1. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 1 Norbert Tesch, A. Leuschner, M. Schmitz, A. Schwarz Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany ICRS 10 / RPS 2004 – Madeira – 13 th May 2004 A. Introduction B. Thermal Aspects C. Radiolysis and Pressure Waves D. Shielding and Activation E. New Idea: Gas Dump Design Studies for an 18 MW Beam Dump at the future e + e - Linear Collider TESLA

2. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 2 A.1 TESLA Linear Collider Length33 km Earth cover10-30 m Particle typeselectron/positron Maximum Energy400 GeV Luminosity 5.8  10 34 cm -2 s -1 Electrons per bunch train 6.8  10 13 σx=σyσx=σy 0.55 mm Bunch train length 860  s Repetition rate4 Hz Energy per bunch train4.4 MJ Total power per beam18 MW

3. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 3 A.2 Water Beam Dump  Problem: How to dump 18 MW? Solid, fluid or gas based beam dump?  Solid dump: graphite-copper-water dump with heat conduction from copper to water  Even with a fast sweeping system (needed to distribute the energy) the solid option was not practicable for the given beam power in terms of heat extraction  Therefore the base line design was the fluid (water) dump option ! Thermal Aspects  Heat extraction external / internal Problems to be addressed: Other Processes  Radiolysis  Pressure waves Radiation Handling  Shielding  Activation  Dismantling and disposal of activated material @ final shut down The basic parameters of the water beam dump  Cylindrical H 2 O volume with L=10 m, Ø=1.5 m and p=10 bar  T boil =180°C  Fast (within bunch train) circular sweep with R fast = 8 cm needed to avoid local boiling  Not considered here: beam window (vacuum/water, huge design effort!!!) and beam pipe

4. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 4 water-system air treatment water-dump vessel dump shielding containment shielding commissioning beam spent beam hall basin exhaust / chimney sand general cooling water A.3 Schematic Layout of Water Beam Dump

5. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 5 Water Dump 18m 3, 10bar Pump A Heat Exchanger A Static Pressure 10bar Hydrogen Recombiner Heat Exchanger B Pump B Static Pressure  10bar Water Filtering (ion exchanger, resin filter) 80°C Storage Container Primary Loop 18MW /  T=30K  140kg/s Secondary Loop general cooling water 70°C 40°C 60°C30°C 40°C 50°C  Two-loop system with p B  p A Scheme of Water System 1% to 10% of total water flow  Water flow of 140 kg/s needed to remove 18 MW  Main piping DN 350mm B.1 External Heat Extraction  Recombination system should be directly in return pipe !

6. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 6 B.2.1 Internal Heat Extraction - Introduction  T inst : instantaneous temperature rise caused by energy deposition of 1 bunch train, dE/dV(r,z) = c     T inst (r,z), thermal diffusion within 1ms only 10  m in water  T eq : temperature rise assuming a time independent heat source S, with average power and spatial distribution given by subsequent bunch trains, S(r,z) = 4Hz  dE/dV(r,z)  conservative estimation for the temperature at a given position ŝ=(r, ,z): T(ŝ)  T 0 +  T eq (ŝ) +  T inst (ŝ) ; with T 0 = water inlet temp. (50°C) time temperature 1/ rep  T inst  T eq under the given external water mass flow of 140kg/s, create a suitable water velocity field inside the dump vessel, in order to: keep T(ŝ) well below boiling point (180°C) at any position, i.e minimize  T eq (ŝ) Heating Process Task T0T0

7. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 7 B.2.2 Internal Heat Extraction - Heat Source radial power density @ z=300cmlongitudinal power density  T inst (r,z) = 1/(c   )  dE/dV(r,z)  (  T inst ) max = 40K @ r = 8cm, z  200cm   T inst = 28K @ r = 8cm, z  300cm 1 bunch train in water, 6.8  10 13 e - @ 400GeV  x =  y = 0.55mm and fast sweep R fast = 8cm 4Hz bunch train repetition:  (dP/dz) max  50kW/cm @ z  300cm  dP/dz dz = 18MW  dP/(dzdr) dr = 50kW/cm z=300cm e-

8. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 8 B.2.3 Internal Heat Extraction – Fichtner*  vortex flow, velocity  f(z), CFD-ACE 6.6 code  front / rear part split and water mixing  internal flow 140 to 280 kg/s, here 260 kg/s  water velocity at inlet nozzle  30 m/s !  p (in-out)  5 bar  130 kW pump power !  2d (r,  ) stationary simulation at z=3m : T 0 + max (  T eq +  T inst ) = 54°C+47K+28K = 125°C well below 180°C boiling point ! 130kg/s 120kg/s 130kg/s 10kg/s 260 kg/s 130kg/s out: 140kg/s, 80°C in: 140kg/s, 50°C T 0 =54°C 59°C82°C z=3m e- 0 1 2 [m/s] velocity (r,  ) T 0 +  T eq (r,  ) @ z=3m [°C] T 0 =54 71 61 81 101 91 max(  T eq ) = 47K 1.5m * calculations done by Fichtner GmbH & Co KG

9. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 9 B.2.4 Internal Heat Extraction – Framatome*  longitud./radial flow, 3d, PHOENIX 3.4 code  internal flow = external flow = 140kg/s  tube 1/2: 0.1/0.02% porosity  15% radial flow  max. tube 2 temp., 50°C+45K+0K = 95°C  max. water temp. between tube 1 & 2 T 0 + max (  T eq +  T inst ) = 50°C+58K+0K = 108°C  max. tube 1 temp. is at z  4m, r=130mm T 0 + max (  T eq +  T inst ) = 50°C+34K+7K = 101°C [m/s] velocity (r, z) [°C] T 0 =50 108 max(  T eq ) = 58 K in:  =140kg/s, 50°Cout:  =140kg/s, 80°C e- T 0 +  T eq (r, z) 3.3m 10m 125 mm tube 1tube 2 50mm z r 0 0 v  2.8 – 2.4 m/s z r 125mm tube 1 tube 2 0 5m6.7m * calculations done by Framatome ANP GmbH

10. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 10 C.1 Pressure Waves - TÜV-Nord*  consider 1 bunch train 860  s long as dc-beam source: S = 1/860  s  dE/dV for 0  t  860  s and S = 0 otherwise  CFD code Fluent 6.0 without handling of phase transition Assumptions e- z  in water:  p max  3.7bar near z-axis @ 100  s  p min  -1.6bar near z-axis @ 950  s  reduces boiling temp. & solubility of gases !!!  at vessel cylinder:  p max  1.8bar @ 650  s  at front/rear face (windows):  p max  0.5bar  pressure wave decay to 0 after  3ms (<<250ms) 400GeV,  =0.55mm, 8cm fast sweep 75cm 10bar, 50°C v sound  1.5km/s r 10m Results r [cm]  p [bar] 01030405060702075 0 3 1 2  p(r) @ z=2.5m 0  t  800  s  p(r) @ z=2.5m 0  t  800  s 1050100150200 400 300 500 700 800 600 r [cm]  p [bar] 010304050607020 75 2 -2 1 0  p(r) @ z=2.5m 0.8  t  1.6ms  p(r) @ z=2.5m 0.8  t  1.6ms t [  s] 0.8 1.0 0.95 0.9 1.1 1.2 1.3 1.4 1.5 1.6 t [ms] Pressure if close to boiling temperature (imperfect beam with   6mm, no sweep, after 325  s)  in water:  p max  9bar,  p min  -6bar  at vessel cylinder:  p max  2.7bar  at front/rear face (windows):  p max  0.5bar  pressure wave decay to 0 after  20ms * calculations done by TÜV-Nord Gruppe

11. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 11 C.2 Radiolysis  H 2 O cracked by shower of high energy primary electron  net production rate at 20°C and 10 bar: 30 ml/MJ H 2 and 15 ml/MJ O 2 corresponding to 0.27 g/MJ H 2 O with spatial distribution according to dE/dV profile  solubility in water at 60°C:H 2 : 16 ml/l and O 2 : 19.4 ml/l Fundamentals  18 MW: 4.8 g/s H 2 O cracked  whole primary water (30m 3 ) would be radiolysed in 72 days ! recombination needed with 0.54 l/s H 2 + 0.27 l/s O 2  4.8 g/s H 2 O + 58 kW (0.3%  P beam )  solubility limit during 1 bunch train at 10 bar dE/dV  530 J/cm 3 for H 2 & dE/dV  1300 J/cm 3 for O 2 ; our case (dE/dV) max = 160 J/cm 3 Our Case  solubility during bunch train passage can be exceeded locally due to local pressure drops with negative  p or rise of  T inst  danger of H 2 gas bubbles comparable to local boiling  if not all H 2 is recombined, H 2 can accumulate at special locations (local pockets)  danger of explosion (e.g. nuclear power plant Brunsbüttel)  recombination in gas-phase without expansion doubtful  recombination should happen directly in return pipe of dump vessel to ensure that 100% of the water will reach the decompress-compress stage So far it looks almost good, BUT H 2 -control is a critical thing:  Framatome proposal  Fichtner proposal

12. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 12 D.1 Radiation Handling Shielding of water vessel towards soil, groundwater and surface*  soil & groundwater: 3m normal concrete or equivalent to reach planning goal of 30  Sv/a due to incorporation  surface: 3m normal concrete or equivalent + 7m sand or equivalent to reach planning goal of 100  Sv/a due to direct radiation 3m normal concrete 7m sand surface soil & groundwater dump 3m normal concrete Activation of primary circuit* 18MW, 30m 3 water  Main contribution of activation in water comes from 3 H and 7 Be 3 H: 20keV  -, t 1/2 =12a, A sat =250TBq, A(5000h)=8TBq, A(10a)=110TBq -no direct dose rate, but problem if released due to accident or maintenance ! 7 Be: 478keV , t 1/2 =54d, A sat =108TBq, A(5000h)=102TBq -main contributor to local dose rate, assume equal distribution in water system  300mSv/h at surface of component and 50mSv/h in 50cm distance ! (after 5000h) -accumulation in resin filters, but also adsorption on circuit surfaces (esp. heat exchanger)  local shielding needed !  2cm thick stainless steel dump vessel gives 400mSv/h on its axis (5000h and 1 month cooling)  regular inspection of vessel (welds,...) seems to be problematic ! * calculations done with FLUKA code

13. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 13 D.2 Radiation Handling Activation of containment air* 18MW, 3000m 3 air  necessity of closed containment, „closed“  under-pressure by continuous exchange rate of 1vol/h and controlled exhaust  looks fine except for short lived isotopes: need „delay line“ of about 1 hour ! A sat A(5000h)A_specific(5000h) [Bq/m 3 ] w/o air exchange with air ex- change 1vol/h allowed limit 3H3H 1.4GBq43MBq14 00031 000 7 Be 390MBq370MBq120 000706 000 z containment air 2m 10m 5m dump 20cm steel + 1.8m concrete r exhaust Scheduled opening of primary circuit 30m 3 water, 100TBq of 3 H  flush water into storage tank,  100l remain (0.1mm on 1000m 2 ), vent system with dry gas via 95% efficient condenser  5l  10GBq tritium have to be released to outside air  meeting the limit of 1kBq/m 3 needs venting with 10 7 m 3 air  this takes 1000h=42days with 10 4 m 3 /h  using a chimney is necessary (acceptance!) Dismantling of activated system after final shut down after 20 years, 200TBq of 3 H  primary water solidifying as concrete  5000 barrels (200l, 40GBq)  steel components (150t,  10 6 Bq/g) & concrete shielding (1500t,  200Bq/g)  = a lot of M€ * calculations done with FLUKA code

14. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 14 E.1 New Idea: Gas Dump Problems and disadvantages of water dump:  High tritium production (to reduce: larger atomic number of dump material)  Critical window design, 10 bar static + 0.5 bar dynamic (reduce pressure)  Radiolysis, local and instantaneous effects represent a severe risk (to avoid: one-atomic gas)  Handling of water during maintenance and final shutdown (less tritium)  Disposal costs not negligible (less tritium) To overcome most of the problems and disadvantages the following gas beam dump was proposed:  Material: Noble gas (first attempt: Argon @ 1 bar) in inner tube (r=4 cm) acts as scattering target, (energy deposition of 0.5 %) and distributes the beam energy longitudinally (no sweeping)  Main part of the energy is dumped in Iron shell of radius 52 cm (average power loss 18 kW/m)  Surrounded by 4 cm thick Water cooling system  Dump system has diameter of 1.20 m and length of 1000 m  Can be used as  -  dump as well tunnel gas dump

15. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 15 E.2 Gas Dump: Energy Density  Energy density in GeV/cm 3 in r-z view for one 400 GeV electron* * calculations done with FLUKA code

16. Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 16 E.3 Gas Dump: Comparison Disadvantages of gas dump:  Length of dump inside collider tunnel  Space for additional shielding needed  adopted tunnel design necessary  Not easy to reach constant energy density of 18 kW/m over whole length Conclusion:  The fluid (water) beam dump seems to be feasible, but with severe disadvantages !!!  The gas (argon) beam dump option seems to be a very attractive alternative and will surely be considered in an early design stage of the next linear collider !!! Water DumpArgon Dump A sat Tritium 250 TBq (in water) 29.3/0.7/0.02 TBq (in iron/gas/water) Beam Window 10 bar static and 0.5 bar dynamic, size 20 cm 1 bar static and 0.01 bar dynamic, size 8 cm Radiolysis see abovenone Advantages of gas dump:  Tritium production  Beam window  Radiolysis  Maintenance and disposal  Cases of emergency  Acceptance and permission !!!