CHARACTERISTICS OF RADIOLOGICAL DISPERSAL DEVICES (RDD)

Transcription

1 CHARACTERISTICS OF RADIOLOGICAL DISPERSAL DEVICES (RDD) Michael Soucie, MS, RT (N) Research Scientist II NYS Department of Health Bureau of Environmental Radiation Protection

2 What is a Radiological Dispersal Device? Anything that can disperse radioactive materials Dirty Bomb Adding radioactive materials to a ventilation system Crop duster or other sprayer Contamination of water supply

3 Potential consequences of dispersal of radioactive material into... Facility ventilation systems Inhalation (internal) dose hazard Expensive cleanup costs The general environment ( dirty bombs, crop dusters, fire, sprayer, etc..) Low likelihood of acute radiological effects May require population shelter or evacuation May be difficult to clean outdoor areas Water supplies High dilution Not likely to result in individually significant doses.

4 What is a Dirty Bomb? A Dirty Bomb is conventional explosives combined with radioactive material with the intention of spreading the radioactive material over a relatively large area. A Dirty Bomb is NOT a nuclear explosion; the radioactive material does not enhance the explosion.

5 Consequences of a Dirty Bomb Very few deaths would be expected from acute radiological exposure (the greatest hazard would likely be from the effects of the conventional explosives). The contamination will hamper emergency response efforts and can delay hospital treatment. Widespread contamination can prevent the use of facilities and areas and have a significant psychological impact on the exposed population.

6 Types of Injuries If radioactive material is dispersed by an explosive, the main injuries are expected to be due to the explosive blast. Few injuries are expected from the resulting exposure to ionizing radiation as RDDs are primarily economic and psychological weapons.

7 Close to Site of the Explosion Possible trauma injuries and burns Possible high whole body or partial body irradiation & high levels of contamination Possible inhalation/imbedding of radioactive material (unlikely to be life-threatening)

8 Away from Site of Explosion Serious radiation injuries VERY unlikely Significant psychological impact Nuisance levels of contamination

9 Despite Widespread Contamination, There Are Relatively Small Exposures... EPA recommends shelter or evacuate areas >1 REM (Less than 0.1 miles downwind)

10 Despite Widespread Contamination, There Are Relatively Small Exposures REM out to 2 miles (Dose similar to a chest x-ray or 10% of natural background)

11 Rules of Thumb For outdoor explosions, most of the airborne radioactive dust will have settled to the ground within 10 minutes. In the absence of any other information, evacuate to 500 meters (1650 feet) from the detonation site in all directions.

12 QUESTIONS?

13 Radiation Safety Concepts

14 Radiation vs. Radioactive Material Radiation: energy transported in the form of particles or waves (alpha, beta, gamma, x-rays and neutrons) Radioactive Material: material whose atoms emit radiation (i.e., iodine-131, cesium-137)

15 Radiation Exposure External exposure From radiation sources external to the body Internal exposure From radioactive materials inside the body (inhalation, ingestion, absorption through wounds) Absorbed dose Radiation energy absorbed in tissue

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17 Radiation Protection: External Exposure Time: Limit the time spent in an areas of high radiation Distance: Exposure decreases dramatically as you increase your distance from the source. Shielding: Radiation is blocked by mass. When practical, operate behind objects (fire trucks, buildings, etc.)

18 Time Exposure is proportional Half time equals half dose 5 % reduction in time =?

19 E ~ 1/D 2 Double = 1/4 Triple = 1/9 Quadruple= 1/16 Distance Works for sources that are small relative to distance away

20 Shielding Alpha Particles Stopped by a sheet of paper Radiation Source Beta Particles Stopped by a layer of clothing or less than an inch of a substance (e.g. plastic) Gamma Rays Stopped by inches to feet of concrete or less than an inch of lead Neutrons Stopped by a few feet of concrete

21 Exposure vs. Contamination Exposure: Irradiation of the body à absorbed dose Contamination: Radioactive material on person (external) or within person (internal)

22 Radioactive Contamination Radioactive material forms: Solid Loose ( solid, liquid or gas) Loose material is kept in containers Radioactive contamination: radioactive material in an unwanted place

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24 Radiation Protection: Contamination Contamination can be reduced by Use of gloves Anticontamination clothing Internal contamination can be reduced by Use of respirators Avoiding contaminated food or drink

25 Radiation Measurement Most common detector is a Geiger- Mueller (GM) Tube. Also called a Geiger Counter or pancake probe.

26 GM Probe & Survey Meter Used for alpha, beta & gamma Detection and measurement Ratemeter cpm Exposure rate in Roentgen/hr (R/hr) or milliroentgen/hr (mr/hr)

27 Prepare instrument and measure background Put in batteries Check batteries using range or bat function Turn audio on Move range switch to most sensitive setting (if any). Measure background for 60 sec write it down. Common readings: count/min or approx 0.02 mr/ hr

28 Instrument Demonstration Battery Test Source Check Calibration Date

29 Other Instruments Micro R Meter Alpha Scintillator (ZnS) Sodium Iodide (NaI) Isotope Identifier Pressurized Ion Chamber (PIC)

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