Soil, Groundwater and Cooling Water

Transcription

1 Laboratory Note DESY D3-114 March 2001 Soil, Groundwater and Cooling Water Activation at the TESLA Beam Dump N. Tesch Deutsches Elektronen-Synchrotron DESY Abstract The main dump system of the linear collider TESLA has to absorb a power of about 12 MW (per side) during operation. On the one hand this results in significant activation of the main dump material, the primary cooling water of the main dump system, which will have important consequences for the construction of this system. On the other hand the activation of soil and groundwater near the main beam dumps has to be kept well below the legal limits. Using the Monte Carlo program FLUKA99 together with a simple model of the beam line and dump geometry the following results are found: For the activation of the primary cooling water mostly two long-living radioactive isotopes are relevant: Tritium ( H) and Be. Their saturation activities for a beam power of 12 MW are 167 TBq and 72 TBq respectively. After one year (5000 hours) of operation 5.3 TBq H and 68 TBq Be are produced. For activation of reposing groundwater the following activity concentrations close to the dump shielding were found: 2.6 Bq/g for H and 0.45 Bq/g for Na after one year of operation for 3 m concrete shielding of the main beam dumps. Taking into account the motion of groundwater in the main dump area following the expert report it can be shown that for distances greater than about 100 m from the main dumps in direction of the groundwater flow one can even take the whole drinking water from that groundwater resulting in doses less than 30 Sv per year. It can be shown that the large entrance windows of the main beam dumps, necessary because of the sweeping system, will not represent a problem in terms of activation of soil and groundwater.

2 1 Main Beam Dump System 1.1 Requirements and basic concept Each of the main dumps has to handle an average beam power of about 12 MW. This represents a 50% increase in the average power requirement compared to the CDR parameters [1], where a graphite based dump was considered as the primary option. Since heat conduction defines the power capability of solid absorbers, their technical solution becomes already difficult beyond several hundreds of kw of beam power and is highly impractical in the MW regime as required here. Thus the only reasonable and technically feasible solution is a water dump system. Such a scheme handles the high power by a sufficient mass flow towards an external heat exchanger and is most flexible with respect to a later power upgrade as required here. Figure 1 shows the conceptual layout of the main parts of the dump system. The same dump is used for the main 12 MW spent beam and for the fast emergency extraction line (FEXL). As a result the dump requires an entrance window at both ends of the water vessel. A single cooling system (per side) is intended to serve both the main spent beam dump and the beamstrahlung collimator. If a second IR is constructed, then the same cooling plant can also be used for the additional dumps, since the total power at any given time can never exceed 12 MW. More information about the TESLA dump system can be found in [2, 3, 4, 5]. Dump Hall Tunnel Fast e- emergency and commissioning extraction line Emergency Extraction Sweeping Exit Window beamstrahlung collimator Water System cooling / preparation Water Dump 3 11m, 10bar 2 entrance windows ~250m Exit Window Tunnel ~15mrad e- e+ Fast Sweeping spent beam collimator spent beam extraction line IP e+ Figure 1: Schematic view of the main linac beam dump system. 1.2 Water vessel Most of the beam power should go into the water and not into the mechanical container: hence the vessel must be built from a minimum amount of mechanically strong and corrosion resistant material, which in addition represents a small source of induced radioactivity. The dump consists of about 11 m of water, which is housed in a 10 m long (27.7 radiation length) cylindrical titanium vessel, with a radius of 60 cm (6.3 molière radii), and a wall thickness of 15 mm. According to 250 GeV shower simulations using the MARS code, energy escaping from the absorber is at the 1 2% level, and is dominated by radial leakage. Since penetration of the shower varies only logarithmically with energy, the leakage fraction 2

3 (normalized to incident beam power) increases only slightly at 400 GeV. The same vessel will be used for the 400 GeV upgrade and power (in absolute numbers) leaking into the shielding grows by 50%, since it linearly scales with the incoming beam power. 1.3 Water system Removal of the heat dissipated by the beam in the water vessel will be done by a special water in- and outlet system. On the one hand a water flow of 0.5 m/s perpendicular to the shower axis renews the volume of the water that the shower core sees for each beam pulse. This avoids pulse to pulse accumulation of instantaneous heat in areas of high energy deposition. On the other hand a continuous flow of 100 kg/s, or 360 m /h of vessel water towards an external heat exchanger handles the 12 MW average heat load with a 30 K temperature drop between in- and outlet. The heat exchanger is part of an ambitious water preparation plant, schematically shown in figure 2. The system must also handle the radiological and chemical aspects of the dump water. Pump 1 Pump 2 Emergency / Commissioning 30 C 40 C Heat 75 C Exchanger 50 C A 80 C Gas Analysis Heat Exchanger B Secondary Loop Gas Buffer (He) Pressure Control Hydrogen Recombiner Water Dump 3 11m, 10bar, 2 entrance windows 70 C Primary Loop 12MW / T=30K / 95kg/s General Cooling Water Water Level Control 1% to 10% of total flow Spent Beam Water Filter Delay Line Water Analysis Water Level Control Storage Container Figure 2: Schematic overview of the water system required for the main beam dump. 3

4 2 The Model All calculations for the activation of soil, groundwater and primary cooling water at the TESLA beam dump were carried out with the FLUKA99 code [6]. This code has been proven to be well suited to calculate residual nuclei produced in electromagnetic and hadronic cascade processes [7]. 2.1 Geometry and material To calculate the activation of soil, groundwater and primary cooling water at the TESLA beam dump the above described dump system has been simplified. The tunnel has an inner diameter of 5 m and an outer diameter of 6 m. The main beam dumps and the beamstrahlung (BS) dumps are cylinders of 10 m length and 1.2 m diameter. Both start at 240 m from the interaction point (IP) and consist of pure water. All tunnel walls and the shielding of the dump halls are made out of ordinary concrete. Soil with a water content of 27% is surrounding the complete TESLA tunnel and the dump halls. The standard composition of concrete and the surrounding wet soil used can be found in table 1. The shielding of the main dump and the BS dump are at minimum 3 m ordinary concrete in all directions. The BS dump is located at the position of the beam line, whereas the main dump is 2 m below the beam line. Therefore the beams are kicked by 15 rad downwards at 130 m from the IP for the luminosity operation mode and at 380 m from the IP for the fast extraction mode. All these connections and beam pipes are simulated as simple vacuum tubes. For the main dumps the aperture for the luminosity operation mode has a diameter of 100 cm and for the fast extraction mode a diameter of 20 cm. In case of the BS dump the aperture for the luminosity operation mode has a diameter of 30 cm and a beam pipe going through the whole dump with a diameter of 2 cm. The model of the TESLA interaction region and the dump area can be found in figure 3. In figure 4 the model for the main beam dump hall is shown in an undistorted view. element weight % concrete wet soil H C O Mg Al Fe Ca Si Na g / cm 1.8 g / cm Table 1: Material composition of concrete and wet soil (soil with a water content of 27%). 4

5 600. Tunnel Wall 500. Dump Hall BS Dump Interaction Point BS Dump Main Dump Tunnel Wall Main Dump Dump Halls Figure 3: Model for the TESLA beam delivery system and the dump region (all numbers in cm). Dump Hall BS Dump Main Dump Figure 4: Model for the TESLA main beam dump hall in an undistorted view (all numbers in cm). 2.2 Beam parameter All relevant beam parameter used for the following calculations are given in table Calculation of activation The option RESNUCLEi of FLUKA results in a table of nuclei (corresponding to a region of material) produced per primary electron, either by inelastic reactions or by low energy neutrons ( low means 20 MeV). The multiplication of the numbers of produced nuclei per electron by the rate of electrons results in saturation activities. Saturation activity is the maximum achievable activity obtained by an infinitely long period of irradiation and the decay rate being equal to the production rate. The activity after a certain period of operation for a specific nuclei can be calculated taking into 5

6 Energy 250 GeV Repetition rate 5 Hz No. of bunches per pulse 2820 Beam pulse length 950 s Bunch spacing 337 ns Bunch charge 1/e Pulse current 9.5 ma Emittance at IP (x,y) 10, 0.03 m Beta at IP (x,y) 15, 0.4 mm Beam size at IP (x,y) 553, 5 nm Bunch length at IP 0.3 mm Beamstrahlung dp/p 3.2 % Luminosity cm s Table 2: TESLA beam parameter for 250 GeV. account that period of operation and the corresponding half life of the nuclei. 3 Results 3.1 Activation of primary dump cooling water In a first step the electron beam as described in table 2 is colliding under a 15 rad downward kick with the main beam dump at 240 m from the IP. The results of the activation calculations of the dump material, which is identically equal to the primary dump cooling water, for the luminosity operation mode are listed in table 3 (for the fast extraction mode the results are comparable). Only the relevant nuclei with half lives greater than 1 s and saturation activities greater than 0.1 TBq are shown. The saturation activities are given as well as the activities produced after 1 year (5000 h) of operation and the activities after 1 hour, 1 day and 1 week after shut down (following 1 year of operation) for the luminosity operation mode. For the activation of primary cooling water of the TESLA dump system mostly two long-living radioactive isotopes are relevant: Tritium ( H) and Be. Their saturation activities for a beam power of 12 MW are 167 TBq and 72 TBq respectively. After one year (5000 hours) of operation 5.3 TBq H and 68 TBq Be are produced. It can be seen in table 3 that these activities will not change very much with time due to the long half lives of the nuclei. Comments on the other nuclei in table 3 will be given in the next section. 3.2 Dose rates from primary dump cooling water The most critical nuclei in terms of dose rate in the dump halls during handling with the dump system (for example piping, pumps, heat exchanger, tank, shielding and water) during shut-down (no operation) are H and Be because of their produced activities and half lives. 6

7 nuclei T A "! # (TBq) A (TBq) A &% '% (TBq) A )( (TBq) A * (TBq) H 12 a Be 53 d Be +,.- a Be 14 s C 19 s C 20 m C 5700 a C 2.5 s N 10 m N 7.1 s N 4.2 s O 71 s O 2.0 m Table 3: Activation of primary dump cooling water. But for the construction of the main dump system one also has to keep an eye on the dose rate coming from the dump system during operation. The nuclei with short half lives reach their saturation activities fast which will result in a constant fraction of the dose rate during operation. One has to pay special attention to the nuclei - N and all positron emitting nuclei. - N has a quite high (saturation) activity of 22 TBq and emits extremely high energy gamma rays (6.13 and 7.12 MeV). Therefore the self shielding of the dump system (water, pipes, etc.) is very low and - N will be a major contributor to the radiation level near the primary system piping. With the half life of 7.1 s the saturation activity will be reached immediately, but after stopping the operation the radiation level will be also gone fast. For the positron emitters C (11 TBq), / C (250 TBq), N (42 TBq), O (29 TBq) and O (886 TBq) the emission of the positron itself represents little concern, however, positron annihilation photons can contribute significant to the gamma-exposure field. All the above described problems will be very similar to the problems in cooling systems of nuclear power stations. To calculate the precise dose rates resulting from the above given activities in the dump cooling water is very complicated, because of the dynamics and the geometry of the system. The dump system consists of the water dump and a very extensive system of pipes and heat exchangers as described in section 1.3. Therefore it is without the precise knowledge of the geometry and the dynamics of such a system at the moment not possible to give reliable dose rates at specific components and locations of the system. To give an example one can assume that all Be will be collected in the ion exchanger, such as the saturation activity of 72 TBq will be reached after a certain time at the location of the ion exchanger. The corresponding dose rate in 1 m distance from the ion exchanger will be about 0.6 Sv/h using the conversion factor for Be of msv/h/gbq in 1 m distance. All the above mentioned items should be kept in mind during the construction of 7

8 the dump system and for all detailed design proposals the activities and dose rates have to be recalculated and checked. 3.3 Activation of soil and groundwater near beam dump To calculate the activation of soil and groundwater near the beam dump one has to identify the neutrons escaping from the shielding of the dump halls as well as the neutrons escaping from the tunnel shielding. In figure 5 the z-distributions of the neutrons escaping from the tunnel shielding and the dump hall shielding are shown from a FLUKA99 simulation with initial electrons. On the left the fast extraction mode and on the right the luminosity operation mode is shown. main dump main dump main dump main dump tunnel in direction from large entrance windows Figure 5: Z-distributions of neutrons escaping from the tunnel shielding and the dump hall shielding to the surrounding wet soil. On the left the fast extraction mode and on the right the luminosity operation mode is shown. In the first row of figure 5 the z-distributions of neutrons escaping from the tunnel shielding and the dump hall shielding are shown for the dump region. From these plots one can determine the density of neutrons entering the wet soil and being relevant for the calculation of activation of soil and groundwater. 8

9 Because of the large entrance windows (see figure 3 and 4) of the main beam dumps, which are necessary because of the sweeping system, it has to be checked that the neutrons tunneling through these holes are properly absorbed either in the shielding of the dump hall along the neutron path or in the tunnel walls such that no significant activation of soil and groundwater in the tunnel region can be found. Therefore in the second row of figure 5 the z-distributions of neutrons escaping from the tunnel shielding and the dump hall shielding are shown for the dump and tunnel region. It can be seen very clearly that the amount of neutrons escaping from the tunnel walls and entering the wet soil at positions far away from the dump region is significantly less than the amount in the dump region. So the dominant location of escaping neutrons will be the dump hall region and therefore we will only investigate further the dump hall region in terms of activation of soil and groundwater. To increase the statistics for the very CPU-time consuming calculations shown in figure 5 in a second step all neutrons identified as escaping from the dump hall shielding will be multiplied according to their energy distribution shown in figure 6. Figure 6: Energy of neutrons escaping from the tunnel shielding and the dump hall shielding to the surrounding wet soil. On the left the fast extraction mode and on the right the luminosity operation mode is shown. In the model of the second step the surrounding material is a system of wet soil rings covering the concrete shielding. The system is static that means for the moment we assume reposing groundwater. The inner ring 1 starts at 3 m radius and ends at 3.5 m radius. Rings 2-5 start at 3.5/4/4.5/5 m and end at 4/4.5/5/5.5 m. The total activities in the single layers of wet soil after 5000 h of operation as well as the corresponding activity concentrations are given in table 4. The saturation activity concentrations as well as the activity concentrations after 5000 h of operation for the most relevant nuclei can be found in table 5 for the luminosity operation mode. The most significant nuclei in terms of half life and amount of activity are: H, 0 Na, V, Mn and Fe. For activation of the groundwater only H (0.69 Bq/g in the inner ring of wet soil after 5000 h of operation) and Na (0.81 Bq/g in the inner ring of wet 9

10 ring 1 ring 2 ring 3 ring 4 ring 5 rest sum 3-3.5m 3.5-4m 4-4.5m 4.5-5m 5-5.5m A (GBq) A1 (Bq/g) Table 4: Activities and activity concentrations after 5000 h of operation in the surrounding wet soil rings for the luminosity operation mode. 2 2 in T ring 1 ring 2 ring 3 ring 4 ring 5 Bq/g 3-3.5m 3.5-4m 4-4.5m 4.5-5m 5-5.5m H 12 a 22./ / / / /0.02 Be 53 d 8.8/ / / / / F 110 m 1.2/ / / / /0.04 ) Na 2.6 a 5.8/ / / / /0.03 Na 15 h 11./ / / / / Mg 21 h 0.11/ / / / /0.00 P 14 d 0.36/ / / / /0.01 P 25 d 0.68/ / / / /0.03 S 88 d 0.15/ / / / / Ar 35 d 15./ / / / /0.38 K 12 h 0.18/ / / / /0.01 K 22 h 0.18/ / / / / V 16 d 0.27/ / / / /0.01 V 330 d 0.39/ / / / /0.01 Cr 28 d 1.5/ / / / /0.07 Mn 312 d 4.1/ / / / /0.04 / Fe 2.7 a 9.8/ / / / /0.03 Table 5: Saturation activity concentrations and activity concentrations after 5000 h of operation in Bq/g for the most relevant nuclei in the surrounding wet soil rings for the luminosity operation mode. soil after 5000 h of operation) are important, because all other nuclei produced in wet soil can be neglected because of their low solubility (see [8]). H is produced in soil and water and 100% will be dissolved in water, whereas the solubility of Na in water amounts to only 15%. Taking into account the mixture of dry soil and groundwater (73% dry soil and 27% water, see table 1) the activation of groundwater results in 2.6 Bq/g H and 0.45 Bq/g Na in the inner ring (first 50 cm behind the concrete shielding). These numbers can be compared with the numbers given in the former note [9]. There for a concrete shielding of 3 m and reposing groundwater 0.72 Bq/g H and 0.17 Bq/g / Na in the inner region were found. To compare these numbers with the ones given above one has to consider the beam power of 8 MW (factor 1.5) and 30 cm of additional concrete for the hall building (approximately factor 2) used in the former note. Taking into account this factor of 3 the numbers found here are perfectly consistent with the numbers found in [9]. 10

11 3.4 Doses from activated groundwater near beam dump There are no direct limits for the activation of soil and groundwater in the German Regulations for Radiation Protection ( Strahlenschutzverordnung ) given. In contrast to soil the groundwater transports the radioactive nuclei produced in the water itself or dissolved from soil and therefore it can contribute to human exposure following different pathways. In order to get a relation between the activity concentration in groundwater and a dose value in the regulations one can calculate the activity concentration which leads to a dose of 0.3 msv when dissolved in water and ingested. This annual dose of 0.3 msv is the upper limit of radiation exposure to persons in public areas from radiation producing installations given by the German Regulations for Radiation Protection ( Strahlenschutzverordnung ). To estimate an upper limit of activity concentration with respect to the German Regulations for Radiation Protection one can simply follow the assumptions in [8] and therefore take into account a dilution of 1/500 due to the motion of groundwater from the dump area to the place where the water will be ingested. The amount of water per year which a person is drinking is assumed to be 800 liters. The dose of 0.3 msv is equivalent to an ingested activity of 4567 Bq H or 8567 Bq Na. Therefore a person taking the whole drinking water only from the diluted groundwater from the inner ring will get a dose of about 0.1 Sv per year from H and 4.5 Sv per year from Na. So the total dose from this incorporation of activated groundwater is about 4.6 Sv per year and therefore well below the legal limit of 300 Sv per year and also our planning goal of 30 Sv per year. It is clear that this calculation is not very satisfying, because it is very hard to estimate from the expert report [10] the dilution of about 1/500 for the transition from reposing to moving groundwater in the main dump region. Therefore we will follow a different approach which is based on the slow distance velocity of the groundwater and the profile of the site in Ellerhoop in connection with the half lives of the produced nuclei. Baseline is the expert report [10] giving numbers for the profile and the motion of groundwater in the Ellerhoop region. The following approach takes transportation of activity into account and in addition a dilution of 1/10 due to that transport. Diffusion which is always connected to significant dilution of activity is not considered here. We are asking for the region around the dump halls in which the dose per year for a person consuming the whole drinking water (800 liters per year) exclusively from this special region is greater than 1/10 of the legal limit of 300 Sv per year. Then one only has to foresee that no drinking water from that region will be extracted. To illustrate the situation and the results figure 7 shows the Ellerhoop region including the IP and the two main dump halls (north dump and south dump). The topographic profile is given by the lines marked with 8.5 m, 8.0 m and 7.5 m. According to this profile and the given permeability one can calculate the distance velocity as described in [10] for the two dump regions. The result of this calculation is shown in table 6. 11

12 8.0m 7.5m North Dump 8.5m Interaction Point South Dump 7.5m 8.0m Figure 7: Ellerhoop region with interaction point and two dump areas (north dump and south dump), including the 30 Sv/a regions for Na for the distance velocity from the expert report (dashed) and the distance velocity which leads to the maximum distance (dotted). 12

13 0 north dump south dump descent 1m / 750m 1m / 900m permeability 9: m/s 9 m/s filter velocity,<;:2 m/s 9=,>:2 m/s distance velocity : m/s 4=?>: m/s distance velocity 6.9 m/year 6.0 m/year Table 6: Calculation of the distance velocity for the north and south dump. For a large variation of distance velocities as well as for the distance velocities calculated in table 6 the produced activity concentrations of Na in groundwater in the two regions of the north dump (relevant production distance 12 m, see table 7) and of the south dump (relevant production distance 18 m, see table 8) were computed. The production distances can be calculated from the profile and the direction of groundwater flow (see figure 7). Taking transportation of activity, in addition a dilution of 1/10 due to that transport and decay of activity into account one can calculate the time after which the activity concentration is reached which leads to a dose of 30 Sv per year for a person taking the whole drinking water from that region. These times and the corresponding distances (see equation 1) the groundwater has to travel to fulfill the above requirement can also be found in table 7 and 8. Because the doses from / Na are always dominating by more than one order of magnitude all numbers for activity concentrations, times and distances in table 7 and 8 are only given for / WFX"Y HZ K[\]\ Na^_ `Ta+bdcHegf [ \]\ Na in groundwater^_ `Va4b [ :^ Fh / -jik )lm (1) distance A1 (Bq/g) time (years) distance (m) velocity in groundwater for for (m/s) 30 Sv/a 30 Sv/a 4= = = = = = = Table 7: Calculation of Na activity concentrations in groundwater and the time and distance to fulfill the requirement dose L 30 Sv/a for the north dump for different distance velocities. For the dominant Na one can find a maximum distance of about 230 m for the north dump and 340 m for the south dump in direction of the corresponding groundwater flow for the 30 Sv/a zone. For the distance velocities calculated from the expert report [10] in table 6 a distance of about 78 m for the north dump and 76 m for the south 13

14 0 distance A1 (Bq/g) time (years) distance (m) velocity in groundwater for for (m/s) 30 Sv/a 30 Sv/a 4= = = =? = = = Table 8: Calculation of Na activity concentrations in groundwater and the time and distance to fulfill the requirement dose L 30 Sv/a for the south dump for different distance velocities. dump is found. All these regions are also sketched in figure 7 with dashed lines for the distance velocity from the expert report and dotted lines for the distance velocity which leads to the maximum distance. Summarizing one can say that taking into account the motion of groundwater in the dump area and following the expert report in terms of distance velocities it can be shown that for distances greater than about 100 m from the main dump halls in direction of the groundwater flow (see figure 7) one can even take the whole drinking water directly and permanent from the groundwater at any other region resulting in doses always less than 30 Sv per year. 4 Conclusion The main dump system of the linear collider TESLA has to absorb a power of about 12 MW during operation. Therefore there will be significant activation of the main dump material, the primary cooling water of the main dump system. On the other hand the activation of soil and groundwater near the main beam dumps has to be kept well below the legal limits. 4.1 Activation of primary dump water Using the Monte Carlo program FLUKA99 together with a simple model of the beam line and beam dump geometry the following results are found: For the activation of primary cooling water mostly two long-living radioactive isotopes are relevant: Tritium and Beryllium-7, their saturation activities for 12 MW are 167 TBq and 72 TBq respectively and after one year (5000 hours) of operation 5.3 TBq Tritium and 68 TBq Beryllium-7 are produced. During operation one has to pay special attention to the nuclei "- N and all positron emitting nuclei. 14

15 4.2 Activation of soil and groundwater For a shielding of the main beam dumps of 3 m concrete the production of Tritium and Sodium-22 in groundwater for one year of operation is 2.6 Bq/g ( H) and 0.45 Bq/g ( Na) close to the dump hall shielding for reposing groundwater. Taking into account the motion of groundwater in the dump area and following the expert report it can be shown that for distances greater than 100 m from the main dump halls in direction of the groundwater flow one can even take the whole drinking water from that groundwater resulting in doses less than 30 Sv per year. It was also shown that the large entrance windows of the main beam dumps, necessary because of the sweeping system, will not represent a problem in terms of activation of soil and groundwater. References [1] R. Brinkmann, G. Materlik, J. Rossbach, A. Wagner, Conceptual Design of a 500 GeV JHnJ Linear Collider with Integrated X-ray Laser Facility, DESY , ECFA , May 1997 [2] M. Maslov et al., Concept of the High Power J+o Beam Dumps for TESLA, TESLA Report [3] V. Sytchev et al., Concept of the Fast Beam Sweeping System for the J4o Beam Dumps of TESLA, TESLA Report [4] V. Sytchev et al., Concept of an Emergency Extraction Kickersystem for TESLA, TESLA Report [5] M. Maslov et al., Concept of Beam Entrance and Exit Windows for the TESLA Water based Beam Dumps and its related Beam Lines, TESLA Report [6] A. Fassò, A. Ferrari, J. Ranft, P.R. Sala, New Developments in FLUKA Modeling of Hadronic and EM Interactions, Workshop on Simulating Accelerator Radiation Environments SARE-3 (1997) [7] A. Fassò, M. Silari, STp L. Ulrici, Predicting Induced Radioactivity at High-Energy Electron Accelerators, 9 International Conference on Radiation Shielding (1999) [8] K. Tesch, Production of radioactive nuclides in soil and groundwater near the beam dump of a Linear Collider, Internal Report, DESY D3-86, 1997 [9] H. Dinter, Radiologische Auswirkungen auf die Umwelt beim Betrieb des Linear Colliders, Laborbericht DESY D3-97/1, 1998 [10] E. Doerks, A. Kölling, Hydrologisches Übersichtsgutachten Ellerhoop, Fa. Planum, Dec