Common Nuclear Data Problems for Fission Cycling in r-process and Nuclear Energy

1
Common Nuclear Data Problems for Fission Cycling
in r-process and Nuclear Energy

• S. Chiba
• JAEA

2
Fission (cycling) in r-process nucleosynthesis

• Discovery of Th and U in metal poor stars
• For realistic calculation of r-process
  nucleosynthesis
• Is there a termination point? Where is that?
• Possibility of SHE generation and discovery of
  its relics in meteorites
• Impacts on universality (56?Z?75)
• Impacts on nucleo-cosmochronometers
• Th/Eu, U/Th, Th/Os,....

3
238U
S250
208Pb
Supply to medium-weight region by fission, which
is less sensitive to the physical conditions of
r-process sites
132Sn
Continuous flow from the bottom
4
Regions where fissions take place in terms of
KTUY05
5
Competing processes in calculation of fission
cycling

• Spontaneous fission
• Neutron-induced reactions
• Neutron-capture and inverse reaction
• Neutron-induced fission ? FFMD
• ß-decay
• ß-delayed fission ? FFMD
• ß-delayed neutron emission
• ?-induced reactions
• (?,e-xn) reaction
• (?,f) ? FFMD

6
Burn-up of Actinides in Nuclear Reactors
242Cm
243Cm
244Cm
245Cm
242mAm
10.1h
6h (0.16)
152y
241Am
242Am
243Am
244Am
30y
18.1y
163d
4.96h
16h (0.84)
14.9y
238Pu
239Pu
240Pu
241Pu
242Pu
243Pu
87.8y
2.12d
2.36d
?)?????MA?? (???????????)
236Np
237Np
238Np
239Np
?)????????? (?????????????3???)
2.25h
6.75d
23.5m
236U
237U
235U
239U
238U
234U
?)????????? ?????
??) ?????????????????? ????ORIGEN2????????(JE
NDL3.3)
7
Critical mass of 235U with various moderators
????????????(??)?/235U??????
8
Dynamical network calculationTerasawa et al.,
ApJ 562, 470(2001)originally from Prof. Meyer ??

• Reaction rates
• Thielamann , Caughlan-Fowler, Maleney-Fowler,
  Fowler-Hoyle, Rauscher, Mohr, Wagoner,
  Kajino-Boyd, Orito-Kajino-Mathews,
  Kajino-Fukugita,Ohsaki, NACRE96
• Nuclear mass
• Hilf-Groote-Takahashi (modified) ?KTUY05 (Prog.
  Theor. Phys. 305(2005 )113)
• ß-decay rates
• Klapdor ?GT-2 with KTUY05 mass, including 1n
  emission(2007)
• ?-induced spallation rate (A(?,e- xn)A') (x0, 8)
• Langanke (5 ? Z ?100) with dumping
• no fission mode ?ß-delayed fission, spontanious
  fission(KTUY05)
• a-decay (KTUY05 mass)
• Data on expanding matter of SNeII numerically
  read ? exponential model

9
Exponential model for expanding nuclear matter
c.f. General-relativistic hydro-dynamical
simulation by Terasawa, Kajino, Sumiyoshi et al.
(ApJ 562, 470(2001))(dots) lower 2 lines
T9 upper 2 lines density Exponential model
YeYp0.427
10
Entropy-dependence of r-process abundance
11
ß-delayed fissionBf-dependence
12
(KTUY-3MeV(left)?MS96(right))
13
FFMD (Konan model)248Cm, 236U
14
ß-delayed fissionFFMD-dependence
15
Jp-dependence of CN decay
ß-decay, ?-??
TS-1
TS-2
Jp
En
Tn
T?
target
Ex
Bn
Bfi
Bfo
PES
Compound
deformation (elongation)
16
Jp-dependence of compound formation c.s.
s?
p?
d?
17
Decay width
Optical model
Target
Compound
Brink-Axel
Hill-Wheeler
Transition state
18
Fission Probability

• Very strong Jp-dependence
• No-experimental evidence
• How can we verify it?
• Various projectile?(d, 3He, 18O)

19
Level density on the saddle

• How to verify it?

20
Nuclear Structure EffectsSRM-CC

• 238U n
• Coupling scheme G.S. band (0 - 2 - 4 - 6 -
  8)4 side bands
• Soft Roator Model prediction of coupling
  strengths
• OMP E.S. Soukhovitsij, S. Chiba et al., J.
  Phys. G. 30, 905-920(2004).

(coupled-levels)
21
Effects of low-lying levels on reaction c.s.
G.S. Band
22
Bn of Sn isotopes and HF, DSD c.s.
23
U????Bn
24
State-dependence of DSD c.s.
25
Resonances
26
Effects of resonances on MACS
27
Summary

• There are many ambiguities in calculation of
  ß-delayed fission rates, neutron-induced fission
  rates necessary for fission cycling
• Fission barriers, level density (especially at
  the saddle), their Jp-dependence, FFMD,
  deformation parameters and GDR parameters
• Neutron binding energies affect the relative
  magnitude of DSD and HF cross sections
• DSD c.s. is sensitive to the presence and
  energies of the p-states
• Nuclear structure (low-lying levels) is important
  for reaction c.s. calculation