Radiation Effects in Rare-Earth Permanent Magnets

1987 ◽  
Vol 96 ◽  
Author(s):  
J. R. Cost ◽  
R. D. Brown ◽  
A. L. Giorgi ◽  
J. T. Stanley
Keyword(s):  
Neutron Irradiation ◽  
Radiation Effects ◽  
Permanent Magnets ◽  
Hysteresis Loops ◽  
Open Circuit ◽  
Fast Neutrons ◽  
Rapid Loss ◽  
Before And After ◽  
Radiation Induced ◽  
Fission Neutrons

ABSTRACTNd-Fe-B and Sm-Co permanent magnets have been irradiated with fission neutrons and gamma rays. Irradiated samples were periodically removed for room temperature measurements of the open-circuit remanence. Hysteresis loops were measured before and after irradiation. For neutron irradiation, two Nd-Fe-B magnets showed a rapid loss of remanence, while a third magnet from another manufacturer decayed more slowly, suggesting that the radiation hardness of Nd-Fe-B magnets may depend on microstructural details. Irradiation in the Omega West Reactor at Los Alamos with fast neutrons caused the fast-decay samples to have an Wtial loss of remanence of 1% for irradiation at 350 K to a fluence of 1015 n/cm2. Both SmCo5 and Sm2Co17 magnets showed excellent resistance to radiatifg-induied loss of remanence for neutron irradiation to a fluence of 2.6×1018 n/cm2. Results for gamma radiation showed no loss of remanence for a dose of about 49 Mrad using a 60Co source. Possible mechanisms for radiation-induced loss of magnetic properties are discussed.

High-flux neutron irradiation of boron trioxide analyzed with Raman and FTIR spectroscopy

2020 ◽  
Vol 34 (18) ◽  
pp. 2050160
Author(s):  
Matlab N. Mirzayev
Keyword(s):  
Raman Spectrum ◽  
Ftir Spectroscopy ◽  
Functional Groups ◽  
Neutron Irradiation ◽  
Spectrum Analysis ◽  
Boron Oxide ◽  
Fast Neutrons ◽  
Raman Analysis ◽  
Before And After ◽  
Flux Formula

Boron oxide nanopowder is widely used in the production of special glasses and nuclear technology. This paper reports on the optical properties and investigates the formation of new bonds on the structure of nanoboron oxide. In this work, high purity boron oxide samples were irradiated using a energy upto 1 MeV fast neutrons with fluences in the range of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and the neutron flux [Formula: see text] at the room-temperature. Optical properts were determined using Raman spectrum analysis and spectroscopy Fourier transform infrared (FTIR) spectroscopy. FTIR and Raman spectrum analysis were used to explain the chemical bonds and functional groups of nanoboron oxide samples before and after neutron irradiation. When the irradation fluence on [Formula: see text] was increased upto [Formula: see text] it resulted in the formation of a new functional groups [Formula: see text]. From the Raman analysis, the [Formula: see text] was observed to start amorphization after neutron irradiation.

scholarly journals Irradiation-Induced Microstructural Changes in Alloy X-750

1997 ◽  
Vol 3 (S2) ◽  
pp. 551-552
Author(s):  
E.A. Kenik
Keyword(s):  
Power Systems ◽  
Neutron Irradiation ◽  
Nuclear Power ◽  
Base Alloy ◽  
Analytical Electron Microscopy ◽  
Air Cooling ◽  
Probe Diameter ◽  
Before And After ◽  
Radiation Induced ◽  
Composition Profiles

Alloy X-750 is a γ´-strengthened Ni-base alloy that is often used in nuclear power systems for its excellent corrosion resistance and good mechanical properties. However, radiation-induced segregation (RIS) and irradiation-assisted stress corrosion cracking (IASCC) can occur under neutron irradiation. The present study examines the microstructure and composition profiles in a heat of Alloy X-750 before and after neutron irradiation.The material was in the HTH commercial heat treatment (lh at 1121°C + air cooling + 20h at 704°C). Specimens were prepared from both control material and material irradiated at 360°C to a fluence of 2.3 × 1020 n/cm2 (E > 1 MeV), which was estimated to produce -0.4 displacements per atom. High spatial resolution analytical electron microscopy was performed in a Philips EM400T/FEG operated in the STEM mode with a probe diameter of ∼1.4 nm (FWHM). Composition profiles were acquired in two different ways: all energy dispersive X-ray spectrometry (EDS) and some parallel-detection electron energy-loss spectrometry (PEELS) profiles were acquired as individual spot analyses, whereas the majority of the PEELS profiles were acquired as spectrum lines with ∼10 s acquisition times per point. The quoted compositions are as measured (wt%); no deconvolution for the effect of the excited volume was performed.

A study of neutron irradiation damage in α-iron with magnetoacoustic and Barkhausen emission

1987 ◽  
Vol 414 (1846) ◽  
pp. 221-236 ◽  
Keyword(s):  
Neutron Irradiation ◽  
Neutron Radiation ◽  
Irradiation Damage ◽  
Post Irradiation ◽  
Recovery Processes ◽  
New Information ◽  
Before And After ◽  
Radiation Induced ◽  
Examination Methods ◽  
Cold Worked

Magnetoacoustic emission (MAE) and Barkhausen emission (BE) in α-iron are sensitive to the presence of precipitates and of dislocations. These techniques have been used to examine radiation damage and post-irradiation recovery processes in α-iron containing low levels of interstitial impurities in the annealed and cold-worked conditions, both before and after neutron irradiation at 60 °C to 2.9 × 10 19 n cm -2 (greater than 1 MeV). Irradiation leads to the suppression of domain wall pinning in annealed material, as indicated by reductions in low-field BE and MAE activities. Furthermore, cold-worked irradiated α-iron exhibits reduced thermal stability during post-irradiation annealing in the temperature range 250-550 °C, compared with the unirradiated annealing response. The results are interpreted in terms of radiation-induced dissolution of α"-Fe 16 N 2 and γ'-Fe 4 N nitrides, solute-point defect trapping/dissociation, and enhanced dislocation recovery processes. The studies demonstrate that BE and MAE measurements can pro­vide new information to complement more conventional examination methods for characterization of low-dose irradiation effects in α-iron. The techniques show promise for non-destructive examination of ferrous materials in neutron-radiation environments.

scholarly journals Positron annihilation spectroscopy study of radiation-induced defects in W and Fe irradiated with neutrons with different spectra

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
O. V. Ogorodnikova ◽  
M. Majerle ◽  
J. Čížek ◽  
S. Simakov ◽  
V. V. Gann ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Radiation Effects ◽  
Defect Formation ◽  
Wide Spectrum ◽  
High Energy ◽  
Primary Radiation ◽  
Vacancy Clusters ◽  
Mean Size ◽  
Radiation Induced ◽  
Fission Neutrons

Abstract The paper presents new knowledge on primary defect formation in tungsten (W) and iron (Fe) irradiated by fission and high-energy neutrons at near-room temperature. Using a well-established method of positron-annihilation lifetime-spectroscopy (PALS), it was found that irradiation of W in the fission reactor and by high-energy neutrons from the p(35 MeV)-Be generator leads to the formation of small radiation-induced vacancy clusters with comparable mean size. In the case of Fe, smaller mean size of primary radiation-induced vacancy clusters was measured after irradiation with fission neutrons compared to irradiation with high-energy neutrons from the p(35 MeV)-Be generator. It was found that one of the reasons of the formation of the larger size of the defects with lower density in Fe is lower flux in the case of irradiation with high-energy neutrons from the p(35 MeV)-Be source. The second reason is enhanced defect agglomeration and recombination within the energetic displacement cascade at high energy primary knock-on-atoms (PKAs). This is consistent with the concept of the athermal recombination corrected (arc-dpa) model, although the measured dpa cross-section of both fission neutrons and wide-spectrum high-energy neutrons in W is between the conventional Norgett–Robinson–Torrens (NRT-dpa) and arc-dpa predictions. This means that the physics of the primary radiation effects in materials is still not fully known and requires further study through a combination of modeling and experimental efforts. The present data serve as a basis for the development of an improved concept of the displacement process.

scholarly journals Dielectric properties of alumina ceramics for fusion applications

Energetika ◽  
2017 ◽  
Vol 63 (2) ◽  
Author(s):  
Darío Cruz ◽  
Rafael Vila ◽  
Begoña Gómez-Ferrer
Keyword(s):  
Dielectric Properties ◽  
Neutron Irradiation ◽  
Loss Tangent ◽  
Radiation Effects ◽  
Ceramic Materials ◽  
Dielectric Performance ◽  
Measuring Techniques ◽  
Fusion Applications ◽  
Radiation Induced ◽  
Electrical Permittivity

The insulating materials for radio frequency (RF) windows and different antenna supports for heating systems and some diagnostics are still an unresolved issue in future fusion machines such as DEMO. Alumina ceramic (Al2O3) is one of the main candidate materials for these systems. The dielectric properties, such as electrical permittivity (ε) and loss tangent (tanδ), determine its power losses. Therefore, tanδ values need to be low, between 10–6 and 10–3 depending on the application. However, due to the crucial role of the manufacturing process in determining its final dielectric properties, there is the need to undertake a joint effort with the industry in order to validate a standard manufacturing route that ensures a supply of ceramic material with homogeneous and standardized dielectric properties for future fusion machines. In DEMO, these ceramic materials will be operated under extreme conditions. They will be exposed to considerable levels of neutron irradiation. Radiation Induced Conductivity (RIC) and Radiation Induced Electrical Degradation (RIED) are phenomena that influence notoriously on the dielectric performance of these materials. Therefore, their optimum properties must be tested under relevant irradiation conditions. Hence, it is important to accurately characterize their dielectric properties before irradiation to be able to compare them with the future post neutron irradiation results. Furthermore, other types of radiation such as beta and gamma are also used in the irradiation scheme to provide more information on the variation of dielectric properties of ceramics due to radiation effects. In this work, loss tangent and permittivity values of some pre-irradiated candidate materials will be presented as well as the measuring techniques used at CIEMAT. These techniques have the advantage of covering a very broad range of frequencies required for alumina applications in fusion (from kHz to GHz) and giving the best accuracy for very low losses.

scholarly journals Comparative Study of γ- and e-Radiation-Induced Effects on FBGs Using Different Femtosecond Laser Inscription Methods

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8379
Author(s):  
Antreas Theodosiou ◽  
Arnaldo Leal-Junior ◽  
Carlos Marques ◽  
Anselmo Frizera ◽  
Antonio J. S. Fernandes ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Comparative Study ◽  
Ftir Spectroscopy ◽  
Radiation Effects ◽  
Single Mode ◽  
Electron Radiation ◽  
Temperature Coefficients ◽  
Before And After ◽  
Radiation Induced ◽  
Fibre Bragg Gratings

This work presents an extensive, comparative study of the gamma and electron radiation effects on the behaviour of femtosecond laser-inscribed fibre Bragg gratings (FBGs) using the point-by-point and plane-by-plane inscription methods. The FBGs were inscribed in standard telecommunication single mode silica fibre (SMF28) and exposed to a total accumulated radiation dose of 15 kGy for both gamma and electron radiation. The gratings’ spectra were measured and analysed before and after the exposure to radiation, with complementary material characterisation using Fourier transform infrared (FTIR) spectroscopy. Changes in the response of the FBGs’ temperature coefficients were analysed on exposure to the different types of radiation, and we consider which of the two inscription methods result in gratings that are more robust in such harsh environments. Moreover, we used the FTIR spectroscopy to locate which chemical bonds are responsible for the changes on temperature coefficients and which are related with the optical characteristics of the FBGs.

Phosphors as Sensors for Radiation-Induced Displacement Damage

2012 ◽  
Vol 1471 ◽  
Author(s):  
S. L. Gollub ◽  
R. R. Harl ◽  
S. L. Weeden-Wright ◽  
B. R. Rogers ◽  
D. G. Walker
Keyword(s):  
Radiation Effects ◽  
Spectral Signature ◽  
X Rays ◽  
Displacement Damage ◽  
Particle Radiation ◽  
Before And After ◽  
Radiation Induced ◽  
Significant Change ◽  
Alpha Irradiation ◽  
Rule Out

AbstractThe radiation-induced displacement damage in yttrium borate (YBO3) is studied under X-ray, proton, and alpha irradiation. The photoluminescence (PL) was tested before and after irradiation to determine whether damage occurred and whether it could be queried by examining the PL spectrum. Two different dopants (cerium and europium) were used to activate the phosphor because each provides not only a different spectral signature but also a different mechanism for altering the spectrum between the pre- and post-PL measurements. X-rays, being primarily ionizing radiation, did not show any significant change between the pre and post measurements. We expected protons and alphas to damage the crystal structure, evidence of which could be seen in the change in the spectra before and after irradiation. However, we found no change under alpha exposure (3.6 × 1010 particles/cm2) and a significant change after proton exposure (5 × 1015 particles/cm2). While the material appears to be sensitive to protons, we cannot rule out its sensitivity to alphas because the alpha fluence may be too low to show an effect. This result provides strong indication that our materials are being damaged by particle radiation and that the radiation effects can be quantified.

scholarly journals Micromagnetic Characterization of Operation-Induced Damage in Charpy Specimens of RPV Steels

2021 ◽  
Vol 11 (7) ◽  
pp. 2917
Author(s):  
Madalina Rabung ◽  
Melanie Kopp ◽  
Antal Gasparics ◽  
Gábor Vértesy ◽  
Ildikó Szenthe ◽  
...  
Keyword(s):  
Neutron Irradiation ◽  
Pressure Vessel ◽  
Operating Conditions ◽  
Magnetic Characteristics ◽  
Pressure Vessel Steel ◽  
Training Procedure ◽  
Vessel Steel ◽  
Before And After ◽  
The Individual ◽  
Magnetic Adaptive Testing

The embrittlement of two types of nuclear pressure vessel steel, 15Kh2NMFA and A508 Cl.2, was studied using two different methods of magnetic nondestructive testing: micromagnetic multiparameter microstructure and stress analysis (3MA-X8) and magnetic adaptive testing (MAT). The microstructure and mechanical properties of reactor pressure vessel (RPV) materials are modified due to neutron irradiation; this material degradation can be characterized using magnetic methods. For the first time, the progressive change in material properties due to neutron irradiation was investigated on the same specimens, before and after neutron irradiation. A correlation was found between magnetic characteristics and neutron-irradiation-induced damage, regardless of the type of material or the applied measurement technique. The results of the individual micromagnetic measurements proved their suitability for characterizing the degradation of RPV steel caused by simulated operating conditions. A calibration/training procedure was applied on the merged outcome of both testing methods, producing excellent results in predicting transition temperature, yield strength, and mechanical hardness for both materials.

Effects of Neutron Irradiation on the Mechanical and Electromagnetic Properties of Reactor Pressure Vessel Steels

2017 ◽  
Author(s):  
Li Chengliang ◽  
Shu Guogang ◽  
Chen Jun ◽  
Liu Yi ◽  
Liu Wei ◽  
...  
Keyword(s):  
Neutron Irradiation ◽  
Pressure Vessel ◽  
Power Plants ◽  
Hysteresis Loops ◽  
Reactor Pressure Vessel ◽  
Electromagnetic Properties ◽  
Irradiation Damage ◽  
Indentation Hardness ◽  
Rpv Steel ◽  
Reactor Pressure

The effect of neutron irradiation damage of reactor pressure vessel (RPV) steels is a main failure mode. Accelerated neutron irradiation experiments at 292 °C were conducted on RPV steels, followed by testing of the mechanical, electrical and magnetic properties for both the unirradiated and irradiated steels in a hot laboratory. The results showed that a significant increase in the strength, an obvious decrease in toughness, a corresponding increase in resistivity, and the clockwise turn of the hysteresis loops, resulting in a slight decrease in saturation magnetization when the RPV steel irradiation damage reached 0.0409 dpa; at the same time, the variation rate of the resistivity between the irradiated and unirradiated RPV steels shows good agreement with the variation rates of the mechanical properties parameters, such as nano-indentation hardness, ultimate tensile strength, yield strength at 0.2% offset, upper shelf energy and reference nil ductility transition temperature. Thus, as a complement to destructive mechanical testing, the resistivity variation can be used as a potentially non-destructive evaluation technique for the monitoring of the RPV steel irradiation damage of operational nuclear power plants.

A HYBRID MODEL ON HYSTERESIS LOOP AND COERCIVITY IN NANOSTRUCTURED PERMANENT MAGNETS

2006 ◽  
Vol 05 (04n05) ◽  
pp. 627-631 ◽  
Author(s):  
M. J. SUN ◽  
G. P. ZHAO ◽  
J. LIANG ◽  
G. ZHOU ◽  
H. S. LIM ◽  
...  
Keyword(s):  
Thin Films ◽  
Domain Wall ◽  
Grain Boundary ◽  
Magnetic Moment ◽  
Permanent Magnets ◽  
Hysteresis Loops ◽  
Bulk Materials ◽  
Rotational Model ◽  
Moment Distribution ◽  
Coercivity Mechanism

A simplified micromagnetic model has been proposed to calculate the hysteresis loops of nanostructured permanent magnets for various configurations, including thin films, exchange-coupled double-layer systems and bulk materials. The reversal part of the hysteresis is based on the Stoner–Wohlfarth coherent rotational model and the coercivity mechanism is due mainly to the motion of the transition region (a domain wall like magnetic moment distribution in the grain boundary). The elements of nucleation and pinning models are also incorporated.

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