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SUMMARY:Study of the dependence of the ${}^{238}$U(n\,f) reaction cross-se
 ction on neutron energy
DTSTART;VALUE=DATE-TIME:20261027T162500Z
DTEND;VALUE=DATE-TIME:20261027T163000Z
DTSTAMP;VALUE=DATE-TIME:20261028T101825Z
UID:indico-contribution-6462@cern.ch
DESCRIPTION:Speakers: Artem Nesynov ()\nThe ${}^{238}$U(n\,f) reaction pla
 ys an important role in modern nuclear energy\, so to date many measuremen
 ts of the cross-section of this process as a function of incident neutron 
 energy have been performed. In most works\, the energy interval below 20 M
 eV\, which is most relevant for modern reactor technologies\, has been stu
 died. At the same time\, the 20–200 MeV region\, which will be in demand
  in future technologies\, has been studied somewhat less – see\, for exa
 mple\, [1]. In particular\, if the uncertainty of the evaluated ${}^{238}$
 U(n\,f) cross-section in the 1–20 MeV region does not exceed 1.5%\, then
  in the 30–50 MeV interval this uncertainty increases to 2–2.5%\, and 
 above 100 MeV it exceeds 4% [2].\n\nIt is important\, however\, to underst
 and that experimental data on fission cross-sections can be obtained only 
 for relatively stable isotopes of heavy elements irradiated by neutrons. B
 ut in nuclear facilities\, short-lived isotopes\, which also fission under
  neutron action\, are produced in reactions of the type (n\,2n) or (n\,p).
  The fission cross-sections of such isotopes cannot be measured\, but they
  can be estimated using model approaches. At the same time\, a method base
 d on such approaches can be developed only by calculating the fission cros
 s-sections of relatively stable isotopes\, such as ${}^{238}$U\, and compa
 ring the results with measured cross sections.\n\nIn this work\, the energ
 y dependence of the ${}^{238}$U(n\,f) fission cross-section induced by neu
 trons in the range from 0.1 to 50 MeV has been modeled using the TALYS-2.2
  code [3]. At the first stage\, the results of calculations performed with
  default parameters (which\, as a rule\, are parameters from the RIPL-3 li
 brary [4]) were compared with experimental data from the EXFOR library [5]
 . Discrepancies between the calculated and measured cross-sections were re
 vealed in a number of energy intervals. At the next stage\, possibilities 
 for minimizing the discrepancies were studied by adjusting the fission bar
 rier parameters\, using alternative approaches for calculating the level d
 ensity of excited states\, as well as for modeling pre-equilibrium process
 es. As a result\, fission barrier and collective enhancement parameters fo
 r the nuclei ${}^{239-232}$U were determined\, allowing the main features 
 of the measured energy dependence of the ${}^{238}$U(n\,f) cross-section t
 o be reproduced. A high sensitivity of the cross-section to the parameters
  of rotational enhancement of the level density and to the shape of the nu
 cleus at the fission barriers has also been established.\n\nhttps://indico
 .particle.mephi.ru/event/626/contributions/6462/
LOCATION:Sevastopol hotel Conference Hall 1
URL:https://indico.particle.mephi.ru/event/626/contributions/6462/
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