Neutron-induced cross sections of actinides via de surrogate - - PowerPoint PPT Presentation

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Neutron-induced cross sections of actinides via de surrogate - - PowerPoint PPT Presentation

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Neutron-induced cross sections of actinides via de surrogate reaction method B. Jurado 1) , Q. Ducasse 1) , M. Aiche 1) , L. Mathieu 1) , T.Tornyi 2) , A. Goergen 2) , J. N. Wilson 3) , G. Boutoux 5) , I. Companis 1) , S. Czajkowski 1) , F.

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SLIDE 1

Neutron-induced cross sections of actinides via de surrogate reaction method

  • B. Jurado1), Q. Ducasse1), M. Aiche1), L. Mathieu1), T.Tornyi2),
  • A. Goergen2), J. N. Wilson3), G. Boutoux 5), I. Companis1),
  • S. Czajkowski1), F. Giacoppo2), F. Gunsing3), M. Guttormsen2),
  • A. C. Larsen2), M. Lebois4), J. Matarranz1), V. Méot 5),T. Renstrom2),
  • O. Roig5), S. Rose2), O. Serot6), S. Siem2), I. Tsekhanovich1),
  • G. M. Tveten2), T. Wiborg-Hagen2), M. Wiedeking7)

1)CENBG, Bordeaux, France 2)University of Oslo, Norway 3)IPN, Orsay, France 4)CEA/Saclay, Gif-sur-Yvette, France 5)CEA/DAM, Arpajon, France 6)CEA/Cadarache, Saint Paul lez Durance, France 7) iThemba LABS, Somerset West, South Africa

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SLIDE 2

Neutron-induced cross sections of short-lived nuclei in reactor physics

  • Incineration of minor actinides
  • 232Th/233U cycle

The data are missing (in particular for capture) due to the high radio-toxicity of the targets involved!

Fission and capture cross of e.g. 241,243Am,243Cm(29.1y), 244Cm(18.1y),245Cm (8500y) Fission and capture cross sections of e.g. 232U(69y), 231Th (26h), 233Th(22m)

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SLIDE 3

Neutron-induced reaction

n + A (A+1)*

Indirect (n,f) and (n,γ) measurements: the surrogate method

Calculated (Optical model calculations CEA/Bruyeres le Chatel)

Measured Surrogate reaction

Cramer and Britt (Los Alamos 1970…!!)

X + Y

  • Compound nucleus!
  • The same spin/parity
  • r no dependence on

J/π!

1 1 ( , )( *)

( *). ( *)

A A A n

E E P E

χ χ

σ σ

+ +

=

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SLIDE 4

2 4 6 8 10 Neutron Energy /MeV 1 2 3

Fission cross section /b

241Am(n,f)

CENBG Dabbs et al. JENDL-3.3 & JEFF-3.1 ENDF/B-VII

  • G. Kessedjian, et al., Phys. Lett B 692 (2010) 297

How about radiative capture??

Surrogate method and fission cross sections

243Am(3He,4He)242Am

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SLIDE 5

Surrogate method applied to capture in rare-earth region Results for 174Yb(3He,p)176Lu 175Lu(n,γ)

  • G. Boutoux, et al., Phys. Lett B 712 (2012) 319

Very important discrepancies!

Spin distributions

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SLIDE 6

Sn=6.27MeV

n’

E*

γ

7/2+

175Lu

7‐

176Lu*

11/2+ ‐ 251 keV 9/2+ ‐ 113 keV J=7

Due to the high spin of the decaying nucleus, neutron emission to the ground- and first excited states is highly improbable and gamma emission is highly enhanced! Things should get better when the level density of the nucleus after neutron emission increases --> better for actinides

15/2+ ‐ 595 keV Why do we obtain such big differences?

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SLIDE 7

239 U 238 U 237 U

238 U

d (15 MeV) (d,p) (d,d) (d,t) 238U+n Good quality neutron-induced data exist! (d,p) interesting for inverse kinematics 236U+n

238 Np 239 Np 237 U

238 U

3He (24 MeV) (3He,t) (3he,d) 237Np+n Good quality neutron-induced data exist 236U+n

240 Np

(3He,p) (3He,4He)

Surrogate method applied to capture in actinide region Experiment at the Oslo cyclotron: Reactions studied

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SLIDE 8

Experimental set-up at the Oslo cyclotron

238U

Ejectiles 4 PPACs Fission-fragment detection 28 Scintillators γ-ray detection

  • Fiss. fragments

γ

High efficiency Simultaneous measurement of gamma and fission decay

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SLIDE 9

Determination of decay probability

Light-particle kinematics + Q-values

E* of the CN ΔE/ Ch E/ Ch

3He (24 MeV) + 238U

d t 3He 4He p

*

1

n n

A E E B A = + +

( ) ( ) ( ) ( )

* * * * co f C in N

P E N E E N E E ff = ⋅

E*/ MeV Counts

238U(3He,4Heγ)237U

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SLIDE 10

First preliminary results: Fission

E*/ MeV

Fission Probability of 239U*

ENDF-VII.1 238U(n,f) CENBG 238U(d,p) at 15 MeV

238U(d,p) at 18 MeV

  • H. C. Britt , J. D. Cramer, PRC 2 (1970) 1758

Deuteron breakup! The neutron is emitted before CN formation (I. Thompson, 2012)

Britt, Cramer 238U(d,p) at 18 MeV

E*/ MeV

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SLIDE 11

First very preliminary results: Fission (Analysis with very low statistics, only 1 telescope strip!)

238U(3He,4Hef)

Fission Probability 237U*

E*/ MeV

ENDF-VII.1 (neutron induced) CENBG (surrogate)

236U(n,f)

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SLIDE 12

238U(3He,tf)

Fission Probability 238Np*

E*/ MeV

ENDF-VII.1 (neutron induced) CENBG (surrogate)

237Np(n,f)

First very preliminary results: Fission (Analysis with very low statistics, only 1 telescope strip!)

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SLIDE 13

First very preliminary results: gamma decay

E*/ MeV Ncoin/NCN 238U(d,pγ)239U*

This ratio needs to be corrected for the gamma-cascade detection efficiency to get Pgamma!

Sn Fission sets in

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SLIDE 14

Conclusions…

  • Surrogate-reaction method :
  • ->works well for fission
  • ->important discrepancies for capture in rare-earth region due to spin

selectivity of neutron emission

  • New experiment to study capture in actinide region at the Oslo cyclotron

d+238U & 3He+238U 238U(d,p): fission cross section 25% lower than 238U(n,f), d breakup! Preliminary fission probabilities from 238U(3He,4He) & 238U(3He,t) agree well with n-induced data Analysis on the way to extract gamma-decay probabilities

…Perspectives

  • Further study of d-breakup involving theoreticians
  • Gamma-decay probabilities to be extracted for:

238U(d,p)239U <-> 238U(n,γ) 238U(d,t)237U <-> 236U(n, γ) 238U(3He, 4He) 237U <-> 236U(n, γ) 238U(3He, t) 238Np <-> 237Np(n, γ)

  • Evaluate to which extent the surrogate method can be used to extract

unknown capture cross sections of short-lived actinides