inthe L/ILW program, several investigations at various lo-cations led to the proposition in 1993 of a potential hostrock (Valanginian Marl) at a pre-alpine site (Wellenberg).This site was subsequently studied in great detail duringthe following years until the construction of an explora-tion drift was required to allow further geological/hy-drogeological investigation. Site exclusion criteria wereagreed upon prior to the construction of this drift, in-cluding the spatial distribution of low conductivity hostrock, the rate of groundwater inflow into the drift, and thegroundwater chemistry.Even with such measurable and clearly defined crite-ria, a few scientific reviewers did not agree to the con-clusions drawn by the specialists of the applicant andregulator involved in the site characterisation and selec-tion process. Political, social and/or personal motivationssignificantly influenced scientific statements made byearth scientists, giving politicians the required argumentsused in public debates. This was only one of many rea-sons that in 2002, the application for a concession for anexploratory drift of the Wellenberg site was rejected bythe people of the State of Nidwalden (57% against 43%),causing a major stop in the L/ILW program. Although theFederal Council had already granted the licence for thisdrift and the Cantonal Government had already grantedthe necessary concessions, the ensuing political develop-ments require that today we must re-evaluate the entireL/ILW disposal concept, discussing and defining newlegal constraints on a national level. A new Nuclear En-ergy Law that clarifies the roles of various stakeholdershas recently passed the Swiss Parliament and was pub-lished for public discussion.Turning to the challenges that the Swiss protectionobjectives pose to nuclear waste disposal professionals,the assessment of the specific site criteria discussed aboveis a relatively easy task compared to the evaluation of thetwo protection objectives described above. For example,it is already known that for a HLW/LILW repository in ahighly overconsolidated claystone at 600–800 m depth(Opalinus Clay), complex coupled thermo-hydro-me-chanical (and geochemical) processes exist influencingthe behaviour of the host rock. Fractures in the excava-tion-disturbed zone (EDZ) develop in response to theexcavation of shafts, drifts and caverns. These fracturesconduct fluids and gases and change their properties inresponse to swelling bentonite backfill, the heat pulsegenerated from waste, geochemical reactions, and fluidand gas pressures derived from the geosphere and/orwaste. Aspects of these processes are the subjects ofcurrent studies in underground test facilities such as MontTerri and in other ordinary laboratories involving so-phisticated experiments, but are limited with respect tothe selected coupled process components and are rarely atthe scale of the disposal project.As an engineering geologist who is also involved inseveral big tunnelling projects, this writer had to learn inthe past that nature (the rock mass) sometimes looks verydifferent from what is expected and reacts in new andunexpected modes. Sometimes, such surprises were en-countered in areas where it was thought that the geologywould be simple and well known. In tunnelling, the timescales between exploration, prediction, design and con-struction are in the order of 10 years; the operationalphase lasts approximately 100 years. For nuclear wasterepositories the time scales involved are obviously com-pletely different and in the case of the Swiss protectionobjectives, there are no time limits. Robust (simple)scenario analyses and monitored geological disposal fa-cilities help to reduce some of the corresponding uncer-tainties but they will not allow detailed prediction of whatwill happen in a couple hundred thousand years. There-fore the limits of current knowledge and the uncertaintyof predictions both in space, time and conceptual under-standing should be carefully discussed.122Hydrogeology Journal (2004) 12:121–122 DOI 10.1007/s10040-004-0337-1

Nuclear waste disposal in Switzerland: science, politics and uncertainty

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Nuclear waste disposal in Switzerland: science, politics and uncertainty

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