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Microscopic Description of Fission Process University of Tennessee

Microscopic Description of Fission Process University of Tennessee SSAA grant DOE DE-NA0001820 ( since 2003). N,Z. elongation necking. N=N 1 +N 2 Z=Z 1 +Z 2. split. N 2 ,Z 2. N 1 ,Z 1. UTK Team. PI: Witold Nazarewicz

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Microscopic Description of Fission Process University of Tennessee

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  1. Microscopic Description of Fission Process University of Tennessee SSAA grant DOE DE-NA0001820 (since 2003) N,Z elongation necking N=N1+N2 Z=Z1+Z2 split N2,Z2 N1,Z1

  2. UTK Team PI: Witold Nazarewicz PhD students: Jordan McDonnell (Ph.D. 2012; postdoc at LLNL), Erik Olsen, Kemper Talley Postdocs: JhilamSadhukhan Visitors: AndrzejStaszczak, AndrzejBaran, JavidSheikh, KasiaMazurek + JacekDobaczewski + Nicolas Schunck, Jordan McDonnell + NUCLEI www.phys.utk.edu/witek/fission/fission.html • Fission is a complex process involving the collective motion of all nucleons – One of the most difficult problems in nuclear physics • Most practical applications have been based on simplified theories tuned to existing data

  3. Fission: our strategy Stability of the heaviest nuclei, r-process, advanced fuel cycle, stockpile stewardship… Large-scale Simulations on Leadership-class Computers Dynamics Quality Input PRC 84, 054321(2011) PRC 85, 024304 (2012) Confrontation with experiment; predictions PRC 80, 014309 (2009) Numerical Techniques PRC 80, 014309 (2009) PRC 78, 014318 (2008)

  4. Spontaneous Fission Lifetimes SF fission lifetimes in the actinides Quality input A. Staszczak et al., Phys. Rev. C 87, 024320 (2013) J. McDonnell et al.

  5. The SF half-life along the axially symmetric sEF pathway is Tsf=1013.82 s. Triaxialeffects along sEF reduce it to 109.39 s, and the inclusion of reflection-asymmetric shapes (aEF) brings the SF half-life of 306122 down to Tsf=106.22 s, which corresponds to an overall reduction of Tsfby about seven orders of magnitude.

  6. A. Staszczak et al., Phys. Rev. C 87, 024320 (2013) Oganessian et al. SF fission “Death Valley” in SHE

  7. Third minimum around 232Th J.D. McDonnell et al., Phys. Rev. C 87, 054327 (2013) Csige et al., Phys. Rev. C 85, 054306 (2012) J. Blons et al., Phys. Rev. Lett. 35, 1749 (1975).

  8. J.D. McDonnell et al.

  9. J.D. McDonnell et al.

  10. Curious Fission of 180Hg b+/EC b+/EC g g g • 2 step process: b+/EC decay of a parent180Tl nucleus populates an excited state in the 180Hg daughter, which then might fission (in competition with the g decay to the g.s.) • Low-energy fission! (E*<QEC=10.8 MeV) • 10 cases know so far (neutron-def. Uranium region) 180Tl QEC Bf deformation 180Hg • Before the ISOLDE experiment: expected SYMMETRIC split in two semi-magic 90Zr • The most probable fission fragments are 100Ru (N=56,Z=44) and 80Kr (N=44,Z=36) • N. Andreyev et al., • Phys. Rev. Lett. 105, 252502 (2010)

  11. M. Warda, A. Staszczak, WN, Phys. Rev. C 86, 024601 (2012) • N. Andreyev et al., • Phys. Rev. Lett. 105, 252502 (2010)

  12. Fission half-lives WKB: b collective inertia (mass parameter) Several collective coordinates The action has to be minimized multidimensional space of collective parameters a c a b

  13. Program announcement: Quantitative Large Amplitude Shape Dynamics: fission and heavy ion fusion Institute for Nuclear Theory, Seattle September 23 – November 15, 2013 Organizers: W. Nazarewicz (witek@utk.edu), A. Andreyev, G. Bertsch, W. Loveland • Main topics: • Reevaluation of basic concepts • Microscopic theory and phenomenological approaches • Nuclear interactions and energy density functionals • Time-dependent many-body dynamics • Key experimental tests • Experimental data needs • Spectroscopic implications • Computational methodologies for dynamics • Quality data for nuclear applications. Keywords: fission, fusion, shape coexistence, self-consistent mean field theory, nuclear density functional theory and its extensions, time dependent methods, adiabatic and diabatic dynamics, synthesis of superheavy elements, fission recycling in the r-process, stockpile stewardship, advanced fuel cycle

  14. SUMMARY • There are fundamental problems in fission that cry to be solved • Basic science (nuclear structure, nuclear astrophysics) • Programmatic needs • Fission is a perfect problem for the extreme scale • Quantum many-body problem is tough! • We are developing a microscopic model that will be predictive • Fission probabilities • Properties of fission fragments • Cross sections • Level densities • Quantification of Margins and Uncertainties is important

  15. Backup

  16. UNEDF1 functional: focus on heavy nuclei and fission big improvement for fission Comparison with RIPL-3 (IAEA) data:

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