RD&D-Programme 2004 - SKB

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18.2.7 Gas transport/dissolution Gas transport in the backfill is not judged to be an important process. If gas can find its way through the buffer, the transport capacity of the rock is sufficient for the pathway through the backfill to be uninteresting. 18.2.8 Swelling and compression It is important that the backfill can swell to prevent the formation of conductive transport pathways in the boundary zone between backfill and rock, see sections 17.2.4 and 18.2.17. Compression properties are important. They may not be such that the swelling of the buffer against the backfill in the deposition holes is too great. Compression properties are mainly a function of the density of the backfill. Determining the compression and swelling properties and the density that can be achieved in compaction of the backfill is an important part of the studies of different backfilling concepts and materials, see section 18.2.2. 18.2.9 Mechanical interaction buffer/near-field rock The permeability of the backfill is determined by its material composition. The mechanical properties of both the backfill and the near-field rock determine the backfill’s stabilizing capacity. An understanding of the interplay between rock and backfill is of great importance in both design and site-specific safety assessment in conjunction with the site investigations. The following factors are of importance for the interaction between backfill and near-field rock: • Swelling pressure and weight of the backfill. • Indirect effects of the buffer’s upswelling. • Creep movements in the rock around the tunnel. Conclusions in RD&D 2001 and its review The conclusion is unchanged that the swelling pressure against the roof is dependent on what density can be achieved in compaction of the clay phase. The difficulties of compaction against the roof make it difficult to guarantee a given swelling pressure. The swelling pressure is caused by the bentonite in the space between the particles of crushed rock and is dependent not only on the mean density of the bentonite but also on its homogeneity. An inhomogeneous mixture can give rise to a high swelling pressure to start with in certain spots. It is not known whether the swelling pressure subsequently decreases due to homogenization because the bentonite swells out from pores with high bentonite density. Newfound knowledge since RD&D 2001 General aspects of the problem of spalling and the stability of the walls of the deposition holes are discussed in /18-7/, and particularly the importance of a light support pressure from the buffer to prevent initiation and propagation of failure that can lead to spalling. Background material is the theory of brittle failure developed at AECL’s Underground Rock Laboratory (URL) in Canada. The general conclusion, that a small support pressure is enough to improve stability, also applies to other types of failure, for example breakout of rock wedges in the tunnel periphery. Experience from the URL Mine-by Test Tunnel in Canada confirms the importance of light support. Removal of floor muck led to rock breakout /18-8/. For slow creep movements that take place over a long period of time and lead to stress relaxation in large rock volumes, swelling pressures on the order of several hundred kPa are of no importance /18-9/. To limit such a slow creep-induced convergence, the tunnel RD&D-Programme 2004 235
ackfill must have a compression modulus that is several orders of magnitude greater than is theoretically possible. Programme Even if the tunnel backfill cannot limit the creep-induced tunnel convergence, the backfill is affected. A programme for computational bounding of tunnels and other cavities in the host rock has been initiated with literature studies and will be followed up by application calculations. 18.2.10 Thermal expansion The importance of this process will be illustrated with simple scoping calculations in SR-Can. The thermal expansion of the structure and the particle phase in the backfill is small and has only a marginal effect. On the other hand, the thermal expansion of the water is great and rapid heating in a water-saturated backfill where the expanding water does not have time to drain off can give rise to large pressures against a rigid host medium. In a deep repository, heating is so slow in relation to hydraulic conductivity that the expanding water has time to drain. 18.2.11 Advection Conclusions in RD&D 2001 and its review The backfill has a hydraulic conductivity and a diffusivity that lie in a range where both diffusion and advection can be important transport mechanisms. Newfound knowledge since RD&D 2001 Water flow in backfill is being studied on a full scale in the Backfill and Plug Test in the Äspö HRL, see sections 18.2.2 and 18.2.6. Programme Water flow in backfill will be studied in the laboratory and on a full scale in the Backfill and Plug Test, see sections 18.2.2 and 18.2.6. The importance of advection in the backfill for radionuclide transport will be examined in SR-Can. 18.2.12 Diffusion If the backfill material has low hydraulic conductivity, diffusion will be the dominant transport mechanism for dissolved species. 18.2.13 Osmosis Due to limitations in existing compaction technique, combined with the quantity of bentonite mixed into the backfill material, the density of the montmorillonite phase is considerably lower than in the buffer. In the basic state, the montmorillonite has therefore swelled to a volume equivalent to the maximum swelling at a given salinity. If the salinity exceeds this critical limit, the pore structure changes, leading to a sharp increase in hydraulic conductivity, lost contact with the rock, and an increased risk of piping at high water flows. With the compaction results that can be achieved today, there is a risk of considerable deterioration in the function of the backfill even at relatively low groundwater salinities (several percent TDS). 236 RD&D-Programme 2004
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Technical Report TR-04-21 RD&D-Prog
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Preface SKB, Svensk Kärnbränsleha
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welding and nondestructive testing
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Alternative methods. SKB is followi
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5.5 Nondestructive testing of canis
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15 Fuel 163 15.1 Initial state in f
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18.1.10 Swelling pressure 229 18.1.
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Part I SKB’s programme and plan o
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Nuclear power plant Clab m/s Sigyn
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Figure 1-2. The Äspö HRL consists
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Figure 1-4. Interior from the Canis
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Siting SKB’s main alternative is
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Transport tunnel KBS-3V Deposition
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2.1 Nuclear fuel programme In Swede
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Encapsulation plant 2003 2004 2005
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2.2 LILW programme Parts of the sys
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environment. The barriers can also
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this cooperation entails that the o
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4 Overview - technology development
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4.7 Design of the deep repository T
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Diameter 1,050 Diameter 949 Diamete
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Conclusions in RD&D 2001 and its re
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Figure 5-3. Graphite shapes in cast
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Figure 5-5. Positions for test bars
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Programme The development project c
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Programme Trial fabrication of all
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The technology and procedures for c
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A method and equipment based on las
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Spacer plate Defect A Defect B Chan
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Newfound knowledge since RD&D 2001
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2004 2005 Process model welding met
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6.2.2 The welding process In parall
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Figure 6-9. Lid weld L028. Section
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Tensile test bars have been taken o
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6.3.3 The welding process The param
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A limitation in the evaluation of t
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Nondestructive testing methods such
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a b Through-transmission Reflection
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simulation program, and the body of
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SKB has devised a quality system fo
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8 Canister - encapsulation The desi
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Figure 8-2. Work stations in the en
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The filled canister transport casks
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Stages encapsulation plant 2003 200
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Figure 8-4. Possible location of a
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9 Transportation of encapsulated fu
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9.3 SKB’s transportation system -
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absorbs neutron radiation. The lid
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Applicable international and Swedis
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een specified yet. Since the size o
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• Methods exist for full-face dri
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Programme SKB keeps track of curren
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Judgement with regard to long-term
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Furthermore, it must not have an ad
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Studies of equipment will be conduc
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A third type of seal is intended to
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10.6.1 Requirements and premises In
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the long-term safety of the concept
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11.3 Execution - stepwise design Si
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Programme Design step D, which incl
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12 Deep repository - monitoring SKB
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• Trigger levels for action. •
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Part III Safety assessment and rese
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As a complement to the numerical mo
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Table 13-2. Research on the initial
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13.2.4 Backfill Together with Posiv
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Table 13-3. Projects and experiment
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spent nuclear fuel. It was neverthe
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concepts or whose descriptions requ
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14.2.2 Radionuclide transport and d
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At present, the computational time
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Inflow Nuclides in a soluble phase
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15.1.2 Geometry The deep repository
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7 6 BWR 55 MWd/tU PWR 42 MWd/tU PWR
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15.1.11 Gas composition Conclusions
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15.2.5 Heat transport Dealt with in
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simulating the repository environme
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238 U 237 Np 239 Pu Concentration,
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The catalytic effect of uranium dio
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oxidant consumption in the bulk sol
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The influence of hydrogen peroxide
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A research programme to study cast
Page 175 and 176: Newfound knowledge since RD&D 2001
Page 177 and 178: 16.2.3 Heat transport No new knowle
Page 179 and 180: Programme The ongoing experiments w
Page 183 and 184: Programme Short-term tests aimed at
Page 185 and 186: Swelling properties The buffer must
Page 189 and 190: have been performed for some ten co
Page 191 and 192: 17.1.13 Impurity levels Bentonite i
Page 193 and 194: out when the buffer swells, but our
Page 195 and 196: These processes have been studied i
Page 199 and 200: • The gas injection phase will be
Page 203 and 204: Conclusions in RD&D 2001 and its re
Page 205 and 206: 19 9 D=205 d=175 D=172 d=170 D=168
Page 207 and 208: • Tests of the wetting process cl
Page 211 and 212: Figure 17-4. Natural redox front in
Page 213 and 214: These phenomena have been studied b
Page 215 and 216: 17.2.24 Radionuclide transport - ad
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Page 219 and 220: 18.1.6 Smectite content SKB, togeth
Page 221 and 222: Programme See section 18.2.2. 18.1.
Page 223 and 224: The wetting of the backfill from th
Page 225: Conclusions in RD&D 2001 and its re
Page 229 and 230: Programme See section 17.2.17. 18.2
Page 231 and 232: 18.2.23 Radionuclide transport - so
Page 233 and 234: 10 -5 I-129 Release rate (moles/yea
Page 235 and 236: and the rock matrix, is also crucia
Page 237 and 238: A thermal model will be constructed
Page 239 and 240: In a continuation of the super-regi
Page 241 and 242: A thorough overview has been done o
Page 243 and 244: The authorities are of the opinion
Page 247 and 248: 19.2.11 Advection/mixing - groundwa
Page 249 and 250: a so-called Markov-directed Random
Page 251 and 252: Diffusion measurements in the labor
Page 253 and 254: Uranium series analyses from clay-
Page 255 and 256: 19.2.18 Microbial processes Conclus
Page 257 and 258: 19.2.20 Colloid formation - colloid
Page 259 and 260: 19.2.23 Methane ice formation Concl
Page 261 and 262: 19.2.26 Integrated modelling - radi
Page 263 and 264: development that has taken place ha
Page 265 and 266: 20.2 Review of RD&D 2001 Following
Page 267 and 268: work will continue, particularly in
Page 269 and 270: 2 In Sea (mol) 3 Water Sea (mol/m 3
Page 271 and 272: The above work will be pursued in c
Page 273 and 274: certain substances, such as uranium
Page 275 and 276: In connection with the Safe project
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20.9 International work and dissemi
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the underlying material are current
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These reports describe dominant fun
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Glacial Permafrost Permafrost Borea
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Shoreline displacement has an isost
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The hydromechanical modellings that
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model that includes these factors a
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The salinity of the sea, inland sea
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• Public opinion and attitudes -
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Socioeconomic impact • Local deve
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Previously existing material is bei
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• The driving forces behind the d
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• Very effective methods for tran
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• A subcritical nuclear reactor w
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out in Cadarache, France. Hindas an
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Important results since 2001 includ
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Programme The goal of SKB’s resea
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Kasam says that disposal in Very De
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24 Decommissioning The facilities c
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SKB is responsible for management a
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25 Low- and intermediate-level wast
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25.2.1 Repository for short-lived L
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Programme Work on the design of the
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observation is that isosaccharinic
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stored so that the material can be
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6-4 Claesson S, 2004. Elektronstrå
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Chapter 14 14-1 SKB, 2004. Interim
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15-42 Ekeroth E, Jonsson M, 2003. O
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17-19 Le Bell J C, 1978. Colloid ch
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19-29 Hudson J (ed), 2002. Strategy
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19-77 Bath A, Milodowski A, Ruotsal
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20-19 Kautsky U (ed), 2001. The bio
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20-73 Blomqvist P, Jansson P-E, Esp
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20-119 Berggren J, Kyläkorpi L, 20
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23-10 NEA, 2002. Accelerator-driven
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SKB’s master plan Appendix A
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A1 Introduction A1.1 Background The
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generations unnecessarily. Another
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Encapsulation plant 2003 2004 2005
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facilitated by the fact that the re
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A2.3 System design A2.3.1 Fundament
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The system analyses will be largely
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Two safety reports will therefore b
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KBS-3H Basic Design Detailed engine
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Time horizon 2017 The current phase
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2003 2004 2005 2006 2007 2008 Phase
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In the subsequent phase, verificati
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The canister development work will
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Deep repository Year 2003 2004 2005
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A4.2 Site investigations Site inves
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Already in the feasibility study, l
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In step D2, the facility descriptio
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Table 4. Current situation and prel
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2003 2004 2005 2006 2007 2008 Desig
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Table 5. Continued. Technology issu
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A4.6.1 Siting factors Before priori
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A possible alternative scenario is
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of the NPPs starts, however, long-l
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Between now and 2008, an organizati
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Appendix B Abbreviations Abaqus ACL
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GIA Gis Goldsim Hindas HMC HPF HRL
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PMMA POD Posiva Prism Proper Protot
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ISSN 1404-0344 CM Digitaltryck AB,
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