[en] Iron spheres 20, 30 and 50 mm in diameter were placed at a height of 1.7 m above the floor. A ²⁵²Cf source was placed in the centre of the sphere. The spectra of penetrated neutrons within the energy range of 10 keV to 10 MeV were measured using the differential spectrometric method based on the detection of recoil protons. Within the energy range 0.5 to 10 MeV the spectra were measured using a scintillation spectrometer with a stilbene crystal. Within the energy range 10 keV to 800 keV detection was carried out by a hydrogen filled SP-2 spherical chamber. The arrangement of the experiment is given. The obtained spectra were evaluated using the ENKA, SPE and SPEC programs. The results are compared with those obtained by other authors. Within the energy range 100 to 650 keV good agreement was reached with the results published by H. Werle et al. (KFK 2219, 1975) and for the energy range above 800 keV agreement was reached with results published by E.A. Trykov et al. (FEI 943, 1979). (J.P.)

[en] A method is reported of neutron spectra unfolding from measured proton spectra. The method involves corrections for proton escape and double-scattered neutrons. The corrections are based on the assumption that the geometry of the detector is spherical and its self-shielding is negligible. The method is thus only suitable for spherical hydrogen-filled counters and for a scintillation spectrometer with equilateral stilbene crystal. (author)

No abstract available

[en] The compensation of background gamma radiation in neutron spectrometry is based on the measurement of the total energy spectrum of all protons and electrons, and of the energy spectrum of those protons and neutrons which are in coincidence with the discriminating signal derived from the integral of the counting rate distribution by pulse shape. The benefits of the method consist in the possibility of using standard single-parameter apparatus, in considerably smaller demands on the memory capacity and the possibility of a substantially finer division of the spectrum and more accurate compensation of the background than has been the case with methods used so far. A practical application is shown in a block diagram. (J.B.)

[en] Measurements were made in the energy range 10 keV to 10 MeV using a scintillation spectrometer with a stilbene crystal and the SP-2 proportional counter filled with hydrogen. Used were iron spheres 20, 30 and 50 cm in diameter and a ₂₅₂Cf neutron source. The evaluation of the neutron spectra was made by computer. Evident is the rapid drop in the flux density of neutrons with an energy of more than 1.5 MeV with increasing thickness of iron. The range of 0.8 to 1.5 MeV is transient while at neutron energy of less than 0.8 MeV an increase occurs in neutron flux density within the whole range of measured thicknesses of the iron. A comparison is made of the results with available results published in the literature. (M.D.)

[en] The limiting factor of the service life of the WWER reactor pressure vessel is the radiation damage to material by fast neutrons escaping from the core. Radiation damage to the material is determined by tell-tale samples placed in a test reactor on which changes in mechanical properties due to radiation are periodically ascertained. Experimental reactor LR-0 is the testing reactor simulating conditions in the WWER 440 and WWER 1000 reactor cores. The arrangement of the experiment is described as are the measuring of neutron spectra and the distribution of neutron flux density, and detectors used for the experiment. The most frequent neutron detector was a hydroaen-filled proportional counter, a stilbene monocrystal and liquid scintillators. The result of theoretical studies and highly accurate experimental measurement is the determination of the radiation load of the pressure vessel walls. (M.D.)

[en] A brief analysis is made of the method of recoil protons using the combined measurement with a scintillation spectrometer with a 10 mm dia. by 10 mm thick stilbene crystal and a set of spherical proportional chambers filled with hydrogen to a pressure of 392.4; 981; 392.4; 98.1 kPa. Pulse shape discrimination was used for gamma radiation discrimination. Programs in FORTRAN IV identical for all detectors were used for evaluating the spectra. The evalution proceeded from the hardest to the softest components of the spectrum. Prior to the evaluation, energy calibration was made of each of the components. The energy calibration is described of detectors which is related to the adjustment of optimal operating modes of detectors. One source of errors is the anisotropy of the detectors. The spherical hydrogen chambers were tested in the neutron beam and differences were found in absolute values of the spectra measured at neutron impingement angles 0 and π/2 to the detector anode; the efficiency of the chambers varied roughly by 10 to 20%. The efficiency of the scintillation spectrometer was determined by measuring the neutron spectrum from the fission of ²⁵²Cf, the source-to-detector distance being 1 m. A comparison of the computed and measured spectra showed good agreement in absolute values and in the spectrum shape with an error smaller than 5% in the energy range 1 to 10 MeV. Deviations of actual efficiency from theory were found when the chambers were tested by comparison with the scintillation spectrometer. (J.P.)

[en] Neutron spectra were measured in the core of the TR-0 heavy water reactor (the critical assembly of the KS-150 reactor). The measurements were carried out by a spherical proportional counter filled with hydrogen (4 kp.cm^-2) and by a scintillation spectrometer with a stilbene crystal in an energy range of 10 keV to 9 MeV. A brief description of the measurements and a survey of results are presented. (author)

No abstract available

[en] The evaluation of neutron spectra measured by hydrogen-filled proportional counters and a scintillation spectrometer with a stilbene crystal can be divided in four stages. The first stage consists of the gain calibration of the measuring equipment and the detector. The second stage consists of the transformation of the measured spectra in the pulse amplitude scale into the proton energy scale and their grouping by the chosen energy regions. In the third stage proton spectra are corrected for the effect of proton leakage from the detector and for double neutron scattering. The corrected (ideal) proton spectra are transformed to neutron spectra by direct differentiation. The above methodology may only be applied to spherical counters filled with hydrogen and to a scintillation spectrometer with an equilateral cylindrical stilbene crystal. (Kr)