Rad Data Handbook 20.. - Voss Associates
Rad Data Handbook 20.. - Voss Associates
Rad Data Handbook 20.. - Voss Associates
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Inverse Square Law<br />
2 2<br />
X<br />
1<br />
(D)<br />
1<br />
= X<br />
2<br />
(D)<br />
2<br />
X<br />
1<br />
= Measured exposure rate<br />
2<br />
D<br />
1<br />
= Distance from source for the measured exposure rate<br />
X<br />
2<br />
= Exposure rate to be calculated<br />
2<br />
D = New distance from the source<br />
2<br />
Applying the Inverse Square Law to Dose Reduction<br />
Given: A high activity source at an unknown distance.<br />
Find: Exposure rate from the source at 30 cm without<br />
approaching closer to the source.<br />
X<br />
2<br />
is measured exposure rate at distance Y<br />
X<br />
3<br />
is measured exposure rate at distance Y + 100 cm<br />
2 2<br />
X<br />
2<br />
(Y) = X<br />
3<br />
(Y + 100 cm)<br />
2 2<br />
Y = X (Y + 100 cm) / X<br />
3 2<br />
Set up this equation by entering the exposure rates you<br />
measured at distances Y and Y + 100 cm<br />
Let us assume 100 mr/hr and 50 mr/hr for those two points.<br />
2 2 2<br />
Y = 50 (Y + 100 cm) / 100 = 0.5Y + 100Y + 5,000<br />
2<br />
simplify this to Y - 200Y - 10,000 = 0<br />
This quadratic equation can be factored into two answers.<br />
The positive answer for Y is 241.42 cm.<br />
Now we know the distance for exposure rate X<br />
2<br />
and we can<br />
calculate the exposure rate at any distance.<br />
The exposure rate at 30 cm would be 6,476 mR/hr but we<br />
were able to calculate that exposure rate without entering the<br />
High <strong>Rad</strong>iation Area.<br />
A simpler method without having to factor a quadratic equation<br />
is to back AWAY from the source until the exposure rate is 1/4<br />
of the initial rate. The distance you moved away is equal to the<br />
original distance to the source. Now you can use the inverse<br />
square law to calculate the 30 cm exposure rate.<br />
63<br />
Inverse Square Law<br />
2 2<br />
X<br />
1<br />
(D)<br />
1<br />
= X<br />
2<br />
(D)<br />
2<br />
X<br />
1<br />
= Measured exposure rate<br />
2<br />
D<br />
1<br />
= Distance from source for the measured exposure rate<br />
X<br />
2<br />
= Exposure rate to be calculated<br />
2<br />
D = New distance from the source<br />
2<br />
Applying the Inverse Square Law to Dose Reduction<br />
Given: A high activity source at an unknown distance.<br />
Find: Exposure rate from the source at 30 cm without<br />
approaching closer to the source.<br />
X<br />
2<br />
is measured exposure rate at distance Y<br />
X<br />
3<br />
is measured exposure rate at distance Y + 100 cm<br />
2 2<br />
X<br />
2<br />
(Y) = X<br />
3<br />
(Y + 100 cm)<br />
2 2<br />
Y = X (Y + 100 cm) / X<br />
3 2<br />
Set up this equation by entering the exposure rates you<br />
measured at distances Y and Y + 100 cm<br />
Let us assume 100 mr/hr and 50 mr/hr for those two points.<br />
2 2 2<br />
Y = 50 (Y + 100 cm) / 100 = 0.5Y + 100Y + 5,000<br />
2<br />
simplify this to Y - 200Y - 10,000 = 0<br />
This quadratic equation can be factored into two answers.<br />
The positive answer for Y is 241.42 cm.<br />
Now we know the distance for exposure rate X<br />
2<br />
and we can<br />
calculate the exposure rate at any distance.<br />
The exposure rate at 30 cm would be 6,476 mR/hr but we<br />
were able to calculate that exposure rate without entering the<br />
High <strong>Rad</strong>iation Area.<br />
A simpler method without having to factor a quadratic equation<br />
is to back AWAY from the source until the exposure rate is 1/4<br />
of the initial rate. The distance you moved away is equal to the<br />
original distance to the source. Now you can use the inverse<br />
square law to calculate the 30 cm exposure rate.<br />
63<br />
Inverse Square Law<br />
2 2<br />
X<br />
1<br />
(D)<br />
1<br />
= X<br />
2<br />
(D)<br />
2<br />
X<br />
1<br />
= Measured exposure rate<br />
2<br />
D<br />
1<br />
= Distance from source for the measured exposure rate<br />
X<br />
2<br />
= Exposure rate to be calculated<br />
2<br />
D = New distance from the source<br />
2<br />
Applying the Inverse Square Law to Dose Reduction<br />
Given: A high activity source at an unknown distance.<br />
Find: Exposure rate from the source at 30 cm without<br />
approaching closer to the source.<br />
X<br />
2<br />
is measured exposure rate at distance Y<br />
X<br />
3<br />
is measured exposure rate at distance Y + 100 cm<br />
2 2<br />
X<br />
2<br />
(Y) = X<br />
3<br />
(Y + 100 cm)<br />
2 2<br />
Y = X (Y + 100 cm) / X<br />
3 2<br />
Set up this equation by entering the exposure rates you<br />
measured at distances Y and Y + 100 cm<br />
Let us assume 100 mr/hr and 50 mr/hr for those two points.<br />
2 2 2<br />
Y = 50 (Y + 100 cm) / 100 = 0.5Y + 100Y + 5,000<br />
2<br />
simplify this to Y - 200Y - 10,000 = 0<br />
This quadratic equation can be factored into two answers.<br />
The positive answer for Y is 241.42 cm.<br />
Now we know the distance for exposure rate X<br />
2<br />
and we can<br />
calculate the exposure rate at any distance.<br />
The exposure rate at 30 cm would be 6,476 mR/hr but we<br />
were able to calculate that exposure rate without entering the<br />
High <strong>Rad</strong>iation Area.<br />
A simpler method without having to factor a quadratic equation<br />
is to back AWAY from the source until the exposure rate is 1/4<br />
of the initial rate. The distance you moved away is equal to the<br />
original distance to the source. Now you can use the inverse<br />
square law to calculate the 30 cm exposure rate.<br />
63<br />
Inverse Square Law<br />
2 2<br />
X<br />
1<br />
(D)<br />
1<br />
= X<br />
2<br />
(D)<br />
2<br />
X<br />
1<br />
= Measured exposure rate<br />
2<br />
D<br />
1<br />
= Distance from source for the measured exposure rate<br />
X<br />
2<br />
= Exposure rate to be calculated<br />
2<br />
D = New distance from the source<br />
2<br />
Applying the Inverse Square Law to Dose Reduction<br />
Given: A high activity source at an unknown distance.<br />
Find: Exposure rate from the source at 30 cm without<br />
approaching closer to the source.<br />
X<br />
2<br />
is measured exposure rate at distance Y<br />
X<br />
3<br />
is measured exposure rate at distance Y + 100 cm<br />
2 2<br />
X<br />
2<br />
(Y) = X<br />
3<br />
(Y + 100 cm)<br />
2 2<br />
Y = X (Y + 100 cm) / X<br />
3 2<br />
Set up this equation by entering the exposure rates you<br />
measured at distances Y and Y + 100 cm<br />
Let us assume 100 mr/hr and 50 mr/hr for those two points.<br />
2 2 2<br />
Y = 50 (Y + 100 cm) / 100 = 0.5Y + 100Y + 5,000<br />
2<br />
simplify this to Y - 200Y - 10,000 = 0<br />
This quadratic equation can be factored into two answers.<br />
The positive answer for Y is 241.42 cm.<br />
Now we know the distance for exposure rate X<br />
2<br />
and we can<br />
calculate the exposure rate at any distance.<br />
The exposure rate at 30 cm would be 6,476 mR/hr but we<br />
were able to calculate that exposure rate without entering the<br />
High <strong>Rad</strong>iation Area.<br />
A simpler method without having to factor a quadratic equation<br />
is to back AWAY from the source until the exposure rate is 1/4<br />
of the initial rate. The distance you moved away is equal to the<br />
original distance to the source. Now you can use the inverse<br />
square law to calculate the 30 cm exposure rate.<br />
63