Radiation Shielding for the Radiochemist

Earl Jacobson, Rick Kaisner, Dan McAlister

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ALARA

2

Time

Distance

Shielding

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Refresher on Types of Radiation

3

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Attenuation (Interaction with matter)

4

It is important to choose the best type of material to shield the type(s) of radiation with which you are working.

1) Attenuation of Primary Radiation

2) Secondary radiation produced by interaction with shielding material

3) Activation Products

4) Physical Form/Damage

5) Cost

Attenuation

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Alpha Particles

6

n p+

p+ n

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐e‐

e‐e‐

e‐e‐

e‐e‐

e‐4He2+

4 MeV AlphaParticles can travel ~2‐3 cm in air

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Alpha Particles

Most alpha particles will be shielded by container, air, or dead layer of skin

Protection from alpha particles focused on preventing uptake into the body

‐Direct (spills, wounds, dust)‐Alpha Recoil‐Gaseous daughters (Rn, At)‐Ruptured Sources (He‐pressure)‐Embrittled containers

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Beta Particles

8

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐e‐

e‐e‐

e‐e‐

e‐e‐

e‐

e‐

scattering

Bremsstrahlung

Cerenkov

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Beta Particle Scattering

smaller mass

Higher velocity

easily deflected

Angles of emmission and energies of scatterd betas can be used to identify materials

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Bremsstrahlung

Coulomb interaction with nucleus of shielding material, loss of energy

More important for High Z absorbers

More important for high energy betas

Raises background in gamma detectors

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Cerenkov

High Energy Beta Particles

Energy released as particle slows

Enters medium faster than speed of light

Can be used to detect high energy betas

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Gamma and X-Rays

12

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐

e‐

e‐e‐

e‐e‐

e‐e‐

e‐e‐

e‐e‐

e‐

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Attenuation

130 300 600 900 1200 1500

0.1

1

H2O

T-Flex(R)

50

T-Flex(R)

Fe

T-Flex(R)

W

Pb Sheet

Fe Sheet

mas

s abs

orpt

ion

coef

ficie

nt (

, cm

2 /g)

gamma energy (keV)

I = Io e‐t = atten. coeff. = densityt = physical thickness

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PhotoElectric

14

200 400 600 800 1000 1200 14000

10

20

30

40

50

60

70

80

90

100

TFlex-W TFlex-Bi

Pb

TFlex-50TFlex-Fe

% o

f Tot

al A

ttenu

atio

n by

Pho

toel

ectri

c E

ffect

Gamma Energy (keV)

H2O

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Compton Scattering

15

200 400 600 800 1000 1200 14000

10

20

30

40

50

60

70

80

90

100

TFlex-W TFlex-Bi

Pb

TFlex-50TFlex-Fe

% o

f Tot

al A

ttenu

atio

n by

Com

pton

Sca

tterin

g

Gamma Energy (keV)

H2O

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What are you seeing?

16

Gamma Spectrum of Co‐60Using HpGe (High‐Purity Germanium) Detector

1173 keV 1333 keV

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Mass in the Path

17

0 200 400 600 800 1000 1200 1400 16000

20

40

60

80

100

120

Co-58 Co-60

Bi

W

H2O

% A

ttenu

atio

n R

elat

ive

to E

qual

Mas

s of

Pb

Gamma Energy (keV)

Fe

Cs-137

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0 200 400 600 800 1000 1200 1400 16000

20

40

60

80

100

120

140

1.00

7.86

9.8

19.3

Co-58 Co-60

BiW

H2O

% A

ttenu

atio

n R

elat

ive

to E

qual

Thi

ckne

ss o

f Pb

Gamma Energy (keV)

Fe

Cs-137

= g/cm3Shielding Thickness

18

T-Flex®

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T-Flex® Products

20

• Several materials– Tungsten– Iron– 50/50 – 50% Tungsten/50% Iron– Boron (neutron)– Bismuth – we can do it….

• Multiple durometers– D10– D20– D40– Experimented with D50

• Layers of color• Embedded hardware

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T-Flex® Products

21

• Ribbons or Ribbon Wrap

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T-Flex® Products

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• Pipe Shields

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T-Flex® Products

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• Heater Shields or Penetration Shields

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T-Flex® Products

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• Elbow and Valve Shields

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• Tiles and Slabs

T-Flex® Products

25

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T-Flex® Products

26

• Embedded magnets

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• Embedded Hardware

T-Flex® Products

27

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T-Flex® Products

28

• Custom Shapes

Probe Shield

Vial Shields

Conductivity Cells

Vial Carrier

Lead

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Lead Blankets

30

• Standard sizes– 1’x3’, 10 lb/ft2 or 15 lb/ft2

– 1’x4’, 10 lb/ft2 or 15 lb/ft2

– 1’x5’, 10 lb/ft2 or 15 lb/ft2

– 1’x6’, 10 lb/ft2 or 15 lb/ft2

• High-temperature Alpha Maritex covers – sewn

• Multiple colors for cover• Printing can be applied

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Lead Blankets

31

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Lead Blankets

32

• Segmented• Snakes

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Lead Blankets

33

• Custom shapes

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Lead Products

34

• Encased

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Lead Products

35

• Magnetic

Water

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Water Shields

• 1’ of water = 1” of lead

37

Attenuating Neutrons

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• Neutron Attenuation

Dry-Cask cont’d

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Dry-Cask cont’d

40

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 30

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

T F le x - 5 % B 4 C B o r a te d P o ly e th y le n e - 5 % P o ly u r e th a n e - 1 1 % B 4 C T F le x - W T F le x - F e

% A

ttenu

atio

n (C

f-252

neu

trons

)

S h ie ld in g T h ic k n e s s ( I n c h e s )

A t t e n u a t io n o f C f - 2 5 2 S p o n t a n e o u s F is s io n N e u t r o n sD o s e L o g g in g , 2 5 0 0 p o in t s , E x t r a p o la te d f r o m 1 in c h

• Neutron Attenuation

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Dry-Cask cont’d

• Cask Lid

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Borated PE

Tungsten T‐Flex®

Borated PE

1” thick portion

~21% neutron attenuation

~73% gamma attenuation at 0.9 MeV (average shutdown energy)

3” thick portion

~60% neutron attenuation

~80% gamma attenuation at 0.9 MeV (average shutdown energy)

42

Dry-Cask cont’d

• The Ring Design