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Appendix D - Training Program

Radiation Hazards / Instrumentation

Objectives/Samples of Behavior:

  1. Describe radiation characteristics for alpha, beta, and gamma.

  2. State the EPA action level for radiation.

  3. Explain the primary methods for reducing external radiation exposure.

  4. Identify the features on the Micro-R gamma detector.

A.  Radioactivity

  1. The tendency of unstable atoms to undergo radioactive decay (transformation).  Radioactive materials are called radionuclides.

  2. Atom tries to become stable by emitting:

 alpha,  beta(), and gamma

  1. Ionizing radiation - ionizes (strips electrons) or excites (raises to higher energy state)

  2. Different decay rates - seconds to years

  3. Half-life - T1/2          100   50     25

  4. Half-life directly related to amount of radiation emitted.

B.  Radiation - Characteristics of 3 Major Types

Source

Symbol

Form

Mass/Chg

Ioniza/cm

Path in Air

Hazard Location

Alpha

  

Particle

4
+2

100,000s

<1 inch

Internal

Beta

  

Particle

0.00055
+/-1

100s

inches-
meters

Internal/ external

Gamma

  

EMR

0
0

?

meters - kilometers

Internal/ external

C.  Definitions

  1. Activity:

  1. Curie (Ci) - unit of measure for amount (activity - not mass) of radioactive material

  2. Becquerel = 1 dps

  3. 1 curies = 3.7 x 1010 Bq

  1. Exposure:

  1. Roentgen - unit of measure for alpha and gamma exposure in air.

  2. Counts per minute (cpm)

3.  Dose:

  1. Rad - unit of measure for radiation energy some absorbing mass

  2. Gray (Gy) = 100 rads

  3. 1 cGy = 1 rad

  1. Equivalent dose:

  1. Rem - unit of measure which represents the risk associated with the radiation exposure

  2. Sievert (Sv) = 100 rem

  3. 1 cSv = 1 rem

  1. Quality factor - factor by which absorbed doses are multiplied to obtain a quantity that expresses the risk associated with the dose.

 

Rad x QF

= rem

Gamma

1 rad x 1

= 1 rem

Beta

1 rad x (1 to 2.6)

= 1 to 2.6 rem

Alpha

1 rad x 20

= 20 rem

6.  Subunits:

  1. 1000 mR (or mR/hr) = 1 roentgen ( or 1R/hr)

  2. 1000 uR = 1 mR

  3. 1000 mrem = 1 rem

  4. 1000 urem = 1 mrem

D.  Exposure Risk

  1. Acute exposure risk:

700 rem = LD100

600 rem = LD99

450 rem = LD50

200 rem = LDLO

100 rem = TDLO

25 rem = EDLO

  1. Chronic exposure risk

  1. A normal U.S. citizen has a 25% risk of cancer.  One rem increases risk to 25.03%.  100 rem increases risk to 28%.

  2. Background radiation:

is unavoidable

comes from cosmic sources & earth materials

averages 0.01 to 0.02 mR/hr gamma in U.S.

  1. US EPA action level:

1 mR/hr gamma above background

  1. Maintain exposure ALARA (As Low As Reasonably Achievable)

  2. Exposure reduction mechanisms

  1. Time

  2. Distance

  3. Shielding

E.  Radiation Monitoring

  1. Purposes of radiation monitoring:

  1. Determine risk of exposure

  2. Determine types of radiation

  1. Interpretation of instrument data:

  1. mR/hr (`beta / gamma) - used to make exposure estimates

  2. cpm (alpha or beta) - used to determine activity of the source

  1. Limitations and considerations

  1. Annual calibration (minimum)

  2. Worker training

  3. Worker curiosity / horseplay

  4. Instruments calibrated for one type of radiation

  5. Calibration to specific isotope