Conceptual Design Development for a Demonstration Fusion Power Reactor

Conceptual Design Development for a Demonstration Fusion Power Reactor

Ronald Wenninger, Gianfranco Federici, PPPT PMU Team, PPPT Project Leaders, WPPMI Physics Contributors

Power Plant Physics and Technology

Outline

• Background

• DEMO Design

• Selected DEMO Design and Physics Integration Studies

• Highlights of Selected Projects

• DEMO Physics Integration Challenges Beyond ITER

• Development of the DEMO Wall Load Specification

• Summary

Outline

• Background

• DEMO Design

• Selected DEMO Design and Physics Integration Studies

• Highlights of Selected Projects

• DEMO Physics Integration Challenges Beyond ITER

• Development of the DEMO Wall Load Specification

• Summary

What is different in DEMO compared to ITER

• DEMO needs to produce net electricity

• DEMO needs be Tritium self-sufficient

• Fusion power increases by a factor >4

• Discharge duration: 6min → 2h or more

• DEMO needs to be controlled with a reduced set of sensors

• Neutron fluence: <3dpa → ∼20dpa

• ...

R. Wenninger | ICFRM 2015 |Aachen (Germany)| 11/10/2015| Page 5

Emphasis on:

 Central role of ITER

 DEMO as a single step to commercial FPPs

 Demonstrating production of electricity early 2050

• An ambitious roadmap implemented by a Consortium of Fusion Labs (EUROfusion)

• Focus around 8 Missions

DEMO IPH

IPH

1. Plasma Operation 2. Heat Exhaust

3. Neutron resistant Materials 4. Tritium-self sufficiency 5. Safety

6. Integrated DEMO Design 7. Competitive Cost of Electricity 8. Stellarator

Background

EU Roadmap to Fusion Electricity

PPPT Development of DEMO Concept Design

• EU Fusion Roadmap: The development of a conceptual design for DEMO is one of the main priorities in this decade

• The development of machine components and overarching concepts is implemented in 11 projects

• Activities of especially integrative nature are implemented in the work

package PMI

Pre-concept

• Engage DEMO SHG and define DEMO HLRs

• Study machine configurations and key parameters.

• Optimisation / trade-off studies

• SE approach to solve design integration issues

• Resolve Plant System Architecture with variants

• Address key technology R&D needs (mainly PoP, fabrication feasibility, performance tests)

• Develop and qualify materials / fill database gaps

• Identify DEMO pre-requisites

• Identify main design and technical challenges Preliminary assessment technical solutions

• Prioritization of R&D for the Roadmap

• Select design options from leading technologies

• Select divertor concept

• Select breeding blanket concept and BoP/ H&CD

• Finalise Plant Architecture

• Safety Analysis report

EUROfusion PPPT 2014-2018

~220 ppy/year (no ENS)

~5 M€/year

>2020

Conceptual Study/ Design Phase Preparatory Phase

Concept Design Approach

DEMO Concept Design Scope

CDA EDA Construction

Commissioning/ Operation

ITER pre-concept (INTOR)

~10 years, ~150 ppy/year

ITER concept (NET/ITER)

~10 years, ~360 ppy/year

~15 M€/year

ITER EDA

>10 years

EFDA PPPT 2011-2013

• Because of limitations of T-supplies there is enough T after ITER for only one DEMO reactor in the world that must operate and produce its own tritium not much later than 2050!!

2018

Organisation of Design and R&D Activities

Breeding

Blanket Magnets Divertor H & CD Systems

Tritium Fuelling &

Vacuum

PHTS &

BoP

Contain Structures

• A project-oriented structure set-up

• Distributed Project Teams aiming at the design and R&D of components

• Project Control and Design Integration Unit

MAG SAE

TFV MAT

D&C

BOP PMU

ENS

DIV PMI

H&CD RM

BB

A project-oriented structure with a central Project

Control and Design/

Physics Integration Unit and

distributed Project

Teams aiming at the

design and R&D of

components

Concept Design Approach

Systems Engineering Approach

Basic Process Flow for Conceptual Design Work

Outline

• Background

• DEMO Design

• DEMO Engineering Principles

• Selected DEMO Design and Physics Integration Studies

• Highlights of Selected Projects

• DEMO Physics Integration Challenges Beyond ITER

• Development of the DEMO Wall Load Specification

• Summary

DEMO Design

Design features (near-term DEMO):

• 2000 MW_th~500 MW_e

• Pulses > 2 hrs

• SN water cooled divertor

• PFC armour: W

• LTSC magnets Nb₃Sn

• B_max conductor ~12 T (depends on A)

• EUROFER as blanket structure

• VV made of AISI 316 (stainless steel)

• Lifetime: starter blanket: 20 dpa (200 appm He); 2^nd blanket 50 dpa; divertor: 5 dpa (Cu)

Open Choices:

• Operating scenario

• Breeding blanket design concept selection

• Primary Blanket Coolant/ BoP

• Protection strategy first wall (e.g., limiters)

• Advanced divertor configurations

• Number of coils

• …

DEMO Design Point Development I

Sytem codes are used to develop many conceptual designs with a range of materials and technology assumptions

Every major plant system is modelled:

•Site and buildings

•Heat and power systems

•Magnets (TF and PF)

•Shield and vessel

•Blanket

•Divertor

•Plasma

–Fusion power

–Confinement

–Pressure and density limit –Radiation

–Bootstrap current –Etc. etc.

R. Kemp (IAEA 2012)

DEMO Design Point Development II

System Code:

• Fast execution

• Max 1D

• All aspects relevant for the feasibility and the performance of the device

State-of-the-art investigation:

• Slower execution

• Up to 6D

• Only selected aspects

Design point: System Code Solution

Modification to parameters or modules in the system code

DEMO Design Options

EU DEMO design options

• DEMO1

• Pulsed operation, conservative

assumptions

• DEMO2

• Steady state operation, more optimistic

assumptions ^{ITER DEMO1}

(2015) A=3.1

DEMO2 (2015) A=2.6 R₀ / a (m) 6.2 / 2.0 9.1 / 2.9 7.5 / 2.9

Κ₉₅ / δ₉₅ 1.7 / 0.33 1.6 / 0.33 1.8 / 0.33

A (m²)/ Vol (m³) 683 / 831 1428 / 2502 1253 / 2217 H non-rad-corr / β_N (%) 1.0 / 2.0 1.0 / 2.6 1.2 / 3.8

P_sep (MW) 104 154 150

P_F (MW) / P_NET (MW) 500 / 0 2037 / 500 3255 / 953 I_p (MA) / f_bs 15 / 0.24 20 / 0.35 22 / 0.61

B at R₀ (T) 5.3 5.7 5.6

B_max,_conductor (T) 11.8 12.3 15.6

BB i/b / o/b (m) 0.45 / 0.45 1.1 / 2.1 1.0 / 1.9

Av NWL MW/m² 0.5 1.1 1.9

Concept Design Approach

DEMO Physics Basis / Operating Point

Readiness of underlying physics assumptions makes the difference.

Outline

• Background

• DEMO Design

• Selected DEMO Design and Physics Integration Studies

• Highlights of Selected Projects

• DEMO Physics Integration Challenges Beyond ITER

• Development of the DEMO Wall Load Specification

• Summary

Design and physics integration challenges

Results of Selected Studies

• Investigate impact of Aspect Ratio, A

• Sensitivity to plasma physics uncertainties

• TBR sensitivity analysis

• Optimisation of the upper null and investigation of alternative architectures

• Strike point sweeping parametric scan

• Investigate divertor configurations with a lower X-point height and larger flux expansion as a more favourable compromise between pumping and power exhaust for DEMO.

• Explore advanced divertors including DN Configuration: higher plasma performance with improved vertical position control, and an accompanying reduced machine size.

• Investigate magnetic field ripple: trade-off between RH access, coil size, and NBI access.

• Estimate dwell time and evaluate impact of trade-offs on CS, BoP, pumping, etc.

A number of studies that have strong implications on machine parameter selection and architectural layout have been initiated. They include:

-6 -4 -2 0 2 4 6

3 5 7 9 11 13

Z (m)

R (m) ITER

DEMO1 (A=2.6)

DEMO1 2015 (A=3.1) DEMO2 2015

Results of Selected Studies

Sensitivity study: Aspect Ratio

Topic A

2.6

A 3.1

A 3.6 Vertical stability ↑ → ↓ Fast disruption loads

on blanket and divertor

↑ → ↓

Toroidal field ripple ↑ → ↓ Tritium breeding ↑ → ↓ Physics basis

established

→ ↑ →

Remote

maintenance

↓? →? ↑?

Cost of device / electricity

? ? ?

Sensitivity studies are not only computer runs, but time consuming engineering assessments requiring some level of design detail.

Results of Selected Studies

DEMO physics basis uncertainties

P_el t_burn

1.53

0.33

17 MW/m 1.2

2.1 1

0.27 1020 A/W m2

0.35

R. Kemp (CCFE)

System Code: PROCESS

Results of selected studies

TBR sensitivity analysis

Neutron wall load:

Blanket design:

•Breeder/multiplier materials are within a box and covered by a FW.

•Box is reinforced by stiffening grids

 n-absorption by steel

Blanket size (radial thickness):

• Inb: ~80 cm / Out: ~130 cm

 Requirement: TBR ≥ 1.05

(after integration of diagn/ H&CD)

 Configuration: About 85% of the plasma must be covered by the breeding blanket.

 Integration issue: Space for divertor, limiters, and auxiliary systems is limited.

Potential Tritium breeding contributions: Total TBR:

• Significant improvement of TBR due to reduction of divertor size.

• DN configuration with two small divertors seems possible regarding TBR.

P. Pereslavtsev

Outline

• Background

• DEMO Design

• Selected DEMO Design and Physics Integration Studies

• Highlights of Selected Projects

• DEMO Physics Integration Challenges Beyond ITER

• Development of the DEMO Wall Load Specification

• Summary

WPBB: Breeding Blanket

Concept Breeder/

Multiplier

Coolant T-Extraction

HCPB Ceramic Breeder / Beryllium

Helium He low pressure purging

HCLL PbLi Helium PbLi slow recirculation

WCLL PbLi Water PbLi slow

recirculation

DCLL PbLi Helium

PbLi

PbLi fast recirculation

Helium Cooled Pebble Bed (HCPB)

Dual Coolant Lithium Lead (DCLL)

Helium Cooled Lithium Lead (HCLL)

Water Coolant Lithium Lead (WCLL) Li₄SiO₄ Be

ITER TBM important: qualify fabrication technologies/validate tools and predictive capabilities

WPDIV: Divertor Design/Technology

Cassette Design & Integration CAD models

Cooling schemes/cooling condition Loads specification

(thermal, hydraulic, EM, neutronic, static) System/interface/functional requirements

Target Development

Analysis guidelines & design rules

1 baseline & 7 advanced design concepts Novel materials for heat sink & interlayer (e.g. W

/Cu composite, W/Cu laminate)

Mock-up fabrication

High heat flux tests & evaluation

Initial model (2014)

Revised model (2015)

Single circuit Dual circuit

W/Cu laminate tube Thermal break layer

WPMAG: Magnets System

- TF magnet design investigated and 3 winding pack (WP) options

- Thermohydraulic and mechanical

studies conducted on the 3 WP options - R&D on HTS is progressing well with

tests of irradiated tapes and medium- current cables

The 3 TF conductor options WP#2 (ENEA) WP#1 (CRPP)

WP#3 (CEA)

WPRMS: In-vessel maintenance

• Remote handling is a key driver for the overall architecture

• Recently a vertical maintence concept is applied

• Situation would be significantly more complex for a stellarator

Removal of the outer blanket banana

M. Coleman (FED 2014)

WPSAE: Safety and Environment

• Plant Safety Requirements outlined

• Basic safety approach and principles set

• Likely future regulatory regime considered

• Radioactive source terms

preliminary assessment on going

• Selected codes and models for safety analysis

• Safety analyses to establish effects of design choices/needs of protection / mitigation

• Selection of accident scenarios for detailed analyses (FFMEA)

• Models developed and validation needs assessed

• Experimental studies on critical topics

• Studies of radioactive waste management

• In particular, detritiation techniques to remove tritium from bulk of structure etc.

• All radioactive inventories contained in the primary or secondary confinement in case of accident

• Negative pressure cascade versus external atmosphere maintained by the air detritiation system in accident conditions

WPTFV: Innovative concept for the DEMO inner fuel cycle

WPENS: Early (Fusion) Neutron Source

Objective: Develop a facility to perform material irradiation test with DEMO-relevant parameters

IFMIF IFMIF-DONES

Beam current 2 x 125 mA (Li target)

1 x 125 mA (Li target) Beam energy 40 MeV 40 MeV Neutron

production 10¹⁸ n/s 5 x 10¹⁷ n/s

Typical

Damage Rate

40 dpa/fpy

@>60cm³ + 20 dpa/fpy

@>400cm³

20 dpa/fpy

@>60 cm³ +

10 dpa/fpy

@>400 cm³

10^-3 10^-2 10^-1 10⁰ 10¹ 10⁰

10¹ 10² 10³ 10⁴ 10⁵ 10⁶ 10⁷

CDA Design (1996) Present Design (2003) DEMO fusion reactor

High Flux Volume

n-flux density [1010 s-1 cm-2 MeV-1 ]

Also DEMO relevant He production

Outline

• Background

• DEMO Design

• Selected DEMO Design and Physics Integration Studies

• Highlights of Selected Projects

• DEMO Physics Integration Challenges Beyond ITER

• Development of the DEMO Wall Load Specification

• Summary

Key areas of DEMO Physics Challenges beyond ITER

• First Wall Loads

• Divertor Loads

• Edge Localized Modes

• Vertical stability

• Disruptions

• Confinement

• Impurity transport

• LH threshold

• Toroidal field ripple

• Pedestal transport

• Fast particles

• …

Divertor Strategy

• Baseline Strategy

• Lower Single Null Configuration

• Detached divertor operation

• Psep/R≈17MW/m similar as in ITER

• P^rad,main/P^heat significantly higher ITER DEMO1

Pα+Paux [MW] 130 460

R [m] 6.2 9.0

AUG: A. Kallenbach IAEA 2014

• Alternative Strategies

✴ Advanced magnetic configurations (Double Null, Snow Flake,…)

✴ Liquid metal plasma facing components

• Central problem

✴ Capability to reliably predict divertor operation has not been

attained

Main size drivers:

Divertor protection and H-mode operation

PROCESS / DEMO1: R. Kemp

• Main objectives:

• Protect divertor

• P

/R=17MW/m

• H-mode operation

• f

P

/P

→ confinement quality and controllability

• Analysis with system code PROCESS:

• P

=500MW

• 𝜏

=2h

• minimize R

P

uncertainty implications

95% confidence interval of the ITPA threshold scaling for ITER ≈ from 50% to 200% of P

In DEMO (P

=500MW, 𝜏

=2h): P

=2 P

roughly corresponds to

doubling the major radius

Edge Localized Modes (ELMs)

Typical numbers for DEMO:

Plasma energy content: 1-2GJ Relative ELM loss: 10%

Fraction to the divertor: 75%-90%

A. Kirk PPCF 2007

ELMs - Mitigation Needs

• Considered limit: Divertor energy impact

• Assume Δt

=Δt

⇒ ΔW/A≤0.5MJ/m

Type I ELMs

Limit

b~∆W/W

• Pessimistic assumption:

Broadening b=1 for ΔW/W<1%

⇒ DEMO1 limit: ΔW/W≤0.14%

• Optimistic assumption: b=6

⇒ DEMO1 limit ΔW/W≤0.84%

• Natural ELMs for this 𝜈*: ΔW/W≈10%

• Mitigation of ΔW/W by a factor 15-90 required for DEMO1 (DEMO2: 25-150)

• Not considered limits: Main chamber

heat loads and ELM flushing

Strategies to deal with ELMs in DEMO

• Small/no ELM regimes

• No present machine can sim- ultaneously match n/nGW and 𝜈*

• If pedestal physics dominates, need methods for low 𝜈*

• So far demonstrated for rel. 𝜈*:

• QH-mode

• Resonant Magnetic Perturbations

• I-mode (marginal)

• Alternatives: ELM pacing by

pellets / vertical kicks, relying on fELM×ΔW≈const

ITER: P. Lang, NF 2013

DEMO

RMPs I-mode

• For all candidate mitigation methods important R&D has to be carried out

• Solving the ELM problem for ITER ⇏ Solving the ELM problem

for DEMO

Disruptions

• Disruptivity (disruptions per operation duration)

• Extrapolated from existing devices to DEMO not possible

• Probabilistic engineering approach: Assume that disruptions are only caused by component failures

• Damage

• The crack limit of W is exceeded even in the case of perfectly mitigated disruptions

• How many events with a certain heat impact factor are acceptable before the first wall has to be exchanged?

• Additional challenge

• Progress in the understanding and simulation of disruptions are crucial to make robust

DEMO predictions

Example (DEMO1):

• Wkin≈1GJ

• Thermal quench wall load during a perfectly mitigated disruption:

0.5Wkin in 1−3ms

Melt limit

Crack limit

η

Energy confinement time

• Challenge

• Prediction of 𝜏E is of key importance for DEMO Design Point Studies

• IPB98(y,2) scaling: Typical DEMO design points lies outside the region of confidence in input parameters for at least β, n/nGW, Prad/Ptot

• Strategies

• Develop a more DEMO relevant scaling of 𝜏E

based on a new database

– From various devices including JET – In DEMO relevant conditions including

the identified DEMO gaps (high beta, low torque and highly radiative

conditions)

• Use prediction of the pedestal height and width (e.g. EPED) in combination with state- of-the-art core transport simulations

PROCESS / DEMO1: R. Kemp Pel,net=500MW, 𝜏burn=2h

ΔPel,net

Δ𝜏burn

Impurity transport

DEMO1: E. Fable

• DEMO will have a higher level of impurities

•

Z

≈2.6

•

Intrinsic impurities: He, W

•

Candidates for seeding: Ne,Ar,Kr,Xe

•

More core radiation necessitates more seeding

• Key uncertainties

•

How does the effective He confinement 𝜏*

/

extrapolate for DEMO-like pumping

•

It is even unclear, if DEMO will have peaked or hollow impurity profiles

•

Also the ratio of impurity concentrations in

confined plasma and SOL is highly uncertain

Outline

• Background

• DEMO Design

• Selected DEMO Design and Physics Integration Studies

• Highlights of Selected Projects

• DEMO Physics Integration Challenges Beyond ITER

• Development of the DEMO Wall Load Specification

• Summary

Breeding Blanket Wall Load Limits

• Design assumptions

• Armour material: W

• Structural material: EUROFER

• Coolant / Heat Exchange: H2O at high temperature or He

• No high heat flux components outside the divertor

• Wall clearance >22cm

• Expected wall load limits based on engineering constraints ∼ 1MW/m²

• Comparison:

• A large fraction of ITER’s main chamber wall is specified for 3.6MW/m² or more

• DEMO Wall Load Specification needs to be developed now

• Based on this a DEMO first wall concept can be developed

W (2mm) EUROFER H2O

LiPb

J. Aubert: WCLL Blanket

ITER: Mitteau (JNM 2011)

Load Types

• Relevant Heat Load Types

• Stationary loads

• Thermal charged particles (majority/impurities) including blob effects

• Radiation / MARFEs

• Neutrals

• Fast particles

• Dynamic loads

• Limiter configuration during ramp-up/down

• ELM filaments

• Confinement transients (e.g. H-L-transition)

• Vertical displacement events / disruptions

• Particle Loads

• Steady state and dynamic first wall erosion yield

Charged Thermals - Example

• Assumptions (DEMO1):

• Psep=150MW

50%↑,50%↓

transferred by charged thermals

• 100% into the long-λq- channel

• qpeak≈0.6MW/m²

• ITER experienced an increases of the peak loads of more than 10 when going to more realistic designs in 3D!

𝑞_∥ = 𝑞₀ ∙ 𝑒⁻

𝜆𝑑_𝑞

𝑞₀

Portion intersecting upper FW

FL intersecting divertor

 

λ_q=17cm Mitteau (JNM 2011)

R. Wenninger | ICFRM 2015 |Aachen (Germany)| 11/10/2015| Page 43

Charged Thermals - λ

Scan

6.16 6.18 6.2 6.22 6.24 6.26

5.94 5.95 5.96 5.97 5.98 5.99 6 6.01 6.02 6.03

_q = 60mm , P_SOL = 150/2[MW/m²]

0.09 MW/m2

0.09 MW/m2

0.09 MW/m2

0.10 MW/m2

0.11 MW/m2

0.11 MW/m2

0.12 MW/m2

0.12 MW/m2

0.12 MW/m2

0.13 MW/m2

0.13 MW/m2

0.13 MW/m2

0.13 MW/m2

0.14 MW/m2

0.14 MW/m2

0.14 MW/m2

0.15 MW/m2

0.14 MW/m2

0.15 MW/m2

0.15 MW/m2

0.16 MW/m2

0.16 MW/m2

0.16 MW/m2

0.17 MW/m2

0.17 MW/m2

0.17 MW/m2

0.17 MW/m2

0.18 MW/m2

0.18 MW/m2

0.19 MW/m2

0.20 MW/m2

0.22 MW/m2

0.22 MW/m2

0.23 MW/m2

0.24 MW/m2

0.24 MW/m2

0.25 MW/m2

0.25 MW/m2

0.25 MW/m2

0.25 MW/m2

0.26 MW/m2

0.27 MW/m2

0.27 MW/m2

0.28 MW/m2

0.28 MW/m2

0.29 MW/m2

0.29 MW/m2

0.30 MW/m2

0.31 MW/m2

0.32 MW/m2

0.32 MW/m2

0.32 MW/m2

0.33 MW/m2

0.33 MW/m2

0.34 MW/m2

0.35 MW/m2

0.36 MW/m2

0.37 MW/m2

0.40 MW/m2

0.41 MW/m2

0.42 MW/m2

0.43 MW/m2

0.44 MW/m2

0.45 MW/m2

0.45 MW/m2

0.46 MW/m2

0.47 MW/m2

0.48 MW/m2

0.49 MW/m2

0.50 MW/m2

0.51 MW/m2

0.49 MW/m2

0.49 MW/m2

0.50 MW/m2

0.51 MW/m2

0.52 MW/m2

0.53 MW/m2

0.54 MW/m2

0.55 MW/m2

0.57 MW/m2

0.58 MW/m2

0.59 MW/m2

0.60 MW/m2

0.62 MW/m2

0.63 MW/m2

0.64 MW/m2

0.65 MW/m2

0.67 MW/m2

0.68 MW/m2

0.70 MW/m2

0.70 MW/m2

0.68 MW/m2

0.70 MW/m2

0.71 MW/m2

0.72 MW/m2

0.74 MW/m2

0.73 MW/m2

0.72 MW/m2

0.73 MW/m2

0.75 MW/m2

0.76 MW/m2

0.78 MW/m2

0.79 MW/m2

0.81 MW/m2

0.73 MW/m2

0.72 MW/m2

0.73 MW/m2

0.74 MW/m2

0.76 MW/m2

0.77 MW/m2

0.78 MW/m2

0.79 MW/m2

0.75 MW/m2

0.76 MW/m2

0.77 MW/m2

0.79 MW/m2

0.81 MW/m2

0.82 MW/m2

0.84 MW/m2

0.85 MW/m2

0.86 MW/m2

0.88 MW/m2

0.89 MW/m2

0.91 MW/m2

0.73 MW/m2

0.67 MW/m2

0.67 MW/m2

0.68 MW/m2

0.69 MW/m2

0.73 MW/m2

0.74 MW/m2

0.75 MW/m2

0.76 MW/m2

0.75 MW/m2

0.68 MW/m2

0.69 MW/m2

0.70 MW/m2

0.71 MW/m2

0.71 MW/m2

0.72 MW/m2

0.73 MW/m2

0.59 MW/m20.51 MW/m2

0.52 MW/m2

0.52 MW/m2

0.53 MW/m20.53 MW/m2

0.53 MW/m2

0.53 MW/m2

0.35 MW/m20.35 MW/m2

0.35 MW/m2

0.35 MW/m2

0.36 MW/m2

0.32 MW/m2

0.16 MW/m2

0.16 MW/m20.16 MW/m2

0.16 MW/m20.17 MW/m2

0.14 MW/m20.06 MW/m20.06 MW/m20.06 MW/m20.06 MW/m20.06 MW/m20.07 MW/m20.07 MW/m20.07 MW/m20.07 MW/m20.07 MW/m20.07 MW/m20.07 MW/m20.06 MW/m2 W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2W/m2

Results: λ

far-SOL scan 1cm to 17cm

*

*

• Maximum q

= 0.91MW/m

found for λ

= 6cm (far-SOL)

• The peak heat load is not a monotonic function of λ

Charged Thermals - Upper Null optimisation

• There is potential to reduce the charged particle heat loads by adjusting the equilibria and possibly the first wall contour

• Possible side effects

• Reduction of the triangularity

• Reduction of the TBR

q_surf,max=1.83 0.58 0.31 MW/m² δ= 0.53 0.45 0.38

λ_q= 0.02 0.11 0.17 m

q_surf,max=0.58 0.42 0.35 MW/m² δ= 0.45 0.41 0.37

λ_q= 0.11 0.14 0.17 m

Charged Thermals - Effect of Blobs

Open question: fraction of P

that comes out in ‚blobs‘

• Blobby SOL transport may dominate in DEMO

• Due to the very long connection length, power will end up on first wall

• Exact distribution depends on localisation of blob birth zone

Guiding parameter Λ

DEMO Recent devices

M. Siccinio:

Preliminary

D. Carralero:

PRL 2015

Charged Thermals - Towards more realistic designs

• DEMO charged thermal particle load assessments done for idealised plasma and idealised wall in 2D

• Best approach to determine the wall contour is under discussion

• ITER experienced significant increases of the peak loads when going to more

realistic designs in 3D

• Severe penalties on inaccuracies of the device or plasma inhomogeneities are suggested

• We expect clear problems to keep

charged particle loads within the limits

• This might necessitate significant design changes (e.g. high heatflux limiters

protecting the breeding areas)

Mitteau (JNM 2015)

Radiation

• Sustainable operation in DEMO requires that a high fraction of the power is exhausted via radiation.

• 3D Calculation of the radiation distribution on the wall using Monte Carlo approach :

• Two regions are defined:

• Core radiation: Radiation from within the confined plasma

• SOL radiation: Radiation from unconfined plasma

• Core radiation:

• Limited by LH power threshold 𝑃_𝐿𝐻

• Sources: Bremsstrahlung, Impurities (Ar, Xe, W, …)

• SOL radiation:

• Sources: Impurities and main species

B. Sieglin:

EFPW2014

Radiation - DEMO 1 Plasma

• Core radiation with

Tungsten and Xenon as impurities

• Main contributors Xenon and Bremsstrahlung

• Assumption for SOL

• All power radiated

• Constant power density on field line

• Exponential decay

R. Wenninger, IAEA 2014

Radiation – Tungsten & Bremsstrahlung

Radiation – Xenon & SOL

Radiation - Total Heat Load

• Total Power: ~ 500 MW

• Peak Heat Load:

𝑞_𝑚𝑎𝑥 ≈ 0.64 MW m²

• Peaking factor around 2

• Highest load on top and bottom of machine

• Divertor targets well shadowed

Core W

Core BS

Core Xe

SOL P_tot [MW] 11 53 290 150 q_peak [MW/m²] 0.013 0.065 0.33 0.25

Effects of radiation clustering

It has been observed that radiation can have a significant poloidal peaking

• Seeded scenarios

• MARFEs

M. Bernert: EPS 2015

Radiation in Kr seeded detached plasma

Example:

• 150MW radiating from x-point

• Peak radiation 1.9MW/m

on the dome

• Divertor baffle: <0.6MW/m

Fast Particles

First result from ASCOT with a 2D first wall:

A. Snicker:

Preliminary

• Recent assumption: Same power load limits as for

thermals apply for fast particles

• Including ferritic inserts

(δ

≈0.3%) reduces the peak loads and moves them to the divertor

• Investigations with engineering design of the first wall are

carried out at the moment

TF – No Ferritic Inserts

TF – With Ferritic Inserts

Summary I

• The demonstration of electricity production ~2050 in a DEMO Fusion Power Plant is a priority for the EU fusion program

• ITER is the key facility in this strategy and the DEMO design/R&D will benefit largely from the experience gained with ITER construction

• There are outstanding gaps requiring a vigorous integrated design and technology R&D (e.g., breeding blanket, divertor, Remote Handling, materials)

• In 2014 a traceable design process with SE approach was started to explore DEMO design/ operation space to understand implications on technology requirements

• Main difficulty with designing is dealing with uncertainties

• DEMO reactor design suffers from high degree of system integration/ complexity/

system Interdependencies.

• Keep reasonable flexibility at the beginning. Trade-off studies with multi-criteria optimisations, including engineering assessments are underway.