![1.E+07
1.E+06
PYRO Product
1.E+05
NOT IN PYRO
1.E+04 Pu-Odd
Pu-Even
1.E+03
Ci/MTHM
Np-237
Cs-137 + Sr-90
1.E+02
Fission Products Excluding
1.E+01 Tc-99 + I-129
TOTAL
1.E+00 TOTAL LOW
1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 Am
1.E-01
1.E-02
1.E-03
Years After Discharge
: The radioactivity profile of SNF throughout time calculated by the author with ORNL’s Scale6 code system [SCALE6] for a Westinghouse 50 MWd/kg
HM and 4.5% enriched PWR fuel assembly. The dotted line indicates the time when the SNF cooled in reactor cooling ponds are moved to interim
storages such as dry casks. The actinides are generally represented by the thicker lines and thinner lines correspond to the actinides. Notice that
after the fission products (especially Cs-137 and Sr-90) decay the actinides, and Tc-99 and I-129 will start to dominate the profile. Notice also that
the pyroprocessing products will after several decades be at the level of hundreds of Ci and will be below the level that the IAEA considers self-
protective [Kang and von Hippel] since the fission products that would produce a self-protective dose are removed in pyroprocessing (see NOT IN
PYRO label).](https://image.slidesharecdn.com/vsf-module2-aug11-120828192237-phpapp02/85/Vsf-module-2-aug-11-126-320.jpg)
Vsf module 2 - aug 11
- 1. MODULE 2 ,CHAPTER 1
- 2. Dose Radioactivity Alpha Decay Isotopes
- 8. But at theend of this module you will know a lot of fundamentals!
- 9.
- 10. All you needto know is.. 1. Nuclear Physics is about probabilities (interaction). 2. Particle interactions can be understood in terms of simple billiard balls. 3. You have to think like a neutron
- 11. MODULE 2 ,CHAPTER 2
- 13. Dose Radioactivity Alpha Decay Isotopes
- 15. A BLAST FROM THEPAST n P P n T = Tritium D = Deuterium D,T n He-3 Sr-90 I-131 Cs-137 Actinides U-235, U-238, Pu-239, Pu-240
- 16. 92 238.029 Chemical Properties U
- 17. Those were thechemical properties
- 18. Those were thechemical properties
- 19.
- 20. 2 Types ofDecay, α and SF
- 21. Final Method ofDecay + + α + + + + + + β+, β- + ++ +++++ + + + +++ + + + + ++ +++++++ + ++ + + + + ++++ + + +++++++++ + + + ++ + + + + ++ + + + + ++++ ++ + + + ++++ + + + + ++ + + ++ + + ++ + + + + + + +
- 22. The probability =1/(7e-11)=1.4e12
- 23. Same probability aswinning the lottery 100 times in a row!
- 24. Final Method ofDecay n n + + + ++ ++ ++ ++ + ++ ++ + + + ++ + + ++ + + ++ ++ + + +++++++ + + +++ ++ ++ + ++ + + + +++ +++ +++ + + ++ + ++ + + + + ++ + + + ++ + + ++ + ++ + + + + ++++ + ++ + n SPONTANEOUS FISSION A VERY RARE FORM OF DECAY FOR URANIUM-235
- 25. FINAL TYPE OFDECAY FISSION ALL FISSILE MATERIALS UNDERGO FISSION “Fission” Used with Permission: Benoît Kloeckner
- 26. Plutonium Uranium Pu-239 U-235 0.711% Pu-240 U-238 99.289% Pu-238 Actinides Minor Actinides = All except U and Pu Transuranium = TRU
- 27. FISSION PROCESS Fissile Material Fission Fission Product Product Spontaneous Fission Induced Fission
- 29. MODULE 2 ,CHAPTER 2 • Actinides fission and some isotopes can sustain a chain reaction • 2 types of fission – spontaneous and induced fission • Can look up isotope characteristics • A sustained chain reaction can be used for peaceful and non-peaceful purposes
- 30. MODULE 2 ,CHAPTER 3
- 32. Uncontrolled Nuclear ChainReaction 10-8 s Fission =10 ns Number = Shake Gen # neutrons 1 20=1 2 31=3 3 32=3x3=9 4 33=3x3x3=27 5 24=16 6 25=32 64 263=9x1018 80 279=6x1023 81 280=1.2x1024 In U-235 Metal / Pu-239 Metal 82 281=2.4x1024 This happens very fast!
- 33. Energy/Fission 0.94 kg Of U-235 = 200 MeV = 3.2e-11 J 82 generations Knee Bend = 100 J = 2^81 = 2.4x1024 fissions < 1x10-6 s = 1 millionth of a second UNCONTROLLED Total Energy = (2.4e24 fis)(3.2x10-11 J/fis) CHAIN REACTION = 7.68e13 J = 18.3,000 t of TNT! = 18.3 kT TNT = 1.2 X Little Boy Bomb!
- 34. Fissile Materials: Cansustain an explosive fission chain reaction – notably plutonium of almost any isotopic composition and highly-enriched uranium (Def’n, IPFM). Neutrons U-235 Density HIGH Mouse Trap Unclamping FAST Simulates fission U-235 35
- 35. Uncontrolled Reaction http://www.youtube.com/watch?v=Pmy5fivI_4U 36
- 36. Types of Neutron Interactions Gamma (γ) INELASTIC SCATT INELASTIC SCATT (n,3n) (n,2n) neutrons neutrons FISSION ELASTIC ESCAPE SCATTERING (NO INTERACTION) 37
- 37. Critical Mass=Sustain Chain Reaction GUN TYPE WEAPON SELF SUSTAINING = CRITICAL MASS ESCAPE ABSORBED FISSIONS STOPS AFTER SECOND FISSIONS SELF WITH REFLECTOR GENERATION SUSTAINING (CONFINING) INCREASING FISSILE MATERIAL MASS Prevent neutrons from escaping is the goal! 38 Figure: Courtesy Wikipedia
- 38. Crowded Room Analogy:2 Ways to Sustain a Chain REACHING CM BY Reaction INCREASING SIZE OF ROOM INCREASING DENSITY Fissile Material Neutron IMPLOSION WEAPON GOAL: INCREASE Bring nuclei PROBABILITY OF closer together GUN-TYPE WEAPON FISSION TO OCCUR
- 39. Reference: Alex Glaser(IPFM)
- 40. Theodore Taylor (1925-2004) 1 Significant Quantity =25 kg U-235 HEU HEU= >20% U-235 See comment: http://goo.gl/b04i0 “Amounts of U-235 as small as 1 kg are significant quantities. He did not state that anyone can build a bomb with 1 kg of U-235, but did suggest that this is roughly the amount that good designer would need” Consistent with 82 gen’ns NRC 2004 Testimony, “Nuclear Arms Race”, Craig & Jungerman
- 41. Because of thehigh density of uranium metal a SQ will occupy a small volume!
- 42. 1) Prevent neutronsfrom escaping 2) Increase the probability of fissions 3) Prevent neutron absorption GUN TYPE BOMB Two pieces of subcritical HEU brought together for an instant! RECALL: Crowded room analogy make the room bigger so the probability of fission increases before neutrons escape!
- 43. With modern weapons-gradeuranium, the background neutron rate is so low that terrorists, if they had such material, would have a good chance of setting off a high- yield explosion simply by dropping one half of the material onto the other half.Most people seem unaware that if separate HEU is at hand it's a trivial job to set off a nuclear explosion . . . even a high school kid could make a bomb in short order. Luis Alvarez, Adventures of a Physicist (Basic Books, 1987), p. 125.
- 44. • Not verysafe – 2 pieces that are subcritical but if inadvertently combined could cause an explosion. • Must keep away from moderators • Not very efficient – not very high yield • Weapon of choice for non-state actors (terrorists) • Barrier is getting the HEU in the first place!
- 45. • Uranium ismined but is only 0.711% U-235 and 99.289% U-238. • Need to remove the U-238 to increase the proportion of U-235 to U-238. • Start with 7 U-235 and 993 U-238 marbles
- 46. • Start with 7 U-235 and 993 U-238 marbles • To get to 5% HEU it means that 7/140=0.05 • I have to go from 993 to 133! • I need to pull out 860 U-238 marbles! • A large part of the work is done to get from 0.711% to 5% HEU!
- 47. • 7 U-235/133 U-238 = 5% • How do I increase to 90%? • 90% ~ 7 U-235/ (7 U-235 + 1 U-238) • I go from 133 to 1! Need to subtract 132 more which is a big improvement from 853! • BOTTOM LINE: Enriching from 0.711% to 5% is a large part of the work.
- 48. It has todo with “pre-detonation” or triggering the bomb to explode before the optimum conditions have been Established. Nuclide SF /kg per Neutrons/fiss CM (kg) SF/CM 100 μsec ion per 100 μsec U-235 5.627e-7 2.637 45 0.0000 25 U-238 6.776e-4 2.1 Pu-239 6.916e-4 3.172 17 0.0011 Pu-240 48.33 2.257 822 99 % Pu-239 + 1% Pu-240 8 BOTTOM LINE: Gun Type Will Not Work for Plutonium!
- 50. 1) Prevent neutronsfrom escaping 2) Increase probability of fissions 3) Prevent neutron absorption IMPLOSION TYPE BOMB Done with explosive Lenses causing implosion RECALL: Crowded room analogy Increase the density of nuclei so the probability of fission increases before neutrons escape!
- 51. For Plutonium need to use implosion technique! Increase Density! 2 3 6 HEU or Pu is 4 1 7 5 compressed to Critical Mass (bring atoms Closer together)
- 52. Think about Compressing a Waterballoon Between your fingers! Not easy!
- 53. We can getHEU by enriching natural U what about Pu?
- 54. Pu Production inReactors U-238 For Gun Type Bomb U-235 For Implosion n + U-238 U-239 Np-239 Pu-239 Type Bomb 24 min 2.4 days Fissile Material Fertile Material (can sustain chain rxn) (can’t sustain chain rxn but can become fertile) U-238 U-235 Pu-239 is Produced
- 55. • Fissionable =Nuclide undergoes fission after neutron capture • Fissile = Nuclide can sustain a chain reaction (U-235, Pu-239) • Fertile = Nuclide can become fissile after irradiation in a reactor (ex: U- 238)
- 56. Trick: Pu-239 Absorptionof neutron Pu-239 94 p 145 n + = Pu-240 94 p 146 n HIGH To produce WG Pu SF RATE need to remove Pu fuel (not good for (generally U fuel is 1% Pu) NW’s) WG = <7% Pu-240 so that SF rate is relatively low!
- 57. Plutonium Production inNuclear Reactors Plutonium is produced in Nuclear Reactors whereas uranium is found in nature Neutron activation on Pu-239 produces Pu-240 (bad for NW) % Pu-239/Pu-240
- 58. A Policy AnalystsRule of Thumb 1 megawatt-day of operation produces ~ 0.9 gram of plutonium in any reactor using 20-percent or lower enriched uranium Power = 2650 MW Mass Pu-239 = 0.9*2650MW *45 days /1000 g/kg = 106 kg not quite 80 kg
- 59. EXAMPLE • A companyis making a proposal to sell one turn-key LWR’s (2700 MW) to Burma. You are the one responsible for deciding whether a reactor project should proceed from the point of view of proliferation of the nuclear technology to that country. The official in a condescending way claimed that this particular reactor will in one month not produce any Plutonium so that there are absolutely “no risks or worries that should concern you”. What would you say (in a polite way) in response to the official about how much Pu is produced in this reactor/month in terms of SQ? • 1kg = 1000 g, And the rule of thumb is: 1 megawatt-day of operation produces ~ 1 gram of plutonium in any reactor using 20-percent or lower enriched uranium 60
- 60. Answer: • Since therule of thumb is 1 g produced per MW days then in 30 days the reactor produces 2700 MW * 30 days =80,000 MW days • Applying the rule of thumb = 80,000 MW days = 80,000* MW days * (1 g Pu/MW days) =80,000 g Pu and 1 kg = 1000 g =80,000 g Pu * (1 kg / 1000 g) • =80 kg Pu • In terms of SQ this is 10 SQ which is enough roughly for 10 bombs! “Excuse me but your assertion that a 2700 MW reactor will produce only 100 g Pu/month is simply not correct. In fact, if you go through the calculation which I just did while you were talking, you will find that the reactor you propose produces 10 IAEA Significant Quantities per month!” (And the whole room will be silent because they will be impressed at your knowledge) 61
- 61. QUESTION: In thesatellite pictures below why is the lack of steam significant?
- 62. “I remembered theline from the Hindu scripture, the Bhagavad-Gita: Vishnu is trying to persuade the Prince that he should do his duty and to impress him he takes on his multi-armed form and says, “Now I am become death, the destroyer of worlds” I suppose we all thought that, one way or another” R. Oppenheimer, pg 676, R. Rhoades, “The Making of the Atomic Bomb” On the Trinity Shot : first test of an atomic weapon.
- 63. MODULE 2 ,CHAPTER 3 Material Advantage Disadvantag e U (HEU) Testing not Difficult to Necessary get HEU Pu Easy to Testing Produce Necessary
- 64. MODULE 2 ,CHAPTER 4
- 66. Power Reactors: NW: HEU,Pu LEU Large Amount of Energy Large Amount of Energy Slow, Controlled Release of Energy FAST , Uncontrolled Release of Energy
- 68. Energy is expended Slowlyover the period of many months.
- 69. Now the Details! HowDo You Get A Self-Sustaining Reaction : An Analogy
- 70. You have tothink like a neutron
- 71. Nuclide U-235 U-238 Neutron Pu-239 Pu-240
- 72. • Neutron movingslow will easily fission U-235 but not U-238 • Neutron moving fast will easily fission U-238 but also U-235 • Neutron are produced through fission at high energy • It is almost as if the neutron at low energy is completely different from a neutron travelling at high energies
- 73. • Like peoplemeeting.. • When neutron encounters an isotope, it must make a decision how it interacts when it meets 1) Fission 2) Bounce off 3) Be absorbed (give off a gamma) 4) Not interact at all Probabilities described by Size of the target (cross-section)
- 74. U-238 Neutron (Very small target neutron will miss) U-235 Neutron (Large target neutron will hit)
- 75. • Neutrons canalso do other things besides fission (bounce off, be absorbed, not interact) • It all has to do with the size of the target which changes for different neutron energies • You have to think like a neutron
- 76. • Graph of‘Energy’ or speed of the Neutron vs ‘Cross-section’ or probability of interaction or size of the target CROSS-SECTION PROBABILITY NEUTRON SPEED OR ENERGY
- 77. Target size ofU-235 1000X bigger than at 1 MeV Energy Region of neutrons produced by FISSION Size of the target For U-238 Energy Region of neutrons slowed down Thermal Neutrons
- 79. Gamma Ray MeV Incoming Neutron 2-3 Neutrons Fission free to fission U-235 Slow Neutron (Thermal) MeV Incoming Neutron Gamma U-238 Ray Tend to absorb No Fission Not fission! Radiative Capture
- 80. Self-Sustaining Chain Reaction 90%U-238, 10% U-235: NOT SELF SUSTAINING Gamma Particle Absorbed! Not enough U-235 Around to continue process Fission! Absorbed! Gamma Particle
- 81. INCREASE U-235 (Red!) Will Fission! 50% U-238, 50% U-235 : PROBABLY SELF SUSTAINING Will Fission! Fission! Enough U-235 around to continue process Fission! Will Absorb!
- 82. Natural Uranium =0.711 % U-235! Need to get to 50% Need to enrich $
- 83. Neutrons from fission(MeV) Appear to require 50% U-235 and 50% U-238 – this is expensive! THE TRICK: Slow the neutrons down! Moderate them!
- 84. Essentially turn Into From a Neutron point of view (Neutron is travelling slowly and feels the attraction of the neutron for a longer time)
- 86. • Possible tohave self-sustaining chain reaction by using a moderator.
- 87. Need less U-235because they appear bigger for Slow/thermal neutrons Instead of 50% U-235 with trick can use 3-5% U-235
- 88. U-235 atoms havea higher fission interaction probability than U-238 capture Need only 3-5% to Start a sustained Chain Reaction
- 89. Go from here to here In a few bounces Moderation TRICK! FISSION ENERGIES
- 90. FUEL (assembly/rods) 3% 3% 3% LEU LEU LEU UOxide UOxide UOxide Nuclear Reactor has Fissile Material (LEU) just below a Critical Mass (Controlled Chain Reaction) Fission Energy =Heat Produced! Moderator: Slows down neutrons This is the TRICK! so fission with U-235 can occur
- 91. Moderator Characteristic Water (H2O) Good moderator but can also capture neutrons. Can use 3-5% U-235. Most reactors around the world use H2O as moderator Heavy Water (D2O) Excellent moderator. Low probability of neutron capture. Can start with natural (0.7%) uranium. Carbon (Graphite) Not a great moderator (mass A is high) but very small capture probability. Can use natural (0.7%) uranium as long as very pure and no neutrons present.
- 92.
- 95. • Isotopes thatabsorb neutrons. Why would it be useful? Gamma Incoming Neutron Gd-155 Ray No Fission Looks HUGE for incoming Radiative Capture neutron!
- 96. Contain Gd rather than UOx Dropped in by gravity
- 97. Pressurized Water PowerReactor (PWR) So far we have concentrated on the core 98
- 98. Pressurized Water PowerReactor OR NOT! 99
- 99. What is this? Isit dangerous?
- 100. Defense-In-Depth Approach
- 101. Boiling Water PowerReactor
- 102. Partial Batch Refueling A = Removed after 1 cycle B A C B= Removed after 2 cycles C= Removed after 3 cycles Neutron Flux Less at Outside LIKE A BARBECUE!
- 105. Look it upat Wolfram Alpha: Type the iso
- 107. MODULE 2 ,CHAPTER 4 • Basics of how a nuclear reactor works at the core level • The trick was Think like a neutron • Moderators and the moderation trick • Neutron poisons and control rods • Nuclear fuel • Fission products
- 108. MODULE 2 ,CHAPTER 5
- 110.
- 111. •Open pit mining •UndergroundMining •In Situ Leaching •Sea Water Recovery
- 112. Excavated uranium ore milled(crushed) processed into yellow cake
- 113. Excavated uranium ore milled(crushed) processed into yellow cake
- 115. Removal of 500 tYellowcake from Iraq (2008) Natural U contains 99% U-238 which is not very radioactive You could not make a dirty bomb out of natural uranium
- 116. HF+fluorine gas mixedwith yellowcake produces UF6 crystals (at room temperature it is a solid) At this point: Proliferation Risk
- 117. 3-5% for LWR 85-95% for Weapon Utilizing 1% mass difference between isotopes to separate them Remove U-238 until desired ratio U-235/U-238 is reached (93% is WG)
- 118. Gas is“spun” in a supersonic centrifuge, forcing lighter U-235 to the top, where it can be “scooped off” This demands high strength materials and precision engineering. To reach speeds of 100,000 rpm, centrifuges need: Light, strong rotors Well-balanced rotors High-speed bearings (usually magnetic) to reduce friction
- 119. Separation < 1kg SWU/yr Separation much better 300kg SWU/yr
- 123. Pellets are placedin fuel rods rods are combined into fuel assemblies
- 124. Must be securedto prevent non-state actors from getting the material
- 125.
- 126. 1.E+07 1.E+06 PYRO Product 1.E+05 NOT IN PYRO 1.E+04 Pu-Odd Pu-Even 1.E+03 Ci/MTHM Np-237 Cs-137 + Sr-90 1.E+02 Fission Products Excluding 1.E+01 Tc-99 + I-129 TOTAL 1.E+00 TOTAL LOW 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 Am 1.E-01 1.E-02 1.E-03 Years After Discharge : The radioactivity profile of SNF throughout time calculated by the author with ORNL’s Scale6 code system [SCALE6] for a Westinghouse 50 MWd/kg HM and 4.5% enriched PWR fuel assembly. The dotted line indicates the time when the SNF cooled in reactor cooling ponds are moved to interim storages such as dry casks. The actinides are generally represented by the thicker lines and thinner lines correspond to the actinides. Notice that after the fission products (especially Cs-137 and Sr-90) decay the actinides, and Tc-99 and I-129 will start to dominate the profile. Notice also that the pyroprocessing products will after several decades be at the level of hundreds of Ci and will be below the level that the IAEA considers self- protective [Kang and von Hippel] since the fission products that would produce a self-protective dose are removed in pyroprocessing (see NOT IN PYRO label).
- 127. Spent Fuel Problem •Spent fuel remain radioactive for many years • Very hot needs to be cooled down • Cooled in a spent fuel pond for 3-5 yrs • Further cooling in dry casks • Future: emplaced in geological repository or other measures • So far no solution while we have 250k MT waste
- 129. Interim Storage Passive AirCooling: Carries the heat not the radioactivity!
- 130. • Closed fuelcycle – recycle plutonium produced in other fuel • “Russian policy is to close the fuel cycle as far as possible and utilize recycled uranium, and eventually also to use plutonium in MOX fuel. However, its achievements in doing this have been limited - in 2011 only about 16% of used fuel was reprocessed.” (WNA see: http://goo.gl/Zrtvn) • The United States does not reprocess fuel although does advocate research in this area • Controversial because of use of plutonium
- 131. We need apermanent solution
- 132. MODULE 2 ,CHAPTER 5 • Fuel cycle is complex • Open cycle – no reprocessing • Closed cycle – reprocess • Vulnerabilities – After enrichment step if cycle is closed and plutonium is used • Nations differ on policy for reprocessing (US does not reprocess, Russian Federation does) • More detail on all of this in the next Module!
Editor's Notes
- #3 Explain fast and slow fission Know how fast and slow fission are appliedDemonstrate critical massDemonstrate power production by nuclear fissionDemonstrate the difference between fission and fusion reactionsRecognize that a mass greater than the critical mass is needed to produce an uncontrollable chain reaction.
- #14 Explain fast and slow fission Know how fast and slow fission are appliedDemonstrate critical massDemonstrate power production by nuclear fissionDemonstrate the difference between fission and fusion reactionsRecognize that a mass greater than the critical mass is needed to produce an uncontrollable chain reaction.
- #17 Credits:http://uk.ask.com/wiki/Uranium
- #25 Wikipedia