[en] The neutron leakage spectrum behind a 8.4 cm thick iron slab has been measured by a stilbene proton-recoil spectrometer in the range 1-15 MeV. The neutron source is 14 MeV generator with neutron intensity of 1.10¹⁰ s^-1. The neutron spectrum has been modelled by energy-transport 3-d Monte Carlo code using ENDF/B-6 cross-section library. The comparison of calculated with experimental spectra indicates underestimation of the measured spectrum in the range 2-10 MeV. There is an agreement between calculated and measured integrals in the energy ranges 1-2 and 10-15 MeV. It is recommended to include angular dependence in the preequilibrium process for inelastic scattering used for calculation of cross-sections in the ENDF/B-6 library. 1 fig., 1 tab., 11 refs

[en] The results of comparison of calculated and experimentally measured reaction rate for threshhold activation detectors fixed on back side of beryllium plate are discussed. The calculation values are obtained according to the MCNP program utilizing three-dimensional Monte Carlo method. General agreement between measured and calculated results testifies to adequacy of the predicted neutron spectrim in the 2-15 MeV range. This testifies in particular to good prediction of the energy spectrum of secondary neutrons emitted in the (n,2n) reaction at angle from 0 up to 104 deg. 10 refs., 1 tab

[en] Semi-empirical methods based on what is called the removal cross-section are widely used for high-speed evaluation of fast neutron fluxes and the doses they deliver. Determination of this quantity is based on an approximation of the decay of the fast neutron flux beyond a layer of shielding material with an exponential function. In this study data were obtained for the removal cross-section and the relaxation length in the case of neutron flux from a 14 MeV one-directional source passing through layers of iron shielding. The numerical computations of the neutron distributions were performed by the discrete ordinate transport technique and the Monte Carlo method

[en] The semi-empirical removal cross-section method is widely used for the evaluation of neutron radiation behind layers. This paper accordingly presents data on removal cross-section as a function of the threshold energy of detection for a monoenergetic and monodirectional (along the measurement axis) and isotropic 14 MeV source. The removal cross-sections for the basic shielding materials (aluminium, iron, copper and lead) were obtained using numerically derived neutron fluxes which had passed through barriers (1-3) lambdasub(t) in thickness

[en] Neutron and photon calculations have been performed to assess the effect of radiation streaming through the gaps between blanket modules upon the radiation loads to the super-conducting TF-coil at the inboard side. These include the fast neutron fluence to the superconductor, the peak nuclear heating in the winding pack, the radiation damage to the copper stabilizer and the radiation dose absorbed by the Epoxy resin insulator. Three-dimensional Monte Carlo radiation transport code MCNP4C and a suitable 20 deg.-sector model of DEMO reactor, developed by FZK, have been employed in the analysis. The model is based on PPCS AB concept employing HCLL blanket. A 4000 MW fusion power and 40 fpy of plan operation have been assumed. The poloidal profiles of radiation loads in respect to the torus mid-plane have been investigated in several variants of the gap widths and compositions of additional shield plugging the gaps. It was found that the design limit of all the responses considered could only be met if the toroidal and poloidal gaps are plugged by LTS material, the later being made of borated steel, WC and water coolant. (author)

[en] Leakage neutron spectra from a Pu-Be source placed in the center of a 30 cm diameter sphere filled with water, paraffin oil, SiO₂ and river sand were measured using a pulse height response spectrometer (PHRS) in the 1.4-12.0 MeV energy range. The measured leakage neutron spectra have been compared with the calculated results obtained by the three dimensional Monte Carlo code MCNP-4A and point-wise cross sections from the FENDL data file. A comparison of the measured and calculated data has shown that the MCNP-4A code with appropriate data library can approximate reasonably the measured leakage spectra of neutrons. The observed linear dependence of the integrated spectral yield as a function of water content in SiO₂ rendered possible the determination of the moisture content in river sand

[en] Neutron spectra are unfolded by means of differentiating recoil-proton distributions registered in NE213 and stilbene scintillators. Numerically-stable derivatives are computed on the basis of global orthonormal-polynomial fits supported by suitable functional transforms. Special attention is paid to the accurate reproduction of the spectrometer transfer function. Sample processing results are presented. (author)

[en] Neutron leakage spectra through lead slabs with thicknesses of 0.05, 0.075 and 0.125 m were measured by using a proton recoil technique and a differentiation unfolding procedure. The measurements were performed on an absolute basis. The results were compared with the prediction of Monte Carlo calculations by using the MCNP-4A code and pointwise cross-sections from ENDF/B-IV and ENDF/B-VI data fates. The calculations employing ENDF/B-VI data show good agreement with the experimental results, with the exception of the energy region between 5 and 10 MeV, where an underestimation of up to 29% was obtained. (author)

[en] On the basis of MORSE and ANISN codes and ENDL-2 and ENDF/B-IV neutron data the 14 MeV neutron transport through iron collimator and lead layers has been modelled. The calculation results have been compared with experimental data

[en] Neutron spectra are unfolded by means of differentiating recoil-proton distributions registered in NE213 and stilbene scintillators. Numerically-stable derivatives are computed on the basis of global orthonormal-polynomial fits supported by suitable functional transforms. special attention is paid to the accurate reproduction of the spectrometer transfer function. Sample processing results are presents