The concept of disposal of radioactive wastes in mined caverns in geological formations was proposed over two decades ago. During the formulative years of study, the research and development activities were directed primarily to the disposal of wastes in salt beds. During the latter half of the 1970-79 decade, the waste technology programs were expanded substantially in finances and personnel in the USA, canada, Sweden, and West Germany, and in consideration of a broader range of geologic media, including granite, basalt, tuff, and shale. This paper examines the state-of-the-art of the technology developed to date for geologic disposal and the key issues of concern to the public and technical communities, and provides an assessment of what is viewed as being required to transform the notion of geologic disposal from concept to fact. The position is taken that the level of technology is immediately adequate for the geologic disposal of low-level radioactive wastes, and for the retrievable storage of high-level wastes. Furthermore, it is the opinion of the authors that the technology programs planned for the 1980-89 decade will provide the resolution required for safe, permanent disposal of high-level wastes in mined geologic caverns.
In response to a request by the U.S. Atomic Energy Commission (AEC), the National Academy of Sciences--National Research Council (NAS-NRC) established a committee of geologists and geophysicists in 1955 for the purpose of considering the disposal of high-level radioactive wastes in geologic structures within the continental United states. In 1957, this committee proposed disposal of wastes in natural salt formations as the most promising method of the future (NAS-NRC Committee on Waste Disposal,'' 1957). The recommendations of the committee resulted in the initiation of studies of high-level radioactive waste disposal in salt, with early investigations by the oak Ridge National Laboratory (ORNL) directed toward the disposal of liquid waste (Parker, and others, 1960). In 1961, the NAS-NRC Committee reviewed the progress of the work since 1955, and concluded that "… experience both in the field and in the laboratory on disposal of wastes in salt have been very productive, well conceived, and that plans for the future are very promising" (NAS-NRC Committee on Geologic Aspects of Radioactive Waste Disposal, 1961). Moreover, the Committee noted that" … the interpretations relating to disposal in salt are by the very nature of salt deposits capable of being extrapolated to a considerable degree from one deposit to another …" and recommended strongly that "the effect of storing dry packaged radioactive wastes in a salt deposit be tested …". As a consequence of these recommendations, Project Salt Vault was designed and conducted at the carey salt Mine near Lyons, Kansas in the 1960''s, using irradiated fuel elements as a simulant for reprocessing calcined solidified wastes (Bradshaw and McClain, 1971). This study was followed by a conceptual repository design for the bedded salt lithology of the Lyons area, and the Subsequent abandonment of the site in 1972 for a variety of political and technical reasons.
Montoto, M. (Dept. of Petrology, University of Oviedo, Oviedo, Spain) | Montoto, L. (IBM Scientific Center, Madrid, Spain) | Roshoff, K. (Dept. of Rock Mechanics, University of Lulea, Lulea, Sweden) | Leijon, B. (Dept. of Rock Mechanics, University of Lulea, Lulea, Sweden)
Microfissures of thermal origin were investigated in granitic rock specimens, taken from the area of a heater test performed at the Stripa Test Site in Sweden. Optical and electron microscope techniques were simultaneously applied to obtain a complete information of the rock microfractography related to the texture and mineralogy. This microfractography network was quantified by digital image processing. Original microphotographs were digitized by a flat microdensiometer. Then, segmentation, thinning and line-following algorithms were successively applied for enhancing, detecting and measuring the microfissures. The described technique was applied to material subjected to one, slow in situ heating cycle reaching a maximum temperature of about 2200C and to non-heated material taken from the same area. No significant differences in the fissuration density were detected when comparing heated and non-heated material.
A Swedish-American co-operative research program on radioactive waste storage in mined caverns is currently in progress in the Stripa Mine in Sweden (Whitherspoon and Degerman, 1978). The field experiments of the program were initiated 1977, and among the early activities was an in situ, pilot heater test, performed by the Department of Rock Mechanics, University of Luleå, under sponsorship of the KBS Project (Carlsson, 1978). The pilot heater test was followed by a laboratory investigation of the heated material. The investigation concerned possible, chemical and mechanical, micro-scale effects of the artificial heating cycle applied to the rock. Special attention was paid to the state of microfissuration of the material (Leijon et al, 1980). This paper presents the technique applied for the observation and quantification of the micro-crack features of the Stripa Granite. The microcrack density, as observed in both heated and non-heated specimens is evaluated and compared. Several methods have been considered in the past for evaluation of microfissuration of rock. The different manual and automatic procedures are so far tedious and sometimes, when applied to difficult situations under petrographic microscopy, of a very low viability. Among those of automatic character stands out those commercial available; from the 60'', analogic systems, in which the microscope is connected to a black and white TV system.
The microfissures have to be electronically discriminated on the TV screen, by means of brightness and contrast and later evaluated by analog methods. In the particular case of the Stripa Granite, with a very light microfissure network, those methods could not render satisfactory results on account of their low sensitivity and the lack of a precise procedure to enhance and delimite the microfissures. For that reason a recently developed automatic method, based on digital processing techniques on microscope images could be more successfully applied. A detailed description of this method, especially applied to the difficult microfissuration network of the Stripa Granite, is given in this paper.
IN SITU TEST AND SAMPLE AREA
A crosscut of the heater test area, from which all studied rock specimens were taken, is shown in Fig. 1. A central main heater and three peripheral heaters were positioned, remote from excavations, in downwards oriented boreholes.
The paper is concerned with a recent discovery of oil degrading bacteria reducing the effect of a water curtain between two oil storage rock caverns. Attention is drawn to the problem of bacterial growth at the oil/water interface. The importance of establishing water curtains before filling up caverns with oil products is emphasized. Finally, some means of preventing bacterial growth is discussed.
The application of water curtains in order to maintain or obtain a ground water gradient preventing leakage from rock caverns for oil storage, is well known (fig. 1). Furthermore, the occurrence at the oil/water interface of a slimy product - resulting from microbiological activity - has been observed in connection with various storage facilities for oil products. The present paper is concerned with a recent discovery of oil degrading bacteria reducing the effect of a water curtain between two oil storage rock caverns in central Norway. To the authors'' knowledge, this particular effect of an otherwise well known phenomenon has not previously been published. Attention should however be brought to bear on the phenomenon in view of the economic consequences involved.
The plant in question was constructed during the middle seventies. The local bedrock consists of a fairly massive, plutonic granite intruded into a greenstone complex. A fresh-water curtain was established in 1978, in order to stop a considerable leakage of oil product from one cavern (fixed oil level) into the neighboring one (fluctuating oil level) (fig. 1). These two caverns are used for the storage of two different refined oil products. The water curtain reduced the oil leakage to a minimum. This effect, however, proved to be temporary (fig. 2). After a few months only, an increase in loss of oil product from cavern A was again registered. Besides, the water infiltration was strongly reduced, only one out of six drill holes consuming water. At the end of 1979 it was decided to start cleaning the drill holes of the curtain. This was achieved by means of drilling equipment and high pressure water. The holes proved to be completely filled up with a slimy product, a sample of which was taken to the laboratory for investigation. Samples were also taken of the water in the drill holes and of some mineral material (mud and rock particles). The samples of mineral material and slime were taken as filtrates during the washing out of the holes. On the removal of the slime, the water curtain once more proved to be efficient (fig. 2). SAMPLE ANALYSIS
Attention is drawn to fig. 3. In addition to the analysis reported in this figure, examination of mud samples was carried out by means of X-ray diffraction. The mineral composition was found to comply with that of the local bedrock. No trace of swelling clay minerals was found, thus excluding any possibility of such minerals contributing to the sealing of the drill holes. Samples of crushed rock (sand/gravel size) from the drill holes nos. 5 and 6 contained some fragments of calcite, probably originating from joint and fissure fillings.
Problems caused by underdimensioned support systems (transportation, water, power, telecommunications, etc.) in urban areas in developing countries are outlined. Qualitative arguments in favor of the use of the subsurface to relieve the congestion are discussed from social,- environmental, economic and technical viewpoints. Efforts to improve the support systems will, however, not suffice to improve conditions unless land use is controlled. The subsurface should be seen as a valuable resource to be considered in the coordinated, comprehensive planning of land uses and support systems.
The urban population of the world is increasing. Even if projections of the total population of the world today are somewhat lower than they were a few years ago, unanimous projections still indicate a rapidly increasing urban population. The most spectacular increase is projected for the urban population in developing countries, where doubling of the urban population is expected over the next two decades. This will create problems, the solving of which will constitute an enormous task. In developing countries today there are many problems in most urban areas which adversely affect the quality of life. Unless substantial changes in the development process occur, the quality of life in the growing urban areas of the developing world can be expected to deteriorate further. Experience from earlier attempts at ameliorating the conditions is not encouraging. Despite political declarations, professional expertise and not insubstantial resources, the situation in general is not improving. It is against this background that a discussion on the use of the subsurface in urban areas in developing countries should be seen. Incremental measures do not seem to result in the required reasonably rapid improvement of the conditions. In general, it can be stated that the use of the subsurface has not been explicitly considered as a possible resource in the planning for and changes in urban areas. This paper concerns the viability of the use of the subsurface in urban areas in developing countries seen from technical, social and economic viewpoints. The subject has not been studied comprehensively and in the absence of empirical data the discussion must be restricted to qualitative aspects and general observations that may be more or less applicable to different urban areas. It may also be added that these observations are put forward from a planner''s point of view.
CHARACTERISTICS OF URBAN AREAS IN DEVELOPING COUNTRIES
In order to discuss the viability of subsurface use, let us first look at the characteristics of urban areas in developing countries. These characteristics are very generalized and, accordingly, more or less typical of a given urban area. Historically, many of the larger urban areas, or at least their central parts, were given their basic structure of streets and buildings during the colonial period, even if older patterns may have been incorporated and modifications may have been made later. The densities of these urban areas were fairly low until a few decades ago when the more rapid population increase began to be felt. The technical infrastructure (water supply, sewerage, power, telecommuncations, etc.), to the extent that it was at all available, was often installed at the beginning of this century.
A 14.5 km long tunnel in bedrock constitutes an essential part of the heat transmission line by which district heat will be transmitted starting in 1982 from Naantali Power Plant to consumers in the region. This report examines the financial and technical factors which led to the choice of the tunnel alternative, as well as the tunnel design including investigations and studies related to it. The report examines also the environmental harm and risk factors caused by rock excavation and the use of tunnel in a population center. The concluding part of the report deals with the time schedule, mode of implementation and cost of project.
Imatran Voima Oy’s Naantali Power Plant, 3 x 133 MW, constructed in 1958-1978 is situated on the border of a densily populated region comprising two coastal towns Naantali and Raisio and one coastal city Turku. There are 200 000 residents in this region. Until recent years the buildings have taken care of their own heating with their own boilers with the exception of small area heating systems. Steep escalation in the prices of oil - the fuel primarily used - has made the transfer to district heat and to concentrated production of heat more economical in large production units using cheaper fuel. After 1982 the major part of the district heat required by the Turku area will be produced with coal at Naantali Power Plant. Because of this the condensing units with a capacity of 133 MW will be altered to produce district heat. Owing to improved efficiency one unit will produce in addition to 90 MW of electric energy also about 170 MW of district heat. However, the construction of the heat transmission system with its stand-by and peak heat centres form the major part of the project as far as costs are concerned. In order to take care of the construction of the district heat line and heat transmission to consumers at a maximum distance of 25km, the municipalities in the region and Imatran Voima Oy have established a limited company by name of Turun Seudun Kauko Lampö Oy.
The terrain in the Turku region on the shore of the Baltic Sea comprises rocky hills and between them valleys filled with soft clays. It was found that the varying and difficult foundation conditions would increase the cost of an ordinary district heat channel to be sunken in the ground owing to great need for piling and supports in the excavation. Likewise placing large approx. 1.4 x 2.4 m DN 800 district heat culvert in the narrow street areas of the old city would have caused expensive alteration works in the existing municipal pipelines and cables as well as great difficulties in traffic arrangements. It would have been impossible to avoid lowering of the ground water level in sections where the ground water level is high. Even crossing of water courses, with railways and highways would have been cost-increasing details.
This lecture is demonstrating a new technique of supporting a shaft bulge-out used the first time when constructing shaft bulge-out of coal mine General Blumenthal in Germany. It differs from convential design by a step by step supporting of the newly exposed rock face by shotcrete, supporting rings, and rock bolt anchoring fixed to the rock throughout by GD-Topac anchoring system.
The coal mining enterprise General Blumenthal in Germany intends to drive a 6.5 m diameter tunnel between two shafts. It is foreseen due course that a full face tunneling machine shall commence the drive in the shaft number 8 at a depth of about 1000 m. In preparation of the scheme the shaft had to be widened from 7.6 m diameter to 15 m. Further requirements are two wing-like excavations necessary, projecting 17 m laterally from the bulge-out on opposite sides. The central portion of the configuration is 21 m high, whereas the recesses have a threshold height of 13 m. In the vertical direction the total alteration of the original shaft measures 31.5 m overall. About 4800 cubic meters of rock had to be removed. The sprayed concrete lining of the exposed rock covers an area of 1700 square meters approximately.
THE NEW DESIGN CONCEPT
The Department for Construction Methods and Construction Management of the Ruhr- University Bochum was commissioned to proceed with the consulting engineering work for the scheme which is perhaps the first of its kind. It differs from the conventional design concept through the stipulation that the newly exposed rock face should be lined with step by step sequences of sprayed concrete support rings and anchor supports. Traditionally there would have been first the drilling and blasting programme to ensure that the new shaft bulge-out has the correct shape. Then either brick lining or steel arches and concrete panels would be built in as necessary. The new concept, by contrast, is a noteworthy break of the local mining traditions.
SINGLE SHELL SUPPORT SYSTEM
As a result of technical consultations with the Local Mining Authority a single shell lining system was approved. This decision was favorably influenced by the outcome of an investigation programme for this depth and previous mining operations on similar conditions which had shown that the rock was strong and had resisted convergence movements. The approved shaft bulge-out support construction, by contrast, has now been installed in the form of a single shell lining of 200 to 250 mm thick shotcrete. It has steel bar reinforcements, cut and bent on site. At the transition edges between the shaft bulge and the lateral extensions the reinforced concrete thickness has been doubled to 400 mm and attached to the rock at intervals of 1 m by means of 5 m long anchors. The other anchors of the support system are 3.5 m long and have been installed in a pattern of one anchor per square meter due to the safety regulations of the Mining Authorities.
For the past 20 years almost all new storage plants in Finland, Norway and Sweden installed for crude oil and refined products have been constructed in mined, unlined caverns. This has proved to be the cheapest and safest way. However, the promotion of this technology in other countries has been more complicated than expected. Many obstacles have appeared e.g. less favorable geophysical conditions, fears about environmental damage, laws etc. not related to underground storage. Another major obstacle is the present uncertain state of the petroleum world market. The various obstacles we have encountered are discussed in this paper. BACKGROUND
The method of storing crude oil and refined products in mined, unlined caverns is, in Finland, Norway and Sweden, the cheapest and safest way provided that the quantities are not too small. This is confirmed by the fact that during the two last decades nearly all new storage facilities - both commercial and strategic - have been constructed underground. More than 100 plants with a total storage capacity of more than 25 million cubic meters (160 million barrels) have been completed. With this experience and knowledge of all the advantages, considerable efforts have been made to introduce this technology in several other countries. But what was simple and easy in the three countries mentioned above has proved to be more complicated and has taken much longer than expected. We are surprised and somewhat disappointed that this technique has not been generally accepted in other countries and we have difficulties in understanding the reasons for this. Based on the experience of several pre-investigations and feasibility studies executed in South and Central Europe, North America, Africa and Asia the different causes of the obstacles met with are discussed here.
The geophysical conditions in our countries are in general favorable for subsurface constructions. Most of the bedrock consists of very competent granite or gneiss. Decomposed and weathered rock was removed during the last big ice age which means that it is easy to reach the bedrock without any major excavation of overburden. However, it should not be assumed that all rock in these countries is of good quality; now and then we also encounter bad rock conditions. Special methods and equipment have been developed to be used in such cases and the projects can still be completed on a sound economic basis for the owner. The ground water situation is also favorable and it is usually easy to find a stable groundwater table, the level of which is secured and proved by proximity to the sea or lakes. The lack of active seismic zones is also important. It is quite obvious that it is not possible to find places all over the world with this favorable combination of conditions. However, there are several places with similar, good conditions in many areas of the world. Simple estimates also show that there are considerable economic advantages to be gained in constructing storage facilities even in less favorable rock masses; such plants are still able to compete on an economic basis with steel tank storage systems.
Storing oil underground overcomes the detrimental environmental effects of tank storage at the ground surface. But due consideration must be given to other factors. Preventing disturbance to the original groundwater pattern requires a thorough survey of the water table before mining operations begin, arrangements for maintaining a high water table during construction, and monitoring of subsurface water levels and quality during operations. The danger of an accident enabling oil to escape from the top of the shaft must also be prevented, by providing safety valves which operate automatical1y when the oil pressure drops. Underground storage offers environmental benefits in connection with other substances such as industrial and nuclear wastes.
Even if the prime advantage that led to the development of underground oil storage was not environmental protection, there can be no doubt that it has made an important contribution in this area. The excellent safety record of the steadily increasing number of underground facilities throughout the world demonstrates their advantages over the more conventional tank farm as regards safeguardmg the countryside. Today, environmental protection must be one of the developer''s foremost preoccupations before, during and after commissioning of a new store, and the increasingly large place given to environmental impact studies is ample evidence of this. With this trend in mind, we have taken a hard look at the specific precautions needed in connection with underground storage, working towards increasingly sophisticated means of protecting groundwater so as to retain the original properties of the rock formation and prevent migration of the stored products, and avoid any danger of an oil burst at the ground surface as a result of wilful damage as well as under normal operating conditions. Because of its excellent environmental safety, underground storage must inevitably spread to embrace other substances, for which present-day techniques do not provide adequate protection, such as industrial wastes whose neutralization would present an over-arduous pollution problem and radioactive wastes, for which underground repositories are the most logical answer, and should become a reality within the next decade. PROTECTION OF THE COUNTRYSIDE
The advantages of underground storage as regards protection of the countryside need no elaboration, because it has been in use for many decades. We shall merely illustrate the fact by describing the Manosque oil storage facility, which has a capacity of 7.5 million cubic metres in a salt dome underlying public forest land.
Most of the Land is Untouched by the Engineering Works
The topside site area needed for a storage cavity of several hundred thousand cubic metres only represents about fifteen square metres for the top end of the shaft, with the stand pipes and valves only rising to a height of less than three metres. Each shaft head is surrounded by a concrete slab covering about 1,500 square metres, which is fenced off. The control buildings and pump house are practically the only constructions visible in the landscape. And even these have been grouped together at Manosque, so that they only cover an area of three hectares.
Funcken, R. (Tractionel Engineering, Brussels, Belgium) | Mayence, M. (Tractionel Engineering, Brussels, Belgium) | Heremans, R. (CENISCK, Mol, Belgium) | Manfroy, P. (CENISCK, Mol, Belgium) | Vanhaelewyn, R. (CENISCK, Mol, Belgium)
The construction of a shaft and a experimental gallery has started under the site of the Centre d''Etude de l ''Energie Nucleaire (C.E.N./S.C.K.) at Mol in Belgium. The shaft, excavated by means of freezing technique, will be 225 m deep and will give access to anhorizontal gallery 30 meters long with circular cross section, excavated in plastic clay at a depth of -220 m. The C.E.N./S.C.K. will take advantage of the shaft sinking to implant a series of measuring devices in the clay in order to assess certain geomechanical parameters of the in situ clay as well of the resistance characteristics of the shaft lining. This geotechnical campaign will allow to get experience about frozen clay at that depth and to test the measuring devices prior undertaking a long term extensive experimental campaign in the gallery.
Since the end of 1973, the Centre d''Etude de l ''Energie Nucleaire (C.E.N./S.C.K.) at Mol, Belgium, has been working on an R&D-program for the disposal of conditioned radioactive wastes in geological formations. In the scope of this program, the Geological Survey of Belgium has helped in drawing up an inventory of the formations of the Belgian subsoil that would be suitable for that purpose. One of the selected formations is a clay layer at medium depth underneath the C.E.N./S.C.K. facilities (Fig. 1). In Belgium this formation is known as "Boom clay". A drilling campaign along with high accuracy seismic survey have allowed definition of the structure of the formations while intensive laboratory experiments with samples taken in situ during drilling work have led to specifying the physical, chemical, mineralogical and mechanical properties of the clay. A conceptual and feasability study of a facility to dispose conditioned wastes in the clay was carried out. This study yielded a number of plausible burial facilities and a number of plugging techniques. It also evidenced that a large number of major questions would remain unanswered as long as there would not be any experimental facility in the selected layer. C.E.N./S.C.K. therefore undertook preliminary digging work early this year. The whole facility is scheduled operational by the end of 1982.
GEO-TECHNICAL MEASUREMENTS CAMPAIGN
The foreseen underground facilities will be composed of a vertical access shaft, an intermediate room and an horizontal gallery (Fig. 2). The shaft will be cylindrical and will have an inner diameter of 2.65 m. The tunneling of the horizontal gallery will begin from a circular intermediate room at the low end of the shaft. The gallery will have an inner diameter of 3.50 m. its centerline will be at 220 m depth, approximately at mid-depth of the host layer. Its length will be about 25 to 30 m. The shaft, gallery and intermediate room will be used as underground laboratories where a series of in-situ tests will be carried out on the clay (mechanical properties, heat transfer, migration, corrosion, etc.) as well as on the lining material (resistance, deformation, permeability, corrosion, etc.) and where technological drilling tests in the clay core can be made.
In underground air-raid shelters there are located many functions for civilian use, for instance storage and sports. In Turku, Finland, an underground shelter is being built in which two ice-hockey rinks will be situated in adjacent halls. The unusually long spans of the halls (32 m) presume thorough site investigations and accurate calculations. The construction site is composed of firm crystalline rock. Excavation and strengthening work will take place in many different stages.
CIVILIAN USE OF UNDERGROUND BOMB SHELTERS IN FINLAND
According to Finnish legislation new buildings of a volume of at least 3000 m3 shall be provided with air-raid shelters. The air-raid shelter can be built either in the basement of each building or ,alternatively ,regional shelters can be built with spaces provided for several buildings, blocks or a whole district. As the Finnish bedrock generally is of good quality~ in almost every place there is rock available, the large regional shelters are almost always built in rock. In the rock shelters the space reserved for one person is 1.1 ...1.2 m2. Usually the rock shelters have plenty of hall space which can be used for civil purposes. The designing and constructing of rock shelters should always be programmed so that the intended civilian use is known already at the initial stage of the designing process, thus making it possible to design the spaces, technical equipment, passages and entrance structures above ground purposefully. from the point of view of the use as well in crisis as in normal times. When the constructing of the rock shelters started in the early sixties in Finland, the shelters were designed to be used in normal times as simple storage rooms or car parks. When the first shelters were completed it was discovered and generally accepted that the shelters could, with small additional expenses, be equipped for more exacting use and activities. In the rock shelters of today the civilian use is more versatile than earlier. Halls for gymnastics and playing ball, running tracks for athletics, places for jumping and throwing have been built in the shelters and in two towns there are public swimming pools in the rock shelters. In addition to that, provided in the rock shelters. bowling alleys will be built. rinks will be built. hobby rooms for young people and rooms for musical training are In the shelters being designed ''at ''present, cinemas, small ,theatres , In the rock shelter of the Varissuo -residential area in -Turku two ice
THE ROCK SHELTER IN VARISSUO
The building of the Varissuo residential area in Turku was started in 1978 and by now about 60% of the dwelling houses have been built. The total area of the dwelling houses is about 320,000 m2, excluding schools, nursery schools, business buildings etc. The topography of the area varies and there are large exposures of rock. It is possible to build the regional rock shelter for the whole residential area, as the area is being built centralized and rapidly by one and the same builder, the population of the area is sufficient and the bedrock is suitable for the purpose.