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Concept Design of VV of CFETR

Presented by Yuntao,SONG

Vacuum Vessel Design Team

31st May 2012, USTC·Hefei

ASIPPOutline

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Introduction

Concept Design of VV

Thermal requirement

Ongoing design plans

Material for VV

Next-step plan and Optimization

Summary

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Main Parameters for the CFETR VV Design

Main parameters for Tokamak machine

Major radius R 5.5m

Minor radius a 1.6m

Toroidal field Bt 4.5/5.3T@5.5m

Elongation 1.8

Triangularity 0.4

Thickness of blanket 0.8-1.0m

VV design parameters

Torus outer radius 8.6m

Torus inner radius 2.6m

Torus height 9.7m

Shell thickness 50mm

D shape (vertical direction) Symmetry

Ports (average in one sector) 3

Introduction

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Basic Functions

Provide the first confinement barrier for radioactive materials.

Remove decay heat of all in-vessel components, even in conditions when the other

cooling systems are not functioning.

Provide a boundary consistent with the generation and maintenance of a high quality

vacuum.

Mount in-vessel components and support electromagnetic loads during plasma

disruptions and vertical displacement events.

Together with the first wall and blanket, maintain a specified toroidal electrical

resistance and contribute to plasma stability.

Together with the first wall, blanket, divertor, and ancillary equipment in ports,

provide adequate radiation shielding for the superconducting coils.

Provide access ports for in-vessel components maintenance equipment, diagnostics

and plasma heating methods, and blanket test modules.

……

Introduction

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Introduction

Basic Layout

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Concept Design

The design core of VV:

Inner shell ~ 500℃

Outer shell ~ 100℃

VV D-shape(Inner shell) configuration

The basic D-shape

5 arcs and 1 straight line

Max size (Horizontal direction) ~5205mm

Max size (Vertical direction) ~8880mm

ITER VV D-shape : 7 arcs and 3 lines for Inner shell; 6 arcs and 2

lines for out shell; The D-shape is not symmetrical in vertical

direction. CFETR VV D-shape is symmetrical in vertical direction for

all shells.

CFETR VV is easier to design, manufacture and maintenance

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Concept Design

Ports Description

The quantity of upper and lower ports

are both 12.

The equatorial ports include two kinds:

Normal (10) and Full-scale port (2).

Port Type Quantity Function

Upper 12 Diagnostics (5) , Divertors(5), VV/Blanket piping(2)

Equatorial

8 LHCD(1), ECRH(1), Diagnostics(3-4), VV/Blanket piping(2)

2 Neutral Beam Injection

2 full-scale port Sector assembly and maintainance

Lower 12 Diagnostics (5) , Divertors(5), VV/Blanket piping(2)

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The basic structure for CFETR VV

Concept Design

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The basic structure for removable VV sector

The VV has double-shell structure to increase bending resistance and provide

active cooling channel, meanwhile the neutron shielding blocks are placed in

this channel; for different VV design strategy, the double-shell configuration

could have modifications.

Concept Design

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The basic structure for Two full-sector ports

Two full-scale ports are designed to ease the assembly modularization of the inner

components. The inner components are inserted into this port and rotated to the correct

location.

Concept Design

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General sector structure

• The symmetrical in vertical direction for the D-shape

• Supporting rib without housing

• Simplify the triangular support to supporting keys

• Coolant channel inside the double-shell

VV supporting rib New VV blanket support

Concept Design

ASIPPThermal requirement

A obvious character of the CFETR VV is its designed for hot wall

operation, 3 candidate designs are proposed, they can be classified into

two types:

Water-cooled VV: works at 100℃.

Gas-cooled VV: works at 500℃.

Critical thermal environment includes the nuclear heat on the VV, the

coolant effect and the radiation to the VVTS.

Boundary conditions

Typical temperature

distribution

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Gas-cooled

double-shell

Water-cooled

double-shell

Water-cooled double-shell

Inner insulation

Gas-cooled double-

shell

Outer insulation

Inner thermal

resistance design(20mm insulation layer)

Double cooling system design

Outer thermal

resistance design(20mm insulation layer)

Ongoing design plans

ASIPPOngoing design plans

Design type Temperature contour Advantage Disadvantage

Inner thermal

resistance

1. Existing experience

on water-cooled VV,

2. No need of high

temperature

structural material,

3. Compact.

1. Insulation material

needs R&D under

neutron radiation,

2. Difficult to control

inner wall temperature.

Outer thermal

resistance

1. Lower radiation

resistance

requirement to

insulation material,

2. Easy to control inner

wall temperature.

1. Structural material has

to have good

performance at high

temperature,

2. Insulation material has

to have very low

conductivity .

Double cooling

system

1. Easy to control both

inner and outer

surface temperature,

2. Insulation material

need not, only

between the two

double-shells.

1. High space

requirement,

2. Difficult to

manufacture,

3. High temperature

structural material

required.

4. Complicated cooling

system

VVTS (80K)

Water-cooled double-shell(100C)

Insulation(500C)

Blanket(600C+)

VVTS(80K)

Insulation (100C)

Gas-cooled double-shell(500C)

Blanket(600C+)

VVTS(80K)

Water-cooled double-shell(100C)

Gas-cooled double-shell(500C)

Blanket (600C+)

ASIPPMaterial

For the water-cooled designs, the structural material could be stainless steel like

SS316L.

For the gas-cooled designs, the insulation material is inorganic material which could

survive at high temperature, the coolant gas could be N2 or He.

The mechanical material should be a high temperature metal, has good creep strength

and erosion resistance. Candidate types are listed:

Stainless steel, like SS310S and SS30815.

Nicket alloy, like Inconel 718 and x-750.

Titanium alloy, like Ti-6Al-4V

. . . . .

At present SS is preferred to make a balance at performance, manufacture

convenience and cost.

ASIPPNext step plan

Design: optimize the port and space use, make corresponding arrangement for

blanket, divertor, heating, cooling, power supply, diagnostic and other systems.

Material related R&D:

Neutron radiation test for structural and insulation materials.

High performance thermal insulation material development.

Gas cooling system development.

Analysis plays an important role in the next step work, the list of main

analyses concludes:

EM analysis;

Thermal analysis;

Mechanical analysis (including static, seismic and buckling analysis…)

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真空室分析

Electromagnetic analysis

MD (Major Disruption)

VDE (Vertical Displacement Event)

TFCFD (TF Coil Fast Discharge)

The EM scenarios cause huge eddy current and

strong Lorentz force. Plasma current during MD 36ms linear decay and Eddy current on the VV

Seismic analysis

The VV response under seismic loads needs to

be checked, which will also have impact to the

components attached to it. X and Y directions

Reference spectrum for seismic analysis and acceleration result

Analysis Plan

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Structural analysisTo evaluate the strength of the conceptual design of VV,

structure analysis will follow the process below:

Single load (like gravity)

Combined loads (EM loads, thermal loads, SL)

Critical combined loads (Normal/Off-normal)

This load consideration covers all possible and unlikely cases,

to find out the most important load issue and the limit of the

structure design.

Thermal analysisThe aim of thermal analysis is to calculate the thermal stress

caused by temperature difference under the combined load

conditions of nuclear heating and water cooling. The heat

load of the neutron deposition and the radiation from the VV

to the VVTS are concerned, too.

Inner shell

Outer shell

Temperature distribution of two shells of VV

Stress distribution of two shells of VV

Model of structure analysis Stress distribution of 40deg of VV

Analysis Plan

ASIPPSummary

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1. Function and requirement of the VV is proposed.

2. Basic outline of the VV is generated, as well as the space holders.

3. 3 kinds of Thermal designs are proposed and compared .

4. Material candidates are proposed.

5. The design, R&D and analysis work in the next-step are proposed.

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Thanks for your attention!

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