.10.26 Mev Neutrons Cause <sup> 51 </ Sup> V Secondary Neutron Double Differential Cross Section Measurements

The double differential cross section (DDX) of neutron emission from 51V at 10.26 MeV neutrons was measured using normal and abnormal fast neutron TOF spectrometers on HI-13 Tandem Accelerator in China Institute of Atomic Energy (CIAE). The problem of influence from breakup neutrons of the D(d,n) neutron source on secondary neutron spectra was successfully solved.The DDX of neutron emission is one of the most important nuclear data in nuclear design. More precise nuclear data, not only nuclear reaction data but also energy and angular distributions, are required by the development of nuclear engineering. Moreover, precise experimental data are the base of theoretical models and calculations.Up to now, at about 14 MeV, there are some DDX measurement data because the T(d,n)4He reaction is a good mono-energetic neutron source. Below 8 MeV, there are also some measurements because mono-energetic neutron source is available in this region. The measurement data is scarce in 8-13 MeV region due to the lack of mono-energetic neutron sources (In this region, there are breakup neutrons besides the mono-energetic neutrons in the often used neutron sources such as T(p,n)3 He and D(d,n)3He sources. The secondary neutrons induced by breakup source neutrons will seriously contaminate the secondary neutron spectra induced by mono-energetic source neutrons). Therefore, precise measurement for some key nuclides is necessary to check the evaluations in this region.Vanadium is a candidate element for the first wall material of ITER project. So its neutron data are very important. This is the main reason we did such measurement.A lot of methods were used in measurement and data analysis to improve the quality of the data. The measured TOF spectra were simulated by Monte-Carlo code STREUER. The cross sections were determined by comparing the measured TOF spectra with the simulated TOF spectra and the data were normalized to n-p scattering measurement. Finally, the data measured in CIAE were compared with those measured in PTB and evaluated of ENDF/B-VI.