Lesson topic 5.1 Shielding effects on radiation intensity and dose

Enabling Objectives ¶Describe how time, distance, and shielding effect radiation intensity and dose ·Describe the characteristics of the types of nuclear bursts ¸Describe the characteristics of alpha, beta, gamma, and neutron radiation

¹Describe the following nuclear terms: fireball, Electromagnetic pulse, initial radiation, thermal radiation, shockwave, blast wave, column/plume, base surge, residual radiation, fallout, and radioactive cloud ºDescribe the following nuclear terms: radiation, contamination, radioactive half life, dose, dose rate, roentgen, RAD, cintigray, and REM Enabling Objectives

Nuclear Terms zRadiation yRays/particles emitted from an unstable atom zContamination yDeposit of radioactive material on surfaces zRadioactive half-life yTime required for the intensity of a given isotope to decrease to half of its original value

zDose yTotal amount of radiation received by a person regardless of time zDose rate yAmount of radiation received in a unit of time zRoentgen yMeasurement of gamma or x-ray radiation yDesignated "R” yDose Rate = R/hr Nuclear Terms

zRadiation Absorbed Dose (RAD) yA unit of absorbed dose of radiation zCentigray (cGy) yNATO designation for RAD zREM - Unit of biological dose of radiation For radiological calculations, all terms (Roentgen, RAD, Centigray) are a 1 for 1 ratio 10r/hr = 10 RADS per hr Nuclear Terms

Factors Influencing radiation intensity/dose zTime yShorter the exposure time, the smaller the dose received yDose = Intensity x Time zDistance yFarther the distance from the radiation source, the smaller the dose received

zShielding yMaterial that absorbs radiation, decreases radiation intensity yThickness & type of material influences amount of radiation absorbed Factors Influencing radiation intensity/dose

Types of radiation zAlpha particles yTravels 0 to 3 inches in the air yLow penetrating ability zShielding yPaper will completely stop the particle yPersonnel hazard internal zNuclear defense importance: low

zBeta particles yTravel 6 to 10 feet in the air yLow penetrating ability zShielding yAluminum foil sheet yProtective clothing Types of radiation

Beta particles zPersonnel hazard ySkin burns yInternal problems zNuclear defense importance yModerate importance yTravels moderately far

zGamma rays yTravels long distances yHigh penetrating ability zShielding yHigh density material zPersonnel hazard external & internal yPenetrates deep into body tissue Types of radiation

Gamma rays zNuclear defense importance: Grave yHigh penetrating ability & distance traveled

zNeutron radiation yTravels long distances yPenetrating ability depends on shielding yShielding - Hydrogenous material yLead & steel not effective shields Types of radiation

Neutron radiation zPersonnel hazard yCells because of their high water content yCan induce an atom in the body to become unstable/radioactive yMostly external because it travels thousands of yards in air zNuclear defense importance yOnly in the first minute or so of a nuclear burst

Nuclear Weapon Burst Terms zFireball yMaterial present is heated to tens of millions degrees and forms a hot glowing mass zInitial radiation yRadiation emitted during the first minute after a nuclear explosion zElectromagnetic Pulse (EMP) yA sharp pulse of radio frequency electromagnetic radiation yCauses Blueout & blackout

17 BLACKOUT

zThermal radiation yTravels at the speed of light yTemperature reaches tens of millions of degrees (C) and the rate of energy emission is very high. yVery prominent characteristic of a nuclear explosion Nuclear Weapon Burst Terms

zVisible Light ySome of the thermal energy in a nuclear explosion is in the form of visible light yBurst produces an extremely bright initial flash yDo not look at the fireball, Permanent eye injury can result Nuclear Weapon Burst Terms

Shock wave

zExtremely high temperature and pressure zTraveling through air is called a blast wave, or air blast zThe pressure is several million pounds per square inch (psi)

zColumn or plume yHollow cylinder of water & spray thrown up from an underwater burst zBase surge yDense aerosol cloud of small water droplets forms and moves rapidly outward in all directions from surface (or ground) yHighly radioactive Nuclear Weapon Burst Terms

zResidual radiation yRadiological decay after the burst yRadioactive contamination that is created in a nuclear explosion zFall out yRadioactive particles that fall back to earth yEarly fallout is of tactical military significance Nuclear Weapon Burst Terms

Types of Nuclear Bursts

HIGH ALTITUDE AIR BURST OVER 100,000 FEET PRIMARILY USED FOR PRODUCTION OF ELECTROMAGNETIC EFFECTS

AIR BURST UP TO 100,000 FEET FIREBALL DOES NOT TOUCH THE SURFACE OF THE EARTH

28 SURFACE BURST FIREBALL TOUCHES THE SURFACE OF THE EARTH. Maximizes blast and thermal effects against ships/structures covers less area than air burst

29 SUB SURFACE BURST FIREBALL VENTS TO THE WATER SURFACE. EFFECTS: Underwater shock wave, blueout, and base surge.

Summary and Review zNuclear terms zFactors influencing radiation intensity/dose zTypes of radiation zNuclear weapon burst terms zTypes of nuclear bursts