The suitability of the old and operating mines in Finland for the storage and final disposal of the different kinds of nuclear wastes was analysed. Due to several unfavorable factors related to either the design or stability of the free spaces, the geological conditions, or the environmental activities, the possibilities of using existing mines instead of conctructing special new waste repositories proved very small. AIM AND SCOPE OF THE STUDY The study aims at evaluating the possibilities of using existing mines and corresponding underground facilities for temporary storage and final disposal of nuclear wastes. These possibilities are compared with the.alternative plans, i.e. the underground repositories that.should be.constructed especially for nuclear wastes. The scope of the study included any kind of nuclear wastes as divided into three groups. The waste groups and their estimated amounts from the four existing finish nuclear power plant units, which arecalculated to operate approximately 30 years, are as follows: .high-level waste (mainly spent fuel)2100 t, low- and medium-level wastes comprising various vet materials like ion exchange resins, filtration wastes and, evaporator concentrates and mixed solid particles like filters, scrap, and large metal components(after treatment) 17000 m 3 mere solid low-level waste (after treatment) 6000 m 3 Three main questions were raised which the study endeavours to elucidate: Are there such underground facilities (and where) which could (at least partly) be easily transformed into safe repositories for the different kinds of nuclear waste? Can the present mining activities in some mine offer a reasonable opportunity for constructing a deep repository especially for the mentioned types of wastes in the vicinity? Is there any other way of exploiting the existing facilities considering the disposal of nuclear wastes? In order to answer these questions, a concise principal examination of all kinds of rock openings existing in Finland was done. According to it, all the underground facilities that have been constructed for some constant activity near the earth''s surface (transport, water conveyance, defence, power generation, industry, etc.) could be excluded. Their aim and use are in a clear disagreement with nuclear waste disposal. Whereas the utilization of deeper mines - especially the already abandoned ones - can be taken into consideration. In principle the underground mine caverns are solely a byproduct of ore mining and their existence has no independent purpose what so ever. The examination of the required possibilities afforded by the mines was carried out in two stages. Firstly, a preliminary inventory of all mine spaces existing in Finland was carried out at the Geological Survey of Finland. This inventory included both operating mines and Old, abandoned ones, divided into deep (over 400 m in depth) and shallow ones. There were altogether 9 deep mines and 72 shallow mines of which adequate information could be acquired for a critical evaluation. Seven of the deep mines and 26 of the shallow ones were still in operation (by 1978).

Compressed air energy storage in salt caverns induces low-frequency cyclic loading effects in rock salt. An ongoing study is described which will furnish data for assessing associated stability of storage caverns. Some initial findings are presented from laboratory and in-situ mine tests. INTRODUCTION The first compressed air energy storage (CAES) facility near Huntorf, West Germany, reportedly has been operating successfully for over two years. The facility employs two non-compensated (or dry) caverns in the Huntorf salt dome as a storage reservoir (Mattick and co-worker, 1975). Somewhat similar CAES facilities are under consideration in the U.S., and the long-term behavior of the associated storage reservoirs is of considerable interest (Loscutoff, 1979). The objective of this study is to obtain data from a generalized laboratory test program on behavior of rock salt for long-term cyclic loads typical of CAES operations. The data are currently being collected from relatively conventional laboratory tests and also from bench-scale in-situ tests in U.S. Gulf Coast salt mines. In addition, 1imited complementary numerical modeling is performed to aid in planning tests and analyzing resulting data. Figure 1 illustrates schematically the loading of a "typical" noncompensated or dry CAES Cavern. Loading is associated with the time and depth dependent "effective overburden" or cavern "pressure difference", ğ=g-p. Here g is the geostatic stress calculated from the depth and unit weight of overlying geologic materials, and p is the countering and time varying cavern pressure controlled by operators of the storage facility. Conditions at specific locations in the salt around the cavern will depend on the effective overburden, cavern geometry, temperature, material properties, cavern loading history, and site-specific geologic effects (Thoms and Martinez, 1978 and Thoms, 1979). Rapid reductions in cavern pressure result in rapid increases in the effective overburden. Further-, gas filled caverns at large depths will be subjected to effects of large g values if the pressure p is reduced to atmospheric levels. Both of these situations reportedly have caused undesirable effects in natural gas storage caverns in salt domes. Röhr (1974) reported roof falls in a gas test cavern when p was decreased rapidly (approximately 14,500 kPa over 158 hours); and Dreyer (1974) noted significant closure in the Eminence dome gas storage caverns of the U.S. Gulf Coast, with around 40% reduction apparently due to large value of 9 over a period of a few months. The Eminence dome caverns were at depths from 1737 to 2042 m, thus ğ could range up to around 44,000 kPa. Because of this last example, Thoms (1979) has recommended that CAES salt caverns be limited to depths less than 1525 m. and, because of the well known sensitivity of salt to temperature, that temperatures of injected air be such that salt temperatures do not exceed 80°C. This is in contrast to a number of other studies which have been undertaken to determine salt response for static or slowly varying effective overburden loads and temperatures (Hansen, 1977; Wawersik, 1980).

In Stockholm and in many other densely populated areas, Swedish contractors and explosives experts have brought the methods of controlling underground blasting to a fine art. The paper systematically lists the buildings and other objects that set limits for the level of disturbance that can be allowed. The nature of the ground vibration disturbances caused by different blasts at different distances is analyzed and-'methods for predicting and recording their magnitude are presented. Damage criteria for different types of buildings, structures, and other objects are discussed, as well as the separate subject of how to avoid disturbing the neighbors. Methods for optimal planning and implementation of the blasting operation from contract to completion are presented, with a survey of modern explosives systems, accessories and charging equipment. INTRODUCTION The idea of having large scale underground structures in blast-excavated caverns right underneath a city is still a new one in many parts of the world. A person wanting to make reality of such an undertaking may well be faced with the question: How can you guarantee not to damage our fine city or irritate our citizens? In the Stockholm area alone, an average of about 300,000 m3 of rock was excavated underground each year in the decade from 1970 to 1980. This is perhaps the best proof that such guarantees can be obtained. The purpose of this paper is to present, in a reasonably simple form, the know-how developed in Sweden during many decades of underground construction work, and to show how blasting activities can indeed be controlled to prevent damage and disturbances. LIMITATIONS TO IN-CITY BLASTING In all rock blasting in a built up area, some measures of control have to be imposed to make sure no undesired side-effects occur. These controls include limitations in the planning and design stage as well as during the building & construction stage. From a town planning point of view, an obvious obligation is to check the desirability of having an underground installation at the proposed site. Perhaps a different location might leave better space for future installations or it might offer better prospects for long-term stability of the rock surrounding the excavation. Restrictions to the proposed blasting to avoid damage or disturbances should be clarified already at the planning stage, too. If this is done before bidding takes place and before contracts are settled, the contractor can include the necessary costs for the required level of controlled blasting in his bid. This excludes much unnecessary arguing later about who is going to pay for damages or for the cost of preventing them. The restrictions are conveniently divided into three kinds; of these two are external to the blasting site and one is internal. Restrictions are necessary to: ·Avoid damage to nearby buildings ·Avoid disturbing the neighbors ·Avoid damage to the own construction The major factor to control in order to avoid these is the ground vibration caused by the blast, and the remainder of this paper will deal with this factor mainly.

Industrial complex around Korba face acute environmental pollution. Disposal of industrial, mine waste and domestic: refuse need coordinated.approach for evolving a sewage network controlled by local drainage system and geologic constraints. Utilisation of abandoned coal mines for waste disposal, sewage treatment and storage of water can provide viable economic return besides improving pollution problem. INTRODUCTION The Korba town, in an area of approximately 200 sq Jon locates four major industrial complex - such as thermal, alluminium, explosive and fertilizer factories besides an upcoming super thermal power station. The colonies are situated aouth of the industrial plants. The urban and industrial planning of the region, with the growing popUlation to about one million in the near future, calls for a sustained effort in tac:kling the problems relating to base water supply, atmospheric and aquatic pollution and disposal of industrial waste/domestic refuse. The present paper deals with the disposal of waste material in the available underground space. GEOENVIRONMENT AROUND KORBA AND FEATURES CONTROLLING ECOIMBALANCE The landscape around Korba is characterised by low, isolated hills and near flat crest lines with. general rising elevation from south to north. The isolated hills are aligned in E-lf direction with local deviation to NNE-SSW and NE-SWdirections and range in altitude from 274.32 m tg 304.8 m. The isolated hill s have a fairly steep rocky slope of about 50 to 70 and project out as ‘tors’ while the low ground slopes from 5 to 10. The principal drainage- river Hasdo, is aligned in N-S direction and drains mainly through a sedimentary area. The other major tributaries - Belgari and Dhengurnalas have a general ENE-WSW to E-W flow direction on the left bank of Hasdo while on the right bank, the Ahiran nala flows in NW-SE to WNW-ESE direction. The softer sedimentaries control the drainage pattern which is subparallel to subdendritic. The low undulating hills, occupied by clastic and ancient crystalline rocks form the denudation tract while the fan/talus, piedmount/slope wash and the terraces are some of the characteristic fluvial deposits. The valley form is V-shaped at the head reaches while it is flat bottom and rectangular in the main body section of the. streams/rivers, with 2–3 m high steep bank, sloping about 70° -80° to vertical. Banks of Hasdo and its tributaries like Ahiran, Belgari and Dhengur show evidences of mass wasting in the form of debris slip, erosion scar and land subsidence due to soft and erodible clastic rock. The sandstone is soft, friable, arkosic and granular,med1um to coarse grained with hiqh percentage of felspar. The perviousness of sandstone is indicated by porosity to about 15% and due to the presence of erosion channel and cavities. Large quantities of groundwater in the porespaces make the sandstone a good confined and unconfined aquifer due to interlayering with shale. The granite is medium to coarse grained with large size felspar. Physical and chemical weathering of granitic rock is less active on the protuding hills rot are erratic and intense on surfaces in the process of exhumation. This weathered zone, controlled by topography, has limited ground water.

The extreme mobility of natural gas (low viscosity and specific gravity) as well as the very large and rapid pressure variations are two traits peculiar to the storage of gas in salt cavities. In order to reach the objectives set with utmost respect for the environment, Gaz de France has been led to examine with particular care the problems of cavity stability and well tightness. Brine reinjection into a cavity has confirmed the predictions and legitimized the approach adopted. INTRODUCTION For over 10 years now, Gaz de France has been storing natural gas in underground cavities that it hollowed out by leaching in salt formations. The development program is being furthered at the Tersanne and Etrez sites in parallel with the extension and creation of aquiferous underground storages, another storage technique developed by Gaz de France. These developments as a whole must enable a storage capacity of 73.6 × 10 9 kWh (8 % of which in salt cavities) to be available by 1985, in a situation where the part of natural gas in the French primary energy requirement should be 16 %, in conformity with the imperatives fixed for Gaz de France by the French Government. The materialization and operation of salt cavity storage require the mastering and implementation of a number of specific techniques relating to among others: Cavity stability Leaching processes Tightness Thermodynamic behavior of stored gas 1. STABILITY The beginning of any project for the storage of hydrocarbons in salt cavities is the stability study. Two types of problems arise when designing a storage project: location and long term behavior. Rare is the case of a single storage cavity: usually, the storage project concerns for obvious economic reasons a large number of cavities that have to be appropriately positioned. Moreover to ensure the safety of persons and goods at the site as well as to safeguard the environment, the long term stability of this group of cavities has to be studied. To broach these two problems we turn to rock mechanics which bears in fact on the rheological behavior research of the rocky material within which the works will be set. 1.1 Laboratory determination or rock behavior The cores taken out during survey drillings (or during well drilling) and carefully packed in paraffin for clay and salt are subjected to various laboratory tests. Simple and triaxial compression tests are made to determine the elastic characteristics (E Young\'s modulus and ν Poisson's ratio) as well as the material's yield strength. Moreover creep tests (distortion as a function of time with a constant load) and relaxation tests (stress as a function of time under constant distortion) are performed in order to obtain information concerning delayed behavior. The totality of these laboratory tests are synthesized in the form of behavior laws, that is, the determination of the non-elastic deformation progress speeds ε nl and of the hardening variable v i as a function of the stresses. For certain cases these laws can be schematically represented by rheological models, analogic models resulting from the association of springs, shock absorbers and runners.

The paper presents a conceptual design for a four unit (850 MWe each) underground CANDU nuclear power station constructed in a series of large caverns excavated in Precambrian rock. Recent results of a geotechnical test program are described and the corresponding in-situ and laboratory measurements are considered in assessing design of rock cavern support systems, cavern liner requirements, and rock cavern stability under both thermal and seismic loads. The overall safety of the underground station design is also discussed. In this context the predictions of a preliminary analysis of the station accident containment capability suggest that post-accident temperatures and pressures in the rock caverns are below acceptable levels. Operational concerns for the underground CANDU design are also briefly considered. Finally, preliminary station capital cost estimates, based on a construction schedule extended by sixteen months, reveal a penalty of 31–36% relative to an equivalent surface facility. INTRODUCTION Ontario Hydro, Canada's largest power utility with a total installed capacity of 24,000 MWe of which roughly 22% is nuclear generation, has recently completed a two-year investigation of the feasibility, both technical and economic, of constructing an underground CANDU nuclear power station (Oberth and coworkers, 1979). CANDU is a unique Canadian pressure tube reactor design using natural uranium fuel and heavy water as both the coolant and moderator. The investigation, performed by in-house engineering staff with the aid of geotechnical consultants, concentrated on deep rock siting in which reactor units are constructed in caverns excavated in Precambrian rock. This paper presents a conceptual underground design for the rock-sited 4 × 850 MWe CANDU power station, and evaluates the safety, operational, and economic implications of the design. Previous investigations of underground siting in Europe (Lindbo, 1978; Kröger and coworkers, 1976) and in the USA (Allensworth and coworkers, 1977; California Energy commission, 1978) revealed possible benefits such as improved containment, increased station protection and security, and significant reductions in seismic ground motion experienced in underground rock caverns. This paper examines these potential benefits in the context of the CANDU reactor design and Ontario's unique geological situation. The Ontario Hydro study examined two methods of constructing an underground nuclear power station: rock cavern excavation and cut-and-cover burial. Each method has its own set of siting constraints, technical and economic implications, and environmental and safety factors. This paper concentrates on the first of these two underground siting options in which the reactor components are erected within large underground rock caverns with the rock face serving as both the reactor building superstructure and the containment boundary. GEOTECHNICAL INVESTIGATION PROGRAM A number of areas in Ontario were examined for local geological conditions and other general siting considerations. While no specific site was selected for the underground nuclear station design study, the economic benefits of siting close to a large urban load centre provided an incentive to focus on areas near Toronto. These economic benefits include reduced transmission costs and the potential use of waste heat for district heating purposes.

This paper reports the result of closure measurements in roadways driven in salt at a depth of 11OOm. The results obtained from a variety of mining geometries are compared and the implications for the design of underground nuclear waste repositories are discussed. Introduction Ever since Project Salt Vault (Bradshaw, 1971) isolation of nuclear waste in mined openings in rocksalt has been rigorously investigated. To eliminate the possibility of radio-nuclide escape to the biosphere, a primary requirement of the design of an underground repository must be the long term stability of the openings. The stability of excavations in rocksalt is mainly a function of the mining layout, the percentage extraction, depth below surface and the time dependent behavior of the material. Additional factors to be considered in the case of nuclear waste storage are the influence of heat and radioactivity on the behavioral properties of the material. Generally speaking evaporate mining practice is based on either regular room and pillar layouts with fully load bearing pillars or the use of relatively narrow, high extraction panels separated by wide barrier panels. Internal panel pillars are small and designed to yield (Serata, 1976). This paper focuses on a study of the closure behaviour of a variety of mining layouts and configurations driven in salt at a potash mine in North Yorkshire, including: Isolated twin roads. Roads in low extraction panels (25–35%) with 40m pillars Roads in high extraction panels (60–70%) with 4 - 6m wide pillars Roads with 60m pillars driven in the shaft pillar. All roadways are rectangular, 6.7m wide by 3.5m high, driven by means of mechanical miners, except the shaft pillar roads which were drilled and blasted to roughly the same shape and dimensions. The depth below surface is 11OOm given an approximate overburden stress of 25MPa. Roof-floor closure measurements have been taken over periods ranging from days to years. PRESENTATION AND DISCUSSION OF RESULTS Closure measurements from the four basic layouts described above have been collected and are presented in tabular form. The variation of closure rate with time has been found (Hebblewhite, 1977) to follow the curve given by an equation of the general form: C= At B where c is the closure rate in mm/day, t is the time from date of excavation in days, and A and B, constants. Experience based on visual inspection over several years has shown that for roadways to be stable they must have closure rates which fall within the envelope given by the equation: C = 34.81 t −o·785

The technical feasibility of superconductive magnetic energy storage (SMES) is being studied by an interdisciplinary group at the University of Wisconsin, including fundamental research aimed at designing safe and economic undergound rock caverns to house the magnets. Evaluation of cavern stability for alternative magnet designs and proposed rock sites in Wisconsin for a prototype magnet present unique engineering problems requiring comprehensive field, laboratory and numerical studies. Analysis of three promising magnet designs and five possible rock units (granite, quartzite, rhyolite, two dolomites) indicate possible advantages and potential problems. Several conclusions and recommendations regarding tunnel geometry, load transfer, and the interaction between geology and cavern stability and deformation are made. INTRODUCTION The continued development of superconductive magnetic energy storage (SMES) units (Fig. 1) indicates the promise and feasibility of building these large capacity, highly efficient (>90%), quick responding and virtually topographically unrestricted electrical energy storage devices. The virial theorem states that a charged SMES magnet will require a confinement structure proportional to the electromagnetic energy stored, or else, as it charges and discharges to level out the variable daily power demand, it will break apart. For a 10,000 MWh magnet, a prohibitive 777,000 tons of steel would be needed. Thus SMES magnets will be built at depth in rock, a similarly stiff and strong material available for the cost of excavation. The rock chamber for a 1,000 MWh to 10,000 MWh magnet consists of annular shaped tunnels, 5–8 m wide, 8–20 m high, with annular diameters of from 100–1,000 m. The charged magnet develops radial and axial forces which are transferred to the rock by regularly spaced polyester struts. In addition to magnet stresses, there are gravitational and anisotropic tectonic stresses whose effect varies from point to point around each tunnel's circumference. The annular geometry also insures that each tunnel will intersect joint sets at anywhere from very favorable to very unfavorable orientations around the circumference. Moreover, the stacked annular tunnels create two different stress regimes in the rock mass: one on the outside of the tunnels in which the high horizontal stresses are active, and the other on the inside of the tunnels which shield the rock core bounded by the annular caverns. Excessive radial movement (>15 cm) of the rock walls under the complex applied loads will damage the conductors. Groundwater contact with the conductor will result in corrosion and icing which interfere with the magnet's operation. Rock mechanics research seeks to determine the suitability of different rock types and sites for housing an SMES magnet. Such rocks must possess sufficient strength for long-term stability, be stiff enough to prevent excessive conductor deformation, and have groundwater inflows which are neither difficult nor prohibitively expensive to control. The following sections describe the geological and mechanical properties of rocks with potential for SMES sites and their engineering classification. SITE INVESTIGATIONS An energy storage magnet site requires a suitable rock mass with sufficient horizontal and vertical extent to contain the cavern system.

In some designs, the rock at the face of an unlined storage cavity may be stressed beyond its maximum strength, and the article presents how an analytical model can be used to describe the conditions of failure in the rock and their effects on stability. It is henceforth possible to use underground storage techniques at moderate depths in soft rocks or at great depths in hard, brittle rocks. INTRODUCTION Underground storage first developed by making use of very favourable geological conditions like those available in salt domes or large expanses of crystalline rock. The design of facilities to store oil, and liquified or gaseous gas is a relatively simple matter in this kind of context. Over the last decade or so, however, because of the move to capitalize on the unusually high standard of environmental protection and safety associated with underground storage, attention has been focused on extending it to a much wider range of stored products in much less favourable geological conditions and there are even cases of such projects now in the design stage. The new products to be stored produce very different stress conditions in the rock. Liquified natural gas and ethylene involve low-temperature stresses. Residual fuel oil, compressed air and nuclear wastes apply thermal stresses. The alternating and sudden pressure changes associated with the operation of compressed air storage facilities are a severe test of stability. The advantages of underground storage have induced engineers to examine its application in much less favourable geologies, and Geostock is currently engaged in conceptual and project design studies for facilities in weak to very weak soft rock, even down to almost unconsolidated clays. Such formations are very commonly found in the large alluvial plains where the world's major cities are built, so that safety is an obvious criterion. In such rock, it is quite possible that the cavities will not be inherently stable if rock strength is ina dequate to withstand the applied loads. Conventional design rules derived from theoretical rock me chanics models do not enable us to estimate the permissible limits in such design, or to optimize support. In order to provide a means of examining the feasibility of such projects, Geostock has been running a programme of research jointly with the Laboratoire de Mecanique des Solides of the Ecole Polytechnique in Paris since 1974, to investigate materials behaviour when stresses are equal to or in excess of their maximum strength as obtained from crushing tests. A set of experimental data has also been analysed to calibrate the results of this theoretical research, and check the accuracy of the findings. We shall first briefly review the shortcomings of conventional models before going on to describe the main features of the new model and compare findings with a variety of case histories. The article concludes with comments on the new opportunities offered by this model for designing underground storage facilities in poor engineering rock where stress conditions are complex, in strong rock where stresses are expected to exceed rock strength, or where support optimization is a prime consideration.

In connection with the geotechnical study of a proposed underground nuclear plant, a 300 m deep test hole was drilled at Ontario Hydro's Darlington site approximately 65 km east of Toronto. The hydrofracturing method was used to determine the state of stress in the Paleozoic limestones (0–220 m depth) and the Precambrian granitic gneiss (220–300 m). The results of these measurements indicated a state of high horizontal stress along the depth of boring and a consistent orientation of principal stresses in each geologic unit. These results were confirmed by a borehole TV camera survey, and by overcoring tests at shallow depths in the same general area. The measured stresses were used in an assessment of the stability of large reactor caverns for housing the nuclear components of a proposed 4 × 850 MWe underground nuclear power plant in Precambrian hard rock. It was found that under ambient temperature conditions the state of stress alone did not critically affect cavern stability. Next, the occurrence of thermal shock in the cavern under a loss-of-coolant accident condition was also analyzed. To aid in the design analysis of the thermomechanical stability, a series of tests were carried out on the thermal properties of Precambrian rocks at elevated temperatures, including thermal conductivity, thermal diffusivity and coefficient of thermal expansion. The test results on thermal properties are presented in the paper, along with the results of the finite element analysis and other pertinent rock mechanics tests performed. INTRODUCTION Underground siting of nuclear power plants has been receiving increased interest in various parts of the world owing to some potentially important benefits over equivalent surface installations. Reactors housed in deep rock provide an additional safety margin in containing the release of radionuclides, in reducing the damage due to earthquake in high seismic areas, in protecting against sabbotage, aircraft crashing, hurricanes, etc., in supplying high-pressure gravity-fed cooling water to the fuel core in emergency situations, and in minimizing the amount of land use and environmental impact (Oberth and Lee, 1979). These and other potential advantages are still being weighed in the United States against the major drawback of higher construction costs. Norway and Sweden, however, built their first underground power facilities some 20 years ago (McHugh, 1964; ENEA Report, 1962). In Canada, Ontario Hydro has recently embarked on an extensive investigation of the technical and economic implications of building a large 4 × 850 MWe underground CANDU (Canadian Deuterium Uranium) power station in Ontario. The location of the proposed power plant will have to satisfy several siting requirements including the proximity to a major load center to cut transmission costs, and the availability of an adjacent large body of cooling water. A third requirement, that of suitable host rock formation to ensure water tightness and cavern stability was the subject of a preliminary geotechnical investigation which included a geological surface study at the Darlington site, the drilling and coring of an NQ borehole (UN-l), and a number of borehole tests such as permeability and stress measurements.