Speakers
Description
The reduction of the uncertainties of neutron capture and fission cross sections of major and minor actinides is important for the improvement of the design of nuclear reactors and the optimization of nuclear waste management strategies, especially in life extension and higher burnup scenarios. In particular, neutron capture on $^{240}$Pu is the responsible for the formation of $^{241}$Am, via the decay of $^{241}$Pu, and therefore also for the creation of heavier minor actinides.
At present, the only $^{240}$Pu$(n,\gamma)$ data available in EXFOR in the resonance region are those of Weston and Todd [1], who reported the capture cross section between 200 eV and 350 keV averaged in 33 energy intervals. Due to the lack of high-resolution capture measurements, the present evaluations [2] rely on transmission measurements [3].
In this conference we present the results of a high energy resolution $^{240}$Pu$(n,\gamma)$ measurement performed at the n_TOF facility at CERN [4] in the resonance region. These final results are obtained from the combination of two different measurements carried out at n_TOF EAR1 and EAR2, respectively. More in detail, the first one [5,6] was performed at the measurement station located at 185 meters from the spallation target (EAR1), using a 50 mg sample and the n_TOF BaF$_{2}$ Total Absorption Calorimeter [7]. The second measurement [8] was performed at the more intense measurement station located at 20 m (EAR2), using a 1 mg sample and C$_{6}$D$_{6}$ detectors. This latter smaller mass sample allowed us to measure the largest resonances present at low neutron energies more accurately, multiple scattering effects being less important. The resulting yields will be added to the EXFOR database to be used in future evaluations.
[1] L. W. Weston and J. H. Todd, Nucl. Sci. Eng. 63, 143 (1977).
[2] O. Bouland et al., Nucl. Sci. Eng. 127, 105 (1997).
[3] W. Kolar and K. H. Böckhoff, J. Nucl. Energy 22, 299 (1968).
[4] F. Gunsing et al. (the n_TOF collaboration), Nucl. Instrum. Methods B 261, 925 (2007).
[5] C. Guerrero et al. (the n_TOF collaboration), Proceedings of the International Conference on Nuclear Data for Science and Technology, ND2007, Nice, France, EDP Sciences, pp. 167 (2007).
[6] C. Guerrero Doctoral thesis, CERN-THESIS-2010-064 (2008).
[7] C. Guerrero et al. (the n_TOF collaboration), Nucl. Instrum. Methods A 608, 424 (2009).
[8] V. Alcayne et al. (the n_TOF collaboration), EPJ Web Conf. 239, 01034 (2020).
