Speaker
Description
A. Chebboubi1, D. Bernard1, V. Vallet1, G. Kessedjian1, O. Méplan2, Y.H. Kim3, U. Köster3, Ch.E. Düllmann4,5,6, F. Géhin1, M. Houdouin-Quenault1,2, O. Litaize1, C. Mokry4,6, M. Ramdhane2, J. Runke4,5 ,C. Sage3, O. Serot1
1`CEA, DES, IRESNE, DER, SPRC, Cadarache, Physics Studies Laboratory, 13108 Saint-Paul-lès-Durance, France
2 LPSC, Université Grenoble-Alpes, CNRS/IN2P3, 38026 Grenoble, France
3 Institut Laue-Langevin (ILL), 38042 Grenoble, France
4 Department of Chemistry - TRIGA site, Johannes Gutenberg University Mainz, 55128 Mainz, Germany
5 GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany
6 Helmholtz Institute Mainz, 55128 Mainz, Germany
A recent experimental campaign performed at the LOHENGRIN spectrometer at ILL aimed at measuring the independent fission yield of $^{136}$Cs in the $^{239}$Pu(n$_{\text{th}}$,f) reaction. Indeed, recent works from CEA/LEPh have shown that this nuclide can have an important contribution to the total dose rate coming from the decay of radioactive nuclides. Moreover, its impact is of first-order on the uncertainty of the total dose rate calculated in specific areas of Nuclear Power Plants within accidental conditions. The production paths of this nuclide in a nuclear reactor are complex. A sensitivity analysis performed with the DARWIN package [1] has shown that one of the most important production paths was directly from the fission process. Therefore, a new measurement of its independent yield along with a rigorous uncertainty analysis would allow handling its impact on the total dose rate.
The experimental campaign has been performed in June 2021 with a 129 µg/cm$^{2}$ $^{239}$Pu target (99.5% enrichment) produced by molecular plating [2] at the TRIGA Site of the Department of Chemistry at Johannes Gutenberg University Mainz. The experimental setup consisted of a vacuum chamber placed in the focal plane of the LOHENGRIN spectrometer and surrounded by two HPGe clover detectors. Due to its low independent yield, the signal from $^{136}$Cs decays is very low in comparison to the γ–ray background at the measurement position. Therefore, the ions were collected by implantation of the mass-separated beam into Al foil placed inside the vacuum chamber. This foil was then removed and transfer to a low γ-ray background setup located at LPSC. The procedure is then repeated for different LOHENGRIN settings. The low γ-ray background setup features a considerably improved signal-to-background ratio compared to more conventional measurements in the on-line regime [3].
This talk will present the results of this experiment and the improvement on the total dose rate calculation uncertainty.
[1] A. Tsilanizara, T. D. Huynh, Annals of Nuclear Energy 164, 108579 (2021)
[2] J. Runke et al., J Radioanal Nucl Chem 299, 1081 (2014)
[3] S. Julien-Laferrière et al., Phys. Rev. C 102, 034602 (2020)