[en] Study on the ac-electrical conductivity of poly(propylene), before and after X-ray irradiation within the temperature range 300-360 K are reported. The measurements have been performed in a wide range of frequencies (from 0 to 10⁵ Hz) and under the effect of different X-ray irradiation doses (from 0 to 15 Gy). Cole-Cole diagrams have been used to show the frequency dependence of the complex impedance at different temperatures. The results exhibit semicircles which are consistent with existing equivalent circuit model. Analysis of the results reveal semiconducting features based mainly on a hopping mechanism. The study shows a pronounced effect of X-ray irradiation on the electrical conductivity at zero frequency σ_DC. At the early stage of irradiation, σ_DC increased as a result of free radical formation. As the irradiation progressed, it decreased as a result of crosslinking, then it increased again due to irradiation induced degradation, which motivates the generation of mobile free radicals. The study shows that this polymer is one among other polymers which its electrical conductivity is modified by irradiation

[en] MODIF-Code is a computer program for calculating the reflector saving, material buckling, and effective multiplication constant of completely reflected cylindrical reactors. The calculational method is based on a modified iterative algorithm which has been deduced from the general analytical solution of the two group diffusion equations. The code has been written in FORTRAN language suited for the ICL-1906 computer facility at Cairo University. The computer time required to solve a problem of actual reactor is less than 1 minute. The problem converges within five iteration steps. The accuracy in determining the effective multiplication constant lies within +-10^-5. The code has been applied to the case of UA-RR-1 reactor, the results confirm the validity and accuracy of the calculational method

[en] A two group, two dimensional (r,z) program that solves the neutron diffusion equations within a cylindrical nuclear reactor is applied to the vercellese power plant (247 M We). The spatial (in (r,z) coordinates) and temporal variations of the flux distribution are calculated. The reactor core is divided into three radial zones, each of which is divided into four axial zones. In each zone, the average values of fast and thermal fluxes, the isotope number densities and the cross-sections are evaluated after different times of reactor operation (burn-up) and for cold and hot conditions. The reactor parameters η,ζ,RHO,f,K_Α and K_eff are also calculated at cold and hot conditions. The comparison of the temperature variation of K_eff with the corresponding experimental results gives reasonable agreement

[en] Thermodynamic studies of polycrystalline ruthenium (Ru) doped LiKSO₄ have been made for different concentrations of Ru in the range 0%, 0.1%, 0.2%, 0.5%, 1%, 2%, 3% by weight. The thermal behaviour has been investigated using a differential scanning calorimeter in the vicinity of high temperature phases. From this, the effect of electron beam-irradiation on the thermal properties of these polycrystalline samples has been studied. The results showed a change in the transition temperature T_c, as well as the value of specific heat C_Pmax at the transition temperature due to the change in Ru content and irradiation energies. The change of enthalpy and entropy of the polycrystalline have been estimated numerically

[en] The thermal conductivity of amorphous metallic alloys (Fe, Ni, Co)/sub 1-x/ (B, P, Si)/sub x/ is measured in the temperature range 2 to 100 K in the as-produced and heat-treated states. By taking into account the results of Matey and Anderson the influence of the nature of the metalloid and the number of metallic components can be discussed. The change of the thermal conductivity due to a structural relaxation caused by a heat treatment is very different. In the whole range of temperature a rise of the phonon thermal conductivity of the Fe-Co-B alloy is obtained, whereas no change is observed for the Fe-B alloy. At low temperature (< 40 K) the thermal conductivity of the Fe-Ni-P-B alloy increases by heat treatment, whereas at higher temperatures a reduction is observed. Additionally the thermal conductivity of the recrystallized alloy Fe₈₀B₂₀ is investigated. (author)

[en] This paper gives a collective summary of the studies performed at the JRC, ISPRA on the use of computer codes for complex systems analysis. The computer codes dealt with are: CAFTS-SALP software package, FRANTIC, FTAP, computer code package RALLY, and BOUNDS codes. Two reference study cases were executed by each code. The results obtained logic/probabilistic analysis as well as computation time are compared

[en] This paper gives a summary of studies performed at the JRC, ISPRA on the use of computer codes for complex systems analysis. The computer codes dealt with are: CAFTS-SALP software package, FRACTIC, FTAP, computer code package RALLY, and BOUNDS. Two reference case studies were executed by each code. The probabilistic results obtained, as well as the computation times are compared. The two cases studied are the auxiliary feedwater system of a 1300 MW PWR reactor and the emergency electrical power supply system. (author)

[en] The influence of X-ray irradiation on the electrical conductivity and spontaneous strain of admixtured triglycine sulphate crystals is studied. The role of lattice defects in such crystals is also clarified. (author). 10 refs., 3 figs

[en] The elimination of a large number of approximations that lead to numerous errors in the neutronic reactor calculations was the main purpose behind developing Monte Carlo codes. The MCNP series of codes (Monte Carlo Nuclear Particle) are developed and extensively used in neutronic core calculations. Although the neutronic data input to these codes is the pointwise cross section files as presented by ENDF libraries or similar ones, are comprehensive and detailed. Yet the major sources of errors in the core calculations stem from the uncertainty in the cross section data. In this paper the effect of estimated uncertainty in the values of cross sections in the ENDF/B-V1 library, on the neutronic parameters of the ETRR-2 reactor is studied. MCNP code is used to simulate a three dimensional model for the reactor core considering all the materials composition and geometrical details. Perturbation technique is used to determine the effect of uncertainty in cross sections for a number of isotopes in the reactor on the fission rates and a comparison is made between the fission rate values with and without the uncertainty values for the different cross section types and different energy ranges. It is shown that for all the considered isotopes the effect of uncertainty in the cross section data on the fission rate values is very small, where the differences in fission rates do not exceed 10% and this value is accepted

[en] We report on the realization of a quantum dot (QD) based single-photon source with a record-high single-photon emission rate. The quantum light source consists of an InGaAs QD which is deterministically integrated within a monolithic microlens with a distributed Bragg reflector as back-side mirror, which is triggered using the frequency-doubled emission of a mode-locked vertical-external-cavity surface-emitting laser (ML-VECSEL). The utilized compact and stable laser system allows us to excite the single-QD microlens at a wavelength of 508 nm with a pulse repetition rate close to 500 MHz at a pulse width of 4.2 ps. Probing the photon statistics of the emission from a single QD state at saturation, we demonstrate single-photon emission of the QD-microlens chip with g"("2")(0) < 0.03 at a record-high single-photon flux of (143 ± 16) MHz collected by the first lens of the detection system. Our approach is fully compatible with resonant excitation schemes using wavelength tunable ML-VECSELs, which will optimize the quantum optical properties of the single-photon emission in terms of photon indistinguishability