h&cd systems and their impact on scenario/economics · pdf fileh&cd systems and their...

2nd IAEA DEMO Workshop, Vienna December 2013 PR Thomas

© 2013, ITER Organization

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H&CD Systems and their Impact on

Scenario/Economics (Lessons learned from ITER Design)

PR Thomas

ITER Organisation, Route de Vinon sur Verdon, F13115 St Paul-lez-Durance

Grateful acknowledgements to B Beaumont, D Boilson, Federichi(F4E), T

Franke(EFDA), L Grisham(PPPL), R Hemsworth, M Henderson, M Nightingale(CCFE),

E Poli(IPP), K Sakamoto(JAEA), E Surrey(CCFE) and the ITER Heating and Current

Drive Division

The views and opinions expressed herein do not necessarily reflect those of the ITER Organization



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Outline of talk

Introduction

Electron Cyclotron Heating and Current Drive

Ion Cyclotron Heating and Current Drive

(Lower Hybrid Current Drive)

Neutral Beam Heating and Current Drive

Generic technical issues

Conclusions



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ITER H&CD Requirements & Wagner Report

Heating Scenario ECH (MW) NBI (MW) ICH (MW)

Baseline 20 33 20

ECH-dominated 53 0 20

100% ECH 73 0 0

No ICH 40 33 0

ECH&CD system => localized H&CD across 0.0<≤0.9 and ~6.7

MW of counter-ECCD, in the range of 0<<0.45.

Require 3000 sec with duty cycle 25%

Working Group(Chair Fritz Wagner) charged by F4E to assess

the possibility to reduce ITER costs by an evaluation of an ECH-

only or ECH-dominated heating mix and the potential extension

to DEMO of ITER H&CD.

All scenarios have major consequences on buildings, vacuum

vessel, power supplies and the safety system.



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Wagner Report Findings

The heating scenario A with all three heating methods

should be maintained.

Panel commented that the findings of this Report did not

provide hoped for substantial reduction in cost.

This reflected: • Results from extensive simulations taking into account the

constraints from the core physics goals of the ITER missions

=> guarantee to pass H-mode threshold.

• Analysis of specific role of each of the heating systems and

the differences between the costs would not justify any major

change in the ITER heating mix. (ECH running costs)

If DEMO needs substantial current drive power, it will

significantly increase fusion costs if NBI cannot be used.

NBI is an important option for current drive in DEMO

because of its high current drive efficiency.



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Contrast Conditions JET ITER DEMO

Machine Fusion

Power

(MW)

Fusion

Power

Density

(MW.m-3)

Shot

Duration

(s)

dpa/yr Average

neutron

fluence

(MWa/m2)

JET

16 0.16 ~1 ~0 ~0

ITER

500

300

0.5

0.3

400

3000

0.5

0.1

DEMO

2000 2.0 ~few 106 20 7.5

Step from ITER to DEMO seems to be greater than

that from JET to ITER.



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Extra H&CD Requirements for DEMO

Availability

Thermodynamic

Efficiency

Net electrical power

(low Pmag and PBOP)

Physics

D Ward Limit Padd>> Pmag, PBOP

DEMO current drive efficiency ηwp.CD = 0.24-0.27

First wall surface area taken by H&CD, including

structural elements, ~ 6m2 for tritium breeding (~26m2

in ITER)

Very high availability – certainly much better than

overall system availability



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• 12 Power Supplies (F4E & IN-DA)

• 24 Gyrotrons (F4E, IN-DA, JA-DA, RF-DA)

• 24 Transmission lines (USIPO)

• 4 Upper Launchers (F4E)

• 1 Equatorial Launcher (JA-DA)

• EC Main Controller (F4E)

Clash

Upper Launchers

Equatorial Launchers

Transmission Lines

Gyrotrons

Power

Supplies (not shown)

ITER ECH – as-designed system



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ITER ECH – wall-plug efficiency Lower Limit Upper Limt Comment

ηtrans Pout ηtrans Pout

22kV feeds - 50.5MW 45.0MW

PSM PS 95% 48MW 97% 43.6MW Published results from TCV

Gyrotron 50% 24MW 55% 24.0MW Published results from JAEA

MOU ~95% 22.8MW 96% 23.0MW Published results from JAEA

T-line ~91.5% 20.9MW 96% 22.1MW Published results from JAEA

Launcher ~95% 19.8MW 97% 21.5MW JAEA and F4E estimate

Plasma >99.5% 19.7MW >99.5% 21.3MW Codes & Exp. results

Total 39% 19.7MW 47.5% 21.3MW

Aux. 2.5MW 2.2MW Based on JT-60U EC system

Cooling 3.0MW 1.25MW Assume 5 to 10% of

dissipated power

Total 35.2% 56.0MW 43.9% 48.5MW

“Aux.” includes body p/s, SC magnet, magnet compressor, control system and

other less significant power users. M Henderson



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ITER ECH – gyrotrons

IAP RAS GYCOM INF

At 170GHz:

JA: 0.8MW/100s, 1.0MW/1hr

RU: 0.99MW/1000s, 1.2MW/100s,1.5MW/2.5s

Efficiency ~50% at each operating point above

Cost issue in Wagner study arose from comparison of capital + 10 years

operation more powerful gyrotrons

G Denisov and K Sakamoto



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ITER ECH – transmission lines

Aluminium annealing begins at low

temperature. Loses 20% yield

strength at 1300/10000hrs.

Loss of strength compromises

vacuum seal and alignment.

Must remain at < 1200C

Maintain integrity at

10350/2 hours – shutter

valves at penetrations

Alignment accuracy

Building movements

challenge mode purity

requirements

Cooling water chemistry

G Hanson Dec 2013



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:

- Antennas: EU DA, BTP, design under development by F4E and consortium of EU labs

- Transmission lines and matching systems: US DA, at functional specs.

- RF sources and HV Power Supplies: IN DA, at functional specs, + IO (part of HVPS).

&

Switching network

3MW test loads

ITER ICH – as-designed system

http://www.iter.org/



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ITER ICH – antenna design

Strap Housing / Straps

HIP solution with promising

thermal / structural

performance, manufacturing

route explored, assembly

sequence developed

Faraday Screen

Square channel design

developed with supporting

modelling

4 Port Junction

Deep drilled solution with

full assembly sequence

developed

M. Shannon et al, CCFE

Rear Shield Cartridge

Extended, with now deep drilled cooling

solution developed to attenuate neutron

streaming



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ITER ICH – wall-plug efficiency

Input terms (MW) Output terms (MW)

AC input power 40 Plasma launched power 20

Cooling power 1.8 Losses in cooling system 1.8

Heat load into PHTS 1.5

RF sources cooling CCWS 14.5

AC/DC converter cooling

CCWS

0.8

TL line losses CCWS 0.75

Matching losses CCWS 2

Air dissipation 0.45

Total 41.8 41.8

End stage efficiency @ 1.6 MW for various load conditions. The average values

are: 66.9% for matched case, 64% for VSWR=1.5, 56.4% for VSWR=2, and 64.5%

for VSWR=1.5 and dedicated HVPS.

Gives efficiency of 48% (20MW launched and no plasma losses)

B Beaumont



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IC Antenna

ECH and ICH – port-plugs

Port plugs were conceived to permit maintenance of payloads in Hot Cell

Facility

However, 100% remote handling for insertion and removal is not likely to

be achieved – many operations will be hands-on

Sealing and alignment requirements difficult to meet

Tritium contamination/decontamination not yet fully addressed

We are struggling to meet target 100micro-Sv/hr at back of port-plug

Projected area relative to that taken by heat-flux too large for DEMO

DEMO should remove such modules to other side of blanket, at very

least, and “view” plasma through pipes – ECCD steering? Waveguide

material?



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ITER ECH & ICH – windows

Outer removed

Window assembly

IC Antenna VTL

EC diamond windows

EC and IC windows serve as confinement barrier.

Safety requirement, low RF losses, thermo-mechanical

loads and radiation require extensive R&D effort



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Tokamak Bldg NB Cell

Bldg 37 HV Hall

Building 34 LV Power Conversion

2 (+1) HNB + 1 DNB

NB Injectors connected

to equatorial ports 4 & 5

(& 6):

•HNB 1&2(&3) : tangential

•DNB : ~radial

Negative ion technology

Strong R&D Programme

supported by EU, JA & IN

NB – as-designed system



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NB – wall-plug efficiency Extrapolation to DEMO ussing an ITER beam source with a gas neutraliser or an upgraded ion source, RF power supply and either a photon or Li neutraliser.

Gas

neutraliser

Photon

neutraliser

Photon

neutraliser

Li

neutraliser

Li

neutraliser

MW MW MW

Electrical power to the ion source. 1.6 1.2 1.2 1.2 1.2 The ion souce size is reduced as it is assumed that there are no

gaps between the aperture groups horizontally for the photon

and LI neutraliser cases, and the RF power is reduced

proportionately.

The AC to RF conversion efficiency for the ion source power

supplies is 50%.

RF power to ion source 0.8 1.0 1.0 1.3 1.0 The efficiency of the RF power supply is assumed to increase

from 50% to 80% for the photon and Li neutraliser cases.

Accelerated ion power 40.0 40.0 40.0 40.0 40.0

Accelerated, dumped electrons 0.80 0.66 0.66 0.66 0.66 The accelerated electron power is approximately proportional to

the source pressure, which is assumed to be 0.2 Pa for the

photon and Li neutraliser.

Total accelerated power 40.8 40.7 40.7 40.7 40.7

Power lost in the accelerator due to beam particle other

secondary processes

10.1 6.7 6.7 6.7 6.7 The accelerator losses are proportional to the source pressure

and the extracted ion current, and scaled from the gas

neutraliser case.

Energy recovery efficiency 0.0 0.0 80.0 0.0 80.0

DC power to accelerator 50.9 47.4 36.0 47.4 36.0

Electrical power to the accelerator. 58.2 54.1 41.1 54.1 41.1

The AC to DC conversion for the accelerator power supplies is

87.5%.

Neutral power from the neutraliser. 23.2 36.0 36.0 26.0 26.0 Neutralisation for the D2 target is assumed to be 58%, 65% with

an Li neutraliser and with a photon neutraliser it is 90%.

Neutral power after halo loss 2.0 2.0 2.0 2.0 2.0 The halo loss is taken as 2% in all cases, asuming a modified

accelerator that eliminates most of the halo.

Neutral power to DEMO without re-ionisation loss. 21.6 33.5 33.5 24.2 24.2 The geometric transmission is 95% for the core of the beamlets

for both types of injector.

Neutral power to DEMO after re-ionisation loss 20.1 32.8 32.8 23.7 23.7 In the present design the re-ionisation loss is 7%.

In upgrade the source pressure is halved and there is no

neutraliser gas, reducing the total gas influx by a factor of

approximately 5. The re-ionisation losses are proportional to the

gas influx to the injector plus the gas 0utflow from the tokamak.

The re-ionisation loss is calculated to be 2% with the photon

neutraliser and the Li neutraliser.

Injected into DEMO 20.1 32.8 32.8 23.7 23.7

R Hemsworth



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NB – wall-plug efficiency

Electrical power to the residual ion

dump. 1.6 0.0 0.0 1.4 1.4 In the present injector there is additional power due to electrostatic

acceleration of ions onto the dump plates and secondary electrons

from the positive ion collection plate accelerated across the dump

channel. The high neutralisation with the photon neutraliser leads to

low, mainly negative, ion flow from the neutraliser, hence a low power

to the dump

Electrical power to the laser. 0.0 2.0 2.0 0.0 0.0 800 kW of laser power is required to inject sufficient photons into the

neutraliser. Solid state laser arrays now achieve 40% efficiency. Laser power efficiency is 40%.

Electrical power to the active

correction and compensation coils. 1.6 1.6 1.6 1.6 1.6

The AC to DC conversion efficiency

for the ACC coils power supply is

95%.

Electrical power for the cryogen

supply. 0.5 0.3 0.3 0.3 0.3 0.5 MW is estimated (RSH) as the additional power in the cryoplant

needed for the beam cryopumps.

Electrical power for the water

cooling of the beam source, and the

beamline components.

0.8 0.3 0.3 0.7 0.7 0.8 MW is estimated as the power needed for the water pumps with

the gas neutraliser. The power for the Li and photon neutralisers are

scaled as the power to DEMO/electrical power to te injector.

Total electrical power to the injector 62.6 58.3 45.3 58.0 45.0

Overall efficiency (%) 32.1 56.3 72.5 40.9 52.7

ITER design Photon neutraliser Li neutraliser (Without and with energy recovery)

R Hemsworth



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NB – Cs, divergence & source brightness

Cs consumption likely to be ~0.5kg/yr at 80%

availability. (Early ELISE results encouraging – Cs

consumption less)

Migration into beam-line? Evidence conflicting

Note need in ITER for ~annual Cs oven replacement

Current drive efficiency assumes ~<5mrad divergence

ITER design – 285A/m2 deuterium. Significant

improvement would reduce the size of the nuclear

island.



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ITER ECH – “Physics” CD efficiency

Ip = 9MA/ne = 0.7x1020m-3/Te0 = 27keV

• Contrast with «DEMO 1 & DEMO 2 EC» (E Poli, IPP)

modelling, where DEMO2 conditions

(R = 8.5m/Ip = 22.8MA/ne0 = 0.93x1020m-3/ Te0 = 64keV/ f = 230GHz/ flat density profile

CD(0.37) = 0.33

• This increase is presumably a result of the doubling of Te.



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H&CD Current-drive efficiency

System “Physics”

current drive

efficiency CD

Wall-plug

efficiency ηwp

as per ITER

design

Product

ηwp.CD

Product

ηwp.CD with

technical

improvement

ECCD 0.15 0.44 (upper

value)

0.07 0.14 (gyrotron at

70% - K Sakamoto)

ICCD 0.3-0.4

(matching?)

0.48 0.14 - 0.19 HH FWCD

???

NBCD 0.4-0.45 0.32 0.13 – 0.14 0.22 – 0.25 (photon neutraliser)

• DEMO required current drive efficiency ηwp.CD = 0.24-0.27

EC is OK on ηwp but is struggling with CD until Te >50keV

Conventional IC not applicable and FWCD an unknown

NB OK on physics but needs photon neutraliser



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DEMO– (very-)high-harmonic FWCD

Two schemes have been proposed to use fast waves for

current drive:

• High Harmonic FWCD – using folded waveguide

launcher

• Very High Harmonic FWCD – using travelling wave

launcher – see A Garofalo’s this afternoon

Both offer good current drive efficiency (CD = 0.4-0.45 for

HH FWCD) and conventional, high efficiency sources.

Both are compatible with tritium breeding requirements

HH FWCD needs to be tested somewhere. VHH FWCD will

be tested on DIIID.



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Front-end Components in ITER

IC Antenna

EC scanning mirror

NB duct liner

These components do not appear to be compatible with the

DEMO environment – concept changes needed!



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Maintenance – remote handling

Connection rail

Transfer

system

Monorail

crane

Beam Line

Transporter

Beam Source

RH Equipment

Upper Port

Plug RH

Equipment Tools

Ground support

vehicle

Top lid

opening

mechanism

BSV Rear flange

opening mechanism

Have already mentioned maintenance/Remote Handling in

context of port-plugs.

NB has large RH components and has a dedicated,

overhead monorail to carry them to transfer system.

Development of this system is well advanced.



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Maintenance – T2 release/(de)contamination

This is a generic issue, whose resolution at ITER will

greatly benefit DEMO

It is clear from existing experience at JET, TFTR and tritium

labs that it can be dealt with but that mitigation by design

and by detailed development of procedures is absolutely

necessary.

RH bagging of NB source and

transfer to monorail transporter

J Graceffa



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Availability

• It is my opinion that the availability of ITER H&CD

systems is essentially impossible to estimate at present.

• This will change, once production prototype gyrotrons

and NBTF are in operation. (cf JET NBI and DIIID ECH)

• Mitigation is at hand: have made allowance for 1.3MW or

more gyrotrons and H&CD will push for 3rd NB line. Will

also provide insurance in the event that H-mode

threshold is on high side.

• ICH is likely to be highly available but its usefulness will

depend on coupling – ITER-like antenna will be re-

installed on JET to test the concept thoroughly



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Conclusions It is obvious that the DEMO technical requirements for H&CD

are different to those of ITER

Impact of T breeding requirements

Neutron fluence

Current drive efficiency

An aggressive R&D programme should be mounted, after ITER

is in operation to develop high-power (4MW), efficient (70%)

gyrotrons and photon neutralisers for NBI.

It would be enormously helpful if a HH FWCD with a folded

waveguide launcher were mounted on an existing tokamak.

ITER will benefit DEMO in respect of stepwise

technical progress, the physics of H&CD with

a burning plasma, safety and generic

maintenance issues.



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DEMO Cockpit?

Cockpit of Shuttle “Atlantis”

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