1. Nuclear Chemistry at Work
The First Atomic Bombs
Jennifer Christensen
Kristoffer Gerik
Bryan Wagner
November 25, 2008

2. Agenda Introduction Nuclear Chemistry Discoveries Manhattan Project
Background
Fission
239Pu
Manhattan Project
Nazi Regime Attempts
Atomic Bomb Mechanisms
Gun Type
Implosion Type
Conclusion

3. Introduction Political Front: Scientific Front: World War II
Largest world conflict in history
Race for nuclear weapons
United States vs. Nazi Regime
Military superiority
Political consequences
Scientific Front:
Nuclear chemistry
Beginnings of understanding
Application of theories
Nuclear reactors
Nuclear weapons

4. Nuclear Chemistry Discoveries: Background
1932:
James Chadwick discovers neutrons
Bombardment of beryllium with alpha particles from a polonium source
Joliot-Curies discover artificial radioactivity
1934:
Enrico Fermi uses high energy neutron beam to bombard elements
Bombardment of uranium hypothesized to produce transuranic elements

5. Nuclear Chemistry Discoveries: Fission:
Ida Noddack questions Fermi’s theory
Otto Hahn & Fritz Strassmann recreate Fermi’s experiment
Cannot isolate ‘radium’ isotope from barium carrier
Lise Meitner & Otto Frisch confirm discovery of fission
Other scientists analyzed uranium properties
Discovered 235U fissioned with thermalized neutrons
Must isolate 235U isotope for nuclear weapons

6. Nuclear Chemistry Discoveries: 239Pu:
University of Berkley scientists & researchers discover transuranic element, plutonium
Bombardment of uranium with neutrons
239Pu
Mass production potential
238U reactant
Separation techniques
High fission cross section

7. Nuclear Chemistry Discoveries: Pile Reactor
1942:
Fermi lead team to build first nuclear reactor
Fuel: Natural uranium
235U fission produces neutrons to ensure chain reaction of 238U
Successful production of 239Pu
President Franklin D. Roosevelt pledged government support
Manhattan Project

8. Manhattan Project Started in August of 1942 Robert Oppenheimer
Manhattan, New York City
Colonel Leslie Richard Groves
Robert Oppenheimer
Main physicist

9. Manhattan Project continued…
Three main sites:
Oak Ridge, Tennessee
235U production
Hanford, Washington
239Pu production
Los Alamos, New Mexico
Assembly site & testing

10. Oakridge: 235U Enrichment
Main purpose:
Upgrade natural uranium into ~90% 235U product
Enrichment techniques:
Gaseous diffusion
Electromagnetic separation
Liquid thermal diffusion

11. Hanford: 239Pu Production
Produced in reactor, X-10
Separated from fission products
One part of fissionable byproducts to 107 parts plutonium
Bismuth phosphate process
Selective, co-precipitation of plutonium from acid solution
Oxidation-reduction reactions utilized for greater purification

12. Testing 100-ton test “The Gadget” Exploded on July 16, 1945
Plutonium (Implosion type)
Exploded on July 16, 1945
First and only full test before the use of “Little Boy” and “Fat Man” on Japan

13. German Side Conflicting data Major scientists: Werner Heisenberg
Electric power for U-boats
Kurt Diebner
Nuclear reactor project in Stadtilm, Leipzig

14. German Reactors
Germans were using heavy water as a moderator for their reactors
Their main manufacturing plant in Norway was sabotaged, so they never had enough heavy water to support the reactor
They also never had enough 235U to sustain a reaction

15. Atomic Bomb Mechanisms
Gun Type
Implosion Type
Fat Man
Little Boy

16. Gun Type – Little Boy First mechanism designed Not feasible for 239Pu
Excess neutron production from 240Pu side reaction
Two subcritical, fissile pieces
Projectile
Target
Supercritical mass after collision
High confidence level with 235U
No test needed

17. Gun Type – Little Boy 6.5 inch diameter barrel 6 feet long
High alloy steel case (5000 lb)
Fused by four radar units
Measured bomb height above ground
Set to detonate at 1850ft above ground

18. Gun Type

19. Implosion Type Subcritical amount of enriched 239Pu
Neutron initiator to ensure start of chain reaction
Detonation device same as gun type
Conventional explosives encased in steel sphere to cause severe inward compression on fissile material
Subcritical material compressed to supercritical
Neutron initiator released

20. Implosion Type – Explosives
1/32 inch tolerances
Prevent irregularities in compressive shock wave
Constructed of hexagonal and pentagonal blocks –much like a soccer ball

21. Implosion Type

22. Little Boy Contained 135 lbs of 90% 235U enriched uranium
Dropped on Hiroshima on August 6, 1945
Created 16,000 ton TNT equivalent blast
Killed approximately 200,000 people
Fissioned 2 lbs of enriched uranium

23. Fat Man Contained 12 pounds of enriched 239Pu
Dropped on Nagasaki on August 9, 1945
Created explosion equivalent to 22,000 tons of TNT
Killed approximately 70,000 people immediately and eventually a total of 140,000
Fissioned approximately 2 lbs

24. Conclusion Caused massive devastation in Japan
Allied forces victorious
Changed weaponry for warfare
Hydrogen bomb
Requires responsible development in future
Nuclear non-proliferation
Updating weapon supplies

25. References
Settle, Frank. "Nuclear Chemistry." General Chemistry Case Studies Kennesaw State University. 20 Nov 2008 <
"Irène Curie, Frederic Joliot and Artificial Radioactivity." Nov 2008 <
"Why Uranium and Plutonium?" atomicarchive.com AJ Software & Multimedia. 20 Nov 2008 <
Pike, John. "Plutonium Production." Federation of American Scientists Nov 2008 <
"Production Reactor (Pile) Design." Manhattan Project: An Interactive History. Department of Energy: Office of History & Heritage Resources. 20 Nov 2008 <
“Manhattan Project.” Nuclear Age Peace Foundation Nov 2008 <
Sublette, C. “The Manhattan Project.” Nov 2008 <
Bethe, H. A. “The German Uranium Project.” Physics Today Nov 2008 <
daryl “World War II: Nazi Nuclear Weapons.” 18 Nov <
Sublette, C. “Nuclear Weapons Frequently Asked Questions.” Version 2.18: Nov <
Settle, F. “Nuclear Chemistry First Atomic Bombs.” 18 Nov <

26. Questions

27. Backup Slides

28. Gaseous Diffusion
Saturated uranium hexafluoride (UF6) gas enters chamber
Vacuum applied on outer side of porous material
Nickel or aluminum oxide
Gas flows from high to low pressure
235U passes through porous material at greater rate than 238U
Lower molecular weight

29. Electromagnetic Separation
Operated on basis of mass spectrometer
235U & 238U ions will have different paths passing through uniform magnetic field
Same charge & kinetic energy
Different mass & velocity

30. Liquid Thermal Diffusion
Utilizes temperature difference create thermal diffusion
Convection current occurs
Heavier 238U accumulates towards bottom
Lighter 235U accumulates towards top