Nuclear Weapons 101 Nuclear Smuggling p. Nuclear Weapons 101 - PowerPoint PPT Presentation

Nuclear Weapons 101 Nuclear Smuggling – p.

Nuclear Weapons 101 Fissile materials ( 235 U , 233 U , 239 Pu ) are used to make weapons of devastating power. Nuclear Smuggling – p.

Nuclear Weapons 101 Fissile materials ( 235 U , 233 U , 239 Pu ) are used to make weapons of devastating power. As each nucleus fissions, it emits 2 or so neutrons plus lots of energy. 235 U + n → 236 U ∗ → 140 Xe + 94 Sr + 2n + ≈ 200 MeV Nuclear Smuggling – p.

Nuclear Weapons 101 Fissile materials ( 235 U , 233 U , 239 Pu ) are used to make weapons of devastating power. As each nucleus fissions, it emits 2 or so neutrons plus lots of energy. 235 U + n → 236 U ∗ → 140 Xe + 94 Sr + 2n + ≈ 200 MeV Increasing the density creates a ‘chain reaction’ where the emitted neutrons cause other fissions in a self-propagating process. Nuclear Smuggling – p.

Nuclear Weapons 101 Fissile materials ( 235 U , 233 U , 239 Pu ) are used to make weapons of devastating power. As each nucleus fissions, it emits 2 or so neutrons plus lots of energy. 235 U + n → 236 U ∗ → 140 Xe + 94 Sr + 2n + ≈ 200 MeV Increasing the density creates a ‘chain reaction’ where the emitted neutrons cause other fissions in a self-propagating process. Only about 8 kg of plutonium or 25 kg of highly-enriched uranium (HEU) is needed is needed to produce a weapon. Nuclear Smuggling – p.

Nuclear Weapons 101 Fissile materials ( 235 U , 233 U , 239 Pu ) are used to make weapons of devastating power. As each nucleus fissions, it emits 2 or so neutrons plus lots of energy. 235 U + n → 236 U ∗ → 140 Xe + 94 Sr + 2n + ≈ 200 MeV Increasing the density creates a ‘chain reaction’ where the emitted neutrons cause other fissions in a self-propagating process. Only about 8 kg of plutonium or 25 kg of highly-enriched uranium (HEU) is needed is needed to produce a weapon. A Chain Reaction 235 U nuclei neutrons Nuclear Smuggling – p.

Nuclear Weapons 101 Uranium, gun-type nuclear weapon - Tamper High explosive detonates pushing highly- Tamper Gun Tube ������ ������ enriched uranium at high speed into an- ������ ������ ������ ������ other piece of active material. ������ ������ ���� ���� ���� ���� ���� ���� ������ ������ ������ ������ Propellant ������ ������ Two-stage, thermonuclear weapon - Active Material (1) Spherically-shaped high explosive High Explosive detonates crushing the plutonium pri- Uranium Tamper Plutonium mary to a critical density. Fusion Fuel (2)The uranium and plutonium in the sec- Plutonium ondary burn and increase the tempera- Primary Secondary ture until fusion starts. The energy re- leased by the fusion reaction raises the temperature even higher and burns more of the fission fuel. Nuclear Smuggling – p.

Nuclear Weapons 101 - Effects Energy released in the form of light, heat and blast. Blast ≈ 40-50% of total energy. Thermal radiation ≈ 30-50% of total energy. Ionizing radiation ≈ 5% of total energy. Residual radiation ≈ 5-10% of total energy. Figure shows effect of a 15 kiloton bomb (about the size of the Hiroshima bomb) exploded over the . Nuclear Smuggling – p.

Nuclear Weapons 101 - Effects Energy released in the form of light, heat and blast. Blast ≈ 40-50% of total energy. Thermal radiation ≈ 30-50% of total energy. Ionizing radiation ≈ 5% of total energy. Residual radiation ≈ 5-10% of total energy. Figure shows effect of a 15 kiloton bomb (about the size of the Hiroshima bomb) exploded over the . 5−psi effect Nuclear Smuggling – p.

Nuclear Weapons 101 - Why Should You Care? Nuclear Smuggling (Scientific American, April, 2008) Existing and future radiation portal monitors cannot cost-effectively detect weapons-grade uranium hidden inside shipping containers. The U.S. should spend more resources rounding up nuclear smugglers, securing HEU, and blending down this material to low-enriched uranium, which cannot be fashioned into a bomb. Uranium in a haystack 20 feet - length of a typical shipping container (TEU). 297 million - Number of TEUs shipped worldwide in 2005. 42 million - TEUs entering U.S. ports that same year. 6,500 - TEUs arriving at the Port of New York and New Jersey on a light day; up to 13,000 on a busy day. Nuclear Smuggling – p.

Nuclear Weapons 101 - Why Should You Care? Nuclear Smuggling (Scientific American, April, 2008) Existing and future radiation portal monitors cannot cost-effectively detect weapons-grade uranium hidden inside shipping containers. The U.S. should spend more resources rounding up nuclear smugglers, securing HEU, and blending down this material to low-enriched uranium, which cannot be fashioned into a bomb. Uranium in a haystack 20 feet - length of a typical shipping container (TEU). 297 million - Number of TEUs shipped worldwide in 2005. 42 million - TEUs entering U.S. ports that same year. 6,500 - TEUs arriving at the Port of New York and New Jersey on a light day; up to 13,000 on a busy day. Uranium and plutonium detection is a key physics issue. Nuclear Smuggling – p.

Who is the Hottest? Consider two nuclear weapon ‘pits’, one made of 235 U with m U = 24 kg and the other made of 239 Pu with m P u = 8 kg . Their radioactive decay is described by the differential equation dN dt = − λN where N is the number of nuclei, t is time, and λ is the decay constant. This equation has the following solution. N = N 0 e − λt 1. What is the half-life of each isotope? Use the website here. 2. How is the half-life related to the decay constant? 3. Which one decays fastest? 4. What radiation actually comes out? Nuclear Smuggling – p.

Gamma Rays from Uranium and Plutonium Nuclear Smuggling – p.

The 232 U Decay Scheme 1.0 0.36 3.1 M 208 Tl β 61 M α 208 232 228 224 216 212 212 220 Pb U Th Ra Rn Po Pb Bi α α α α α β β α 212 Po 69 Y 1.9 Y 3.7 d 56 s 0.15 s 11 H µ 0.30 s 61 M 1.0 1.0 1.0 1.0 1.0 1.0 0.64 1.0 Nuclear Smuggling – p.

Stopping Power of Gamma-Rays in Uranium Source: http://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z92.html Nuclear Smuggling – p.

Penetrating Radiation Consider an HEU (highly-enriched uranium) pit with m U = 24 kg with a small amount, 1 ppt , of 232 U mixed uniformly throughout the volume. If one of the 232 U nuclei at the center of the pit goes through its decay chain (shown below) a 2.6-MeV gamma ray will eventually be emitted from the decay of the 208 Pb daughter/son/child nucleus. Will that gamma ray get out of the pit? The stopping power of 2.6-MeV gammas in uranium is µ/ρ = 0 . 046 g/cm 2 . The density of uranium is ρ = 19 . 05 g/cm 3 . 1.0 0.36 3.1 M 208 Tl β 61 M α 208 212 232 228 224 216 212 220 Pb U Th Ra Rn Po Pb Bi α α α α α β β α 212 Po 69 Y 1.9 Y 3.7 d 56 s 0.15 s 11 H µ 61 M 0.30 s 1.0 1.0 1.0 1.0 1.0 1.0 0.64 1.0 Nuclear Smuggling – p.

Nuclear Decay Monte Carlo Nuclear Smuggling – p. 1

Nuclear Decay Monte Carlo Nuclear Smuggling – p. 1

Nuclear Decay Monte Carlo Nuclear Smuggling – p. 1

Nuclear Decay Monte Carlo Nuclear Smuggling – p. 1

Nuclear Decay Monte Carlo Nuclear Smuggling – p. 1

Nuclear Decay Monte Carlo Nuclear Smuggling – p. 1

Nuclear Decay Monte Carlo Nuclear Smuggling – p. 1

Nuclear Decay Monte Carlo Nuclear Smuggling – p. 1

Acceptance-Rejection Method to Select Monte Carlo Events Blue � Thrown, Red � Accepted 2500 2000 1500 Counts 1000 500 0 0 2 4 6 8 10 x Nuclear Smuggling – p. 1

Isotropic Decay 120 1500 100 80 1000 Counts Counts 60 40 500 20 0 0 � 1.0 � 0.5 0.0 0.5 1.0 � 1.0 � 0.5 0.0 0.5 1.0 cos Θ cos Θ Nuclear Smuggling – p. 1

Monte Carlo for Self-Attenuation - 1 (* parameters *) nthrows = 1000; ndecays = 0; ngammas = 0; rstep = 0.01‘; mU = 25000.‘; rhoU = 19.05‘; muoverrhoU = 0.046‘; mu = muoverrhoU*rhoU; rU = ((3 mU)/(4 \[Pi] rhoU))ˆ(1/3); (* event loop. *) Do[x0 = RandomReal[{-rU, +rU}]; y0 = RandomReal[{-rU, +rU}]; z0 = RandomReal[{-rU, +rU}]; r0 = Sqrt[x0ˆ2 + y0ˆ2 + z0ˆ2]; rgamma = 0.‘; distance = 0.‘; Nuclear Smuggling – p. 2

Monte Carlo for Self-Attenuation - 2 (* see if we’re in the sphere, then do the decay. *) If[r0 < rU, ndecays = ndecays + 1; (* get a random direction. *) zcosine = RandomReal[{-1, 1}]; zsine = Sqrt[1 - zcosineˆ2]; phi = RandomReal[{0, 2 \[Pi]}]; (* step along the path of the gamma until we leave the sphere. *) While[distance < rU, rgamma = rgamma + rstep; xgamma = rgamma zsine Cos[phi] + x0; ygamma = rgamma zsine Sin[phi] + y0; zgamma = rgamma zcosine + z0; distance = Sqrt[xgammaˆ2 + ygammaˆ2 + zgammaˆ2]; ]; (* end of while loop to get photon out of the sphere. *) Pemission = \[ExponentialE]ˆ(-mu*rgamma); Ptest = RandomReal[{0, 1}]; If[Ptest < Pemission, ngammas = ngammas + 1] (* photon got out? *) ] (* end of If test on being inside sphere. *), {i, 1, nthrows}]; (* End of event loop. *) Nuclear Smuggling – p. 2

Uncertainty in Monte Carlo Calculations Effect of Increasing N throws 0.50 0.30 P meas P exp 0.20 0.15 0.10 10 4 10 5 10 100 1000 N throws Nuclear Smuggling – p. 2