1. Explosions
A Presentation by Paige Bennett and Dillon O’Connor

3. Explosion
 An explosion is a sudden, violent change of potential
energy to work
 Exothermic
 All the stored energy within a substance provides force
across a distance

4. Basics of Explosions
 Contain an oxidizer and a fuel (if it burns)
 Form gases
 Release intense heat
 React rapidly
 Require initiation

5. Explosive Material
 Chemically or energetically unstable
 When initiated:
 Produces a sudden expansion of the material
 Large changes in pressure (explosion)

6. Classifications of Explosives
 Low explosives
 Burn through deflagration
 Initiated by heat and require confinement to explode
 High explosives
 Explode without confinement
 Initiated by shock or heat
 High Brisance (shattering effect)
 Classified by rate of decomposition

7. Low Explosives
 Auto-combustion at various rates ranging from a few
cm/s to 400 m/s.
 Usually serve as propellant
 Example: Gasoline

9. High Explosive
 Detonate at rates ranging from 1,000 m/s to 8,500 m/s
 Two classes based upon sensitivity
 Primary: Extremely sensitive; burn rapidly or detonate if
ignited
 Secondary: Relatively insensitive; may burn when ignited,
require detonation
 Example: Warheads

11. Physical Properties
 There are several key physical properties that define
explosives
 Sensitivity
 Stability
 Power
 Brisance
 Density
 Volatility
 Hygroscopicity
 Toxicity

12. Sensitivity
 Inclination of an explosive to ignite or detonate
 Several kinds of sensitivity
 Impact, Friction, and Heat
 Testing sensitivity
 Impact: distance through which a standard weight must be
dropped to cause the material to explode.
 Friction: what occurs when a weighted pendulum scrapes across
the material
 Heat: temperature at which explosion of the material occurs

13. Stability
 Molecular stability
 Integrity of the compounds structure. If unstable,
decomposition can take place at room temperature.
 Temperature of storage
 Rate of decomposition increases at higher temperatures. Highly
stable between -10 and 35 degrees Celsius
 Resilience to sunlight
 Ultraviolet rays from the sun can cause explosive compounds to
rapidly decompose

14. Power
 Ability to perform work
 Various tests to evaluate
 Cylinder expansion test
 Cylinder fragmentation test
 Detonation Pressure (Chapman-Jouget)
 Determination of critical Diameter
 Infinite diameter detonation velocity
 Pressure versus scaled distance
 Impulse verses scaled distance
 Relative bubble energy (RBE)
 Cylinder Expansion and Air-Blast Tests are common

16. Measuring a Chemical Explosive
Reaction
 Thermochemistry deals with changes in internal energy (as
heat) in chemical reactions.
 Information can be learned based upon chemical laws or by
analysis of products.
 Characteristics that can be theoretically computed
 Oxygen balance
 Heat of reaction
 Volume of products
 Potential energy

17. Nuclear Explosions
 Chemical explosions are relatively simple
 They consist of a series or multiple series of chemical
reactions for their energy
 Nuclear explosions follow a more complex process
 They rely upon fission or fusion to cause powerful chain
reactions at an atomic level for their energy

18. Fission
o Materials used to produce nuclear explosions by fission are certain
isotopes of the elements uranium and plutonium.
o In nature, uranium consists mainly of two isotopes uranium-235 (about
0.7%) and uranium-238 (about 99.3%)
o The less abundant, uranium-235 is the readily fissionable species that is
commonly used in nuclear weapons.
o Since plutonium is only found naturally in insignificant amounts,
plutonium-239, which is the fissionable isotope used, is made artificially
from uranium-238.

19. Fission Process
o A neutron is accelerated towards the
uranium-235 nucleus making the
nucleus unstable and it splits parts into
two fission
products (Barium & Krypton), along
with 2-3
neutrons.
o The neutrons produced by the fission
reaction cause other large atoms to
fission, and their neutron production
causes still other atoms to
fission…leading to a chain reaction
o This entire process is very rapid and
only takes a few millionths of a second.
o The resulting energy production heats
the surrounding air and causes it to
expand in the form of a blast wave.

20. Fission

21. Fusion Reactions
*Much more powerful than fission*
• 2 main stages:
•PRIMARY STAGE:
Regular fission chain reaction & the radiation produced from
this reaction is used to heat the interior of the bomb to
temperatures where fusion can happen.
•SECONDARY:
Composed of lithium deteuride which splits apart under intense
heat into 6 Li atoms and deuterium ions.
1 neutron from fission reaction reacts with the 6Li to produce 4
He and 3 H

22. Stars = or < sun Stars > sun

23. Damage
o 4 categories:
1.Blast, (40 – 50%)
2. Thermal Radiation, (30 – 50%)
3. Ionizing Radiation, (5%)
4. Residual Radiation (5-10%)
However, depending on the design of the weapon and
the environment in which it is detonated the energy
distributed to these categories can be increased or
decreased.
http://www.youtube.com/watch?v=WwlNPhn64TA&feature=related

24. BLAST EFFECTS
o The air immediately behind the shock
front is accelerated to high velocities and
creates a powerful wind.
oThese winds in turn create dynamic
pressure against the objects facing the
blast. Shock waves cause a virtually
instantaneous jump in pressure at the
shock front.
oThe combination of the pressure jump
(called the overpressure) and the dynamic
pressure causes blast damage. Both the
overpressure and the dynamic pressure
reach to their maximum values upon the
arrival of the shock wave.
oThey then decay over a period ranging
from a few tenths of a second to several
seconds, depending on the blast's strength
and the yield.

25. THERMAL
RADIATION
o A primary form of energy from a nuclear explosion is thermal
radiation. Initially, most of this energy goes into heating the bomb
materials and the air in the vicinity of the blast. Temperatures of a
nuclear explosion reach those in the interior of the sun, about
100,000,000° Celsius, and produce a brilliant fireball.
oTwo pulses of thermal radiation emerge from the fireball. The first
pulse, which lasts about a tenth of a second, consists of radiation in the
ultraviolet region. The second pulse which may last for several seconds,
carries about 99 percent of the total thermal radiation energy.
oIt is this radiation that is the main cause of skin burns and eye injuries
suffered by exposed individuals and causes combustible materials to
break into flames.
oThermal radiation damage depends very strongly on weather
conditions. Clouds or smoke in the air can considerably reduce effective
damage ranges versus clear air conditions.
http://www.youtube.com/watch?v=gz3F-
02FwZc&feature=related

26. Nuclear Radiation
1. Ionizing Radiation:
• High energy particles and rays are created.
• They have enough energy to “ionize” neutral atoms
• Some of this ionized radiation is absorbed by the air, but neutrons
and gamma and X-rays (extremely high energy forms of light) do
reach the ground, and create damage.
• Close to ground zero of both explosions, dosages were high enough
to be immediately lethal for persons not already killed by the blast or
fire.

27. Nuclear Radiation (cont.)
2. Residual Radiation, the hazards in the “Fallout”
• This radiation comes from the weapon debris, fission products, and, in
the case of a ground burst, radiated soil.
•There are over 300 different fission products that may result from a fission
reaction. This radiation hazard comes from radioactive fission fragments
with half-lives of seconds to a few months, and from soil and other
materials in the vicinity of the burst that were made radioactive.
•Their principal mode of decay is by the emission of beta particles and
gamma radiation. Most of the radiation hazard from nuclear bursts comes
from short-lived radionuclides external to the body; these are generally
confined to the locality downwind of the weapon burst point.

28. Particles found in Fallout
o Many fallout particles are especially hazardous biologically.
Some of the principal radioactive elements are as follows:
Strontium 90
Iodine 131
Tritium
Cesium 137
Plutonium