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Radiotoxicity and spent fuel

Radiotoxicity and spent fuel. 237 Np case. (n, γ ). (n, γ ). β. (n, 2n). β. 238 U 237 U 237 Np . Tovesson & Hill, PRC 75 034610 (2007) . 235 U 236 U 237 U 237 Np. Motivations.

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Radiotoxicity and spent fuel

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  1. Radiotoxicity and spent fuel

  2. 237Np case (n,γ) (n,γ) β (n,2n) β 238U 237U 237Np Tovesson & Hill, PRC 75 034610 (2007) • 235U 236U 237U 237Np

  3. Motivations • Transmutation and incineration of long-lived nuclear wastes : Np, Am, Cm, (Pu ?) • Higher concentration of minor actinides in reactor cores • Need of accurate cross section of actinides

  4. Neutron Capture  decay β- Uranium cycle β- Thorium cycle β- β- 232Th + n  233Th  233Pa  233U (fissile) 238U + n  239U  239Np  239Pu (fissile) 232U 233U 234U 235U 236U 237U 238U 231Pa 232Pa 233Pa 234Pa 235Pa 230Th 231Th 232Th 233Th 234Th • Lower production of minor actinides • Thermal breeder possible, with low fissile inventory

  5. Neutron balance for breeding of fissile nucleus only (capture/fission) We start with 1 fission : -number of destroyed fissile nuclei: 1+a (fission+capture) • neutrons needed for next fission: 1+a(fission+capture) • neutrons needed to restore the fissile nucleus (breeding): 1+a • neutrons released by fission: • available additional neutrons:

  6. Neutron balance for breeding

  7. Concentration of fissile in fuel

  8. Time of flight principle Velocity :

  9. Motivations for fission cross section measurements • Need of accurate fission cross sections for actinides - candidates to incineration : 237Np - involved in the 232Th/233U : 232Th, 233U, 234U • Broad neutron energy spectrum (ADS) up to spallation domain

  10. Detection layout

  11. Fission detection : coincidence method • Détection of the 2 fission fragments • High level of rejection for alphas and high energy reactions (>10 MeV) : spallation • Severe constraint : detectors and target backings very thin

  12. f for 234U

  13. f for 237Np around 40 eV

  14. f for 237Np above threshold

  15. f for 209Bi

  16. f for natPb

  17. Neutron Capture  decay Future : f of 231Pa 232U 233U 234U 235U 236U 237U 238U 231Pa 232Pa 233Pa 234Pa 235Pa 230Th 231Th 232Th 233Th 234Th

  18. Future : f of 231Pa

  19. Angular distribution : combination of spins Basically : J combines incident spins and orbital momentum K projection along fission axis If K << J forward peaking If K ~ J sideward peaking (even-even target nucleus) The angular distribution may vary quickly with the energy according to (J,K) of the vibrational resonances

  20. Poor knowledge above 10 MeV 237Np 232Th nTOF well suited for describing the quick variations with energy

  21. Spallation domain ? Tutin et al., NIM A457 (2001) 646 Need to confirm the high anisotropy of 232Th at high energy

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