Mirion Technologies

Industrial Sources

• Radiography/Density Gauges
• Medical, Lab, Pharmaceutical Facilities
• Nuclear Power Plant
• Vehicular Transportation of Radioactive Waste/Material
• Food Irradiation Processing Facility

Accidents

• A passing radioactive cloud or smoke (plume from a Nuclear Power Plant)
• A large point source emitting a strong radioactive beam
• Exposure from contamination deposited on the ground

Misuse, Terrorism

• Exposure of public to a radiation source
• Disperse radioactive material using conventional means (aircraft, ventilation, etc.)
• RDD (Incendiary/Explosive or Dirty Bomb)
• Detonate a Nuclear Weapon (Tactical Backpack Device)

How Does A Radiation Detector Work?

A Radiation Detector works by counting electrical pulses using a tube filled with an inert gas. This happens when ionizing radiation interacts with the gas, causing it to become conductive. This creates a cascade effect where all the gas becomes briefly ionized, and is “collected” to the sides of the tube, creating one “pulse” after which the gas returns to normal until the next particle or photon of radiation hits it.

How do we Measure Radiation Dose?

Human dose is measured in rem (rem, mrem, μrem) or sieverts (Sv, mSv, μSv).

• 1 Sv = 100 rem
• 1 rem = 1,000 mrem = 1,000,000 μrem
• 1 rem poses the same risk for any type of ionizing radiation (alpha, beta, gamma, X) for both internal and external exposure
• External radiation exposure measured by dosimetry (TLD, film badge, electronic device)
• Internal radiation exposure measured using bioassay: (e.g.: urine/fecal sample analysis)

Rad

Unit used to measure a quantity of absorbed dose (Radiation Absorbed Dose).

Rem

Used to derive a quantity called equivalent dose; this relates the absorbed dose in human tissue to the effective biological damage of the radiation. Not all radiation has the same biological effect, even for the same amount of absorbed dose.

• Typical units: mRem, mRem/hr, mRem (mR), mR/hr

Sievert

The sievert (symbol: Sv) is the International System of Units (SI) SI derived unit of dose equivalent radiation.

• Typical units: mSv, mSv/hr

Dose

The quantity of radiation or energy absorbed. Dose is affected by the TYPE of radiation, the amount of radiation and the physical properties of the material itself.

Dose Rate

The dose delivered per unit of time; used to indicate the level of hazard from a radioactive source per unit of time.

• Dose rate = dose x time. Example: 100 mrem/hr = 100 mrem x 60 minutes

Dose (R)	Effects
25 - 50	First sign of physical effects (drop in white blood cell count)
150 - 350	Nausea, vomiting, fatigue, hair loss (epilation), skin reddening (erythema)
450 - 600 LD 50/30	~ 50% die within 60 days with medical care ~ 50% die within 30 days without medical care
1,000 LD 100/60	~ 100% die within 30-60 days

Understanding Radiation and its Effects

• Radiation is energy given off by unstable atoms and some machines. Radioactive Material contains unstable atoms that give off radiation when they “decay.”
• Contamination is Radioactive Material spread someplace where you don’t want it. Radiation damages our cell’s DNA, fortunately our body has very efficient repair mechanisms.
• Large acute doses of radiation can cause sickness or even death. The severity of the effects are proportional to the dose.
• All exposures to presumed to increase the risk of cancer. The amount of “increased risk” is proportional to exposure.

Radiation Interactions

Radiation particles differ in mass and energy, and can be stopped or shielded by various types of material.

This graphic demonstrates the basic methods in which particle radiation can be effectively shielded.