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Gilson and Voss - Voss Associates

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CALCULATING NEUTRON SHIELD THICKNESSES<br />

I = I0e -óNx<br />

where; I = final neutron flux rate<br />

I<br />

0<br />

= initial neutron flux rate<br />

ó = shield cross section in square centimeters<br />

3<br />

N = number of atoms per cm in the shield<br />

x = shield thickness in centimeters<br />

CALCULATING GAMMA SHIELD THICKNESSES<br />

"Good Geometry" (narrow beam) I = I0e -ìx<br />

I = shielded exposure rate<br />

I<br />

0<br />

= unshielded exposure rate<br />

ì = linear attenuation coefficient<br />

x = shield thickness<br />

-ìx -ìenx<br />

"Poor Geometry" (broad beam) I = B x I0e OR Ie<br />

0<br />

B = buildup factor<br />

ìen = linear energy absorption coefficient<br />

Half-Value Layer (HVL) = ln 2 / ì<br />

Tenth-Value Layer (TVL) = ln 10 / ì<br />

Transmission Factor (F) = I / I OR F = e -ìx<br />

CALCULATING TRANSMISSION FACTOR (F)<br />

FOR SHIELDING AN X-RAY DEVICE<br />

F =<br />

2<br />

Pd / WUT (BCF)<br />

P = permissible dose rate (mrem/wk)<br />

d = distance to point of interest<br />

W = workload (mA-min / wk)<br />

U = use factor<br />

T = occupancy factor<br />

BCF =<br />

2<br />

beam conversion factor (R / mA-m )<br />

0<br />

CALCULATING NEUTRON SHIELD THICKNESSES<br />

I = I0e -óNx<br />

where; I = final neutron flux rate<br />

I<br />

0<br />

= initial neutron flux rate<br />

ó = shield cross section in square centimeters<br />

3<br />

N = number of atoms per cm in the shield<br />

x = shield thickness in centimeters<br />

CALCULATING GAMMA SHIELD THICKNESSES<br />

"Good Geometry" (narrow beam) I = I0e -ìx<br />

I = shielded exposure rate<br />

I<br />

0<br />

= unshielded exposure rate<br />

ì = linear attenuation coefficient<br />

x = shield thickness<br />

-ìx -ìenx<br />

"Poor Geometry" (broad beam) I = B x I0e OR Ie<br />

0<br />

B = buildup factor<br />

ìen = linear energy absorption coefficient<br />

Half-Value Layer (HVL) = ln 2 / ì<br />

Tenth-Value Layer (TVL) = ln 10 / ì<br />

Transmission Factor (F) = I / I OR F = e -ìx<br />

CALCULATING TRANSMISSION FACTOR (F)<br />

FOR SHIELDING AN X-RAY DEVICE<br />

F =<br />

2<br />

Pd / WUT (BCF)<br />

P = permissible dose rate (mrem/wk)<br />

d = distance to point of interest<br />

W = workload (mA-min / wk)<br />

U = use factor<br />

T = occupancy factor<br />

BCF =<br />

2<br />

beam conversion factor (R / mA-m )<br />

0<br />

Page 56<br />

Page 56<br />

CALCULATING NEUTRON SHIELD THICKNESSES<br />

I = I0e -óNx<br />

where; I = final neutron flux rate<br />

I<br />

0<br />

= initial neutron flux rate<br />

ó = shield cross section in square centimeters<br />

3<br />

N = number of atoms per cm in the shield<br />

x = shield thickness in centimeters<br />

CALCULATING GAMMA SHIELD THICKNESSES<br />

"Good Geometry" (narrow beam) I = I0e -ìx<br />

I = shielded exposure rate<br />

I<br />

0<br />

= unshielded exposure rate<br />

ì = linear attenuation coefficient<br />

x = shield thickness<br />

-ìx -ìenx<br />

"Poor Geometry" (broad beam) I = B x I0e OR Ie<br />

0<br />

B = buildup factor<br />

ìen = linear energy absorption coefficient<br />

Half-Value Layer (HVL) = ln 2 / ì<br />

Tenth-Value Layer (TVL) = ln 10 / ì<br />

Transmission Factor (F) = I / I OR F = e -ìx<br />

CALCULATING TRANSMISSION FACTOR (F)<br />

FOR SHIELDING AN X-RAY DEVICE<br />

F =<br />

2<br />

Pd / WUT (BCF)<br />

P = permissible dose rate (mrem/wk)<br />

d = distance to point of interest<br />

W = workload (mA-min / wk)<br />

U = use factor<br />

T = occupancy factor<br />

BCF =<br />

2<br />

beam conversion factor (R / mA-m )<br />

0<br />

CALCULATING NEUTRON SHIELD THICKNESSES<br />

I = I0e -óNx<br />

where; I = final neutron flux rate<br />

I<br />

0<br />

= initial neutron flux rate<br />

ó = shield cross section in square centimeters<br />

3<br />

N = number of atoms per cm in the shield<br />

x = shield thickness in centimeters<br />

CALCULATING GAMMA SHIELD THICKNESSES<br />

"Good Geometry" (narrow beam) I = I0e -ìx<br />

I = shielded exposure rate<br />

I<br />

0<br />

= unshielded exposure rate<br />

ì = linear attenuation coefficient<br />

x = shield thickness<br />

-ìx -ìenx<br />

"Poor Geometry" (broad beam) I = B x I0e OR Ie<br />

0<br />

B = buildup factor<br />

ìen = linear energy absorption coefficient<br />

Half-Value Layer (HVL) = ln 2 / ì<br />

Tenth-Value Layer (TVL) = ln 10 / ì<br />

Transmission Factor (F) = I / I OR F = e -ìx<br />

CALCULATING TRANSMISSION FACTOR (F)<br />

FOR SHIELDING AN X-RAY DEVICE<br />

F =<br />

2<br />

Pd / WUT (BCF)<br />

P = permissible dose rate (mrem/wk)<br />

d = distance to point of interest<br />

W = workload (mA-min / wk)<br />

U = use factor<br />

T = occupancy factor<br />

BCF =<br />

2<br />

beam conversion factor (R / mA-m )<br />

0<br />

Page 56<br />

Page 56

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