Prediction of the Cross Sections of p ~(11)C and d ~(11)C Reactions for Energy up to 25 MeV

~(11)C (half time is 20.3 min) is a proton-rich radioactive nucleus. The cross sections of p ~(11)C and d ~(11)C reactions were predicted in energy region up to 25 MeV. From the calculated results one can see some features of nuclear reactions of proton-rich radioactive nuclei. The calculated results also show that the experimental measurement to ~(11)C d reaction is more feasible than to ~(11)C p reaction at HI-13 tandem accelerator.     

Neutronic analysis for core conversion (HEU–LEU) of Pakistan research reactor-2 (PARR-2)

Neutronic analyses for the core conversion of Pakistan research reactor-2 (PARR-2) from high enriched uranium (HEU) fuel to low enriched uranium (LEU) fuel has been performed. Neutronic model has been verified for 90.2% enriched HEU fuel (UAl₄–Al). For core conversion, UO₂ fuel was chosen as an appropriate fuel option because of higher uranium density. Clad has been changed from aluminum to zircalloy-4. Uranium enrichment of 12.6% has been optimized based on the design basis criterion of excess reactivity 4 mk in miniature neutron source reactor (MNSR). Lattice calculations for cross-section generation have been performed utilizing WIMS while core modeling was carried out employing three dimensions option of CITATION. Calculated neutronic parameters were compared for HEU and LEU fuels. Comparison shows that to get same thermal neutron flux at inner irradiation sites, reactor power has to be increased from 30 to 33 kW for LEU fuel. Reactivity coefficients calculations show that doppler and void coefficient values of LEU fuel are higher while moderator coefficient of HEU fuel is higher. It is concluded that from neutronic point of view LEU fuel UO₂ of 12.6% enrichment with zircalloy-4 clad is suitable to replace the existing HEU fuel provided that dimensions of fuel pin and total number of fuel pins are kept same as for HEU fuel.     

The necessity of sample quality assessment in 14C AMS dating: The case of Cova des Pas (Menorca – Spain)

The Cova des Pas cave is a karstic cave in the cliffs of the Barranc (canyon) de Trebalúger. It is a small cave only 6.5 m deep, 4.5 m wide and 1.7 m high. Yet more than 70 burials, in foetal position, from the Early Iron Age were found in this small cave. The conservation of the archaeological remains was very unusual. Not only wood, ropes and other plant material was found, but also remains of body tissue, hair and leather. In spite of the remarkable preservation of the bodies and artefacts, the state of conservation of the bone material was very bad. The bones contained little and heavily deteriorated collagen and the organic plant material was very fragile. The special environmental conditions of the cave are the cause of these unusual preservation conditions. Although the cave is situated in a limestone cliff, the soil of the cave is very acid. Unexpectedly bad sample quality seemed to be the major drawback for AMS radiocarbon dating on hair, wood, ropes and bone collagen, as well as on bio-apatite.     

Dielectric properties of SiC fiber-reinforced SiC matrix composites in the temperature range from 25 to 700 °C at frequencies between 8.2 and 18 GHz

The complex permittivity of a SiC fiber-reinforced SiC matrix (SiCf/SiC) composite was measured in a temperature range of 25–700 °C at frequencies from 8.2 to 18 GHz. The SiCf/SiC composite exhibited a positive temperature coefficient, that is, its complex permittivity increased with temperature. The observed positive temperature coefficient can be interpreted by Debye theory, by which the theoretical predictions were in well agreement with the experimental results.     

Design and testing of a 5 GHz TE10–TE30 mode converter mock-up for the lower hybrid antenna proposed for ITER

The design and overall dimensions of a 5 GHz TE₁₀–TE₃₀ mode converter are presented. This mode converter is a RF element of a 20 MW CW lower hybrid system proposed for ITER. A low power mock-up of this device has been manufactured at CEA/IRFM and measured at low power. RF measurements indicate a return loss of 40 dB and a transmission loss of 4.78 dB ± 0.03 dB for the three outputs. The forward conversion efficiency from TE₁₀ mode to TE₃₀ has been measured from electric field probing to 99.9%. The good RF performances obtained validate the RF design of this element.     

Thermal hydraulic and safety analysis for core conversion (HEU–LEU) of Syrian Miniature Neutron Source Reactor

The paper presents the behavior and properties analysis of the low enriched uranium fuel compared with the original high enriched uranium fuel. The MNSR reactor core was modeled with both fuel materials and the reactor behavior was studied during the steady state and abnormal conditions. The MERSAT code was used in the analysis. The steady state thermal hydraulic analysis results were compared with that obtained from the experimental results hold during commissioning the Syrian MNSR. Comparison with experimental data shows that the steady-state behavior of the HEU core was accurately predicted by the MERSAT code calculations. The validated model was then used to analyze LEU cores with two proposed UO₂ fuel pin designs. With each LEU core, the steady state and 3.77 mk rod withdrawal transient were run and the results were compared with the available published data in the literatures for the low enriched uranium fuel core. The results reveal that the low enriched uranium fuel showed a good behavior and the peak clad temperatures remain well below the clad melting temperature during reactivity insertion accident.     

Calculation of Excitation Function of Some Structural Fusion Material for (n, p) Reactions up to 25 MeV

Fusion serves an inexhaustible energy for humankind. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, Furthermore, there are not radioactive nuclear waste problems in the fusion reactors. In this study, (n, p) reactions for some structural fusion materials such as ²⁷Al, ⁵¹V, ⁵²Cr, ⁵⁵Mn and ⁵⁶Fe have been investigated. The new calculations on the excitation functions of ²⁷ Al(n, p) ²⁷ Mg, ⁵¹ V(n, p) ⁵¹ Ti, ⁵² Cr(n, p) ⁵² V, ⁵⁵ Mn(n, p) ⁵⁵ Cr and ⁵⁶ Fe(n, p) ⁵⁶ Mn reactions have been carried out up to 30 MeV incident neutron energy. Statistical model calculations, based on the Hauser–Feshbach formalism, have been carried out using the TALYS-1.0 and were compared with available experimental data in the literature and with ENDF/B-VII, T = 300 K; JENDL-3.3, T = 300 K and JEFF-3.1, T = 300 K evaluated libraries.     

A small long-cycle PWR core design concept using fully ceramic micro-encapsulated (FCM) and UO2–ThO2 fuels for burning of TRU

In this paper, a new small pressurized water reactor (PWR) core design concept using fully ceramic micro-encapsulated (FCM) particle fuels and UO₂–ThO₂ fuels was studied for effective burning of transuranics from a view point of core neutronics. The core of this concept rate is 100 MWe. The core designs use the current PWR-proven technologies except for a mixed use of the FCM and UO₂–ThO₂ fuel pins of low-enriched uranium. The significant burning of TRU is achieved with tri-isotropic particle fuels of FCM fuel pins, and the ThO₂–UO₂ fuel pins are employed to achieve long-cycle length of ～4 EFPYs (effective full-power year). Also, the effects of several candidate materials for reflector are analyzed in terms of core neutronics because the small core size leads to high sensitivity of reflector material on the cycle length. The final cores having 10 w/o SS303 and 90 w/o graphite reflector are shown to have high TRU burning rates of 33%–35% in FCM pins and significant net burning rates of 24%–25% in the total core with negative reactivity coefficients, low power peaking factors, and sufficient shutdown margins of control rods.     

A New Comparison of Empirical and Semi-empirical Formulae for the (n, 3He) Reaction Cross-sections at 14–15 MeV

New empirical and semi-empirical formulae have been suggested for the (n, ³He) reaction cross-sections with dependent on asymmetry parameter, S = (N − Z)/A. The (n, ³He) reaction cross-sections at the energy of 14–15 MeV have been investigated for two different parameters groups by the classification of nuclei into 31 ≤ A ≤ 103 and 133 ≤ A ≤ 181. The obtained results have been compared with the other systematics and experimental data for the (n, ³He) reaction cross-sections. Some improvement has been got in describing the (n, ³He) reaction cross-sections compared with the existing relations.     

Measurements of activation cross sections for Lu(n, α)Tm,Lu(n, α)Tm and Lu(n, p)Yb reactions induced by neutrons around 14 MeV

The cross sections for the ¹⁷⁵Lu(n, α)¹⁷²Tm, ¹⁷⁶Lu(n, α)¹⁷³Tm and ¹⁷⁵Lu(n, p)^175m+gYb reactions have been measured in the neutron energy range of 13.5–14.8 MeV using the activation technique. The first data for ¹⁷⁵Lu(n, α)¹⁷²Tm reaction cross sections are presented. In our experiment, the fast neutrons were produced via the ³H(d, n)⁴He reaction on K-400 Neutron Generator at Chinese Academy of Engineering Physics (CAEP). Induced gamma activities were measured by a high-resolution (1.69 keV at 1332 keV for ⁶⁰Co) gamma-ray spectrometer with high-purity germanium (HPGe) detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The neutron fluences were determined by the cross section of ⁹³Nb(n, 2n)^92mNb or ²⁷Al(n, α)²⁴Na reactions. The neutron energy in the measurement was by the cross section ratios of ⁹⁰Zr(n, 2n)^89m+gZr and ⁹³Nb(n, 2n)^92mNb reactions. The results were discussed and compared with experimental data found in the literature and with results of published empirical formulae.     

Comparison of Level Density Models for the <Superscript>60,61,62,64</Superscript>Ni(p,n) Reactions of Structural Fusion Material Nickel from Threshold to 30 MeV

The knowledge of level density for reaction cross-section calculations are needed for various applications such as fission and fusion reactor design, accelerator driven sub-critical systems, nuclear medicine, neutron capture and astrophysics. In this study, the excitation functions for (p, n) reactions from reaction threshold to 30 MeV proton incident energy on ⁶⁰Ni, ⁶¹Ni, ⁶²Ni and ⁶⁴Ni isotopes were calculated using TALYS 1.6 nuclear code involving the level density models. This is of importance to the validation of nuclear model approaches with increased predictive power. There are several models of level density that can be used to predict cross-section. In this work, the (p, n) cross-sections would be calculated using three different model of level density, such as constant temperature model, back-shifted fermi gas model and generalized superfluid model on ^60,61,62,64Ni reactions. The (p, n) reaction cross-section calculations for ^60,61,62,64Ni target nuclei were compared with each other and the experimental nuclear reaction data obtained from EXFOR database.     

Measurement of isomeric yield ratios for 90Zr(γ, n)89m,gZr, natZr(γ, xn1p)86m,gY, and 89Y(γ, xn)87m,g,86m,gY reactions with 50-, 60-, and 70-MeV bremsstrahlung

We measured the isomeric yield ratios in the photonuclear reactions of ^natZr(γ, n)^89m,gZr, ^natZr(γ, xn1p)^86m,gY, and ⁸⁹Y(γ, xn)^87m,g,86m,gY by the activation method. The high-purity natural Zr and Y metallic foils in disc shape were irradiated with uncollimated bremsstrahlung beams of 50-, 60-, and 70-MeV generated from an electron linear accelerator at Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometric system consisting of a high-purity germanium detector and a multichannel analyzer. The obtained isomeric yield ratios in the formation of ^89m,gZr, ^87m,gY, and ^86m,gY are compared with the corresponding values found in the literature. The measured isomeric yield ratios at the bremsstrahlung energies of 50-, 60-, and 70-MeV are the first measurement except ⁸⁷Y at 50-MeV bremsstrahlung.     

Investigation of Some Structural Fusion Materials for (<Emphasis Type="Italic">n</Emphasis>, <Emphasis Type="Italic">α</Emphasis>) Reactions at the 14–15 MeV Energy Region

In fusion reactor structures, a serious damage mechanism has been gas production in the metallic resulting from diverse nuclear reactions, mainly through (n, α) and (n, p) reactions above a certain threshold energy. The neutron incident energy around 14–15 MeV is enough to excite the nucleus for the reactions such as (n, p), (n, d), (n, 2n), (n, t), and (n, α). Design of the fusion reactor, about the 14–15 MeV neutron incident energy reaction cross sections is of great importance for various target nuclei. In this study, the experimental data have been taken only at 14–15 MeV energy regions from EXFOR database. The (n, α) reactions for some structural fusion materials such as ²⁷Al, ⁵¹V, ⁵²Cr, ⁵⁵Mn, ⁵⁶Fe and ⁵⁸Ni have calculated by using evaluated empirical formulas developed by Tel et al. at 14–15 MeV and calculated with the pre-equilibrium models up to 20 MeV. The calculated results are discussed and compared with the experimental data taken from EXFOR database.     

(3He,xn) Reaction Cross-Section Calculations for the Structural Fusion Material 181Ta in the Energy Range of 14–75 MeV

The theoretical neutron-production cross-sections produced by ¹⁸¹Ta(³He,xn)^184?xRe reactions (x = 1–7) for structural fusion material ¹⁸¹Ta in ³He-induced reactions have been performed in the incident ³He energy range of 14–75 MeV. Reaction cross-sections, based on theoretical pre-equilibrium nuclear reaction models, have been calculated theoretically by means of the TALYS 1.6 two component exciton, EMPIRE 3.1 exciton, ALICE/ASH geometry dependent hybrid (GDH) and ALICE/ASH hybrid models. The neutron-production cross-section results of the models have been compared with the each other and against the experimental nuclear reaction data (EXFOR). Except the ¹⁸¹Ta(³He,2n)¹⁸²Re and ¹⁸¹Ta(³He,7n)¹⁷⁷Re reactions, the ALICE/ASH cross-section calculations show generally agreement with the experimental values for all reactions used in this study. The ALICE/ASH–GDH model can be suggested, if the experimental data are unavailable or are improbably to be produced because of the experimental troubles.     

Investigation of 14–15 MeV (<Emphasis Type="Italic">n,t</Emphasis>) Reaction Cross-sections by Using New Evaluated Empirical and Semi-empirical Systematic Formulas

In the hybrid reactor, tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. Working out the systematics of (n, t) reaction cross-sections are of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at energies up to 20 MeV. In this study we have investigated asymmetry term effect for the (n, t) reaction cross-sections at 14–15 neutron incident energy. It has been discussed the odd–even effect and the pairing effect considering binding energy systematic of the nuclear shell model for the new experimental data and new cross-sections formulas (n, t) reactions developed by Tel et al. We have determined a different parameter groups by the classification of nuclei into even–even, even–odd and odd–even for (n, t) reactions cross-sections. The obtained empirical and semi-empirical formulas by fitting two parameter for (n, t) reactions were given. All calculated results have been compared with the experimental data and the other semi-empirical formulas.     

Calculation of 14–15 MeV (<Emphasis Type="Italic">n,d</Emphasis>) Reaction Cross Sections Using Newly Evaluated Empirical and Semi-empirical Systematics

In this study, we have investigated the asymmetry term effect for the (n, d) reaction cross sections at 14–15 neutron incident energy. It has been discussed the odd–even effect and the pairing effect considering binding energy systematic of the nuclear shell model for the new experimental data and new cross section formulae developed by Tel et al. for (n, d) reactions. We have determined different parameter groups by the classification of nuclei into even–even, even–odd and odd–even for (n, d) reactions cross sections. The obtained empirical and semi-empirical formulae by fitting two parameters for (n, d) reactions were given. By using the new cross sections formulae for (n, d) reactions the obtained results have been discussed and compared with the available experimental data.     

Measurements and statistical model calculations of activation cross-sections for 26Mg(n,α)23Ne reaction between 13.6 and 14.9 MeV neutron energies

Activation cross-sections were measured at neutron energies from 13.6 to 14.9 MeV for the reaction ²⁶Mg(n,α)²³Ne. The production of relatively short-lived activity and the spectra accumulation have been carried out by the cyclic activation method. Corrections were made for the effects of gamma-ray attenuation, random coincidence summing (pulse pile-up), dead time, and scattered low energy neutron contribution. Statistical model calculations for which the pre-equilibrium emission effects are taken into consideration were also performed. Results were compared with the previous investigations.