Measurement of the delayed-neutron multiplicity and time constants in the thermal neutron induced fission of 235U at ILL
1 CEA, DEN, DER/SPRC/LEPh Cadarache, F-13108 Saint-Paul-lez-Durance, France
2 CEA, DEN, DER/SPESI/LP2E Cadarache, F-13108 Saint-Paul-lez-Durance, France
3 CEA, DEN, DER/SPESI/LDCI Cadarache, F-13108 Saint-Paul-lez-Durance, France
4 LPSC, Université Grenoble Alpes, F-38000 Grenoble, France
5 CENBG, Université de Bordeaux, F-33170 Gradignan, France
6 LPC, Université Caen Normandie, F-14000 Caen, France
7 Institut Laue-Langevin, F-38042 Grenoble, France
Published online: 30 September 2020
Delayed-neutron (DN) data is essential in inherent reactor safety and reactor control since it is needed for the estimation of the reactivity. Nowadays, discrepancies among the data in various international databases (JEFF, ENDF, JENDL) are large and bring excessive conservatism in the safety margins. The ALDEN (Average Lifetime of DElayed Neutrons) experiment, built in a collaboration between CEA and CNRS, aimed at re-measuring the DN data associated with several fissioning systems (average delayed-neutron yield and kinetic parameters). The first experimental campaign consisted in the integral measurement of the DN activity after the irradiation of an 235U target. It took place under the cold neutron flux of ILL (Institut Laue-Langevin) at the beginning of September 2018, in the PF1b experimental zone (doi:10.1016/j.nima.2006.03.020). The data analysis gave an average DN yield of 1.631E-02(2) DN/fiss and a mean precursors’ half-life of 8.93(9) s. The results are consistent with the literature, but they are affected by one third of the uncertainty.
© The Authors, published by EDP Sciences, 2020
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