U(n, γ) measurements at LANSCE

The Th-U fuel cycle, in which the 233U plays an important role, has been proposed as an

alternative to the U-Pu fuel cycle due to its reduced amount of transuranium elements.

The experimental 233U(n,γ) cross section data available in the literature are scarce and

were measured decades ago [1, 2, 3]. An accurate measurement of the 233U(n,γ) cross

section is required by the NCSP (National Critically Safety Program) to complete the

neutron-induced cross section data, and also, as reported by the ORNL, a new evaluation

with revised (renormalized) fission cross section is needed on 233U.

For 233U fission is around one order of magnitude more likely than capture, hence, the

accuracy in the capture cross section measurement relies on the discrimination between

the γ’s produced in capture and fission reactions. This discrimination method requires the

use of an experimental setup combining capture and fission detectors. Therefore a new

measurement has been performed at LANL combining the Detector for Advanced

Neutron Capture Experiments (DANCE) to measure γ’s, with the NEUtron detector array

at dANCE (NEUANCE) to detect neutrons coming from fission and determine by

coincidence the γ’s produced by fission reactions tagging them.

This measurement will provide cross section data in the Resonance Region (RR),

focusing in the Unresolved Resonance Region (URR) in the keV neutron energy.

References

[1] E. Berthoumieux et al., Proceedings of the International Conference on Nuclear Data

for Science and Technology April 22-27, 2007, Nice, France (EDP Sciences, 2008) pp.

571-574.

[2] L. W. Weston et al., Nucl. Sci. Eng. 34, 1 (1968).

[3] J. C. Hopkins and B. C. Diven, Nucl. Sci. Eng. 12:2, 169-177 (1962).