Bonn 2010 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 15: Struktur und Dynamik von Kernen III

HK 15.6: Talk

Tuesday, March 16, 2010, 15:15–15:30, HG II

Measurement of the prompt neutron emission spectrum of 235U(n,f) induced by cold neutrons using time-of-flight spectrometry and neutron activation — •Imrich Fabry¹, Franz-Josef Hambsch¹, Nikolay Kornilov², Stephan Oberstedt¹, Goeran Loevestam¹, Mikael Hult¹, and Tamas Belgya³ — ¹European Commission, JRC-IRMM, B-2440 Geel, Belgium — ²Accelerator Lab, Ohio Univ., Athens, OH 45701, USA — ³Inst. of Isotopes HAS, Budapest, Hungary

As 235U is the most important isotope for nuclear energy production, it is essential for a safe and economic use of nuclear power, as well as for the development of new generation of power plants, to understand the correct prompt fission neutron emission spectrum (PFNS). The PFNS of 235U(n,f) at 100 oK incident neutron energy was measured in two experiments at the Budapest Reactor. The experiments were motivated by the long-standing discrepancy between differential literature data and the fact that the measured PFNS at thermal incident neutron energy cannot be reproduced by theory and contradict integral and benchmark experiments. The measured PFNS at thermal energy does not confirm the model calculations based on the assumption that fission neutrons are emitted from fully accelerated fragments alone. Instead, a new neutron production mechanism, scission neutron emision, is proposed to play an important role in the generation of the spectrum. In the second experiment, a new neutron activation method (DONA) was used to validate our new results. Results are presented.