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Radiation Safety

Background Information
Gamma Radiation
Health Concerns

Radiation Theory
Nature of Radiation
Sources of High Energy

Rad for Ind Radiography
Decay and Half-life
Energy, Activity, Intensity   and Exposure
Interaction with Matter
Measures Related to   Biological Effects

Biological Effects
Biological Factors
Stochastic (Delayed) Effects
  -Genetic Effects

Nonstochastic (Acute) Effects

Safe Use of Radiation
NRC & Code of Federal
Exposure Limits
Controlling Exposure
  -Time-Dose Calculation
  -Distance-Intensity Calc
HVL Shielding
Safety Controls

Survey Techniques

Radiation Safety Equipment
Radiation Detectors
Survey Meters
Pocket Dosimeter
Audible Alarm Rate Meters
Film Badges

Video Clips



Calculating Intensity with the Inverse Square Law

I1/ I2 = D22/ D12

I1 = Intensity 1 at D1
I2 = Intensity 2 at D2
D1 = Distance 1 from source
D2 = Distance 2 from source

Example Calculation 1
The intensity of radiation is 530 R/h at 5 feet away from a source. What is the intensity of the radiation at 10 feet?

Rework the equation to solve for the intensity at distance 2
            I2 = I1 x D12 / D22

Plug in the known values
           I2 = 530R/h x (5ft)2 / (10ft)2

Solve for I 2
           I2 = 132.5 R/h

In this instance the distance has been doubled and the intensity at that point has decreased by a factor of four.

Example Calculation 2
A source is producing an intensity of 456 R/h at one foot from the source. What would be the distance in feet to the 100, 5, and 2 mR/h boundaries.

Convert R/hour to mR/hour

       456R/h x 1000 = 456,000 mR/h

Rework the equation to solve for D2


Plug in the known values and solve


         D2= 67.5 feet

Using this equation the 100mR/h boundary would be at 68 feet, the 5mR/h boundary would be at 301.99 feet, and the 2mR/h boundary would be at 477.5 feet. Sources are seldom operated for an entire hour, and collimators are often used which reduce these distances considerably.