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[en] The α parameter and the thermal to epithermal flux ratio (f) have been determined for irradiation channels (LS3, LS5, LS9, LS11 and LS25) of nuclear reactor Triga Mark II of the Regional Nuclear Centre of Kinshasa. The three methods - Cd radio method covered Cd monitor method and base monitor method used for evaluation of α parameter give the same result in each irradiation position. The thermal to epithermal flux ratio f has been determined by the Cd ratio method. Results show that nuclear parameters α and f, change from one point to another of the reactor; α being negative, the resonance integrals I.(α) are increased.
[en] The effect of epithermal neutrons on nano-silicon fusion by IR spectroscopic absorption was investigated. Specific IR-absorption strips have been identified in nano-silicon in the 4000-400 sm-1 frequency range. Under the influence of epithermal neutrons, the kinetics of change of their concentrations in relative units were investigated depending on the radiation time of these components observed in IR-spectra.
[en] To measure the thermal and epithermal flow was used the direct method using indium sheet as detector. Among the studies performed longitudinal variations of this flows was determined. The magnitude of the thermal flow measured was 8.10 3 n cm-2 s-1 and the epithermal was twice lower. The longitudinal dependence, measured taking into account the sources axis, a light dependence of these was observed. Finally, searching a better irradiation condition to practicals goals the flow was measured employing paraffin as thermalizator. The results show a significative increase of the thermical flow which medium value was of 8.57.10 4 n cm-2 s-1
[en] For several decades now, the method of remote neutron and gamma spectrometry of objects in the Solar System (Moon, Mars, Mercury) has made it possible to estimate the nuclear composition of the object and the hydrogen abundance in its subsurface layer. For measuring the neutron component of low energy, proportional gas counters based on helium-3 (3He) are most often used, having the maximum efficiency of recording thermal and epithermal neutrons. However, the experience of LEND and FREND space experiments with helium counters of large volumes and pressures showed the noise in lower channels of the neutron component due to the sensitivity of such counters to space charged particles. The article describes a model of a promising neutron detector with anti-coincidence protection that does not have this disadvantage.
[ru]Вот уже несколько десятилетий метод дистанционной нейтронной и γ-спектрометрии объектов Солнечной системы (Луна, Марс, Меркурий) позволяет оценить ядерный состав этого объекта и степень присутствия водорода в его приповерхностном слое. Для измерения нейтронной компоненты низких энергий чаще всего используются пропорциональные газовые счетчики на основе гелия-3 (3He), имеющие максимальную эффективность регистрации тепловых и эпитепловых нейтронов. Однако опыт космических экспериментов LEND и FREND с гелиевыми счетчиками больших объемов и давлений показал зашумление младших каналов нейтронной компоненты за счет чувствительности таких счетчиков к заряженным частицам космического пространства. В статье описывается макет перспективного нейтронного детектора с антисовпадательной защитой, не имеющий данного недостатка.
[en] We present here a collection of works reporting on the recent experimental and theoretical activities taking advantage of epithermal neutron spectroscopy, and in particular focusing on recent results presented during the VII International Workshop on Electron-Volt Neutron Spectroscopy held in Rome on 7-8 November 2018. (paper)
[en] An experimental technique was developed aiming to determine uranium and thorium, in coal, using the activation analysis with thermal neutrons. (E.G.)
[pt]Foi desenvolvida uma tecnica experimental para a determinacao de uranio e torio, em carvoes minerais, utilizando o metodo de analise por ativacao com neutrons epitermicos. (E.G.)
[en] The development of an epithermal neutron porosity has been greatly aided by model calculations to supplement laboratory measurements of environmental effects. Accurate computational models of this device have been developed using discrete ordinates and Monte Carlo techniques. The ability of the models to predict individual detector counting rates is demonstrated for the case of the basic porosity response. The validity of the models is further established by comparison with laboratory measurements of the experimental tool response to formation porosity, formation matrix, borehole size, tool stand-off, and temperature. 3 refs