CNRS Université Bordeaux

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ACEN group

Aval du Cycle et Energie Nucleaire
Nuclear Data for nuclear energy, new fuel cycle and nuclear waste transmutation



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The ACEN group’s research activities are dedicated to fission and capture reaction studies on nuclides of interest for present or future fuel cycle and for nuclear waste transmutation.

The group is involved in national and EU programs dedicated to nuclear data measurement, i.e. precise determination of neutron induced reaction cross section fission and capture cross section measurement, in the fast neutron energy range (MeV) or in the resolved resonance region (1-100 eV). Experiment are performed at AIFIRA local facility, and at several national and European facilities (IRMM Geel, IPN Orsay, CEA/DAM Bruyeres-le-Chatel, Oslo University, GSI Darmstadt).

We are also interested in fission fragment experimental studies (fission fragment charge, mass and energy distribution) and modelisation.

Research activities of the ACEN group are mainly organized around neutron induced fission and radiative capture cross section measurement for nuclides involved in the present fuel cycle (U-Pu) or potential Th-U, and for highly radioactive nuclides present in nuclear waste produced in present nuclear power plants (mainly the minor actinides: Np, Am, Cm).

Our group has been formally constituted at the early 2000. It has now five permanent members (from CNRS or the University of Bordeaux), and doctoral and post-doctoral members.

Thorium cycle, minor actinides and the Generation IV power plants.

Almost all present nuclear power plants are 235U enriched uranium and plutonium based fuel. Non fissile neutron capture from uranium and 239Pu plutonium generate the class of nuclear waste of highest radiotoxicity : the so-called minor actinides (neptunium, americium, curium), the alpha activity of which remain very high for several thousands of years. The amount of minor actinides could be significantly reduced by using a thorium based fuel cycle, in which the fissile element is 233U uranium isotope, and/or by burning up these nuclides using dedicated G-IV reactors (fast neutron reactors or ADS).

Development of new generation of reactors based on Th-U cycle or dedicated to minor actinides burnup needs the knowledge of cross sections of interest with a much better accuracy than the one given by the present data bases.

For some nuclei, there are very few data available. More, even for the present U-Pu cycle, the development of the new generation of fast neutron reactors needs a reevaluation of several data, including fission product distribution.

ACEN group’s contribution to nuclear data for new fuel cycle and waste transmutation

Our group has developed since its beginning a program for precise measurement of fast neutron induced fission and capture cross section for nuclides involved in the thorium cycle ( 232Th, 233Pa, 233U). Original techniques have been developed for direct neutron measurements, such as fission cross section measurements relative to (n,p) scattering, and a complete renewal of an indirect method to access to reaction studies on short lived and highly radioactive nuclides out of range by direct experiments: the surrogate reaction method. These techniques have been developed and have been extended to minor actinide studies. We have been involved in time-of-flight technique measurement in the resolved resonance region (1-100 eV neutron energy) too. In parallel, we are also involved in experiments on fission fragment properties and distribution studies and in fission process modelling, via the development of a performant code (GEF).

ACEN: nuclear data for nuclear energy, new fuel cycle and nuclear waste transmutation