Energy radiated from an object in the form of waves or particles which travel through space.

• Ionizing radiation
  • X-rays
  • Electrons
• Non-Ionizing radiation
  • Microwaves
  • Visible Light 
  • Heat 
  • Radio waves

• Ionization – the process by which electrons are removed from an atom.
• Ionization events on the cellular level may disrupt normal metabolism and cell division.

For our purposes, “Radioactive material” will refer to any substance which spontaneously emits ionizing radiation. 

Radiation is a part of our everyday environment. Both natural and artificial radiation contributes to an average American’s yearly exposure of 360 mRem.

• high-energy gamma radiation originating in outer space.

Exposure rates at:

• Sea Level ……………………………. 26 mRem/year
• Atlanta, Georgia (1,050 feet) ………. 31 mRem/year
• Denver, Colorado (5,300 feet) …….. 50 mRem/year

• naturally radioactive elements in the soil and water such as uranium, radium, and thorium.

Exposure rates:

• United States (avg.) ……………. 26 mRem/year
• Denver, Colorado ………………. 63 mRem/year
• Paris, France …………………….. 350 mRem/year
• Pacos De Caldas, Brazil …….. 7,000 mRem/year 

• Radon
• Food and Water
  • Approximately 20mRem/yr
• Medical Treatments 
  • Chest X-ray 10mRem
  • Dental X-ray 100mRem
  • Nuclear Medicine Diagnostic Study 200mRem
• Consumer Goods
  • Cigarettes @ 2 packs/ day = 8000mRem/yr dose to the lungs!!
• Nuclear Fallout
  • Testing of nuclear weapons contributes 1mRem/yr 

Curie – quantifies the intensity of radioactive material decay (activity)

• 1 Ci = 1000 mCi (millicuries)
• 1 mCi = 1000 μCi (microcuries)

Rem – quantifies the amount of radiation absorbed in human tissue (exposure)

•yearly exposure limit to radiation workers = 5000 mRem

mR/hr – quantifies the equivalent rate of exposure (Dose Rate)

•Exposure rate at the surface of a package = 1.0 mR/hr

cpm – counts per minute

dpm – disintegrations per minute 

A half-life is the fixed period of time it takes for the activity of a radioactive substance to naturally decay to 1⁄2 its original value.

• Half-life of P-32 is about 14 days.
  • 1.0 mCi on 5/1/04 will decay to 0.5 mCi on 5/15/04
  • 1.0 mCi on 5/1/04 will decay to 0.25 mCi on 5/29/04 

Time

• Decrease time near a radioactive source → decrease exposure to radiation

Distance

• “Inverse Square Law”: Intensity = 1/ (Distance)2
  • If the distance between you and the source doubles (2x), the intensity becomes 1/4 (0.25)
  • If the distance triples (3x), the intensity becomes 1/9(0.111)

Shielding

• The proper substance between you and a source will absorb radiation and reduce your exposure! 

The natural decay of radioactive material results in one of four types of “radiation” being emitted:

• Alpha particles
• Beta particles
• Gamma rays
• Neutrons 

• Helium nuclei with a +2 charge
• Relatively large and energetic
• Dangerous to cell nucleus
• Easily shielded
• Not commonly found in research settings 

• Electrons with a –1 charge
• Ionizations occur as the particle penetrates matter
• The ability of a Beta particle to penetrate matter is a function of its energy
• Commonly used Beta emitters : H-3, C-14, P-32, P-33, S-35 

Properties of commonly used β -emitters

• X-ray having no charge or mass
• Ionization occurs as it passes directly through matter
• Greatest penetrating ability of all
• Commonly used γ emitters: Cr-51, I-125 

• Particles having no charge
• Interacts with matter
  • Moderation
    • Elastic and inelastic collision
  • Absorption
    • Gamma ray production
    • Fission 

• All Beta emitters used in the laboratory can be safely shielded by 1cm thick Plexiglas.
  • The energy of the Beta particle emitted by H-3 and C-14 is so low that no shielding is necessary.
• Gamma emitters must be shielded by lead.
  • Cr-51 0.2 mm of lead
  • I-125 3 mm of lead
  • Remember, Gamma has the most penetrating ability, so increasing distance alone may not be enough to protect yourself and others.
• Neutron emitters may be shielded by low density material like paraffin wax or water.
  • Shielding neutron sources usually results in the production of low level gamma rays.
  • Usually shielding for neutron sources will require special handling procedures – contact your PI for more details.

• Shield all four sides when necessary
• Check integrity of shielding material
• Waste and source material may also require shielding! 

• Lab coat, disposable gloves are MANDATORY!
• No exposed skin when handling RAM (shorts, skirts, open-toed shoes)
• Must be worn when handling any samples or equipment bearing a RAM label.

• Dosimetry program monitors the amount of radiation exposure
• Submit a “Radiation Badge Service Card” to order or cancel badge
• A dosimetry badge must be worn by those who:
  • May receive over 10% of the annual exposure limits
  • Use more than 1 mCi per month of P-32 or S-35
  • Exemptions: H-3 and C-14 users
• Radiation badge worn at the highest area of exposure (lapel)
• Store your badge away from areas of potential exposure!

Note: Workers who use > 10mCi of a high-energy β-emitter or > 1 mCi of a γ-emitter must also wear a ring badge.

• Eating, drinking, smoking, chewing gum,
• Application of cosmetics
• Storage of food or drink
• Preparation of food (microwave, coffee maker, etc.)
• Unauthorized repair or removal of labeled equipment

• Areas where RAM is stored or used must be locked or attended at all times!
• An empty room with a “Radioactive Materials” sign on the door is still a RAM use area!
• Visitors must adhere to all radiation safety guidelines.

• RAM workspaces must be clearly identified (with a sign or tape) and protected by absorbent coverings.
• RAM must be labeled with a radioactive trifoil, isotope, activity, and date. This includes stock vials, stored radioactive samples, and all radioactive waste.
• Equipment that may be used with RAM (pipettes, centrifuges, water baths) must be labeled with a radioactive trifoil.

• All RAM must be transported in shielded, spill-proof containers.
• Any RAM entering or leaving the University of Chicago must be facilitated by the Office of Radiation
• Safety. Call ORS immediately if a radioactive package is delivered directly to your lab, or you intend to have a package shipped off-campus.
• Transfer of RAM from one Private Investigator to another requires pre-approval by ORS. 

• Irradiators
  • Multi-Curie size Ir192or Co60 sources are often used for non-destructive testing and Radiography. (Rems/sec).
• Particle accelerators
  • Used in industry as research tools and laboratories.
• Small sources
  • C14 and Cs-137 for counting and detection equipment quality control testing.
• Backscatter gauges
  • for road construction
• Flow detectors in industrial setting for flow detection for piping fluids.
• Paper mills
  • Flow detectors and thickness detectors for paper manufacturers.
• Swimming pool reactors
  • for research labs and Universities
• Food and Pharmaceutical irradiators.
  • Mega- Curies of Cs137 of Co60. 

Meter base	End-window probe	Pancake probe

• Beta particles must have sufficient kinetic energy to pass through the detector window and into the gas-filled, sensitive volume of the detector.

• A survey meter’s ability to detect radiation can be expressed as the detector’s efficiency:

• Required each time the meter is turned on

1. Move switch on base to “BAT” position. - The indicator needle must deflect to the “BAT TEST” range. - If it does not pass, you may not use the instrument! Change the batteries or call ORS for assistance.

• Must be performed each day the instrument is used

• With the meter turned on, hold the probe flush against the check source location (black X) on the side of the meter.

1. The display must read within the range limits on the “Checksource Measurement” sticker.
2. 
3. 

  - Contact ORS if the reading falls outside the range. Do not use this instrument!

• After battery check and operational check, set the dial switch to the lowest scale.
• “Instrument Background” is the highest reading when no radioactive material is present.
  • Average Backgrounds (end window or pancake probe):
    • 0.02- 0.04 mR/hr
    • 30 – 100 cpm
    • 0.3 – 1 cps
  • If your background is too high you must move to another area, re-perform the operational check, and try again. A short in the cable or a contaminated probe can cause elevated backgrounds!
• Always remove red cap before surveying.
• Proper survey distance is 1cm from the surface – don’t let the probe make contact with the object you are surveying!
• Keep the probe face parallel to the area being surveyed.
• You can never survey too slowly. Recommended survey speeds range from 2-5 cm/second. Keep in mind that the efficiency of your meter varies with the isotope you are trying to detect!
• Survey with the audio “on”!

• Detection of gamma from I-125
• Average background 100 to 500 cpm –Results in cpm only!
• 20-30% efficiency
• Red cover is not removable!

• Detection of low energy β-emitters
• Required whenever tritium (H-3) is used
• Results measured in cpm
• Average background < 50 cpm

• Use small pieces of absorbent material (Kimwipe, filter paper, paper towel, cotton-tipped applicator)
• Surface area wiped ~ 100 cm2
• Wipe all potentially contaminated areas in an S-shaped pattern
• Add appropriate type and volume of cocktail (4ml for a 5 ml vial)
• “Blank wipe” must be counted to determine background readings.
• 1 minute count time per vial
• LSC protocols must be programmed for detection of the appropriate isotope energies! 

• Remove the radioactive material by cleaning, shielding, or disposal of the offending item(s).
• Threshold levels (when must I decontaminate?)
  • GM survey – > 0.25mR/hr (600 cpm or 6 cps)
  • Wipe test – > 400 cpm
  • NaI probe – > 1000 cpm
• Required documentation
  • Corrective Actions
  • New survey results

• H-3, C-14 products – anything bound to lipids or cell membrane components can easily absorb through skin.
• “Free” iodine-125 can penetrate latex gloves, so wear two pair!

• S-35 bound to amino acids (methionine) is easily volatilized. Opening the stock vial in a designated fume hood is mandatory!
• Unbound I-125 such as NaI in NaOH must always be used in the fume hood. RIA kits and iodine bound to antibodies do not require special measures. 

• Your dosimeter badge detects exposure to the body, but not to the extremities! Limit the amount of time spent holding stock vials of high-energy β-emitters like P-32.
  • 1mCi of P-32 in 1ml solution — contact exposure of 13,000mR/min!
• You aren’t working with radioactive material today, but someone else may be! Wear your badge on your lab coat whenever you are in a radioactive materials laboratory.

• H-3 and C-14 are nearly undetectable during your experiment, so wear two pairs of gloves and change them frequently. Store stock vials and samples in an area that is self-contained in case of a spill.

• Maximum permissible dose limits for adult radiation workers (> 18 yrs)

• (Optional) Pregnancy Declaration
  • A worker may declare their pregnancy in writing to the Radiation Safety Officer, and will receive additional monitoring for the fetus.

•Estimated increase in cancer risk

• 25% of all adults will develop cancer from all possible causes in a population.
• At occupational limits of 5 rem/year, an individual working for 20 years would result in an lifetime exposure of 100 rem.
• This level of exposure would result in a 3% INCREASE in incidence of cancer or a 28% chance vs a 25% chance.

• 1000 rem = Lethal Dose
  • This level of exposure (given all at once) will result in dizziness, nausea, vomiting and 90% to 100% fatality.
• 100 rem = Clinical Dose
  • This level of exposure (given all at once) may result in minor white blood cell decrease and a < 5% chance of any noticeable symptoms.
• 1 rem = Sub-clinical Dose
  • This level of exposure (given all at once) produces no symptoms or effects. There is no evidence of any internal or external physical changes.