Saanio and Riekkola Oy

Helsinki, Finland

Saanio and Riekkola Oy

Helsinki, Finland
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Reijonen H.M.,Saanio and Riekkola Oy | Marcos N.,Saanio and Riekkola Oy
Geological Society Special Publication | Year: 2017

It is planned to use bentonites as buffer materials in various types of geological repositories designed to host radioactive waste. For the bentonite materials, the hydrological and hydrogeochemical conditions are two of the main environmental factors affecting their evolution, assessed for a period of up to 1 Ma. Since it has been observed in laboratory tests that smectite, in particular montmorillonite, forms colloids and disperses in very dilute conditions, a scenario for chemical erosion has been discussed at length, especially in relation to geological repositories located in future glaciated terrains and locations otherwise potentially hosting dilute groundwaters. General understanding, based on laboratory experiments, is that bentonite erosion does not occur when the total charge equivalent of cations in groundwater is higher than 4 mM. However, based on current knowledge, it seems that chemical erosion is not observed in repository-relevant natural systems where groundwater conditions are below the given limit. Further investigation is therefore suggested to provide a better scientific understanding of the mechanisms involved in stabilizing smectites in these natural systems.

Siren T.,Aalto University | Hakala M.,Nokia Inc. | Valli J.,Pöyry | Kantia P.,Geofcon | And 2 more authors.
International Journal of Rock Mechanics and Mining Sciences | Year: 2015

The primary goals of the experimental work described in this paper were to establish the in situ spalling/damage strength of the intact rock, to establish the state of the in situ stress, and for the work to act as a Prediction-Outcome exercise within the context of confirmatory underground site investigations being conducted at the nuclear waste disposal site at Olkiluoto, in Western Finland. To establish the in situ mechanical properties, Posiva (the Finnish implementer) formulated the in situ Posiva Olkiluoto Spalling Experiment (POSE) in 2009. The outcome of this experiment was that rock failure mainly occurred due to structurally controlled factors, rather than being dictated solely by the expected location of the maximum stress. The POSE experiment also showed that the onset of fracture initiation in the Olkiluoto rock occurs at 40 MPa, and the rock mass strength is ca. 90 MPa-compared to the mean laboratory value of 104 MPa. In view of these observations made at the projected disposal depth, the vertical disposal concept, KSB-3V, will involve initiation of new fractures, although the horizontal disposal concept would be less affected by such fracture initiation. However, neither of the disposal concepts is expected to suffer any major rock mass failure, and the vertical disposal holes are not particularly sensitive to fracture initiation if the disposal tunnels are oriented within 30° trend of the major principal stress direction. © 2015 Elsevier Ltd.

Lusa M.,University of Helsinki | Lempinen J.,University of Helsinki | Ahola H.,University of Helsinki | Soderlund M.,University of Helsinki | And 3 more authors.
Radiochimica Acta | Year: 2014

Soil samples from three forest soil pits were examined down to a depth of approximately three metres using 1M ammonium acetate extraction and microwave-Assisted extraction with concentrated nitric acid (HNO3), to study the binding of cesium (Cs) at Olkiluoto Island, southern Finland. Ammonium acetate was used to extract the readily exchangeable Cs fractions roughly representing the Cs fraction in soil which is available for plants. Microwave-Assisted HNO3 extraction dissolves various minerals, e.g. carbonates, most sulphides, arsenides, selenides, phosphates, molybdates, sulphates, iron (Fe) and manganese (Mn) oxides and some silicates (olivine, biotite, zeolite), and reflects the total Cs concentrations. Cs was mostly found in the strongly bound fraction obtained through HNO3 extraction. The average Cs concentrations found in this fraction were 3.53±0.30mg/kg (d.w.), 3.06±1.86mg/kg (d.w.) and 1.83±0.42mg/kg (d.w.) in the three soil pits, respectively. The average exchangeable Cs found in the ammonium acetate extraction in all three sampling pits was 0.015±0.008mg/kg (d.w.). In addition, Cs concentrations in the soil solution were determined and in situ distribution coefficients (Kd) for Cs were calculated. Furthermore, the in situ Kd data was compared with the Cs K d data obtained using the model batch experiments. The in situ K d values were observed to fairly well follow the trend of batch sorption data with respect to soil depth, but on average the batch distribution coefficients were almost an order of magnitude higher than the in situ K d data. In situ Cs sorption data could be satisfactory fitted with the Langmuir sorption isotherm, but the Freundlich isotherm failed to fit the data. Finally, distribution coefficients were calculated by an ion exchange approach using soil solution data, the cation exchange capacity (CEC) as well as Cs to sodium (Na) and Cs to potassium (K) ion exchange selectivity coefficients. The calculated distribution coefficients corresponded well with the in situ distribution coefficient values. © 2014 Walter de Gruyter Berlin/Boston.

Sievanen U.,Saanio and Riekkola Oy | Hollmen K.,Saanio and Riekkola Oy | Mustonen S.,Posiva Oy | Syrjanen P.,ElyManagement Oy
Geotechnical Special Publication | Year: 2012

A Finnish company, Posiva Oy, is responsible for the research and management of the spent nuclear fuel from the Finnish nuclear power plants. Posiva Oy is constructing an underground research facility ONKALO, which is planned to be a part of the deep repository for high level nuclear waste. ONKALO has reached the depth of about -440 m. The construction started 2003 and the repository will be in use 2020. ONKALO is located in crystalline bedrock of which the fracturing properties, groundwater pressure and groundwater chemistry vary a lot with place and depth. The target for groundwater inflow is < 80 l/min in total for ONKALO (absolute acceptable maximum is 140 l/min). There are also local targets for major water conductive fracture zones. At the same time there are limitations for acceptable materials. The grouting materials have been studied and developed within several international R&D projects. During the tunnel driving, probe holes have been systematically bored and investigated by traditional water loss measurement and by Posiva flow log -device. Besides these, core drilled pilot holes have been drilled in places as the access tunnel has proceeded. In these holes detailed investigations have been done. These holes have produced much valuable data for grouting design. The grouting result has been controlled by measuring the groundwater inflow into the tunnel and by mapping of the leakage areas. The strict targets set for water inflow have been reached, except locally when the fracture zone HZ20 was intersected at the depth of ~300 m. When the access tunnel was about 4500 m long and three shafts were raise bored to the depth of -270 m, the total inflow was ~31 l/min. In the first 500-1000 m of the access tunnel, fracturing was quite dense and fracture apertures were reasonably large for the use of cement-based grouts. The first 1 km was nearly systematically pre-grouted, grouting fans and grouts were designed individually for each place. After 1 km the fracture density decreased considerably and fractures became less open. As the tunnel has gone deeper the need for grouting has diminished. At the same time grouting has become more difficult due to the small fracture apertures and the high groundwater pressure. Besides the production grouting, Posiva Oy has developed acceptable grouts and grouting techniques for the deep rock and performed R&D projects have ended up to many recommendations e.g. the use of low pH grouts, analytical approach for grouting design, use of time and grout flow rate as stop criteria and the use of typical designs. The materials and design methods have been used and tested in ONKALO and results have been promising. © 2012 American Society of Civil Engineers.

Grolimund D.,Paul Scherrer Institute | Wersin P.,University of Bern | Brendle J.,Upper Alsace University | Huve J.,Upper Alsace University | And 2 more authors.
Clay Minerals | Year: 2016

The Swedish and Finnish nuclear waste repository design, KBS-3H, foresees horizontal emplacement of copper canisters-bentonite modules surrounded by a titanium shell. The interaction of titanium with bentonite was studied here using a combination of wet chemistry and a spectroscopic approach to evaluate the potential impact of Ti corrosion on the clay. For natural analogue clays with high Ti contents, spectroscopic investigations showed that titanium occurs as crystalline TiO2. In contrast, the Ti in the MX-80 bentonite occurs in the clay structure, presumably in the octahedral sheet. Hydrothermal tests conducted at 200°C using synthetic montmorillonite showed little if any change in the montmorillonite structure at near-neutral and acidic conditions. Under alkaline conditions, limited alteration was observed, including the formation of trioctahedral clay minerals and zeolite. These changes, however, occurred independently of the addition of Ti. In the batch tests conducted at 80°C, Ti did not occur as separate TiO2 particles. The comparison of experimental data with spectroscopic simulations provides sound evidence that Ti was incorporated in a neoformed phyllosilicate structure. © 2016 Mineralogical Society 2016.

Sedighi M.,University of Cardiff | Masum S.A.,University of Cardiff | Thomas H.R.,University of Cardiff | Bennett D.P.,University of Cardiff | And 2 more authors.
3rd International Conference on Computational Methods for Thermal Problems, ThermaComp 2014 | Year: 2014

This paper presents the results of an investigation into the thermal behaviour of a site proposed for the deep geological disposal of high level radioactive waste in Finland. Temperature data, collected from 57 boreholes at depths of up to 1000m have been studied. The thermal behaviour of the rock at the site, which is based in ONKALO, is discussed. The results achieved provide an improved understanding of in-situ rock thermal conditions at the site; information which is required for the long term safety assessment of the disposal option.

Uotinen L.K.T.,Aalto University | Salo O.,Saanio and Riekkola Oy | Rinne M.,Aalto University
Rock Characterisation, Modelling and Engineering Design Methods - Proceedings of the 3rd ISRM SINOROCK 2013 Symposium | Year: 2013

Yield-Line Theory (YLT) has been in wide spread use since the 1960's. YLT allows determining of the upper-bound bending resistance of reinforced concrete slabs using the concept of virtual work. YLT can be used for two purposes in the design of sprayed concrete support: the determination of quality assurance demands for the sprayed concrete or in the design of adequate sprayed concrete layer thickness against a bending failure. The square slab energy absorption test (EN 14488-5) and the round panel flexural toughness test (ASTM C1550-12a) are used. Solutions for both tests are given and conversion equations are derived. Testing results produced during normal quality assurance testing process in Länsimetro project (Finland) are shown for comparison. Finally, the merits and draw-backs of the test types are discussed. © 2013 Taylor & Francis Group.

Kemppainen K.,Posiva Oy | Hakala M.,Nokia Inc. | Johansson E.,Saanio and Riekkola Oy | Kuula H.,WSP Finland Oy | Hudson J.A.,Imperial College London
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

As part of the preparations for the design of an underground repository for radioactive waste at Posiva's site on the west coast of Finland, there has been considerable site investigation work. One of the key elements of this work has been the estimation of the in situ stress field and determination of the mechanical properties of the crystalline rocks present. The stress field is required as the boundary condition for numerical modelling and to determine a suitable orientation for the repository tunnels. The mechanical rock properties are required, inter alia, to establish whether there is any potential for rock spalling at the ca. 400-450 m anticipated depth of the repository. A key aspect of the analysis is the understanding of the in situ spalling strength in order to be able to predict the spalling potential, not only during deposition tunnel and deposition hole excavation but also in the longer term when the rock mass is subjected to canister heating up to temperatures close to 60°C. The in situ spalling strength is of the order of 60% of the uniaxial compressive strength. Accordingly, an in situ rock mechanics experiment has been designed and conducted in a niche tunnel off the main ONKALO ramp at the Olkiluoto site in Finland. The experiment has the acronym POSE: Posiva's Olkiluoto Spalling Experiment. The experiment has involved the drilling of two closely located full-scale simulated deposition holes, 1.524m in diameter, which concentrate the in situ stress and enable rock spalling to be observed at close hand. In addition, heaters have been used to simulate the rock temperature increase due to radioactive canister heat generation, further altering the in situ stress field. The preliminary POSE experimental results and the thermo-mechanical simulations are illustrated and presented in this paper. © 2012 Taylor & Francis Group, London.

Lehtonen A.,Saanio and Riekkola Oy | Cosgrove J.W.,Imperial College London | Hudson J.A.,Imperial College London | Johansson E.,Saanio and Riekkola Oy
Engineering Geology | Year: 2012

When rock cores are loaded in uniaxial compression, acoustic emission occurs when the stress reaches a level greater than that which the rock has previously experienced. This phenomenon, known as the Kaiser Effect, has been used as an indirect method of estimating the in situ stress field in rock masses. If the procedure is valid, then the Kaiser Effect method has the advantage that the stress field can be estimated through laboratory tests on rock cores, rather than the field drillhole methods of overcoring and hydraulic fracturing. However, the Kaiser Effect method is an enigma: on the one hand, there are good reasons why the method cannot be valid; on the other hand, there are reports in the literature of it being successfully applied. In this paper, we explore the variety of geological and mechanical factors involved and report on a case example for the Olkiluoto crystalline rock site in western Finland. We conclude that the Kaiser Effect method for stress measurement is only likely to be successful if it is supported by key geological and other stress measurement information and if certain procedures are followed as explained in the paper. © 2011 Elsevier B.V.

Hudson J.A.,Imperial College London | Cosgrove J.W.,Imperial College London | Kemppainen K.,Posiva Oy | Johansson E.,Saanio and Riekkola Oy
Engineering Geology | Year: 2011

Brittle deformation zones at the Olkiluoto nuclear repository site in western Finland play critical roles in the strength and hydrology of the host rock mass. We present a procedure implemented there for incorporating information on deformation zones obtained through boreholes into quantitative engineering design. First, ductile and brittle deformation zones are classified based on their characteristics in drillhole cores as brittle joint clusters, brittle fault zones, or semi-brittle fault zones, with an awareness of the geologic processes that caused the zones to develop as they did. Next, it is shown that the mechanical properties of the brittle deformation zones can be calculated by one of several methods, each of which has advantages and disadvantages. The site geology must be kept in mind at all stages to arrive at meaningful estimates of the mechanical properties of the deformation zones. © 2010 Elsevier B.V.

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