Neutron Inelastic Cross Section Measurements for Sodium

A. J. M. Plompen, C. Rouki, S. Kopecky, N. Nankov, M. Stanoiu, C. Borcea and A. Negret

J. Korean Phys.Soc. 59,1660 [doi: 10.3938/jkps.59.1660 | PDF Download]

Inelastic scattering cross sections for sodium are of interest to the development of sodium cooled fast reactors. A recent OECD-NEA subgroup analysed the sensitivity of reactor parameters to cross sections and accordingly determined target uncertainties for the nuclear data. Comparing these target uncertainties with the current status of nuclear data uncertainties and covariance data resulted in a list of target priorities. Among these features sodium inelastic scattering for which a target uncertainty of about 5% was established, approximately two to three times as good as the uncertainty for current evaluated data les for this isotope (see OECD-NEA High Priority Request List, http://www.nea.fr/html/dbdata/hprl/hprlview.pl?ID=448). At IRMM, the GAINS gammaarray for inelastic neutron scattering was developed with the purpose of measuring cross sections with uncertainties at or below the target uncertainties for nuclides like 23Na using the (n, n´γ)-technique. Measurements were performed at the GELINA facility at a 200 m flight path with eight high purity germanium detectors. The sample was an 80 mm diameter metallic disk prepared at IRMM by cutting, pressing, rolling and punching. For the experimental work, a careful review was made of the gamma-efficiency calibrations and the flux normalization in order to investigate in detail the corrections and the nal uncertainties that may realistically be achieved. An elaborate account will be presented of the data analysis and checks that have been made and implications for earlier work by our group will be discussed. First results will be shown for the gamma-production cross sections of the main transitions in the energy range from threshold to 10 MeV.