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Nuclear Fusion

Bringing a Star To Earth

October 11, 2011

M. Ulrickson

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration

under contract DE-AC04-94AL85000.

MAU 2 5/20/2003

• Nuclear Energy • Introduction • Plasma Confinement • Fusion Device Engineering • Energy Recovery and T Breeding • Chambers • Plasma Materials Interactions • Fusion Reactors • Alternate Magnetic Fusion Concepts • Inertial Fusion Energy • Additional Information

Outline

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Alternatives for Nuclear Energy - I

• Nuclear Fission – Splitting High Z nuclei increases the average

binding energy yielding net energy – Long lived radio-isotopes are produced – Actinide production poisons the fuel requiring

reprocessing or replacement – Fuel supply in a reactor is about 1 years worth – Fuel is in limited supply

• Without reprocessing (~ 50 years) • With reprocessing (hundreds of years)

MAU 4 5/20/2003

Alternatives for Nuclear Energy - II

• Nuclear Fusion – Two low atomic number atoms combined (e.g.,

D+T) – Deuterium is present in all water – Tritium is manufactured from Lithium using fusion

neutrons – Fusion fuel is widely available – Fuel supply in reactor is only a few seconds worth – With proper choice of materials, no long lived

isotopes are produced. Recycle is possible in <100 years

MAU 5 5/20/2003

Nuclear Binding Energy

Fission Energy

Fusion Energy

MAU 6 5/20/2003

Introduction

• A plasma is an ionized gas where the electrons are completely separated from the atomic nuclei (temperature about 10-100 MC). Partially ionized plasmas exist at lower temperatures (e.g., fluorescent lamp)

• Typical terrestrial plasma densities are 1012 – 1014 /cm3 (inertial fusion 100-1000 times solid density)

• Most of this talk is about magnetically confined fusion plasmas. Inertial confinement is at the end.

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Typical Plasmas

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MAU 9 5/20/2003

What is Fusion Energy? • Fusion reactions power

the sun and stars • In terrestrial fusion:

– hydrogen isotopes—deuterium and tritium

– fuse under high temperature and pressure

– produce energy, neutrons, and helium

• Requires temperatures of 100 million degrees Celsius

• Plasma or ionized gas is formed

MAU 10 5/20/2003

Features of a Magnetic Fusion Device

• Circular or “D” shaped coils to make field in the long direction around the torus.

• Poloidal field coils to shape the plasma and provide horizontal and vertical stability

• A vacuum vessel to protect the plasma from the atmosphere

• Plasma facing components to absorb plasma power

• Heating and fueling devices • A breeding blanket to make tritium (future)

MAU 11 5/20/2003

Terminology

• Toroidal Direction: the long direction around a torus

• Poloidal Direction: the short direction around a torus

• Ohmic Solenoid: Coil set that induces toroidal current in the plasma

• Elongation: the ratio of vertical height to horizontal width

• Triangularity: ratio of the x-point radius to the plasma radius

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Plasma Confinement

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Plasma Confinement

• Stars are confined by gravity.

• Terrestrial plasmas are confined by either magnetic fields (many configurations see later) or inertially (inward momentum confines the plasma long enough for reactions to take place)

• The most common magnetic scheme is the tokamak (bottom figure).

MAU 14 5/20/2003

Plasma Flux Surfaces

Nested Toroidal Flux surfaces in toroidal geometry

Helical field lines making a magnetic bottle

MAU 15 5/20/2003

Alternate Magnetic Fusion Concepts

MAU 16 5/20/2003

Alternate Concepts for MFE Spherical Torus Stellarator

Reverse Field Pinch

Spheromak

Field Reversed Configuration

MAU 17 5/20/2003

Spherical Torus

•Aspect ratio is 1.5 (compared to ~3 for a conventional tokamak

•Large ratio of rotational transform from inside to outside

•Natural divertor and elongation

•Much lower toroidal field

MAU 18 5/20/2003

The Stellarator Concept

Note large aspect ratio and complex coils

MAU 19 5/20/2003

The Compact Stellarator Concept

MAU 20 5/20/2003

Fusion Progress

20

The Fusion triple product nτET has increased by a factor of 2 every 2 years Six orders of Magnitude in 50 years is a major accomplishment The time delay for stellarators is due to technology development.

MAU 21 5/20/2003

Scientific Readiness for Burning Plasma

• The present operational boundaries are understood. • Abnormal events can be avoided or mitigated. • The required plasma purity can be obtained, including helium

removal. • Techniques exist to characterize and evaluate the important

parameters. • Plasma control techniques exist to produce and evaluate burning

plasma physics

MAU 22 5/20/2003

The Constellation of Fusion Devices

MAU 23 5/20/2003

Fusion Devices

23

MAU 24 5/20/2003

Fusion Device Engineering

MAU 25 5/20/2003

Engineering Issues for Fusion

• Super conducting coil design – “D” shape for constant tension – Wedging and overturning forces (complex

structures) • Vacuum chamber and gas removal (H/D/T and He)

– Neutron shielding (45 cm e-folding) – Breeding Blanket (Li + Be) – Cryogenic pumping and enclosure

• High heat flux removal – Thermal stress and fatigue – Erosion and fuel gas trapping

MAU 26 5/20/2003

Plasma Elongation

Standard Tokamak Divertor Configuration

TF Coil

Plasma

Solenoid

Divertor Coils

Vertical Field Coils

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Options for Defining a Plasma

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International Thermonuclear Experimental Reactor (ITER)

Central Solenoid

Outer Inter-coil Structure

Toroidal Field Coil

Poloidal Field Coil

Machine Gravity Support

Blanket Module

Vacuum Vessel

Cryostat

Port Plug

(IC Heating)

Divertor

Torus Cryopumping

MAU 29 5/20/2003

Engineering Details of Coil Structures

Compression Structure

Divertor Coils

Stability Coils

Ohmic Solenoid

Toroidal Field Coil

Coil Support Structure

MAU 30 5/20/2003

Assembly of Coil Structures

• Solenoid is placed between tensioning caps

• Poloidal field coils are mounted on tensioning caps

• Toroidal field coils rest against the solenoid

• Coil supports are placed between the TF coils

• Vacuum vessel is placed with TF coils in segments

MAU 31 5/20/2003

Plasma Heating and Fueling

• Heating Methods – Neutral beams (add hot particles 100keV-10 MeV) – Ion cyclotron radio frequency (heat the ions 50-200 MHz) – Electron cyclotron radio frequency (heat electrons 100-

200 GHz) – Ohmic heating (plasma current heats the plasma)

• Fueling Methods – Gas injection (low efficiency and increases wall recycling

and erosion) – Frozen DT pellets (good efficiency but cools plasma)

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Chambers

MAU 33 5/20/2003

Fusion Plasma Chamber

• Outer skin removed to show stiffening ribs and shielding

• Large access ports are for heating and diagnostics

• Small access ports are for pumping and divertor cooling

• Vessel is lined with copper plates for passive stability

• Forces can be several atmospheres

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Energy Recovery and T Breeding

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Breeding Blanket Concept

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Breeding Blanket Module

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Liquid Breeding Blanket Concept

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Plasma Materials Interactions

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Plasma Edge Region

• Transport along field lines is much more rapid than perpendicular transport

• The confined plasma is surrounded by open field lines that carry plasma leaking from the confined region to either a limiter or the divertor

• The width of the edge region is very narrow (~ few cm in a reactor)

• Implies high heat and particle fluxes

MAU 40 5/20/2003

Limiter vs. Divertor Operation

MAU 41 5/20/2003

Divertor Edge Plasma Details

MAU 42 5/20/2003

Magnetic Fusion Energy Heat Fluxes

10-4 10-3 10-2 10-1 100 101 102 103 104 105 106

Duration (s)

10-1

100

101

102

103

104

105

106

Hea

t Flu

x (M

W/m

2 )

Fusion Divertor

Radiant Flux at Sun SurfaceFast Breeder

Fission Reactor

Fusion First Wall

Fusion Disruption

Fusion ELM

Rocket Nozzle

MAU 43 5/20/2003

Fusion Plasma Materials Interactions

• The core plasma must be kept clean of impurities and He ash

• The plasma facing component surface sees high density and temperature plasma and must remove high heat flux

• Key issues are hydrogen trapping, erosion, and thermal fatigue

• Spans science from ionized gases to materials science Core

Plasma Boundary Plasma

Plasma Facing Material

20-100 M K 0.1-2 M K 800-3500 K

Energy and particles

Fuel and impurities

Ionization and transport

Trapping

Sputtering Evaporation

MAU 44 5/20/2003

Plasma Facing Components

Heat Sink

Coolant

Fatigue. Creep, Fracture

Heat Flux

Critical Heat Flux

Heat removal

Erosion, Melting & Evaporation

Joint

MAU 45 5/20/2003

Materials Choices for PFCs

• Divertor applications – Only W and C are acceptable for the highest heat

flux (C limited because of T retention and neutron damage)

– With some radiation in the divertor W, C, Mo, Ta, and Nb? are candidates (Cu is not acceptable because of erosion)

• For first wall applications – Iron alloys (ferritic steel), V, Be, and all the divertor

materials

MAU 46 5/20/2003

Heat Flux Capability

Al Be C PyC Cr Co Cu Au Fe Mg Mo Ni Nb Pt Ag Ta Ti W V ZrMaterial

0

10

20

30

40

50

Lim

iting

Hea

t Flu

x (M

W/m

2 )

Typical Maximum

Normal Operation

Typical Minimum

MAU 47 5/20/2003

Recycling feasibility (from INEEL) 1

H

3

Li4

Be

41

Nb

5

B

6

C

8

O

2

He

10

Ne

65

Tb

63

Eu

nostable

isotopes

77

Ir

nostable

isotopes

cd<10 10Šcd<102 102Šcd<103 103Šcd<104 104Šcd<105 105Šcd<106 106Šcd<107

72

Hf

44

Ru

7

N

75

Re

76

Os

80

Hg

58

Ce

67

Ho

71

Lu

9

F

11

Na

12

Mg

13

Al

14

Si

15

P

16

S

17

Cl

18

Ar

19

K

20

Ca

21

Sc

22

Ti

23

V

24

Cr

31

Ga

32

Ge

33

As

35

Br

39

Y

40

Zr

42

Mo47

Ag

48

Cd

49

In

52

Te

53

I

57

La

59

Pr

60

Nd

68

Er

69

Tm70

Yb

74

W

79

Au

81

Tl

82

Pb

83

Bi

µSv/hTop half of box: µSv/h after 10 yearsBottom half of box: µSv/h after 100 years

34

Se

51

Sb

25

Mn

26

Fe

27

Co

28

Ni

29

Cu

30

Zn

36

Kr

37

Rb

38

Sr

45

Rh

46

Pd

107Šcd

50

Sn

54

Xe

55

Cs

56

Ba

62

Sm

64

Gd

66

Dy

73

Ta

78

Pt

Based on C. B. A. Forty, et al., Handbook of Fusion Activation Data; Part 1. Elements Hydrogen to Zirconium, AEA FUS 180, May 1992. Assumes 4.15 MW/m2 for 25 years.

MAU 48 5/20/2003

Qualify for Class C waste (from INEEL) 1

H

3

Li4

Be

11

Na

12

Mg

19

K

20

Ca

21

Sc

22

Ti

23

V

37

Rb

39

Y

40

Zr

41

Nb

55

Cs

56

Ba

57

La

73

Ta

24

Cr

42

Mo

74

W

25

Mn

26

Fe

28

Ni

46

Pd

47

Ag

30

Zn

48

Cd

5

B

31

Ga

49

In

6

C

14

Si

32

Ge

50

Sn

15

P

33

As

8

O

52

Te

9

F

53

I

69

Tm68

Er

66

Dy

65

Tb

63

Eu

60

Nd

59

Pr

no stable

isotopes

83

Bi

82

Pb

81

Tl

79

Au

77

Ir

no stable

isotopes

70

Yb

72

Hf

27

Co

45

Rh

44

Ru

13

Al

7

N

17

Cl

16

S

29

Cu

34

Se

38

Sr

51

Sb

75

Re

76

Os

78

Pt

80

Hg

58

Ce

62

Sm

35

Br

64

Gd

67

Ho

71

Lu

unlimited 10% 1% .1% .01% .001% .0001%

Top half of box: hard spectrum Bottom half of box: soft spectrum

.00001%

From: S. J. Piet, et al., Fusion Technology, Vol. 19, 1991, pp. 146-161. Assumes 5 MW/m2 for 4 years; and E. T. Cheng, Journal of Nuclear Materials, Vol. 258-263, 1998, pp. 1767-1772.

MAU 49 5/20/2003

Fusion Reactors

MAU 50 5/20/2003

The ARIES Reactor Concept

Fusion Energy Device (1000 MW)

MAU 51 5/20/2003

FESAC 35 Year Roadmap

MAU 52 5/20/2003

Inertial Fusion Energy

MAU 53 5/20/2003

Inertial Fusion Energy Characteristics

• All involve heating a small (few mm to few cm) DT ice pellet by compression to much greater than solid density

• Four drivers are under investigation – Uniform laser driven implosion – Above with small very high power laser trigger – Particle beam driven x-ray source (indirect drive) – Z-Pinch driven implosion

• Burn duration is about 10 ns and the repetition rate is 0.1 to a few Hz (high peak to average power)

MAU 54 5/20/2003

Inertial Fusion Energy

MAU 55 5/20/2003

Indirect Drive Capsule

• Driver can be either laser light or heavy ion beams

• The x-rays generated in the cylinder heat and compress the fuel capsule in the center

• The outer cylinder shields the pellet from ambient conditions

MAU 56 5/20/2003

Photon Drivers For IFE

• Diode pumped solid state lasers are one option for repetitive laser drives (work at LLNL)

• KrF lasers use electron beams to stimulate the gas in the laser (work at NRL)

• Z-Pinch can also create an x-ray source for pellet compression (Sandia work)

MAU 57 5/20/2003

Additional Information

MAU 58 5/20/2003

Interesting Places to Visit

• fire.pppl.gov • fusion.gat.com • science.doe.gov • fusionpower.org • fusion.ucla.edu • nrl.gov • llnl.gov

MAU 59 5/20/2003

Books and Journals

• “The Plasma Boundary of Magnetic Fusion Devices” Peter Stangeby, Institute of Physics Publishing, 2000

• “Introduction to Plasma Physics”, Rutherford and Goldston • “Burning Plasma, Bringing a Star to Earth”, National

Academy Press, 2003 • Nuclear Fusion Journal • Journal of Nuclear Materials • Fusion Engineering and Design • Fusion Technology