Cover: Jörg Uttinger,Schwyz
The basic problem
Since ever, mining has always been faced with three major challenges:  First, fresh air had to be introduced into the mine in order to meet acceptable requirements for working conditions and to reduce dust and the explosive gas mixtures that were already known at an early stage. Secondly, the ancient miners were already aware of the hazards to their mines from collapse and water ingress, which could only be controlled to a limited extent with the technical means available at the time. Finally, the extracted raw material, ore (or coal) had to be brought out of the mine, which required the cleverest possible arrangement of transport routes to the surface. Ventilation, i.e. the supply of fresh air, the stabilization of galleries, the control of water ingress or flooding risks, and the transportability of raw materials determined the possibilities and limits of underground mining from the very beginning. These three elements of underground mining have remained decisive for every deep mining facility to this day and are also accentuated in the planning of deep geological repositories for nuclear waste and chemo-toxic underground storage facilities. This is because, in contrast to the extraction of raw materials, the final disposal of highly toxic substances has another safety-determining condition: in contrast to the raw materials that are extracted from underground, the path of highly toxic substances leads in the opposite way. They are taken underground, which implies fundamentally different requirements for underground safety. On the one hand, the cavities in the underground must be excavated using techniques that are as gentle as possible in order to minimize the inevitable damage to the rock. On the other hand, the accesses to these man-made repositories have to be permanently sealed watertight, which poses a challenge of unprecedented dimensions. Waste storage tunnels also pose significantly higher conditions in terms of the length of time during which the cavities must remain stable for storage and possible monitoring.
Most of the deep mines were operated by vertical shafts with elevator systems. However, especially in regions with strong topography, underground facilities were also served by «ramps», i.e. horizontal or inclined access tunnels.
The ramp as a key element of the project
Significantly, the search for repositories for radioactive waste, in addition to facilities in the crystalline basement (SKB – project in Sweden), focused very early on salt mines. Already in the mid-1950s, former salt mines were considered as possible sites for the disposal of radioactive waste.  After first incidents and failures , the deep mine concept was reformulated in a central point starting in the mid-1970s. New facilities, specifically designed for final waste disposal, were to be planned and built, such as proposed by the Lawrence Berkley Laboratory, or such as realized at Gorleben in Germany respectively the facilities planned as part of the Swedish SKB repository.
Figure 1: Access options in the Swedish SKB concept. On the left, according to the original concept with shafts , on the right with ramp and shafts from the mid-1990s .
Figure 2: Evaluated connection systems for the final disposal of high-level radioactive waste in the Swedish geological subsurface. Finally, the KBS-3 system was selected .
Finland followed the Swedish example and developed a similar layout for the construction of the underground repository (Figure 3). This tower-like ramp for the «Onkalo» (cave) geological repository has now been built.
Figure 3: Tower-like winding access ramp in the Finnish project .
Straight ramps with fixed inclinations – so-called access tunnels or «descenderies» – found their way into the projects of Andra in Bure (Figure 4) or the former US-American project in Yucca-Mountain.
Figure 4: The access to the planned Andra repository in Bure with a straight double ramp (https://www.andra.fr/cigeo/les-installations-et-le-fonctionnement-du-centre/les-installations-et-leur-localisation [15.03.2021])
Nagra, which had originally adopted the “crystalline rock concept” of SKB, also followed this same model in the course of the 1990s with regard to the access variant. In the Report «Demonstration of feasibility of disposal 2002»(Entsorgungsnachweis), the repository was connected by means of a multiple winding ramp (so-called helixes). This concept has been used for two decades in all technical presentations and reports of Nagra (Figure 5), including those of recent years (Figure 6). The authorities – namely the Swiss Federal Nuclear Inspectorate (ENSI) and the Swiss Federal Office of Energy (SFOE) – adopted Nagra’s model of a deep geological repository with a multiple helical ramp (Figure 7)  in their publications; although they always emphasized that both «shaft» and «ramp» variants had advantages and disadvantages, but were equivalent overall. Since ramps would be possible access solutions in any case, there would be no need to unnecessarily restrict the locations planning of the surface facilities. With ramps, it would be possible to access the underground storage from a wide radius around the potential storage areas. This was the premise of the now almost ten-year discussion on the placement of surface facilities, the core element of the public participation process on site selection within the framework of the Deep Geological Repository sectoral plan of Switzerland.
Figure 5: «Demonstration of feasibility of disposal 2002» with transport ramp, after Nagra 2002 .
Figure 6: Nagra’s access concept with a ramp (access tunnel), prioritized during about two decades, after Nagra 2014 .
Figure 7: The unquestioned acceptance of the Nagra concept  by the authorities: on the left according to ENSI, on the right according to SFOE .
During summer 2020, a reorientation appeared in the Nagra communication: the Safety Section of the Zurich North-East Regional Conference held a technical meeting on the topic of “retrievability” of waste from a deep disposal in Andelfingen on August 27. The specialist group invited Maurus Alig, project manager for stage 3 of Nagra’s Deep Geological Repository sectoral plan, on the one hand, and the author of the present blog contribution on the other, as speakers. During this very interesting event, Maurus Alig presented a new concept for the development of the deep geological repository using shafts, which led to questions and discussions following the presentations. The new access concept, based exclusively on shafts, was to be included in virtually all presentations and graphics by Nagra and the authorities from that time onwards (Figures 8 and 9). The development concept of the geological repository had thus been fundamentally revised, and in a way that is to be welcomed without any ifs and buts on this point.
Figure 8: Deep repository accessed exclusively by shafts (from Nagra NAB19-19, p. 2).
Figure 9: New Nagra access concept with shafts only, according to TFS 2020 .
The reorientation proves that those early critics of the sectoral plan were right, who had called for consistent planning “from the bottom up” and doubted the usefulness of early localization of the surface facilities, linked to the deep repository by a ramp.
The question is now, as to whether Nagra has actually progressed so far in defining the location of underground storage fields that a definitive spatial planning of the shaft locations makes sense. The statement that the placement of surface facilities is a purely spatial planning issue without safety aspects needs to be reviewed again.
Why is the concept amendment not officially annouced and publicly discussed?
According to statements by a large number of stakeholders in the Sectoral Plan procedure, there was no explanation for this conceptual change from ramps to shafts. Nagra, as well as the responsible authorities are silent about the reasons of this change. Also, in the first Nagra Work Report NAB19-19 on «Placement of Main Access Areas (HEBs) in the Siting Areas» (Nagra 2019) , one searches in vain for explanations for this substantial modification. The project of placing main development areas is justified by ENSI requirements from 2018: «With regard to the repository project planning in Stage 3, ENSI states: ‘The level of detail of the repository project planning is to be deepened in Stage 3 in such a way that the constructional criteria 4.1 and 4.2 of the Sectoral Plan can be evaluated on the basis of the repository projects to be prepared. The planned underground structures (including access structures, main access areas, multifunctional areas and other relevant transitions between access structures and storage level, branches to storage tunnels/caverns, sealing elements, storage tunnels, storage caverns) are to be designed to the required level of detail (cf. ENSI 2018).» This line of reasoning suggests that ENSI leads the process and sets the requirements that the implementing organization, Nagra, would have to meet and follow.
However, there is another reading for this silence and hiding of the causes and reasons for this major change in the design of the access facilities to the deep underground repository. This silence has causally to do with the extremely widespread inability to admit mistakes. In the last two blog contributions, we have once again encountered and described the defensive behavior adopted by the actors in the field of nuclear energy when it comes to diagnosing, admitting and correcting errors.  This motive is also at the forefront of the discussion about the connection between the surface facilities and the deep geological repository.
The advantages of shafts and the disadvantages of ramps were made abundantly clear to Nagra as well as to the authorities in the context of the so-called “Research Project on Repository Design”, which was started in Stage 2 from autumn 2011. At that time, the blog author already fundamentally questioned the equivalence of «ramp» or «shaft» advocated by ENSI. In a first written statement of January 10, 2012, we stated in this partial report submitted to the authorities and experts of the expert group: «In the 17 elements and criteria considered» for the comparison of shaft / ramp «8 of them did not result in any clear advantages for one or the other development variant. These 8 elements or criteria can be solved by technical or planning measures. In the case of the remaining 9 elements and criteria, the advantages in terms of accessibility are clearly in favor of the shaft variant. Ramps have clear and understandable disadvantages. Thus, the choice of a ramp for the development of the Swiss repositories has other reasons. »  In particular, the advantages of ramps claimed by Nagra and ENSI regarding potential operational risks (e.g., falling objects in a shaft with fatal consequences) to transport advantages – have also been refuted in other expert reports. For example, a report by the German Society for Plant and Reactor Safety (Gesellschaft für Anlagen- und Reaktorsicherheit GRS) from the summer of 2011, also failed to identify any advantages of transporting high-level waste via ramps (see Box 1).
|Box 1 Assessment of transport risks of transport containers with high-level waste via ramp or shaft according to a report by the German GRS, published July 2011* |
«The transport vehicle on a ramp carries fire loads in the form of hydraulic oil, lubricants and plastic parts. Depending on the type of drive, tires and diesel fuel are added. Ignition sources cannot be ruled out regardless of the drive type. Examples are short shots or overheated components. The transport vehicle will be equipped with fire detectors and fire-fighting equipment. These fire protection measures generally have a certain probability of failure in the event of a fire. The potential for manual fire suppression will be limited by route geometry, weatherization, and the time it takes for external forces to arrive on scene. » (p. A3-45) «The consideration of possible mechanical impacts on the waste package during transport via a ramp into the repository mine leads to a comparable evaluation as the consideration of possible thermal impacts. When driving over a distance of several kilometers with a slope of about 10% and, if applicable, a large number of spirals, a human or technical failure resulting in considerable mechanical impacts on the waste package cannot be excluded. Whether the release of a swelling term can occur as a result of an assumed impact depends in turn on the technical boundary conditions of the transport and the properties of the waste package.» (p. A3-46) And with regard to risks and incidents, the report states, “Even if the release of a source term can be ruled out in the event of a possible thermal or mechanical impact on the waste package during transport on the ramp, the recovery of the transport vehicle from the ramp and the restoration of the ramp for repository operation would, if necessary, have significant consequences for further repository operation. » As well as: “With regard to a possible accident, it is becoming apparent that in the case of a transport of waste packages via a ramp into the repository, the frequency of occurrence to be expected for accidents with thermal and/or mechanical effects on the waste package to be transported will be higher than this is to be expected comparably for a transport with a shaft conveyor. The incidents to be considered in connection with shaft hoisting are reliably avoided by the design of the shaft hoisting system with regard to their expected frequency of occurrence over the operating time of the repository. Designing the shaft hoisting system to limit the effects of the accidents not expected to occur over the operating lifetime of the repository is also possible.»«A clear argument in favor of the construction of a ramp for the transport of radioactive waste to underground ultimately does not result from the consideration of possible accidents. » (p. A3-47) * GRS, 2011, Analysis of operational experience and its significance for the facility concept and operation of a repository for heat-generating radioactive waste, Gesellschaft für Anlagen- und Reaktorsicherheit GRS, Final Report on Project 3608R02612, July 2011, https://www.grs.de/sites/default/files/pdf/GRS-A-3613.pdf (08.03.2021).
During winter of 2012, the discussion in the «Repository Design» expert group revolved precisely around this issue of risks and the long-term safety of the shaft/ramp. The review of our draft report on this topic for ENSI, which we requested on several occasions, was blocked. Neither ENSI nor Nagra wanted an open discussion that could have led to a questioning of the ramp concept. What is usual in any scientific process was deliberately circumvented and overridden in this case, namely the process of external review by the experts and scientists involved: the so-called review. In the book «Wohin mit dem Atommüll? » («Where to go with nuclear waste? ») of April 2019  there are excerpts from this discussion and the refusal by authorities and Nagra to have a real scientific discussion (Box 2). Succinctly, therefore, ENSI (5 April 2021) concludes on the question of «ramp or shaft as access» : «There is a great deal of national and international experience in the construction of underground structures, for example from the construction and operation of mines and tunnels. From the current point of view of the federal authorities, access to the deep geological repository by means of a ramp or a shaft is possible in principle. Both variants have advantages and disadvantages.» But the question is not – as stated at the beginning of this blog – whether tunnels and mines can be built. Because, in terms of construction, that experience has been there for at least 150 years. The all-important question in the case of the deep geological repository is a different one: namely, whether it is possible to gently excavate the access to the geological subsurface in accordance with the requirements and whether a safe long-term closure is feasible under the given conditions and with the help of the closure materials. This question has not been tested in any way today due to the lack of concrete empirical values, and past practice with open mines has confirmed the hydraulic hazard to the underground again and again – even in the case of mines that were opened in more recent times .
|Box 2: Excerpts from the shaft/ramp discussion in the book «Wohin mit dem Atommüll?» |
(Where to go with nuclear waste?), Rotpunkt Verlag, pp. 154-155: «In the ‘Repository Design’ project, an analysis of the two access variants to the deep geological repositories is under discussion at the outset – shafts with direct vertical connection into the subsurface on the one hand, and slowly inclining tunnels, so-called ramps, on the other. Nagra favours the ramp variant due to logistical considerations and the freer connection of the repository to the surface. On the other hand, for risk considerations and long-term safety considerations, I recommend shafts – they cross water-bearing horizons more directly and are easier to confine, i.e., to close. I present a draft report ordered by ENSI to the scientists and authority members participating in the project in early 2012, including representatives of Nagra, the safety authority, the Federal Office of Energy SFOE, and experts from the cantons, ETH and other technical consulting offices. But the discussions that follow this presentation get out of hand. In addition, the review procedure, which is standard for scientific work and which should clarify points of dissent, is being circumvented – not only by Nagra, but also by ENSI. Not a single comment is returned on the feedback I requested on my report, although I follow up several times. For example, on 8 February 2012, the then technical director of Nagra wrote to me in response to my renewed request for comments that ENSI was of the opinion that it would not be opportune for Nagra to comment on my draft report and would therefore refrain from doing so. For his part, the head of ENSI’s section also wrote to me on 19 March to say that Nagra had informed him that it did not wish to comment on my draft. Which, of course, raises questions about what applies now and who determines the process here. One of the most central principles of scientific rigor, namely transparent fact-checking, is being undermined here, in an area where safety issues are central. Discussion of these central questions is being evaded in this way. And there is a system to this approach: time and again, Nagra steers and controls procedures and issues in this way from the background, leaving little or no room for fundamental review. This is because it shies away from an open scientific discussion that would bring other solutions to the fore. It is really only concerned with getting its own repository concept through the sectoral plan procedure as unscathed as possible and presenting it as the result of discussions and debates with scientists and affected authorities and representatives of the siting regions. The events and discussion rounds organized for this purpose serve precisely the purpose of validating the predetermined concepts. »
What is missing? Where is it sticking?
So, what are the real reasons for the lack of an open discussion culture in the Swiss waste management project, which once again becomes apparent in the question of connecting the ramp/shaft to the deep underground? For the repeatedly mentioned resistance of Nagra and the authorities to face up to scientific facts? For the incomprehensible insistence on outdated ideas of host rocks up to design options? If one looks at the course of nuclear waste management in Switzerland from the beginning, you will find this behavior of nuclear institutions and organizations in charge, which is contrary to all reason, again and again. As an explanation for this paradoxical cultural style, terms such as lack of knowledge, incompetence, strategic overload, lack of foresight, or lack of error culture come to mind. But all these explanations fall short. Both Nagra and Ensi, as well as the various commissions and expert committees, have the necessary skills and knowledge to correctly address and answer questions such as the development of the underground via shaft/ramp. So where are the real reasons for this hardly comprehensible misbehavior?
The answer is basically simple: What is at stake here is nothing else than power and enforcement claims under the pecuniary pressure of nuclear interests in Switzerland. The main objective of the Deep Geological Repository sectoral plan is to finally obtain the general license for a repository that the nuclear industry has been longing for four decades. By hook or by crook. The parties behind this project want to have sovereignty over the lead of the project. There is no room for technical discussions. Warnings are thrown in the wind. At best, a culture of learning is asserted in official presentations. Mistakes and missteps are concealed, glossed over or the explanations – as in the case of the unrealistic planning and schedules – are twisted. The introduction of a gripping error culture is deliberately avoided. The formal documentation of project changes (and management changes) is obviously not of interest. The power circle around the nuclear energy does not want a culture in Switzerland that could avoid manipulations of a program like that of the Deep Geological Repository sectoral plan. The management and control of the disposal program is left to institutions that have led the nuclear disposal program to failure time and again. The resistance with which differentiated thinking is met actually only shows how the exclusion of unacceptable knowledge and disturbing opinions is practiced. Because if the unpleasant is excluded, one does not have to deal with it.
The change of the connection from ramp to shaft follows exactly this principle. There is nothing to explain on the part of the planners and the authorities, although the questions are obvious. What were the reasons of this fundamental changes? Who initiated it? For what reasons? Were only safety concerns regarding the bearing design decisive? Or was it ultimately the cost that led to the rethink? Which external experts and companies were involved in this decision? How did the authorities react to the change of course? Why were they not informed? And perhaps as the most important questions in this set, how is this process being logged? Is there change management in place? If not, why not? If yes: why was this not communicated? Doesn’t one finally want to follow the example of Ralph Schulz of ENSI, who at least admitted to having been wrong once ? Do the management personnel in Bern (SFOE), Brugg (ENSI) and Wettingen (Nagra) really believe that credibility can be established with this approach? And above all, what does this change mean for the site selection process and the selection criteria applied in this process?
In any case, there remains the unpleasant aftertaste that the «ramp concept » was primarily intended to give the public opinion the illusion that the population had a certain degree of liberty in the co-determination of the localization of the surface facilities.
What remains of the principles of ENSI?
Thus, at the end of this article, the main intention remains to make the mechanisms of these procedures visible. To this end, we recall some of the principles of ENSI’s self-assessment, which are laid down in the 2014 mission statement (or charter) of the supervisory authority :
- «We are the center of excellence for nuclear safety assessment in Switzerland. We base our decisions on the current state of science and technology. » (Guiding principle 1, bullet 2)
- «Through our supervision, we strengthen the safety culture of the supervised parties and their self-responsible actions. » (Guiding principle 2, bullet 3)
- «We question ourselves and our actions. Differences are addressed openly and resolved together. » (Guiding Principle 3, bullet 3).
- «We are aware of and embrace our role of exemplarity. » (Guiding principle 4, bullet 1)
ENSI’s brochure on the supervision of deep geological repositories of July 2017 , sets out further working principles. E.G.
- Principle 3: «The waste producers develop solutions for the realization of deep geological repositories. ENSI’s central task is to assess the proposed solutions and, in doing so, to evaluate whether the protection goals, guiding principles and safety criteria are met. »
- Or Principle 4: «ENSI addresses safety-related issues of all stakeholders at an early stage and takes safety-related aspects into account in its supervisory activities. »
In any case, the way in which the supervisory authority has dealt with the development of the repository design and the connection to the deep geological repository via shaft/ramp clearly shows: the mandate in accordance with the basics and principles outlined above has simply not been fulfilled.
References and notes
 Rebrik, Boris, 1987, Geologie und Bergbau in der Antike, Deutscher Verlag für Grundstoffindustrie; Rosenthal, P., Morin, De., Photiades, A., Delpech, S. et al, 2013, Mining technologies at deep level in Antiquity: The Laurion mines (Attica, Greece), HAL Archives ouvertes, https://hal.archives-ouvertes.fr/hal-00919534 (08.03.21)
 NAS, National Academy of Sciences, 1957a, The Disposal of Radioactive Wastes on Land. Report of the Committee on Waste Disposal of the Division of the Earth Sciences,National Research Council
 particularly the failure of the Salt Vault project at the Carey mine in Lyons, see Walker, Samuel Jr., 2006/2007, An «Atomic Garbage Dump» for Kansas, The Controversy over the Lyons Radioactive Waste Repository, 1970-1972, Kansas History: A Journal of the Central Plains 27 (Winter 2006–2007): 266–285, https://www.kshs.org/publicat/history/2006winter_walker.pdf (14.03.2021)
 LBL, 1978, Geotechnical assessment and instrumentation needs for nuclear waste isolation in crystalline and argillaceous rocks, Symposium Proceedings, July 16-20, 1978, Lawrence Berkeley Lab., University of California, LBL-7096, p. 218.
 KBS, 1978a, Handling of spent fuel and final storage of vitrified high-level reprocessing waste,Kärnbränslesäkerhet; KBS, 1978b, Handling and final storage of unreprocessed spent nuclear fuel,Kärnbränslesäkerhet.
 Ministry of Industry, o.J., Review of the KBS II Plan for Handling and Final Storage od Unreprocessed Spent Nuclear Fuel, https://inis.iaea.org/collection/NCLCollectionStore/_Public/12/635/12635802.pdf
 SKB, 1993, SKB Annual Report 1992, Stockhom May 1993, S. 63/67, http://www.skb.com/publication/9260/TR92-46webb_Part_I-II.pdf
 SKB, 2000, Integrated account of method, site selection and programme prior to the site investigation phase, Svensk Kärnbränslehantering AB, Swedish Nuclear Fuel and Waste Management Co, December 2000, https://www.skb.se/publikation/18341/TR-01-03.pdf
 In the last 10 years or so, Nagra began to present generic sketches of possible connection options to the subsurface in response to criticism of a lack of systematic analysis of repository configurations, e.g., Nagra, 2016, Generic description of shaft head facilities (auxiliary access facilities) of deep geological repositories, October 2016.https://www.nagra.ch/display.cfm/id/102490/disp_type/display/filename/d_ntb16-08.pdf
 Nagra, 2002, Opalinus Clay Project, Demonstration of feasibility of disposal (Entsorgungsnachweis) for spent fuel, vitrified high-level waste and long-lived intermediate-level waste, Summary Overview, December 2002, https://www.nagra.ch/data/documents/database/dokumente/$default/Default%20Folder/Publikationen/Broschueren%20Themenhefte/e_bro_proj_opa.pdf (08.03.2021)
 Nagra, 2014, Technical Report 14-10, Modelling of Radionuclide Transport Along the Underground Acess Structures of Deep Geological Repositories,NTB 14-10, August 2014, Nagra, 2014, Technical Report 14-10, Modelling of Radionuclide Transport Along the Underground Acess Structures of Deep Geological Repositories,NTB 14-10, August 2014
 ENSI, 2013, Deep Geological Repository, Disposing of Radioactive Waste Safely, https://www.ensi.ch/de/aufsicht/entsorgung/geologische-tiefenlager/ (14.03.2021)
 BFE, 2020, Deep Geological Repository, 5 November 2020, https://www.bfe.admin.ch/bfe/de/home/versorgung/kernenergie/radioaktive-abfaelle/grundlagen-entsorgung/geologische-tiefenlager.html (14.03.2021)
 TFS, 2020, TFS, 2020, Spatial and hydraulic separation of the pilot repository from the main repository, ENSI/Nagra response of October 2, 2020 to question 151, Technical Forum on Safety, https://www.ensi.ch/de/technisches-forum/raeumliche-und-hydraulische-trennung-des-pilotlagers-vom-hauptlager/ (13.03.2021)
 Nagra, 2019, Deep Geological Repository Sectoral Plan Stage 3, Placement of the main access areas (HEB) in the siting regions Jura-East, Nördlich Lägern and Zurich-Northeast, working report NAB 19-19. May 2019. https://www.nagra.ch/display.cfm/id/102909/disp_type/display/filename/d_nab19-019.pdf (12. 03.2021)
 ENSI, 2018, Clarifications of the safety requirements for stage 3 of the sectoral plan for deep geological repositories. ENSI 33/649 (November 2018). Swiss Federal Nuclear Safety Inspectorate ENSI, Brugg.
 Marcos Buser & Jean-Pierre Jaccard, Error culture at ENSI: A book with seven seals? (Fehlerkultur im ENSI: Ein Buch mit sieben Siegeln?) https://www.nuclearwaste.info/fehlerkultur-im-ensi-ein-buch-mit-sieben-siegeln/; Jean-Pierre Jaccard, ENSI is not infallible, it has erred, https://www.nuclearwaste.info/das-ensi-ist-nicht-unfehlbar-es-hat-sich-geirrt/
 Buser, M., 2012, Design of a deep repository: an analysis, January 10, 2012, internal report. (Auslegung eines Tiefenlagers: eine Analyse, 10. Januar 2012, interner Bericht)
 Buser Marcos, 2019, Where to put nuclear waste? (Wohin mit dem Atommüll?), Rotpunkt Verlag, S. 154-155
 ENSI, 2012, Deep geological repository: ramp or shaft as acces (Geologische Tiefenlager: Rampe oder Schacht als Zugang), 5. April 2012, https://www.ensi.ch/de/2012/04/05/geologische-tiefenlager-rampe-oder-schacht-als-zugang/ (15.03.21)
 Industrial Minerals Summary Data,
https://www1.gnb.ca/0078/GeoscienceDatabase/IndustrialMinerals/qryIndMinSummary-e.asp?Num=1116, (21.08.20), see K+S (z.B. UTDs Herfa-Neurode und Zielitz) and EMC (Stocamine) had shareholdings in this mine; Stoeckl, L., Banks, V., Shekhunova, S., Yakovlev, Y., 2020, The hydrogeological situation after salt-mine collapses at Solotvyno, Ukraine, Journal of hydrology, Regional Studies, Volume 30, August 2020; Warren, J. K., 2017, Salt usually seals, but sometimes leaks: Implications for mine and cavern stabilities in the short and long-term, Earth Science Review 165, p. 302-341.
 see, for example, statements by Markus Fritschi, Nagra, in the Einstein television program of March 11, 2021
 see Jean-Pierre Jaccard, 2021, ENSI is not infallible, it got it wrong, nuclearwaste.info, 9. März 2021, https://www.nuclearwaste.info/das-ensi-ist-nicht-unfehlbar-es-hat-sich-geirrt/
 ENSI, 2014, Mission Statement of the Swiss Federal Nuclear Inspectorate (Leitbild des Eidgenössischen Nuklearinspektorats), February 2014, https://www.ensi.ch/de/wp-content/uploads/sites/2/2014/07/ensi_leitbild_charte_de_lifsn.pdf
 ENSI, 2017, Deep Geological Repository Supervision (Aufsicht über geologische Tiefenlage)r, July 2017. https://www.ensi.ch/de/wp-content/uploads/sites/2/2017/08/positionspapier-web-final.pdf (06.03.2021)