Fission cross section measurements of minor actinides for transmutation

The existing reactors produce two kinds of nuclear waste: the fission products and heavy
nuclei beyond uranium called minor actinides (Americium and Curium isotopes). Two options are
considered: storage in deep geological site and/or transmutation by fast neutron induced fission. These
studies involve many neutron data. Unfortunately, these data bases have still many shortcomings to
achieve reliable results. The aim of these measurements is to update nuclear data and complement
them.
We have measured the fission cross section of 243Am (7370y) in reference to the (n,p) elastic
scattering to provide new data in a range of fast neutrons (1 - 8 MeV). A statistical model has been
developed to describe the reaction 243Am(n,f). Moreover, the cross sections from the following
reactions have been extracted from these calculations: inelastic scattering 243Am(n,n’) and radiative
capture 243Am(n,g) cross sections.
The direct measurements of neutron cross sections are often a challenge considering the short
half-lives of minor actinides. To overcome this problem, a surrogate method using transfer reactions
has been used to study few isotopes of curium. The reactions 243Am(3He, d)244cm, 243Am(3He, t)243cm
and 243Am(3He,a)242Am allowed to measure the fission probabilities of 243,244Cm and 242Am. The
fission cross sections of 242,243Cm(162,9d, 28,5y) and 241Am(431y) have been obtained by multiplying
these fission probabilities by the calculated compound nuclear neutron cross section relative to each
channel. For each measurement, an accurate assessment of the errors was realized through variancecovariance
studies. For measurements of the reaction 243Am(n,f), the analysis of error correlations
allowed to interpret the scope of these measures within the existing measurements.
The experimental techniques will be described and the results will be discussed via a variancecovariance
analysis.

Presentation (pdf)