共查询到20条相似文献,搜索用时 15 毫秒
1.
Neutron flux measurements and flux distribution parameters for two irradiation sites of an Am–Be neutron source irradiator were measured by using gold (Au), zirconium (Zr) and aluminum (Al) foils. thermal neutron flux Φth = 1.46 × 104 n cm−2 s−1 ± 0.01 × 102, epithermal neutron flux Φepi = 7.23 × 102 n cm−2 s−1 ± 0.001, fast neutron flux Φf = 1.26 × 102 n cm−2 s−1 ± 0.020, thermal-to-epithermal flux ratio f = 20.5 ± 0.36 and epithermal neutron shaping factor α = −0.239 ± 0.003 were found for irradiation Site-1; while the thermal neutron flux Φth = 4.45 × 103 n cm−2 s−1 ± 0.06, the epithermal neutron Φepi = 1.50 × 102 n cm−2 s1 ± 0.003, the fast neutron flux Φf = 1.17 × 10 n cm−2 s−1 ± 0.011, thermal-to-epithermal flux ratio f = 29.6 ± 0.94, and epithermal neutron shaping factor α = 0.134 ± 0.001 were found for irradiation Site-2. It was concluded that the Am–Be neutron source can be used for neutron activation analysis (NAA). The Am–Be source can be used for neutron activation analysis thereby reducing the burden on GHARR-1 and increasing the research output of the nation. 相似文献
2.
Clark L. Allred Jeffrey T. Borenstein 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,264(1):66-72
A study is made of radiation-induced expansion/compaction in Pyrex® (Corning 7740) and Hoya SD-2® glasses, which are used as substrates for MEMS devices. Glass samples were irradiated with a neutron fluence composed primarily of thermal neutrons, and a flotation technique was employed to measure the resulting density changes in the glass. Transport of Ions in Matter (TRIM) calculations were performed to relate fast (∼1 MeV) neutron atomic displacement damage to that of boron thermal neutron capture events, and measured density changes in the glass samples were thus proportionally attributed to thermal and fast neutron fluences. Pyrex was shown to compact at a rate of (in Δρ/ρ per n/cm2) 8.14 × 10−20 (thermal) and 1.79 × 10−20 (fast). The corresponding results for Hoya SD-2 were 2.21 × 10−21 and 1.71 × 10−21, respectively. On a displacement per atom (dpa) basis, the compaction of the Pyrex was an order of magnitude greater than that of the Hoya SD-2. Our results are the first reported measurement of irridiation-induced densification in Hoya SD-2. The compaction of Pyrex agreed with a previous study. Hoya SD-2 is of considerable importance to MEMS, owing to its close thermal expansivity match to silicon from 25 to 500°C. 相似文献
3.
Dynamic tritium concentration measurement in lithium–lead eutectic (17% Li–83% Pb) is of major interest for a reliable tritium testing program in ITER TBM and for an experimental proof of tritium self-sufficiency in liquid metal breeding systems. Potentiometric hydrogen sensors for molten lithium–lead eutectic have been designed at the Electrochemical Methods Lab at Institut Quimic de Sarria (IQS) at Barcelona and are under development and qualification. The probes are based on the use of solid state electrolytes and works as Proton Exchange Membranes (PEM).In this work, the following compounds have been synthesized in order to be tested as PEM H-probes: BaCeO3, BaCe0.9Y0.1O3?δ, SrCe0.9Y0.1O3?δ and Sr(Ce0.9–Zr0.1)0.95Yb0.05O3?δ. Potentiometric measurements of the synthesized ceramic elements have been performed at different hydrogen concentrations at 500 °C. In this campaign, a fixed and known hydrogen pressure has been used in the reference electrode. The sensors constructed using the proton conductor elements BaCeO3, SrCe0.9Y0.1O3?δ and Sr(Ce0.9–Zr0.1)0.95Yb0.05O3?δ exhibited quite stable output potential and its value was quite close to the theoretical value calculated with the Nernst equation (deviation less than 100 mV). Unstable measurement was obtained using BaCe0.9Y0.1O3?δ as a solid state electrolyte in the sensor. 相似文献
4.
Weld beads on plate specimens made of type 316L stainless steel were neutron-irradiated up to about 2.5 × 1025 n/m2 (E > 1 MeV) at 561 K in the Japan Material Testing Reactor (JMTR). Residual stresses of the specimens were measured by the neutron diffraction method, and the radiation-induced stress relaxation was evaluated. The values of σx residual stress (transverse to the weld bead) and σy residual stress (longitudinal to the weld bead) decreased with increasing neutron dose. The tendency of the stress relaxation was almost the same as previously published data, which were obtained for type 304 stainless steel. From this result, it was considered that there was no steel type dependence on radiation-induced stress relaxation. The neutron irradiation dose dependence of the stress relaxation was examined using an equation derived from the irradiation creep equation. The coefficient of the stress relaxation equation was obtained, and the value was 1.4 (×10−6/MPa/dpa). This value was smaller than that of nickel alloy. 相似文献
5.
M. Roumié R. Awad A. Zein K. Zahraman 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(1):133-139
Ion beam analysis techniques (IBA) were performed to determine the elemental stoichiometry of superconducting samples of type TlBa2Ca2−xScxCu3O9−δ, with 0 ? x ? 0.6, prepared via solid-state reaction technique. By combining particle induced X-ray emission (PIXE) with Rutherford backscattering spectrometry (RBS), the stoichiometry of the samples is determined. However, the oxygen content is obtained by using non-Rutherford backscattering cross-section at 3 MeV proton beam. Furthermore, the prepared samples were also characterized using X-ray powder diffraction (XRD) and electrical resistivity measurements. The X-ray data indicate that the partial substitution of Ca2+ by Sc3+ ions does not affect the tetragonal structure of Tl-1223 superconducting phase. The superconducting transition temperatures Tc, determined from electrical resistivity measurements, was found to be highly correlated to the Sc-content. 相似文献
6.
Alfons Weisenburger Kazumi Aoto Annette Heinzel Tomohiro Furukawa 《Journal of Nuclear Materials》2006,358(1):69-76
The behaviour of protective oxide layers on P122 steel and its welds and of ODS steel in liquid Pb44.5Bi55.5 (LBE) is examined under conditions of changing temperatures and oxygen concentrations. P122 (12Cr) and its welded joints are exposed to LBE at 550 °C for 4000 h with oxygen concentrations of 10−6 and 10−8 wt% (p(O2) = 8.1 × 10−23 bar and 5.2 × 10−27 bar) which change every 800 h. It is found that like in case of constant oxygen concentration of 10−6 wt% a protective spinel layer (Fe(Fe1−xCrx)2O4) was maintained on P122 and also on its welded joint. Two experiments with exposure times of 4800 h are conducted on ODS steel, both with temperatures changing from 550 to 650 °C and back every 800 h, one experiment with 10−6 the other with 10−8 wt% oxygen in LBE. Both experiments show strong local dissolution attack after 4800 h which is in agreement with the behaviour of ODS in LBE at a constant temperature of 650 °C. However, dissolution attack is less in LBE with 10−8 wt% oxygen (p(O2) = 3.0 × 10−25 bar). 相似文献
7.
M. Ali 《Journal of Nuclear Materials》2007,360(2):99-103
Enthalpy increment measurements on La2Te3O9(s) and La2Te4O11(s) were carried out using a Calvet micro-calorimeter. The enthalpy values were analyzed using the non-linear curve fitting method. The dependence of enthalpy increments with temperature was given as: H°(T) − H°(298.15 K) (J mol−1) = 360.70T + 0.00409T2 + 133.568 × 105/T − 149 923 (373 ? T (K) ? 936) for La2Te3O9 and H°(T) − H°(298.15 K) (J mol−1) = 331.927T + 0.0549T2 + 29.3623 × 105/T − 114 587 (373 ? T (K) ? 936) for La2Te4O11. 相似文献
8.
Haider F. Abdul Amir Abdulah Chik 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(18):3032-3036
The main purpose of this study is to provide the knowledge and data on Deuterium-Tritium (D-T) fusion neutron induced damage in MOS devices. Silicon metal oxide semiconductor (MOS) devices are currently the cornerstone of the modern microelectronics industry. However, when a MOS device is exposed to a flux of energetic radiation or particles, the resulting effects from this radiation can cause several degradation of the device performance and of its operating life. The part of MOS structure (metal oxide semiconductor) most sensitive to neutron radiation is the oxide insulating layer (SiO2). When ionizing radiation passes through the oxide, the energy deposited creates electron-hole pairs. These electron-hole pairs have been seriously hazardous to the performance of these electronic components. The degradation of the current gain of the dual n-channel depletion mode MOS caused by neutron displacement defects, was measured using in situ method during neutron irradiation. The average degradation of the gain of the current is about 35 mA, and the change in channel current gain increased proportionally with neutron fluence. The total fusion neutron displacement damage was found to be 4.8 × 10−21 dpa per n/cm2, while the average fraction of damage in the crystal of silicon was found to be 1.24 × 10−12. All the MOS devices tested were found to be controllable after neutron irradiation and no permanent damage was caused by neutron fluence irradiation below 1010n/cm2. The calculation results shows that (n,α) reaction induced soft-error cross-section about 8.7 × 10−14 cm2, and for recoil atoms about 2.9 × 10−15 cm2, respectively. 相似文献
9.
The thermal conductivities of (U0.68Pu0.30Am0.02)O2.00−x solid solutions (x = 0.00-0.08) were studied at temperatures from 900 to 1773 K. The thermal conductivities were obtained from the thermal diffusivities measured by the laser flash method. The thermal conductivities obtained experimentally up to about 1400 K could be expressed by a classical phonon transport model, λ = (A + BT)−1, A(x) = 3.31 × x + 9.92 × 10−3 (mK/W) and B(x) = (−6.68 × x + 2.46) × 10−4 (m/W). The experimental A values showed a good agreement with theoretical predictions, but the experimental B values showed not so good agreement with the theoretical ones in the low O/M ratio region. From the comparison of A and B values obtained in this study with the ones of (U,Pu)O2−x obtained by Duriez et al. [C. Duriez, J.P. Alessandri, T. Gervais, Y. Philipponneau, J. Nucl. Mater. 277 (2000) 143], the addition of Am into (U, Pu)O2−x gave no significant effect on the O/M dependency of A and B values. 相似文献
10.
The thermal conductivities of (U,Pu,Np)O2 solid solutions were studied at temperatures from 900 to 1770 K. Thermal conductivities were obtained from the thermal diffusivity measured by the laser flash method. The thermal conductivities obtained below 1400 K were analyzed with the data of (U,Pu,Am)O2 obtained previously, assuming that the B-value was constant, and could be expressed by a classical phonon transport model, λ = (A + BT)−1, A(z1, z2) = 3.583 × 10−1 × z1 + 6.317 × 10−2 × z2 + 1.595 × 10−2 (m K/W) and B = 2.493 × 10−4 (m/W), where z1 and z2 are the contents of Am- and Np-oxides. It was found that the A-values increased linearly with increasing Np- and Am-oxide contents slightly, and the effect of Np-oxide content on A-values was smaller than that of Am-oxide content. The results obtained from the theoretical calculation based on the classical phonon transport model showed good agreement with the experimental results. 相似文献
11.
Yoshinori Kawamura Kanetsugu Isobe Toshihiko Yamanishi 《Fusion Engineering and Design》2007,82(2):113-121
The blanket tritium recovery system using the electrochemical hydrogen pump with proton conductor membrane has been proposed. The feature of the electrochemical hydrogen pump is that the driving force of hydrogen transportation is a potential difference. Therefore, it might be effective to apply the hydrogen pump to the blanket sweep gas (the low hydrogen and water vapor pressure). Perovskite-type ceramic such as SrCe0.95Yb0.05O3−α, is one of the candidate proton conductor for hydrogen pump and its ionic hydrogen transportation properties have been investigated. In this work, the basic mass transfer equation for hydrogen, in which the apparent proton conductivity is used as the over-all mass transfer coefficient, is proposed. And then, the apparent proton conductivities were estimated from experimental data using these equations, and mass transfer of hydrogen via proton conductor membrane was discussed by using the apparent conductivity. 相似文献
12.
The electrical properties of annealed, fully metamict gadolinite REEFe2+Be2Si2O10 are studied as a function of annealing temperature. Changes due to annealing are also probed by 57Fe Mössbauer spectroscopy and X-ray diffraction. The electrical conductivity measured at f = 100 Hz between 110 and 750 K varies markedly, ranging from 10−10 to 10−6 S m−1 for untreated samples and 10−9 to 10−3 S m−1 for sample annealed in argon at 1373 K. Average measured activation energies for electrical conduction are 0.47 and 0.63 eV for ranges of 400-450 K and 500-600 K, respectively. The dielectric permittivity shows strong dispersion effects above 235 K. After high temperature annealing, the electrical conductivity shows a marked dispersion below 604 K. The combination of polaron hopping and hydroxyl anion migration is proposed for the electrical conduction mechanism. 相似文献
13.
R.G. Abrefah R.B.M. Sogbadji S.A. Birikorang B.J.B. Nyarko 《Nuclear Engineering and Design》2010,240(4):744-746
The MCNP model for the Ghana Research Reactor-1 was redesigned to incorporate an epicadmium-shielded irradiation channel in one of the outer irradiation channels. Extensive investigations were made before arriving at the final design of only one epicadmium covered outer irradiation channel; as all the other designs that were considered did not give desirable results of neutronic performance. The concept of redesigning a new MCNP model which has an epicadmium-shielded channel is to equip the Ghana Research Reactor-1 with the means of performing efficient epithermal neutron activation analysis. After the simulation, a comparison of the results from the original MCNP model for the Ghana Research Reactor-1 and the new redesigned model of the epicadmium-shielded channel was made. The final keff of the original MCNP model for the GHARR-1 was recorded as 1.00402 while that of the new epicadmium designed model was recorded as 1.00332. Also, a final prompt neutron lifetime of 1.5237 × 10−4 s was recorded for the new epicadmium designed model while a value of 1.5571 × 10−7 s was recorded for the original MCNP design of the GHARR-1. The neutron energy causing fission for the original MCNP design of the GHARR-1 was 1.3533 × 10−2 MeV while that of the new epicadmium designed model was 1.3513 × 10−2 MeV. 相似文献
14.
《Journal of Nuclear Materials》2006,348(1-2):26-32
Mass and charge transfer in a proton-conducting ceramic with internal reformation under the supply of CH4 + H2O was experimentally investigated for application to a fuel detritiation system of a fusion reactor. The oxide used in the present experiment was SrCe0.95Yb0.05O3−a, and the electrodes were composed of Ni–SiO2 paste and Ni wire mesh. The system was described by CH4 + H2O∣Ni∣SrCe0.95Yb0.05O3−a∣NiO∣O2 + H2O. Plots of the I–V (electric current density versus cell potential) characteristic curve were determined under the conditions of different H2O/CH4 concentration ratios and temperatures of 600–800 °C. It was found that the system could work well even without any external CH4 reformer. Mass-transfer process in/on the porous Ni electrode and in the ceramic electrolyte was experimentally clarified. The distribution of carbon depositions in the porous electrode was also determined with EDX by scanning over entire surface in the scope of SEM. The ratio of CH4 to H2 direct decomposition to its steam-reforming reaction was found to be different from location to location in the porous Ni electrode. 相似文献
15.
The corrosion behaviour of the martensitic T91 steel and the austenitic AISI 316L steel was analysed. The steels were immersed in stagnant molten Pb-55.2wt%Bi alloy at 823 K for different exposure times (t = 550-2000 h). The corrosion tests were carried out both under Ar and under Ar-5%H2 mixture. Under the oxidising conditions (PO2 = 6 × 10−3 Pa), the formation of oxide layers was observed which prevent the penetration of the liquid alloy into the matrix, while under the Ar-5%H2 mixture (PO2 = 3.2 × 10−23 Pa), two phenomena occurred: a ‘reactive penetration’ at the liquid alloy/steel interface and the competition between oxidation and penetration. 相似文献
16.
M.K. Miller A.A. Chernobaeva K.F. Russell D.Y. Erak 《Journal of Nuclear Materials》2009,385(3):615-178
A high nickel VVER-1000 (15Kh2NMFAA) base metal (1.34 wt% Ni, 0.47% Mn, 0.29% Si and 0.05% Cu), and a high nickel (12Kh2N2MAA) weld metal (1.77 wt% Ni, 0.74% Mn, 0.26% Si and 0.07% Cu) have been characterized by atom probe tomography to determine the changes in the microstructure during neutron irradiation to high fluences. The base metal was studied in the unirradiated condition and after neutron irradiation to fluences between 2.4 and 14.9 × 1023 m−2 (E > 0.5 MeV), and the weld metal was studied in the unirradiated condition and after neutron irradiation to fluences between 2.4 and 11.5 × 1023 m−2 (E > 0.5 MeV). High number densities of ∼2-nm-diameter Ni-, Si- and Mn-enriched nanoclusters were found in the neutron irradiated base and weld metals. No significant copper enrichment was associated with these nanoclusters and no copper-enriched precipitates were observed. The number densities of these nanoclusters correlate with the shifts in the ΔT41 J ductile-to-brittle transition temperature. These nanoclusters were present after a post irradiation anneal of 2 h at 450 °C, but had dissolved into the matrix after 24 h at 450 °C. Phosphorus, nickel, silicon and to a lesser extent manganese were found to be segregated to the dislocations. 相似文献
17.
J. Zhang Y.Q. Wang J.A. Valdez 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(19):3018-3022
The purpose of this study is to investigate the role of stoichiometry on crystal structure transformations in derivative fluorite compounds known as delta (δ) phase. In this study, polycrystalline δ-phase ceramic pellets were prepared with stoichiometries given by Sc4−xZr3+xO12+x/2 (x = 0, 0.77 and 1.20). The pressed and polished pellets were then irradiated under cryogenic conditions with 200 keV Ne+ ions to fluences ranging from 1-5 × 1014 Ne/cm2. An order-to-disorder (O-D) transformation was observed for all compositions, as determined using grazing incidence X-ray diffraction (GIXRD). However, the transformation threshold dose was found to systematically decrease with increasing ZrO2 content: ∼0.2, ∼0.16, and ∼0.08 dpa for Sc4−xZr3+xO12+x/2 with x = 0, 0.77, and 1.20, respectively. These irradiation-induced phase transformation results are discussed in terms of the crystal structure of the δ-phase. 相似文献
18.
Eric J. Pitcher 《Journal of Nuclear Materials》2008,377(1):17-20
The United States Department of Energy is developing technologies needed to reduce the quantity of high-level nuclear waste bound for deep geologic disposal. Central to this mission is the development of high burn-up fuel with significant inclusion of plutonium and minor actinides. Different fuel forms (e.g., nitrides, oxides, and metal matrix) and composition are under study. The success of these cannot be judged until they have been irradiated and tested in a prototypic fast neutron spectrum environment. In 2005, the US Congress authorized funding for the design of the materials test station (MTS) to perform candidate fuels and materials irradiations in a neutron spectrum similar to a fast reactor spectrum. The MTS will use a 1-MW proton beam to generate neutrons through spallation reactions. The peak neutron flux in the irradiation region will exceed 1.2 × 1019 n m−2 s−1 and the fast neutron fluence will reach 2 × 1026 n m−2 per year of operation. Site preparation and test station fabrication are expected to take four years. 相似文献
19.
Y.H. Li Y.Q. WangM. Zhou C.P. XuJ.A. Valdez K.E. Sickafus 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(18):2001-2005
We have recently synthesized “stuffed” (i.e., excess Lu) Lu2(Ti2−xLux)O7−x/2 (x = 0, 0.4 and 0.67) compounds using conventional ceramic processing. X-ray diffraction measurements indicate that stuffing more Lu3+ cations into the oxide structure leads eventually to an order-to-disorder (O-D) transition, from an ordered pyrochlore to a disordered fluorite crystal structure. At the maximum deviation in stoichiometry (x = 0.67), the Lu3+ and Ti4+ ions become completely randomized on the cation sublattices, and the oxygen “vacancies” are randomized on the anion sublattice. Samples were irradiated with 400 keV Ne2+ ions to fluences ranging from 1 × 1015 to 1 × 1016 ions/cm2 at cryogenic temperatures (∼77 K). Ion irradiation effects in these samples were examined by using grazing incident X-ray diffraction. The results show that the ion irradiation tolerance increases with disordering extent in the non-stoichiometric Lu2(Ti2−xLux)O7−x/2. 相似文献
20.
H. Balta? U. Çevik 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(7):1127-1131
The effective atomic numbers and electron densities of YBa2Cu3O7−δ superconductor at 59.5, 65.2, 77.1, 94.6, 122 and 136 keV were calculated by using the measured mass attenuation coefficients. Measurements were made by performing transmission experiments in a well-collimated narrow beam geometry set-up by employing Si(Li) detector with a resolution of 0.16 keV at 5.9 keV. These values are found to be in good agreement with theoretical values calculated based on XCOM data. The observed crystal structure of YBa2Cu3O7−δ superconductor is close to the theoretical structure. Zeff and Nel experimental values showed good agreement with the theoretical values for calcined and sintered YBa2Cu3O7−δ. 相似文献