Nuclear weapons: Difference between revisions

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* Oklo (Gabon) natural reactor - Natural materials:
* Oklo (Gabon) natural reactor - Natural materials:
** Uranium. Terrestrial uranium ore of this epoch tends toward a 99.284%/0.711%/0.0058% <sup>238</sup>/<sup>235</sup>/<sup>234</sup>U split.
** Uranium. Terrestrial uranium ore of this epoch tends toward a 99.284%/0.711%/0.0058% <sup>238</sup>/<sup>235</sup>/<sup>234</sup>U split.
** Thorium.  
** Thorium. For all purposes, entirely <sup>232</sup>Th (look at the half-lives).
* Neutron moderators - fueling - MOX - breeders - feedbacks - inherently safe designs
* Neutron moderators - fueling - MOX - breeders - feedbacks - inherently safe designs
* Recycling - metal oxide fuel - reprocessing - fusion-driven waste fission
* Recycling - metal oxide fuel - reprocessing - fusion-driven waste fission

Revision as of 10:02, 5 January 2010

An angel just got its wings!
Fission cross-sections vs neutron energies
The curve of binding energy
Be/Po initiator schematic
Disassembled B-61 (DOE)
B-61 physics package (DOE)
W-88 schematic
Teller-Ulam-style schematic
Subcritical HEU billet (Y-12). Delicious, but deadly! Do not stack.
Geometrically-subcritical plutonium ingot (LANL). Avoid crushing or melting.
A. Q. Khan teaching disadvantaged youth the 3-6-1 formation.
The greatest Photoshop of all time? Yes.

(12:08:06 PM) elizabeth warren: that'll get you on a list or three

Don't blame me, man. I didn't do it.

Researching Nuclear Weapons

Your modern criticality fetishist has a rough time of things. Since 2001-09-11, great stocks of (unclassified) information have been purged from government sites. Various fellow travelers (see the See Also section) maintain partial archives. Relevant conference proceedings (compressed matter physics, etc) get snapped up on used book sites quickly. My recommendation is a thorough grounding in nuclear engineering and the relevant mathematical methods (which you'll come across in the NucE books), at which point you'll be well-equipped to daydream about your own neutron initiator ideas and radical implosion symmetries. The boys at LANL and similar places haven't been able to do criticality experiments since the CTBT's passage, so everyone's on a level (simulation-only) playing field. Today's supercomputer is tomorrow's slide rule; an HP48GX will certainly get you through spherically symmetric detonations, and a few video cards are a fine platform for running your own hydrocodes.

When the going gets tough, just think to yourself: "If South Africa can do something, so can I."

(Unclassified) Books

The following textbooks range from introductory to advanced material, and all require some basic physics and associated mathematical sophistication. For obvious reasons, textbooks on actual weapon design, testing, engineering and maintenance are difficult to come across. There's a wide variety of excellent books on political theory of nuclear weapons, which I'm unqualified to rate (update: Kahn's On Thermonuclear War is absolutely required reading). Consult your local university's political science department for more information.

There's pretty much an endless line of popular-audience books about nuclear weapons, especially their early design and the characters behind them (I've got about a dozen biographies of J. Robert Oppenheimer alone). These require no particular scientific or mathematic background. Of them, the best include:

Basic Physics

  • Energy-mass equivalence - electron-volts - curve of binding energy - energy scales (chemical vs nuclear vs annihilative)
  • Pressure - temperature - ideal gases - brownian motion - radiative ablation - ionization - plasmas
  • The atom - the nucleus - periodic table - size scales (electron vs proton vs neutron vs alpha particle vs large nucleus vs atomic radius vs molecular size)
  • Shell models of the atom and nucleus - Coulomb potentials - Yukawa potentials
  • Neutron absorption and scattering - fission probability - pre- and post-scission - Doppler broadening
    • Neutron effect is a function of (a) incident neutron energy (b) many-body nucleon-nucleon forces and (c) luck
    • Resonance with nucleus activation energies leads to preferring absorption over scattering
    • An absorption might deform the nucleus sufficiently that a two-body Coulomb system overpowers the SNF
      • This is the probability of fissioning, as opposed to merely emitting a γ.
    • Nucleon-nucleon forces are typically described in per-{isotope X fine structure} terms, ignoring hyperfine details
    • Result: for a given isotope, there's a function taking {excitation level X neutron energy} to {first-order fission probability}
  • Electrodynamics - strong nuclear force - weak nuclear force - quantum tunneling
    • Thermal neutrons can't classically cross Coulomb repulsions, but tunneling permits π-induced fission (π = pion, aka any of 3 π-mesons)
  • Stable and unstable isotopes - half-life / expected time to decay - odd-even mass differences
  • Radiations (alpha, beta, gamma) - transmutations (there are many!)
  • Liquid drop model - superdeformation - hyperdeformation - compound nucleus
  • Nilsson model - (two-humped) fission barrier - fission isomer
  • Madland-Nix (Los Alamos) model - Prompt neutron multiplicity distribution P(ν) - prompt fission neutron energy spectrum - TKE
  • Number of neutrons per fission ("nu-bar", ν) is a function of the fission fragments
    • ...but can be averaged over inputs. In general, plutonium generates more neutrons than uranium, though 233U's not bad.

Reactor Physics/Fuel Cycle

  • Oklo (Gabon) natural reactor - Natural materials:
    • Uranium. Terrestrial uranium ore of this epoch tends toward a 99.284%/0.711%/0.0058% 238/235/234U split.
    • Thorium. For all purposes, entirely 232Th (look at the half-lives).
  • Neutron moderators - fueling - MOX - breeders - feedbacks - inherently safe designs
  • Recycling - metal oxide fuel - reprocessing - fusion-driven waste fission
  • Four-factor formula - criticality control - fuel burnup - fission products - fission poisons - 135Xe - 149Sm
  • Intertial confinement fusion - hydromagnetic confinement fusion - cold fusion - bubble fusion
  • Etienne Parent (2003). "Nuclear Fuel Cycles for Mid-Century Deployment".
  • W. G. Sutcliffe and T.J. Trapp. eds. "Extraction and Utility of Reactor-Grade Plutonium for Weapons", Lawrence Livermore National Laboratory. UCRL-LR-I 15542, 1994 (S/RD).
  • US DOE "Nonproliferation and Arms Control Assessment of Weapons-Usable Fissile Material Storage and Excess Plutonium Disposition Alternatives", 1997.

Fission Weapons

  • Criticality - subcritical - supercritical - prompt criticality - critical insertion time - insertion (gun-type) method - spontaneous fission
  • Implosion method - levitated pits - multi-point implosion
  • 232Th - 233U - 235U - 238U - 249Pu - 240Pu - minor actinides - transuranics - fissile, fissionable, fertile
  • Fission chain reactions release moderately energetic "fission energy" neutrons. They affect materials differently:
    • 233U is fissile, and can be bred from 232Th. Without subsequent physical enrichment, however, it'll be contaminated to some degree by:
      • 232U ((233U,n) -> 232U + 2n, (232Pa,β−) -> 232U), a retarded younger brother notable for meager lifespan and γ-rich decay chain (though note that Georgia Tech researchers have fashioned 232UBe13 (232uranium beryllide) neutron initiators, so it has that).
    • 235U is fissile, but requires enrichment infrastructure (no plausible breeding path). Given sufficient mass of highly-enriched uranium, it's a real dream to work with, and criticality is about as difficult as lighting a Sparkler. With a 700+ million year half-life, it's not going anywhere, either. Modern cores employ 239Pu for three reasons: (a) smaller critical mass (b) beancounting and (c) style.
    • 238U is not fissile, but can be bred into 239Pu. Furthermore, it can be fissioned by the 14.7 MeV neutron resulting from D-T fusion, and there's an absolute ton of it.
    • 239Pu is fissile, and can be chemically extracted from activated actinides (primarily 238U breeding). Without subsequent physical enrichment, however, it'll be contaminated to some degree by:
      • 240Pu becomes a 241Pu rather than compound {241Pu} (fission precursor), meaning two neutrons (and associated time) to yield a fission event. Predetonation hazard due to spontaneous fissions. Burnable in a recycling reactor, but undesirable for weapon material.
      • 241Pu is highly fissile. Undesirable in weapons due to short half-life (α to useless 241Am).
      • 242Pu is plutonium gone wrong every possible way. The only redeeming grace is scarcity. Do not purchase 242Pu, or accept it as a gift.
    • Fission energy neutrons' effects generally follow those of thermal neutrons (probability of fission is generally reduced, but comparable).
  • Enrichment levels - enrichment methods - degradation - downblending
    • Observable properties of processing tech (plutonium's more intensely thermal)
    • Robustness of methodologies/materials/geometries (eg easiest to make a big, wasteful, HEU gun bomb)
    • Safety/reliability of materials/assemblies (Decay of Pu, tritium, polonium, neutron moderation by seawater, fire hazards)
  • Prompt neutrons - delayed neutrons - fast neutrons - slow neutrons - neutron reflectors
  • Neutron sources / initator design - Monroe Effect - Beryllium/Polonium urchin - pulsed neutron tubes - shock initators - UD3/TiD2
  • High explosives - Taylor-Rayleigh instabilities - assembly geometry - neutron multiplications - Rankine-Hugeniot conditions
  • Hydrides (see the Ruth section from Upshot-Knothole)
  • "The B61-based Robust Nuclear Earth Penetrator: Clever retrofit or headway towards fourth-generation nuclear weapons?". Gsponer 2005-11-19.

Fusion Weapons and Boosting

  • Hollow pit - DT infusion - dial-a-yield / FUFO ("full-fusing option") - lithium-deuteride - Li6 - Li7
  • Layer-cake model - sparkplugs - Teller-Ulam design - stage chaining
  • Core boosting - enhanced radiation weapons (neutron bombs) - fissionable jacketing
  • Pure fusion weapons, clean weapons (non-fissionable jacket)

Delivery Systems, Effects, and Defense

  • Blast theory - shock front - double flash - optimum delivery altitudes
  • Miniaturization - MIRV's - penetration aids - neutron fluxes
  • Russian Strategic Nuclear Forces (2004, MIT Press) is awesome

Missile Defense


  • Project Plowshare - Project Orion - Atoms for Peace - Project Rover
  • Testing - test detection - treaties
  • Criticality accidents - Weapon accidents

See Also