Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 –...

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 – 13th May 2004

A. IntroductionA. Introduction

B. Thermal AspectsB. Thermal Aspects

C. Radiolysis and Pressure WavesC. Radiolysis and Pressure Waves

D. Shielding and ActivationD. Shielding and Activation

E. New Idea: Gas DumpE. New Idea: Gas Dump

Design Studies for an 18 MW Beam Design Studies for an 18 MW Beam Dump at the future eDump at the future e++ee-- Linear Linear

Collider TESLACollider TESLA


A.1 TESLA Linear ColliderA.1 TESLA Linear Collider

Length 33 km

Earth cover 10-30 m

Particle types electron/positron

Maximum Energy 400 GeV

Luminosity 5.8 1034 cm-2s-

1

Electrons per bunch train

6.8 1013

σx=σy 0.55 mm

Bunch train length 860 s

Repetition rate 4 Hz

Energy per bunch train

4.4 MJ

Total power per beam 18 MW


A.2 Water Beam DumpA.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 extractionexternal / 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 H2O volume with L=10 m, Ø=1.5 m and p=10 bar Tboil=180°C

Fast (within bunch train) circular sweep with Rfast= 8 cm needed to avoid local boiling

Not considered here: beam window (vacuum/water, huge design effort!!!) and beam pipe


water-system

air treatment

water-dump vessel

dump shielding

containment shielding

commissioning beam spent beam

hall

basin

exhaust / chimney

sand

generalcooling water

A.3 Schematic Layout of Water Beam DumpA.3 Schematic Layout of Water Beam Dump


Water Dump18m3, 10bar

Pump A

HeatExchanger

A

StaticPressure

10bar

HydrogenRecombiner

HeatExchanger

B

Pump B

StaticPressure10bar

WaterFiltering

(ion exchanger,resin filter)

80°C

StorageContainer

PrimaryLoop

18MW / T=30K 140kg/s

SecondaryLoop

general cooling water

70°C

70°C 40°C

60°C 30°C

40°C

50°C

Two-loop system with pB pA

Scheme of Water System

1% to 10% oftotal water flow

Water flow of 140 kg/s needed to remove 18 MW

Main piping DN 350mm

B.1 External Heat ExtractionB.1 External Heat Extraction

Recombination system should be directly in return pipe !

Wärmetauscher 17,5 MW

140 kg/s 140 kg/s

260

kg/s

130 kg/s 130 kg/s

10 kg/s

130 kg/s 130 kg/s

120 kg/s bzw. 0 kg/s0 kg/s bzw. 120 kg/s

140

kg/s

Absorber 17,5m³

Wärmetauscher 17,5 MW

Vorlauf

Rücklauf

Kühlwasserzulauf

Auffangbehälter

Kühlwasserzulauf

Sekundärkühlkreislauf

Primärkühlkreislauf

zum äußeren Kühlkreislauf

Ionen-tauscher

Rekom-binator


B.2.1 Internal Heat Extraction - IntroductionB.2.1 Internal Heat Extraction - Introduction

Tinst : instantaneous temperature rise caused by energy deposition of 1 bunch train,

dE/dV(r,z) = c Tinst(r,z), thermal diffusion within 1ms only 10m in water

Teq :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) T0 + Teq(ŝ) + Tinst(ŝ) ; with T0 = water inlet temp. (50°C)

time

temperature

1/rep

Tinst

Teq

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 Teq(ŝ)

Heating ProcessHeating Process

TaskTask

T0


0 200 400 600 800 10000

5

10

15

20

25

30

z [cm]

r [c

m]

0.1600.2850.5060.9001.602.855.069.0016.028.550.690.0160

Energy Density (1 bunch train), dE/dV [J/cm3]

B.2.2 Internal Heat Extraction - Heat SourceB.2.2 Internal Heat Extraction - Heat Source

05

1015

2025

0.00 5.00 10.00 15.00 20.00

r [cm]

dP

/(d

r*d

z) [

kW

/cm

²]

radial power density @ z=300cm

01020304050

0 200 400 600 800 1000

z [cm]

dP

/dz

[kW

/cm

]

longitudinal power density

Tinst(r,z) = 1/(c ) dE/dV(r,z)

(Tinst)max = 40K @ r = 8cm, z 200cm

Tinst = 28K @ r = 8cm, z 300cm

1 bunch train in water, 6.8 1013 e- @ 400GeV

x= y= 0.55mm and fast sweep Rfast= 8cm

4Hz bunch train repetition:

(dP/dz)max 50kW/cm @ z 300cm

dP/dz dz =

18MW

dP/(dzdr) dr =

50kW/cm

z=30

0cm

e-


B.2.3 Internal Heat Extraction – Fichtner*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 :

T0+max(Teq+Tinst) = 54°C+47K+28K = 125°C

well below 180°C boiling point !

130kg/s

130kg/s

120k

g/s

130kg/s

10k

g/s

260 kg/s130kg/s

out: 140kg/s, 80°C in: 140kg/s, 50°C

T0=54°C

59°C82°C

z=3m

e-

0

1

2[m/s]

velocity (r, )velocity (r, )

T0 + Teq(r, ) @ z=3mT0 + Teq(r, ) @ z=3m

[°C]

T0=54

71

61

81

101

91

max

(T

eq)

= 4

7K

1.5m

* calculations done by Fichtner GmbH & Co KG


B.2.4 Internal Heat Extraction – Framatome*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


max. tube 1 temp. is at z 4m, r=130mm


[m/s]velocity (r, z)velocity (r, z)

[°C]

T0=50

108

max

(T

eq)

= 5

8 K

in: =140kg/s, 50°C out: =140kg/s, 80°C

e-

T0 + Teq(r, z)T0 + Teq(r, z)

3.3m

10m

125

mm

tube 1 tube 2

50mm

z

r

0

0

v 2.8 – 2.4 m/s

z

r

125m

m

tube 1

tube 2

0

5m 6.7m

* calculations done by Framatome ANP GmbH


C.1 Pressure Waves - TÜV-Nord*C.1 Pressure Waves - TÜV-Nord*

consider 1 bunch train 860s long as dc-beam

source: S = 1/860s dE/dV for 0 t 860s and S = 0 otherwise

CFD code Fluent 6.0 without handling of phase transition

AssumptionsAssumptions

e-z

in water: pmax 3.7bar near z-axis @ 100s

pmin -1.6bar near z-axis @ 950s

reduces boiling temp. & solubility of gases !!!

at vessel cylinder: pmax 1.8bar @ 650s

at front/rear face (windows): pmax 0.5bar

pressure wave decay to 0 after 3ms (<<250ms)

400GeV, =0.55mm, 8cm fast sweep

75cm10bar, 50°C

vsound1.5km/s

r

10m

ResultsResults

r [cm]

p [bar]

0 10 30 40 50 60 7020 75

0

3

1

2

p(r) @ z=2.5m0 t 800s

p(r) @ z=2.5m0 t 800s

10 50 100 150 200400

300

500700

800600

r [cm]

p [bar]

0 10 30 40 50 60 7020 75

-1

2

-2

1

0

p(r) @ z=2.5m0.8 t 1.6ms

p(r) @ z=2.5m0.8 t 1.6ms

t [s]

0.8

1.0

0.95

0.9

1.11.2

1.31.4

1.51.6

t [ms]

Pressure if close to boiling temperature

(imperfect beam with 6mm, no sweep, after 325s)

in water: pmax 9bar, pmin -6bar

at vessel cylinder: pmax 2.7bar

at front/rear face (windows): pmax 0.5bar

pressure wave decay to 0 after 20ms* calculations done by TÜV-Nord Gruppe


C.2 RadiolysisC.2 Radiolysis

H2O cracked by shower of high energy primary electron

net production rate at 20°C and 10 bar: 30 ml/MJ H2 and 15 ml/MJ O2 corresponding to 0.27 g/MJ H2O with spatial distribution according to dE/dV profile

solubility in water at 60°C: H2: 16 ml/l and O2: 19.4 ml/l

FundamentalsFundamentals

18 MW: 4.8 g/s H2O cracked whole primary water (30m3) would be radiolysed in 72 days !

recombination needed with 0.54 l/s H2 + 0.27 l/s O2 4.8 g/s H2O + 58 kW (0.3% Pbeam)

solubility limit during 1 bunch train at 10 bar

dE/dV 530 J/cm3 for H2 & dE/dV 1300 J/cm3 for O2 ; our case (dE/dV)max= 160 J/cm3

Our CaseOur Case

solubility during bunch train passage can be exceeded locally due to local pressure drops with negative p or rise of Tinst

danger of H2 gas bubbles comparable to local boiling

if not all H2 is recombined, H2 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 H2-control is a critical thing:So far it looks almost good, BUT H2-control is a critical thing:

Framatome proposal Fichtner proposal


D.1 Radiation HandlingD.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, 30m3 water

Main contribution of activation in water comes from 3H and 7Be

3H: 20keV -, t1/2=12a, Asat =250TBq, A(5000h)=8TBq, A(10a)=110TBq

- no direct dose rate, but problem if released due to accident or maintenance !

7Be: 478keV , t1/2=54d, Asat =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


D.2 Radiation HandlingD.2 Radiation Handling

Activation of containment air* 18MW, 3000m3 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 !

Asat A(5000h) A_specific(5000h) [Bq/m3]

w/o air exchange

with air ex-change 1vol/h

allowed limit

3H 1.4GBq 43MBq 14 000 3 1 000

7Be 390MBq 370MBq 120 000 70 6 000

z

containment air

2m2m

2m

10m

5m5m

5m

dump20cm steel +1.8m concrete

r exhaust

Scheduled opening of primary circuit 30m3 water, 100TBq of 3H

flush water into storage tank, 100l remain (0.1mm on 1000m2), vent system with dry gas

via 95% efficient condenser 5l 10GBq tritium have to be released to outside air

meeting the limit of 1kBq/m3 needs venting with 107m3 air this takes 1000h=42days with 104 m3/h using a chimney is necessary

(acceptance!)Dismantling of activated system after final shut down after 20 years, 200TBq of 3H

primary water solidifying as concrete 5000 barrels (200l, 40GBq)

steel components (150t, 106Bq/g) & concrete shielding (1500t, 200Bq/g) = a lot of M€



E.1 New Idea: Gas DumpE.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


E.2 Gas Dump: Energy DensityE.2 Gas Dump: Energy Density

Energy density in GeV/cm3 in r-z view for one 400 GeV electron*

Energy Density [GeV/cm3]

length [m]

radius [cm]

Argon

I ron

Water

Air


length [m]

radius [cm]


length [m]

radius [cm]

Argon

I ron

Water

Air



E.3 Gas Dump: ComparisonE.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 Dump Argon Dump

Asat Tritium 250 TBq (in water)

29.3/0.7/0.02 TBq (in iron/gas/water)

Beam Window10 bar static and 0.5

bar dynamic, size 20 cm1 bar static and 0.01

bar dynamic, size 8 cm

Radiolysis see above none

Advantages of gas dump: Tritium production Beam window Radiolysis Maintenance and disposal Cases of emergency Acceptance and permission !!!

Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 –...

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