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ADSRs: Proliferation issues

ADSRs: Proliferation issues. Roger Barlow ADSR08 Manchester, 9 th September 2008. Issues and Questions. ‘Dirty bomb’ ‘Little boy’ type device ‘Fat man’ type device Role of 232 U. “Dirty Bomb”. (Spent) fuel rods will contain fission products

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ADSRs: Proliferation issues

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  1. ADSRs: Proliferation issues Roger Barlow ADSR08 Manchester, 9th September 2008

  2. Issues and Questions ‘Dirty bomb’ ‘Little boy’ type device ‘Fat man’ type device Role of 232U UK ADSR Programme

  3. “Dirty Bomb” (Spent) fuel rods will contain fission products Dispersal over civilian areas would cause panic, expense, and few fatalities It is thought that during the 1960s the UK Ministry of Defence evaluated RDDs, deciding that a far better effect was achievable by simply using more high explosive in place of the radioactive material. Wikipedia UK ADSR Programme

  4. Enriched Thorium No UK ADSR Programme

  5. 233U device In principle possible Critical mass ~15kg No spontaneous fission problems: simple gun-type device 233U in fuel stabilises after about 5 years. Extract chemically from Thorium Is this possible? Presumably. If not, easy to find out UK ADSR Programme

  6. 232U 232U decays with a half life of 69 y, producing 228Th which decays producing a 2.8 MeV  ray. Really nasty stuff 5 ppm 232 in 233 gives (long term) ~190 mrem/hr for a worker 0.5m from a 5kg sphere. Health and safety limit 5 rem/y. Lethal doses 200-1000 rem ~2.4% contamination is needed to make 233U ‘safe’ UK ADSR Programme

  7. Origins of 232U 233U(n,2n)232U 4 mb for neutron energies above threshold ~6 MeV 232Th(n,2n)231Th 231Pa followed by (n,) 14 mb for neutron energies above threshold ~6 MeV Fast neutrons from tail of fission spectrum – or spallation Asymptotic ratio for the Energy Amplifier is 0.15% UK ADSR Programme

  8. Possible loophole • Chemically isolate the 233Pa. • Wait (27 d half life) for it to decay to pure 233U • Some MSR schemes use just this UK ADSR Programme

  9. Ionium to the rescue • Ionium is 230Th • It does not occur in Thorium, which is pure 232 • It does occur in Uranium, part of the 238U decay chain • ‘spike’ the Thorium with Ionium UK ADSR Programme

  10. Messy alternative • Add 238 U to ‘denature’ the fuel. 12% 233 in 238 corresponds to 20% 235 in 238 and is deemed unenriched and safe UK ADSR Programme

  11. Conclusions • Safety depends on design • Advantage to have all fuel exposed to fast neutrons to ensure 232U concentration • Ionium may be needed UK ADSR Programme

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