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Radiological Dispersion Devices and Nuclear Weapons An Overview Victor E. Anderson, C.H.P. Radiologic Health Branch California Department of Public Health Use of Radioactive Materials for Terrorist Attack Few, if any deaths due to radiation. Possible deaths due to the explosion. ?

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Radiological dispersion devices and nuclear weapons an overview l.jpg

Radiological Dispersion Devices and Nuclear WeaponsAn Overview

Victor E. Anderson, C.H.P.

Radiologic Health Branch

California Department of Public Health

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Use of Radioactive Materials for Terrorist Attack

  • Few, if any deaths due to radiation.

  • Possible deaths due to the explosion.


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Use of Radioactive Materials for Terrorist Attack

  • Most likely impact will psychological.

  • The most important impact will be economic.

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Radiation Dose Delivery

  • External Dose

    • Source

    • Fragments

    • Fallout

  • Internal Dose

    • Primarily inhalation pathway.

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Radiography Source

Plastic Explosive

Radiological Dispersion Devices can vary in complexity and design.

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Lid w/explosive bolts

Cooling system for decay heat is required

High Level Source

MegaCuries or more

Mechanism for introducing explosive charge and detonating weapon


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Types of RDD

  • Improvised

  • Purpose Built

  • Manufactured

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Most Likely RDD

  • Economy of force and physics

  • Improvised

  • Explosive

  • Possibly incendiary

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Potential Radionuclides.

  • Primary

    • Co-60

    • Cs-137

    • Ir-192

    • Sr-90 (Y-90 in equilibrium)

    • Am-241

  • Based on availability and manufactured quantities.

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Other Radionuclides

  • Pu (Generally Pu-239 or Pu-238)

  • U-235

  • Thorium

    • Heavy Metal issues - ~ 109 mCi/metric ton

  • Radium

    • Issues with obtaining sufficient quantities.

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As the Cloud Moves Down Wind

Radioactive material is deposited as fallout.

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Radiation Issues

  • Ionizing Radiation

    • Emission of energy

    • X & Gamma Radiation

    • Beta and Alpha

  • Measured in rem and millirem

    • Rates: rem/hr; mrem/hr

    • 100 rem = 1 Sievert

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Radiation Issues

  • Dose = Dose Rate X Time

    • 120 mrem/hr X (½ hr) = 60 mrem

  • Immediate damage does not occur until after 100 rem of dose.

  • Annual radiation worker limit: 5 rem/yr

  • Public dose limit: 100 mrem/yr

    • Long term effects have not been detected at these low levels.

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Radioactive Contamination

  • Contamination is the presence of radioactive material in a place where it is not wanted.

  • Radiation Contamination

  • Contamination does emit radiation.

  • Major concern is inside people.

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First Responder Issues


  • Use ICS and SEMS

  • Life saving takes precedence over radiation control issues.

  • Do keep track of first responders radiation dose.

  • Remember: dose rate X time = dose.

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First Responder Issues

  • Call for help.

  • Use SEMS to ask for:

  • Radiologic Health Branch Strike Teams

  • Ca National Guard Civil Support Team

  • DOE Radiological Assistance Program (RAP) Team.

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Care for Contaminated & Injured

  • Contamination levels on patients

    • Will not cause radiation injuries to care givers.

    • Will not cause care givers to become “casualties.”

    • Are a hygiene issue.


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Care for Contaminated & Injured

  • When the patient is stabilized

    • Survey – where is the contamination?

    • Remove clothing as needed.

    • Use gauze, sponges, small amounts of soap and water, or “baby wipes” to clean the contaminated areas.

    • Use sheets and blankets to contain any contamination that can not be cleaned in the field.

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Care for Contaminated & Injured

  • At the ER

    • Do use a special area to survey and receive the patient.

    • At the same time do the usual medical screening.

    • Take care of the patient’s medical problems.

    • Decontaminate last.

    • Don’t lose track of patient’s condition.

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Controlling ContaminationAt the ER




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Downwind Issues

  • Assessment

  • When to evacuate?

  • Mass decontamination and screening

  • Recovery

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  • Use computer models and measurements.

  • Project where contamination is and levels.

  • Determine projected dose rates

  • Rapid

  • Recommendation to Incident Command and Emergency Operations Center

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When to evacuate?

  • Use EPA Protective Action Guides (PAG).

    • Based on dose from deposition.

    • Greater than one rem in 24 hours.

    • Greater than two rem in one year.

  • Use State Dose Assessment Center. If not available use:

    • Radiologic Health Branch Teams

    • Radiation Assistance Team (RAP)

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Mass Decontamination and Screening

  • Radioactive contamination is easily removed – soap and water, waterless cleaners, etc.

  • Radiation dose to contaminated individuals is small.

  • Major issue is decompression of individual and collective fears and concerns.

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Mass Decontamination and Screening

  • A plan is necessary.

  • Gives the population direction and hope.

  • Prevents mass exodus to hospitals.

  • Must plan for large numbers ~ one million persons.

  • Reception centers.

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Mass Decontamination and Screening

  • Giving everyone a shower is not the answer!

    • ~ 10% of the population is medically challenged.

  • Not all will be contaminated.

    • Worried well problem.

  • Some will only be partially contaminated.

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Reception Centers

  • Enough survey meters.

  • Supplies.

    • Decontamination

    • Clothing

  • Concentrate on minimum use of water.

  • Documentation

  • Volunteer Nuclear Medicine Doctors and Radiation Oncologists

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Public Communication


Multiple Languages

Provide Good Information

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Public Communication

  • Can help to prevent panic.

  • Key to keeping uninjured from going to hospitals.

  • Must be followed up by educational materials.

    • What is radiation?

    • What is the danger?

    • What can I do?

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Law Enforcement Issues

  • Evidence Collection and support.

  • Security for first responders with respect to issues such as secondary devices.

  • Security of the site to assure that unauthorized personnel do not enter.

  • Crowd control and assistance for evacuees.

  • Traffic Control

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Surveillance Issues

  • Determine contamination levels.

  • Plume projections help.

  • Need teams to survey ground.

  • Sample for loose and fixed contamination.

    • Loose contamination is radioactive material that is easily transferred from one surface to another.

    • Fixed contamination does not move easily.

  • Suitable air, water, and other environmental testing.

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Laboratory Issues

  • Identification of the radioactive materials

    • Will occur almost immediately.

    • Field methods are sufficient.

  • Laboratories will be needed to:

  • Analyze large numbers of samples for radioactive materials content.

    • Air Plants

    • Water Meats Dairy Products

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Laboratory Issues

  • Does not require environmental sampling sensitivities – e.g., picocuries or less.

  • High throughput

  • Shorter count times.

  • Good documentation.

  • Sample dose rate limits should be based on equipment limits.

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Laboratory Issues

  • Laboratory personnel should be able to easily stay within radiation dose worker limits.

  • Contamination control will be an issue.

  • Storage and documentation of samples.

    • Radioactive

    • Non-radioactive

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Some Thoughts

  • How big – kilotons

  • What will it do?

  • How far?

  • How many?

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Nuclear Weapon Basics

  • What is an explosion?

    • A very fast fire that has no place to go.

  • Chemical Explosion

    • Powered by chemical changes

  • Nuclear Explosion

    • Powered by nuclear changes

      • Fission

      • Fusion

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Fission Process

  • Fissionable Materials – U-233, U-235, Pu-239.

  • Atom is split by a neutron and you get:

    • Two or more smaller atoms

    • Two to three neutrons.

  • Other atoms may or not be split.

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  • Sub Critical

    • Does not sustain fission

  • Critical

    • Neutron Population Steady

    • Cannot extract power

  • Supercritical

    • Neutron population growing slowly

    • Can extract useful power.

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Prompt Critical

  • Neutrons are increasing very fast.

  • Nuclear reaction is running away

  • Result: A very, very fast burning nuclear fire.

  • If confined, so that the explosive forces build up, then an explosion occurs.

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Types of Fission Bombs

  • Implosion Type

High Explosive

Subcritical Core

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Construction Issues

  • Gun type is easiest to make.

    • Less efficient

    • Larger and heavier

  • Implosion type is much harder

    • More efficient

    • Lighter and smaller

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Type of Weapon Used

  • Stolen

    • “Suitcase” bombs ~ 0.1 to 10 kt

    • Tactical Warheads ~ 1 to 20 kt.

  • Improvised

    • Gun type

    • ~10 to 20 kt Range

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National Planning Scenario

  • Ten kiloton Weapon

  • Major urban area

    • Business Centers

    • Ports

    • Malls

  • California CDPH Scenario

    • Ground Burst

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Effects Part One

  • Intense nuclear reaction lasting for a tens to hundreds of microseconds.

  • Fireball formation

  • Light in the form of visible light, heat, and high energy photons (x and gamma rays).

  • Neutron Radiation

  • Electro-magnetic Pulse (EMP)

  • Shock or concussion wave.

  • Radioactive materials leading to fallout.

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The Fireball

  • Temperature starts at millions of degrees centigrade and falls to about 3,000 degrees centigrade at the maximum radius.

  • Size varies with strength.

    • R ≈ 145 (kt)0.4 for contact surface.

    • R ≈ 110 (kt)0.4 for air burst.

    • R ≈ 90 (kt)0.4 for surface burst.

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Immediate Ionizing Radiation Effects

  • Large burst of X, Gamma, and Neutron radiation is given off during the explosion.

  • For a dose of 1,000 rad, essentially 100% fatalities.

  • For a dose of 500 rad, approximately 50% fatalities without medical care.

  • “Natural” shields such as hills, concrete structures, etc. can provide some protection.

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Shock Wave

  • The explosion will create a “wall” of compressed air that expands outward.

  • This creates the blast or concessive effects.

  • Damage is highly dependent on height of burst.

  • Air or Ground

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Shock Wave

  • Ground Burst

  • Wave moves up and along the ground.

    • Broken up by terrain features.

    • Hills

    • Valleys

    • Buildings

  • Less efficient in causing damage.

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Shock Wave

  • Difficult to predict Destructive Effects

  • Rough Guides

    • Generally an over pressure of ~ 5 - 10 psi will severely damage most structures.

    • 10 kt airburst should severely damage all structures out to about ½ mile from the explosion’s center (ground zero).

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Shock Wave Damage

  • Fragments

  • Secondary fires

  • Explosions from gas tanks

  • Damage to vehicles and aircraft.

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Potential Shock Wave Damage 10 Kt

Shattered Glass Injuries

Severe Building Damage

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  • Probably the most dangerous effect from a nuclear weapon.

  • The amount depends on size and type of burst.

  • Ground burst yields the largest amount.

  • Air burst yields the lowest.

  • Weapon can be surrounded with Cobalt or other materials to enhance fallout.

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  • Spread and extent is highly dependent on weather conditions.

  • Individuals may be killed from radiation exposure.

  • Best defense is to leave or get into a shielded shelter (fallout shelter).

  • Arrival time depends on wind speed.

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  • Composed of fission fragments, activation products, and unused nuclear fuel.

  • Initially decays off very rapidly.

  • A(t) = activity after a period of time (t)

  • Ao = equal activity at start.

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  • Dose rate follows previous activity decay law.

  • After about six months, then fallout decays based on the longer lived materials.

  • An initial dose rate of 1,000 rad/hr will fall to about 2 rad/hr in a week.

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10 kt Idealized Fallout Dose Rates and Times

(15 MPH Wind Blowing from the South to the North)

500 R/hr

Arrival Time ~ 35 min

1,000 R./hr

Arrival Time ~ 20 min minutes

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Fallout Issues

  • Get population out of the area fast.

  • Radiation burns from heavy fallout can occur.

  • Recommended that individuals in the areas of greater than 10 rad per hour take a shower.

  • Field decontamination will be complicated by injuries and ill population.

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Response Issues

  • Major event

  • Initial confusion and chaos

  • Set up EOC and Command Posts up wind.

  • Define work areas

  • Safe area

    • < 2 mrem/hr

    • No special radiation precautions

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Work Areas

  • Emergency Zone

    • Area where workers can maintain doses less than or equal to 5 rem per year. (State radiation worker limits).

    • Contamination control may require level A or equivalent PPE.

    • Search and Rescue will be difficult.

  • Life Saving Zone

    • Entry only to save lives.

    • Doses must be less than 100 rem per entry.

  • Lethal Zone

    • No Entry

    • Dose Rates are too high.

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Work Zones

  • Zones will shrink as fallout decays.

  • Controlling rescue worker’s dose is a must.

  • Survivors who have greater than 1,000 rad are dead.

  • Organization will be the key to survival.

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  • CDPH Studies for a 10 kt Ground Burst Indicate

    • Approximately 60,000 individuals killed outright.

    • An additional 60,000 individuals at risk from radiation syndrome death due to fallout.

  • Death due to fallout radiation will be prolonged ranging from days to weeks.

  • An extreme challenge to the local, state, and national medical care system.

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Fallout Injuries

  • Unknown

  • Subject to factors of evacuation and time in area.

  • For a ground burst, clearly higher.

  • Will require decontamination.

  • Beta burns.

  • Possible whole body irradiation.

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Refugee Issues

  • Plan for large numbers.

  • Consider how to screen rapidly.

    • For contamination.

    • For injuries.

    • For needs.

  • Places to go.

  • System must be humane.

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Radioactive Screening

  • Hand held instruments.

    • Inexpensive.

    • Labor intensive.

  • Portal Monitors

    • Expensive.

    • Less labor.

    • Quick.

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Concluding Remarks

  • The planning problem involves many different disciplines.

  • Because radiation issues will affect virtually everything, the Health Physicist ends up as a technical advisor, facilitator, and catalyst .

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Hiroshima Today. Ground Zero is near the Center of the Picture

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Concluding Remarks

  • With correct planning and training a good response can happen.

  • Clear objectives, good equipment, and a well led and organized response organization can prevail.