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Hatem, Mohammed
Publications (10 of 21) Show all publications
Hatem, M., Pusch, R., Knutsson, S. & Warr, L. (2016). Hydrothermal alteration of clay and low pH concrete applicable to deep borehole disposal of high-level radioactive waste: A pilot study (ed.). Paper presented at . Construction and Building Materials, 104, 1-8
Open this publication in new window or tab >>Hydrothermal alteration of clay and low pH concrete applicable to deep borehole disposal of high-level radioactive waste: A pilot study
2016 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 104, p. 1-8Article in journal (Refereed) Published
Abstract [en]

In the very deep borehole (VDH) concept for high level radioactive waste disposal, the combined usage of clay and concrete provides an attractive way of achieving both high strength and low permeability required for sealing the various sections of the hole. The concrete is required for mechanical stability where water-bearing fracture zones are intersected, whereas the clay effectively seals sections in stable rock masses. As both the clay and concrete may be exposed to temperatures in the range of 60–150 °C in various parts of the hole, there is a need to address the stability of these materials under thermally enhanced aqueous conditions. In this pilot study, a new type of organic-free, low pH concrete based on granulated blast furnace slag is tested, which is hardened and altered under hydrothermal conditions in the laboratory. The results presented show that both adequate compressive strength (up to ∼9 MPa) and low hydraulic conductivity (down to ∼5.6 × 10−10) is attained at elevated temperatures ranging up to 150 °C, indicating that clay-concrete sealing can be a successful method used to prevent radionuclides from migrating vertically up through the borehole repository.

National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-10481 (URN)10.1016/j.conbuildmat.2015.12.003 (DOI)000368956500001 ()2-s2.0-84950299787 (Scopus ID)94c58120-e20a-4774-ae29-39c1f197b8fb (Local ID)94c58120-e20a-4774-ae29-39c1f197b8fb (Archive number)94c58120-e20a-4774-ae29-39c1f197b8fb (OAI)
Note
Validerad; 2016; Nivå 2; 20151210 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Hatem, M., Pusch, R., Warr, L., Kasbohm, J. & Knutsson, S. (2015). Interaction of clay and concrete relevant to the deep disposal of high-level radioactive waste (ed.). Applied Clay Science, 118, 178-187
Open this publication in new window or tab >>Interaction of clay and concrete relevant to the deep disposal of high-level radioactive waste
Show others...
2015 (English)In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 118, p. 178-187Article in journal (Refereed) Published
Abstract [en]

A concept for the disposal of highly radioactive waste at depth in the Earth’s crust using very deep bore-holes requires that the upper 2 km’s of the 800 mm diameter, steeply drilled holes, be effectively sealed. This can be achieved by using dense smectitic clay where the rock is weakly fractured and strengthening with concrete when fracture zones are encountered. Earlier investigations have shown that chemical reactions between the clay and concrete can be expected both in the upper part where the temperature is lower than 90oC and in the deeper section where the temperature reaches up to 150oC. To study further this interaction, hydrothermal experiments were conducted using mixed-layer (illite/smectite) Holmehus clay and a low pH slag-based concrete placed in contact under isothermal conditions at 21°C, 100oC and 150oC for a period of 8 weeks. The sample sets, which consisted of two clay discs separated by concrete cast on the lower clay disc, were extracted in undisturbed form and exposed to uniaxial pressure for measuring the compressive strength at successively increasing pressures. Compression tests underenhanced thermal conditions led to strengthening of both the clay and concrete. X-ray diffraction and electron microscopy analysis of the material revealed an increasing degree of cation exchange at higher temperatures with the cement, whereby Ca replaced Na in the interlayer sites of smectite layers. Dissolution of illite/smectite was also evident occurring at enhanced temperatures, with a decrease in K, Mg and Fe content with advanced alteration. The enhanced strength of clay can be partly attributed to the precipitation of cement phases from circulating fluids, including precipitation of gypsum.

Keywords
low-pH slag cement, clay, chemical analysis, mineralogical analysis, stress/strain, hydrothermal treatment, Civil engineering and architecture - Geoengineering and mining engineering, Samhällsbyggnadsteknik och arkitektur - Geoteknik och gruvteknik
National Category
Infrastructure Engineering Geotechnical Engineering
Research subject
Structural Engineering; Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-15405 (URN)10.1016/j.clay.2015.08.008 (DOI)000365056400022 ()2-s2.0-84943649275 (Scopus ID)ee91e90a-7957-48cb-a82e-60d938dbc374 (Local ID)ee91e90a-7957-48cb-a82e-60d938dbc374 (Archive number)ee91e90a-7957-48cb-a82e-60d938dbc374 (OAI)
Note

Validerad; 2015; Nivå 2; 20140905 (mohhat)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2020-01-23Bibliographically approved
Hatem, M., Pusch, R. & Knutsson, S. (2015). Study of cement-grout penetration into fractures under static and oscillatory conditions (ed.). Paper presented at . Tunnelling and Underground Space Technology, 45, 10-19
Open this publication in new window or tab >>Study of cement-grout penetration into fractures under static and oscillatory conditions
2015 (English)In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 45, p. 10-19Article in journal (Refereed) Published
Abstract [en]

Grouting of the rock surrounding high-level waste (HLW) can serve to minimize groundwater flow around it and thereby to retard erosion of waste-embedding clay (buffer) and transport of possibly released radionuclides. Earlier attempts have shown the efficiency of superimposing the injection pressure with oscillations for bringing cement-rich grouts into narrow fractures using organic superplasticizers. However, these are short-lived and can produce radionuclide-bearing organic colloids, and should be replaced by inorganic agents. Portland cement in grouts is not long lived and low-pH cements are preferable as is also reduction of the cement content to an absolute minimum. The present study describes the composition and performance of candidate grouts in laboratory experiments with injection into plane-parallel slots with different aperture. The study included development of a simple and quick method for estimating the viscosity on the construction site for adapting the grout recipe to the injectability of the rock. A simple theoretical model for predicting grout penetration gives fair agreement with laboratory data. The longevity of the grout under various conditions is believed to be sufficient for use in HLW repositories implying waste placement in very deep holes

National Category
Infrastructure Engineering Geotechnical Engineering
Research subject
Structural Engineering; Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-16193 (URN)10.1016/j.tust.2014.08.003 (DOI)000347022600002 ()2-s2.0-84907702992 (Scopus ID)fc99768c-dab0-4683-bf78-031cc581e56b (Local ID)fc99768c-dab0-4683-bf78-031cc581e56b (Archive number)fc99768c-dab0-4683-bf78-031cc581e56b (OAI)
Note
Validerad; 2015; Nivå 2; 20140818 (mohhat)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Hatem, M. (2014). Cement-Poor Concrete and Grout for Use in Underground Constructions (ed.). (Doctoral dissertation). Paper presented at . : Luleå tekniska universitet
Open this publication in new window or tab >>Cement-Poor Concrete and Grout for Use in Underground Constructions
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the composition and properties of cement-based materials, concrete and grout, for use as seals and for stabilizing fracture zones in underground facilities like mines and repositories for chemical and radioactive waste. It is of general character with respect to the composition and preparation of concretes and grouts but focuses on the sealing of boreholes for mineral prospection and site investigation for locating underground repositories of hazardous waste.The proposed principle of constructing concrete seals in very deep boreholes (VDH) where they are intersected by fracture zones is to cast the concrete on-site over placed clay seals to the upper end of the respective fracture zones where the next clay seal is installed. The chemical interaction between concrete and clay causes mutual degradation that must be taken into consideration. Ordinary concrete with Portland cement as binder is not suitable because of its poor chemical stability over long periods of time and because of its high pH, more than 12, which attacks contacting clay seals. Another drawback is that such concrete requires organic superplasticizers for achieving fluidity and they can give off organic colloids that can transport radionuclides. Inorganic fluidizers like talc and use of low-pH cement offer new possibilities to prepare suitable concretes and grouts. They are the focus of this present document.The criteria for the concrete seals are: sufficient fluidity and coherence at casting and sufficiently high bearing capacity and low compressibility for maintaining constant volume conditions under the load of the overlying series of clay and concrete. The hydraulic conductivity of the hardened concrete should be lower than that of the surrounding fracture zone.Since the concrete must perform acceptably for up to 100,000 years and the cement component will ultimately be dissolved and lost, the rest, i.e. the aggregate components, must still provide acceptable support for overlying clay and concrete seals in deep boreholes. The aggregate component must therefore be very densely packed and have a granular composition that resists erosion.The main objectives of this study are: 1) To investigate the performance of new types of cement-poor, organic-free concrete for long-term duty under normal and extreme hydrothermal conditions at varying temperatures. Properties of special importance are fluidity, mechanical strength, rate of strengthening, pH, and minimum impact on contacting seals of smectite-rich clay seals.2) To investigate the function of new cement-based grouts proposed for sealing finely fractured rock around boreholes, tunnels and shafts where concrete seals will be cast, especially with respect to fluidity, rheological behaviour, mechanical strength, rate of strengthening, and penetrability into fine fractures. The study comprised testing of low-pH cement concretes and grouts with talc and other silicate minerals added for achieving fluidity and high strength. They were composed according to modern packing theories for obtaining low porosity and a minimum amount of cement paste. The use of talc is firstly for decreasing the viscosity of the mixture at casting or injection and secondly for assuring that it can really contribute to the mechanical strength by chemical interaction with the cement component. The need for chemical integrity led to the choice of quartzite as main aggregate in the study. The low-pH cement used was Merit 5000 manufactured by SSAB Merox AB, Oxelösund.For one of the candidate grouts, Portland cement was used in order to get quick hardening, whilst the other contained low-pH cement for providing high strength in the course of time. The principle of composing the aggregate was to obtain a filtering function so that the risk of losing fines is minimized in the construction period when local hydraulic gradients may still be high.It was concluded from this study that theoretical modeling as well as experimental results confirm that concrete mixtures can get high packing degrees and bulk densities if the ballast gradation is suitable and that the role of the fine fraction is thereby very important. The achieved density of the concrete is believed to be sufficiently high in order to make the concrete perform acceptably for very long periods of time even after complete loss of the cement. It was documented that talc serves to reduce the viscosity and contribute to the strength. The relatively low pH of Merit concrete (≈10) in contact with clay indicates that chemically generated destruction of either of the materials will be low. Such concrete, containing properly composed quartz-rich aggregate, and with talc added, fulfills the criteria set for its performance under both normal and high temperature conditions. It was also concluded that grout fluidity is positively affected by the hydrophobic nature of talc and negatively by thixotropic action of other silicates and by early cement hydration. The experiments highlight the role of the rheological properties and the need for proper composition of the grouts. A general conclusion from the grout flow study was that effective injection of grouts into fractures narrower than 100 µm requires that the viscosity is as low as 0.05 Pas and that high injection pressures are used.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2014. p. 220
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-17013 (URN)1260cbe7-72c2-4910-8c1f-e31be0cff779 (Local ID)978-91-7583-076-6 (ISBN)978-91-7583-077-3 (ISBN)1260cbe7-72c2-4910-8c1f-e31be0cff779 (Archive number)1260cbe7-72c2-4910-8c1f-e31be0cff779 (OAI)
Note
Godkänd; 2014; 20140924 (mohhat); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Mohammed Hatem Mohammed Ämne: Konstruktionsteknik/Structural Engineering Avhandling: Cement-Poor Concrete and Grout for Use in Underground Constructions Opponent: Professor Leena Korkiala-Tanttu, Department of Civil and Environment, Aalto University, Finland Ordförande: Professor Sven Knutsson, Institutionen för Samhällsbyggnad och Naturresurser, Luleå Tekniska Universitet Tid: Fredag den 5 december 2014, kl 10.00 Plats: F1031, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Hatem, M., Al-Ansari, N. & Knutsson, S. (2014). Enhancement of Workability of Cement-Poor Concrete by Optimizing Paste Content (ed.). Paper presented at . Engineering, 6(13), 869-876, Article ID 4.
Open this publication in new window or tab >>Enhancement of Workability of Cement-Poor Concrete by Optimizing Paste Content
2014 (English)In: Engineering, ISSN 1947-3931, E-ISSN 1947-394X, Vol. 6, no 13, p. 869-876, article id 4Article in journal (Refereed) Published
Abstract [en]

This study describes the performance of concrete in fresh state, intended for sealing deep boreholes in the host rock of radioactive repositories. Set of different paste volumes, combinations of water-to-powder ratios and fine aggregate contents have been performed within the frame of this study. The main objective was to search for tendencies, logical connections and phenomena that occur for different combination of materials regarding the fluidity and segregation and mainly the effect from the (paste) or fine aggregate content. It shall be pointed out that this investigation is a suggestion on how concrete can be optimized using two simple test methods based on changing the paste content. The results highlighted the importance of having sufficient amounts of filler and cement paste for separate and carry larger particles, which gives the concrete good workability and fluidity at casting. It was concluded that the slump behaviors can be optimized based on the adjustments of the superplastisizer dosage.

National Category
Infrastructure Engineering Geotechnical Engineering
Research subject
Structural Engineering; Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-7661 (URN)10.4236/eng.2014.613080 (DOI)610ca7f3-1066-464b-b5d2-f2619dac9dad (Local ID)610ca7f3-1066-464b-b5d2-f2619dac9dad (Archive number)610ca7f3-1066-464b-b5d2-f2619dac9dad (OAI)
Note
Validerad; 2014; 20141209 (mohhat)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Hatem, M., Pusch, R., Knutsson, S. & Jonasson, J.-E. (2014). Performance of Cement-poor Concrete with Different Superplasticizers (ed.). Paper presented at . International Journal of Research and Reviews in Applied Sciences, 18(2), 163-172
Open this publication in new window or tab >>Performance of Cement-poor Concrete with Different Superplasticizers
2014 (English)In: International Journal of Research and Reviews in Applied Sciences, ISSN 2076-734X, E-ISSN 2076-7366, Vol. 18, no 2, p. 163-172Article in journal (Refereed) Published
Abstract [en]

Concrete can be used for casting plugs in deep boreholes where fracture zones are intersected. They will be exposed to flowing groundwater and be in contact with very tight seals of smectite clay installed where the surrounding rock is tight. The cast concrete must be able to carry the clay segments placed over it after a few days. Its bearing capacity does not have to be very high after that since the clay soon adheres to the rock and carries itself. The concrete must be poor in cement for minimizing the risk of creation of voids caused by dissolution of the cement and it should have “inert” aggregate of quartz-rich material. Inorganic superplasticizers instead of conventional organic ones should be used for eliminating the risk of degradation and loss by formation of colloids that can carry radionuclides to the biosphere from holes bored in repository rock. The two concrete types discussed in the present study had Portland and Merit 5000 low pH cement as binders and crushed quartzite as aggregate. Talc mineral powder and ordinary organic Glenium 51 were used as superplasticizers for comparing their impact on the physical properties. The matrix of the cement-poor talc concrete gave ductile behaviour during initial hardening. The very dense matrix of either of the concretes would not lead to compression of the system even after complete loss of cement, which will happen over a longer period of time. The overall conclusion was that talc as superplasticizer and conditioner of the concrete can make the concrete sufficiently fluid for constructing seals at depth in boreholes, and react with cement to provide high strength with some delay. pH is much lower in Merit than in Portland concrete, which causes less impact on the clay seals. Portland concrete has five times higher strength than Merit concrete after a week but three times lower strength after 28 days.

National Category
Infrastructure Engineering Geotechnical Engineering
Research subject
Structural Engineering; Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-8522 (URN)70895446-3a89-416c-8ec1-276f5776f159 (Local ID)70895446-3a89-416c-8ec1-276f5776f159 (Archive number)70895446-3a89-416c-8ec1-276f5776f159 (OAI)
Note
Godkänd; 2014; 20140130 (mohhat)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-26Bibliographically approved
Hatem, M., Pusch, R., Knutsson, S. & Hellström, J. G. (2014). Rheological Properties of Cement-Based Grouts Determined by Different Techniques (ed.). Paper presented at . Engineering, 6(5), 217-229
Open this publication in new window or tab >>Rheological Properties of Cement-Based Grouts Determined by Different Techniques
2014 (English)In: Engineering, ISSN 1947-3931, E-ISSN 1947-394X, Vol. 6, no 5, p. 217-229Article in journal (Refereed) Published
Abstract [en]

The rheological properties of cement-based grouts containing talc or palygorskite were investigated for optimizing fluidity and quick strengthening at injection. The fluidity controls the ability of grout to penetrate fractures and can be determined by pipe flow tests, Marsh funnel tests, mini-slump cone tests and rheometer tests. The grouts were 1) Talc for fluidity and strength by reacting with cement, 2) Palygorskite (attapulgite) for early gelation by being thixotropic, and 3) Powdered quartz for chemical integrity. The freshly prepared grouts behaved as Bingham fluids with viscosities from 0.151 to 0.464 Pas and yield stresses 5.2 Pa to 36.7 Pa. Statistical analysis of the flow test data converted Marsh flow time into viscosity. The pipe flow tests gave 26.5% higher values than the viscometer for grout with Portland cement and talc, and about 13.7% lower than the viscometer data for the grout with low-pH cement and talc. The big Marsh funnel gave valuesdiffering by 5.2% - 5.3% from those of the viscometer for grout with talc and Portland, and Merit 5000 cements. For grout with palygorskite the viscosity was at least twice that of the other grouts. Grout fluidity was positively affected by talc and negatively by palygorskite and early cement hydration

National Category
Infrastructure Engineering Geotechnical Engineering Fluid Mechanics and Acoustics
Research subject
Structural Engineering; Soil Mechanics; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-8666 (URN)10.4236/eng.2014.65026 (DOI)7331101b-0624-4af1-8099-b54c7b9fc3cd (Local ID)7331101b-0624-4af1-8099-b54c7b9fc3cd (Archive number)7331101b-0624-4af1-8099-b54c7b9fc3cd (OAI)
Note
Validerad; 2014; 20140403 (mohhat)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-26Bibliographically approved
Pusch, R., Hatem, M. & Knutsson, S. (2014). VDH – a case of ostrich philosophy or a serious alternative for the disposal of highly radioactive waste? (ed.). In: (Ed.), C.A. Brebbia; G. Passerini; H. Itoh (Ed.), Waste Management and the Environment VII: . Paper presented at International conference on Waste Management and the Environment : 12/05/2014 - 14/05/2014 (pp. 377-390). Southampton: WIT Press
Open this publication in new window or tab >>VDH – a case of ostrich philosophy or a serious alternative for the disposal of highly radioactive waste?
2014 (English)In: Waste Management and the Environment VII / [ed] C.A. Brebbia; G. Passerini; H. Itoh, Southampton: WIT Press, 2014, p. 377-390Conference paper, Published paper (Refereed)
Abstract [en]

Two basically different concepts for disposal of highly radioactive waste are the often cited KBS-3 method implying isolation of such waste in copper canisters in short holes bored from tunnels at a depth of a few hundred meters, and disposal in the lower part of 4 km deep holes (VDH). The deep hole concept has the advantage that the waste packages will be located in very salt, stagnant groundwater in rock that is much less permeable than shallow rock with repositories of KBS-3V type. Disadvantages are that some of the techniques for installation have not yet been demonstrated and that retrieval of damaged or stuck canisters is deemed more difficult than for KBS-3V. Both concepts require precise adaption of canister and seal positions to the rock structure, which, for KBS-3 repositories, is not known until the tunnels have been constructed. For VDH, pilot borings provide such knowledge at low cost at a very early stage. The deep holes need to be supported by casings and all work deeper than 500 m must be made with clay mud in them. Reconsideration of the design and function of VDH shows that it has significant advantages, primarily respecting cost and construction time, and that new types of concrete for sealing purposes can make such repositories safer than KBS-3V disposal since seismic and tectonic events are less detrimental and future glaciations will cause much less disturbance. The most important value is that the groundwater that can possibly become contaminated by failing engineered barriers will stay at more than 2000 m depth and that there is no mechanism that can bring it up to the biosphere

Place, publisher, year, edition, pages
Southampton: WIT Press, 2014
Series
WIT Transactions on Ecology and the Environment, ISSN 1743-3541 ; 180
National Category
Infrastructure Engineering Geotechnical Engineering
Research subject
Structural Engineering; Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-30069 (URN)10.2495/WM140331 (DOI)2-s2.0-84903144145 (Scopus ID)3c489a84-2186-4794-a856-68e4fab8a3d0 (Local ID)978-1-84564-760-5 (ISBN)978-1-84564-761-2 (ISBN)3c489a84-2186-4794-a856-68e4fab8a3d0 (Archive number)3c489a84-2186-4794-a856-68e4fab8a3d0 (OAI)
Conference
International conference on Waste Management and the Environment : 12/05/2014 - 14/05/2014
Note
Godkänd; 2014; 20140313 (mohhat)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-07-10Bibliographically approved
Pusch, R., Warr, L., Grathoff, G., Pourbakhtiar, A., Knutsson, S. & Hatem, M. (2013). A talc-based cement-poor concrete for sealing boreholes in rock (ed.). Paper presented at . Engineering, 5(3), 251-267
Open this publication in new window or tab >>A talc-based cement-poor concrete for sealing boreholes in rock
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2013 (English)In: Engineering, ISSN 1947-3931, E-ISSN 1947-394X, Vol. 5, no 3, p. 251-267Article in journal (Refereed) Published
Abstract [en]

Deep investigation boreholes in crystalline rock for site selection of repositories for high-level radioactive waste are proposed to be sealed by installing a series of dense concrete and clay plugs. These should prevent radionuclides from leaking canisters at depth to migrate to the biosphere through the holes. The concrete seals will be installed where the holes intersect water-bearing fracture zones to serve as stable and low-permeable supports for adjacent clay plugs. Low porosity and microstructural stability must be guaranteed for many thousands of years and ordinary Portland cement with organic superplastizer will not fulfil the requirements since the high pH will cause degradation of contacting clay and the organic additive can produce colloids with a capacity to carry radionuclides up to the biosphere. Very cement-poor concrete (<8 %) based on low-pH cement and with talc as plasticizer is an option but it matures more slowly, which requires that the construction of seals is made so that sufficient bearing capacity for carrying overlying clay seals is reached.

Keywords
Clay, Concrete, Ductility, Strength, Superplasticizers, Talc, Civil engineering and architecture - Geoengineering and mining engineering, Samhällsbyggnadsteknik och arkitektur - Geoteknik och gruvteknik
National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-15658 (URN)10.4236/eng.2013.53036 (DOI)f32796a5-c272-4071-9fb7-6adb5a27100b (Local ID)f32796a5-c272-4071-9fb7-6adb5a27100b (Archive number)f32796a5-c272-4071-9fb7-6adb5a27100b (OAI)
Note
Validerad; 2013; 20130104 (mohhat)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-26Bibliographically approved
Pusch, R., Ramqvist, G., Knutsson, S. & Hatem, M. (2013). Medium-deep or very deep disposal of highly radioactive waste? (ed.). Paper presented at . Journal of Civil Engineering and Architecture, 7(12), 1548-1565
Open this publication in new window or tab >>Medium-deep or very deep disposal of highly radioactive waste?
2013 (English)In: Journal of Civil Engineering and Architecture, ISSN 1934-7359, E-ISSN 1934-7367, Vol. 7, no 12, p. 1548-1565Article in journal (Refereed) Published
Abstract [en]

Several of the commonly proposed concepts for disposal of highly radioactive waste (HLW) imply construction at medium depth (400-600 m) in granitic rock, which is excellent for constructing a stable repository since it provides effective mechanical protection of the waste. A drawback is that major water-bearing fracture zones are frequent and must be avoided in the site selection process since they can undergo large deformations caused by seismic and tectonic events and cause failure of waste containers located in or near them. The effect of such events can be minimized by surrounding them with ductile “buffer” clay that retards groundwater-driven adflow. An alternative concept is placement of HLW in very deep boreholes (VDH) where the rock is much less permeable and where the very salt, heavy groundwater is stagnant. The boreholes are proposed to be 4 km deep and grouped in a small number of sites. The upper 2 km parts, with temperatures lower than about 100oC, are sealed by being filled with perforated supercontainers with dense clay blocks, while the lower part contains supercontainers with waste canisters and dense clay blocks, raising the temperature between 2 and 4 km to 100-150oC. The holes are kept filled with clay mud into which the supercontainers are inserted where the rock contains few fractures, while concrete is cast where the rock is fracture-rich. In the upper part clay migrates through the perforated supercontainers and consolidates the mud. In the lower part clay the same process takes place where the clay block in each supercontainer is located, while the rest of the mud retains its original low density but undergoes stiffening. In the upper, sealed part of the hole, the consolidated clay will be much tighter than the surrounding rock, while in the lower part the mud will be more permeable but still capable of limiting water circulation within the hole. The paper compares the two repository principles and recommends closer examination of the very deep hole concept, which has obvious advantages respecting both performance and cost.

National Category
Infrastructure Engineering Geotechnical Engineering
Research subject
Structural Engineering; Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-8172 (URN)6a3bda16-767a-43f4-b458-e61a0e9a2136 (Local ID)6a3bda16-767a-43f4-b458-e61a0e9a2136 (Archive number)6a3bda16-767a-43f4-b458-e61a0e9a2136 (OAI)
Note
Validerad; 2013; 20130418 (mohhat)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-26Bibliographically approved
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