plasma-material interactions; plasma diagnostic techniques; laser induced breakdown spectroscopy; laser induced ablation spectroscopy;FUSION DEVICES; COMPONENTS

A laser based method combined with spectroscopy, such as laser-induced breakdown spectroscopy and laser-induced ablation spectroscopy , is a promising technology for plasma-wall interaction studies. In this work, we report the development of in situ laser-based diagnostics for the assessment of static and dynamic fuel retention on the first wall without removing the tiles between and during plasma discharges in the Experimental Advanced Superconducting Tokamak . The fuel retention on the first wall was measured after different wall conditioning methods and daily plasma discharges by in situ LIBS. The result indicates that the LIBS can be a useful tool to predict the wall condition in EAST. With the successful commissioning of a refined timing system for LIAS, an in situ approach to investigate fuel retention is proposed.

laser-induced breakdown spectroscopy; plasma wall interaction; fuel retention; deposition; erosion;

Laser-induced breakdown spectroscopy is a well-established elemental composition analysis method as well as one of the most promising candidates for in situ first wall diagnosis of fusion devices. In this work, limiter graphite tiles, which were exposed in the initial operational phase of the Wendelstein 7-X stellarator to He and H plasma, are analyzed ex situ by LIBS employing a picosecond pulsed laser for the first time and compared with post mortem analysis techniques. Depth profiles of each element and 2D profile of the ratio of H and C atoms on the surface are investigated. Both H content and retention depth on the deposition dominated zone are higher than on the erosion dominated zone due to the formation of C-H co-deposition layer. The results from LIBSare in agreement with those from the cross-sectional scanning electron microscopic image and electron dispersive x-ray spectroscopy.

laser induced breakdown spectroscopy; spatial regularities of the laser-induced plasma plume; detection of hydrogen isotopes;EROSION/DEPOSITION; SPECTROSCOPY

ITER plans foresee the quantitative diagnostics of fuel retention in reactor walls at nearatmospheric pressures. Using laser induced breakdown spectroscopy for this purpose assumes a reliable resolving of Balmer a-lines of hydrogen isotopes in spectra of plasma produced by focused laser radiation onto the target surface. To develop LIBS for quantitative diagnostics of fuel retention during the maintenance breaks of ITER, the effect of background gas pressure on the laser-induced plasma characteristics has been studied. The background pressure limits the expansion rate of plasma and as a result it leads to higher plasma concentrations. At the same time the limiting factor of the resolving of hydrogen isotope lines is the lines broadening by Stark effect, which is the function of electron concentration. The resolving of lines become possible recording spectra at longer delay times after the laser pulse. On the other hand, at longer delays the signal-to-noise ratio decreases. As a compromise, we found that at atmospheric pressure and at delay times > 2000 ns, a fitting of H a and D a lines by Voigt contours allows a reliable discrimination of these lines.

ITER relevant coatings; Laser induced breakdown spectroscopy; (LIBS) diagnostics; Ablation rate; Surface morphology;TILES; JET

Laser induced breakdown spectroscopy (LIBS) has been applied to study ITER-relevant coatings with different surface morphology and crystallinity. LIBS elemental depth profiles were compared with those obtained by secondary ion mass spectrometry (SIMS). Depending on surface morphology and crystallinity, the laser ablation rate of the coatings changed by an order of magnitude, the highest ablation rate had samples prepared by thermoionic vacuum discharge. The inclusion of aluminum (proxy for beryllium) increased the ablation rate by a factor of >6. In addition, for W-Al coatings the ablation was non-stoichiometric. (C) 2017 Elsevier B.V. All rights reserved.

Laser-induced breakdown spectroscopy; LIBS; safeguards; pyroprocessing; molten salt; cerium; gadolinium;MELT CRYSTALLIZATION; MOLTEN-SALT; STRONTIUM; CESIUM

Pyroprocessing of used nuclear fuel (UNF) has many advantages-including that it is proliferation resistant. However, as part of the process, special nuclear materials accumulate in the electrolyte salt and present material accountability and safeguards concerns. The main motivation of this work was to explore a laser-induced breakdown spectroscopy (LIBS) approach as an online monitoring technique to enhance the material accountability of special nuclear materials in pyroprocessing. In this work, a vacuum extraction method was used to draw the molten salt (CeCl3-GdCl3-LiCl-KCl) up into 4 mm diameter Pyrex tubes where it froze. The salt was then removed and the solid salt was measured using LIBS and inductively coupled plasma mass spectroscopy (ICP-MS). A total of 36 samples were made that varied the CeCl3 and GdCl3 (surrogates for uranium and plutonium, respectively) concentrations from 0.5 wt% to 5 wt%. From these samples, univariate calibration curves for Ce and Gd were generated using peak area and peak intensity methods. For Ce, the Ce 551.1 nm line using the peak area provided the best calibration curve with a limit of detection (LOD) of 0.099 wt% and a root mean squared error of cross-validation (RMSECV) of 0.197 wt%. For Gd, the best curve was generated using the peak intensities of the Gd 564.2 nm line resulting in a LOD of 0.027 wt% and a RMSECV of 0.295 wt%. The RMSECV for the univariate cases were determined using leave-one-out cross-validation. In addition to the univariate calibration curves, partial least squares (PLS) regression was done to develop a calibration model. The PLS models yielded similar results with RMSECV (determined using Venetian blind cross-validation with 17% left out per split) values of 0.30 wt% and 0.29 wt% for Ce and Gd, respectively. This work has shown that solid pyroprocessing salt can be qualitatively and quantitatively monitored using LIBS. This work has the potential of significantly enhancing the material monitoring and safeguards of special nuclear materials in pyroprocessing.

LA-ICP-MS; INDIVIDUAL PARTICLES; ANALYTICAL-CHEMISTRY; FEMTOSECOND; GLASS; NANOSECOND; IONIZATION

Laser ablation - inductively coupled plasma -mass spectrometry (LA-ICP-MS) in tandem with laser induced breakdown spectroscopy (LIBS) was employed to chemically map and characterize uranium particles. The uranium particles were doped in various concentrations (0.01, 0.1, 1.0, and 2.0%) to a 50 : 50 Ni : Fe mixture. There was an excellent correlation in regards to concentration and the LA-ICP-MS measurements. In addition, the isotopic composition of the uranium particles was determined within 10% measurement uncertainty. LIBS measurements also showed strong agreement in the particle mapping when compared to the LA-ICP-MS analysis. Moreover, the total analysis time for a 5 x 5 mm area was only 50 minutes. These data suggest that the tandem LA-ICP-MS/LIBS technique can provide rapid and valuable information for nuclear material safeguards and actinide material characterization.

Laser-induced breakdown spectroscopy; Uranium; Phase identification;EMISSION; FEMTOSECOND; STRENGTHS; SPECTRA; PLASMA; LIBS

Nuclear forensics goals for characterizing samples of interest include qualitative and quantitative analysis of major and trace elements, isotopic analysis, phase identification, and physical analysis. These samples may include uranium oxides UO2, U3O8, and UO3, which play an important role in the front end of the nuclear fuel cycle, from mining to fuel fabrication. The focus of this study is to compare the ratios of the intensities of uranium and oxygen emission lines which can be used to distinguish between different uranium oxide materials using Laser-Induced Breakdown Spectroscopy (LIBS). Measurements at varying laser powers were made under an argon atmosphere at 585 Torr to ensure the oxygen emission intensity was originating from the sample, and not from the atmosphere. Fifteen uranium emission lines were used to compare experimental results with theoretical calculations in order to determine the plasma conditions. Using a laser energy of 26 mJ, the uranium lines 591.539 and 682.692 nm provide the highest degree of discrimination between the uranium oxides. The study presented here suggests that LIBS is useful for discriminating uranium oxide phases, UO2, U3O8, and UO3. (C) 2017 Elsevier B.V. All rights reserved.

Focused ion beams; Deuterium; He-3; Nuclear reaction analysis; 3HIXE;DEUTERIUM

Micro nuclear reaction analysis (micro-NRA) exploiting the nuclear reaction D(He-3,p)He-4 was used for post-mortem analyses of special marker samples, exposed to deuterium plasma inside ASDEX Upgrade (AUG) tokamak and to the deuterium plasma jet in the Pilot-PSI linear plasma gun. Lateral concentration profiles of deuterium and erosion/deposition profiles of the marker materials were obtained by a combination of micro-NRA and particle inducedX-ray emission by He-3 beam (3HIXE). In the case of AUG samples, where 25 nm thick W marker layers had been deposited on unpolished and polished graphite substrates, the effect of surface roughness on local erosion and deposition was also investigated. The lateral distribution of W concentration showed that erosion is much more distinct in the case of polished samples and the resulting surface shows a ""leopard"" skin pattern of W accumulated on carbon aggregates left on the surface from polishing. The Pilot-PSI samples indicated preferential accumulation of deuterium a few mm off from the centre of the region affected by the plasma beam. This is connected with the largest surface modifications while the thick deposited layers at the centre do not favour deuterium retention per se. The results were cross correlated with those obtained using laser-induced breakdown spectroscopy (LIBS). With its quantitative abilities, micro-NRA provided essential calibration data for in situ LIES operation, as well as for complementary post mortem Secondary Ion Mass Spectroscopy (SIMS). (C) 2017 EURATOM. Published by Elsevier B.V. All rights reserved.

Matrix effects; Laser-induced breakdown spectroscopy; Uranium; Limit of detection;URANIA; WASTE; UO2; ZR

The analysis of light water reactor simulated used nuclear fuel using laser-induced breakdown spectroscopy (LIBS) is explored using a simplified version of the main oxide phase. The main oxide phase consists of the actinides, lanthanides, and zirconium. The purpose of this study is to develop a rapid, quantitative technique for measuring zirconium in a uranium dioxide matrix without the need to dissolve the material. A second set of materials including cerium oxide is also analyzed to determine precision and limit of detection (LOD) using LIBS in a complex matrix. Two types of samples are used in this study: binary and ternary oxide pellets. The ternary oxide, (U,Zr,Ce)O-2 pellets used in this study are a simplified version the main oxide phase of used nuclear fuel. The binary oxides, (U,Ce)O-2 and (U,Zr)O-2 are also examined to determine spectral emission lines for Ce and Zr, potential spectral interferences with uranium and baseline LOD values for Ce and Zr in a UO2 matrix. In the spectral range of 200 to 800 nm, 33 cerium lines and 25 zirconium lines were identified and shown to have linear correlation values (R-2) >0.97 for both the binary and ternary oxides. The cerium LOD in the (U,Ce)O-2 matrix ranged from 034 to 1.08 wt% and 0.94 to 1.22 wt% in (U,Ce,Zr)O-2 for 33 of Ce emission lines. The zirconium limit of detection in the (U,Zr)O-2 matrix ranged from 0.84 to 1.15 wt% and 0.99 to 1.10 wt% in (U,Ce,Zr)O-2 for 25 Zr lines. The effect of multiple elements in the plasma and the impact on the LOD is discussed. (C) 2017 Elsevier B.V. All rights reserved.

Trace radioactive pollutant; Cs in water; Cs in soil; Low pressure plasma; ITO film;SHOCK-WAVE PLASMA; SAMPLES; LIBS

An experimental study has been conducted for the practical and in situ application of laser-induced breakdown spectroscopy (LIBS) for the detection of Cs pollutant in water and soil in the nearby area of Fukushima Nuclear Power Station. The spectrochemical measurements were carried out by means of 355 nm Nd-YAG laser with N-2 and He ambient gases at atmospheric and low pressures. The soil samples were prepared by pelletizing the mixtures of 80% soil and 20% KBr while the aqueous samples were prepared as thin films electro deposited on indium tin oxide (ITO) glass. The resulted emission spectra using 0.5 kPa N-2 ambient gas shows the minimum detectable Cs concentration of 0.2 ppm and 0.3 ppm in the water and soil samples, respectively. The result of this experiment has thus demonstrated the viability of the LIBS equipment employed here as a more practical, in-situ and even mobile alternative to the standard use of gamma-ray spectroscopy using germanium detector. (C) 2017 Published by Elsevier B.V.

INDUCED BREAKDOWN SPECTROSCOPY; STRESS-CORROSION CRACKING; STAINLESS-STEEL CANISTER; CONCRETE; CHLORINE

Extended dry storage of spent nuclear fuel makes it desirable to assess the structural integrity of the storage canisters. Stress corrosion cracking of the stainless steel canister is a potential degradation mode especially in marine environments. Sensing technologies are being developed with the aim of detecting the presence of chloride-bearing salts on the surface of the canister as well as whether cracks exist. Laser-induced breakdown spectroscopy (LIBS) methods for the detection of Chlorine are presented. In addition, ultrasonic-guided wave detection of crack-like notches oriented either parallel or perpendicular to the shear horizontal wave vector is demonstrated using the pulse-echo mode, which greatly simplifies the robotic delivery of the noncontact electromagnetic acoustic transducers (EMATs). Robotic delivery of both EMATs and the LIBS system is necessary due to the high temperature and radiation environment inside the cask where the measurements need to be made. Furthermore, the space to make the measurements is very constrained and maneuverability is confined by the geometry of the storage cask. In fact, a large portion of the canister surface is inaccessible due to the presence of guide channels on the inside of the cask's overpack, which is strong motivation for using guided waves for crack detection. Among the design requirements for the robotic system are to localize and track where sensor measurements are made to enable return to those locations, to avoid wedging or jamming of the robot, and to tolerate high temperatures and radiation levels.

DOUBLE-PULSE; QUANTITATIVE-ANALYSIS; INDUCED PLASMA; DEUTERIUM; ABLATION; CHAMBER; GAS

An experimental study is conducted in search of the much needed experimental method for practical and minimally destructive analysis of hydrogen (H) and deuterium (D) in a nuclear power plant. For this purpose, a picosecond (ps) Nd:YAG laser is employed and operated with 300-500 mu J output energies in a variety of ambient gases at various gas pressures. The sample chamber used is specially designed small quartz tube with an open end that can be tightly fitted to the sample surface. It is found that ambient Ar gas at reduced pressure of around 0.13 kPa gives the best spectral quality featuring fully resolved H and D emission lines with clearly detectable intensities and practically free from surface water interference. The D emission intensities measured from zircaloy plates containing various concentrations of D impurity are shown to yield a linear calibration line with extrapolated zero intercept, offering its potential application to quantitative analysis. The estimated detection limit of less than 10 ppm is well below the sensitivity limit of around 600 ppm required for the regular inspection of zircaloy tubes in a heavy water nuclear power plant. The use of the exceedingly low laser energy is shown to offer an additional advantage of minimum destructive effect marked by the resulted tiny craters of about 5 mu m diameter with 25 mu m depth. These results promise the potential development of the desired alternative analytical tool for regular in situ and real time inspection of the zircaloy tubes in a heavy water power plant.

Ambient gas; Magnetic field; LIBS; EAST; ICRF wall cleaning;TRANSVERSE MAGNETIC-FIELD; INDUCED PLASMA SPECTROSCOPY; OPTICAL-EMISSION; PLUME; PERFORMANCE

In this paper, laser-induced breakdown spectroscopy (LIBS) under magnetic field condition has been studied in laboratory and EAST tokamak. The experimental results reveal that in helium ambient gas, the magnetic field significantly enhances the LIBS signal intensity (similar to 3 times). The effect of time delay and laser fluence on the intensity of LIBS has been investigated for optimizing the signal to background ratio (S/B). The developed LIBS approach has been applied to monitor the cleaning performance of the first wall in the fusion device of EAST using the ion cyclotron range of frequency (ICRF). The experimental results demonstrate that the cleaning performance for Li/D co-deposition layer is effective under helium ambient gas. The removing rate of Li on the surface of W tile is faster than that on Mo tile in He-ICRF cleaning and the D/(D + H) ratio on Mo tile is higher by similar to 1.2 times than that on W tile. This work would indicate the feasibility of using LIBS to monitor the wall cleaning processes in EAST tokamak. (C) 2017 Elsevier B.V. All rights reserved.

LOCA; Secondary hydriding; PWR nuclear fuel cladding; Multiscale quantification of oxygen and hydrogen concentrations; Neutron radiography and tomography; EPMA; mu-ERDA;SIMULATED LOCA CONDITIONS; LOW-TIN ZIRCALOY-4; OXYGEN DIFFUSION; STEAM OXIDATION; PHASE-TRANSFORMATION; HYDROGEN; BEHAVIOR; ALLOYS; SPECTROMETRY; QUENCH-L0

This paper gives an overview of a multi-scale experimental study of the secondary hydriding phenomena that can occur in nuclear fuel cladding materials exposed to steam at high temperature (HT) after having burst (loss-of-coolant accident conditions). By coupling information from several facilities, including neutron radiography/tomography, electron probe micro analysis, micro elastic recoil detection analysis and micro laser induced breakdown spectroscopy, it was possible to map quantitatively, at different scales, the distribution of oxygen and hydrogen within M5 (TM)(1) clad segments having experienced ballooning and burst at HT followed by steam oxidation at 1100 and 1200 degrees C and final direct water quenching down to room temperature. The results were very reproducible and it was confirmed that internal oxidation and secondary hydriding at HT of a cladding after burst can lead to strong axial and azimuthal gradients of hydrogen and oxygen concentrations, reaching 3000-4000 wt ppm and 1.0-1.2 wt% respectively within the beta phase layer for the investigated conditions. Consistent with thermodynamic and kinetics considerations, oxygen diffusion into the prior-beta layer was enhanced in the regions highly enriched in hydrogen, where the alpha(O) phase layer is thinner and the prior-beta layer thicker. Finally the induced post-quenching hardening of the prior-beta layer was mainly related to the local oxygen enrichment. Hardening directly induced by hydrogen was much less significant. (C) 2017 Elsevier B.V. All rights reserved.

Passivation; surface treatment; characterization;

Tritium is highly reactive with many materials. It is adsorbed onto and absorbed through the surface of containment vessels subsequently modifying the contained gas composition by isotopic exchange and catalytic reactions with surface elements and adsorbed gas species. Savannah River Tritium Enterprise (SRTE) uses a proprietary surface treatment that is intended to render the surface inert. Unfortunately, this process has not proven to be sufficiently robust for containing tritium gas standards. SRTE has funded a project that will explore the effects of electropolishing and vacuum and oxidizing thermal treatments on surface passivation of stainless steel (SS). Herein, a statistically designed series of experiments will be discussed that will inform optimized parameters for acid composition, current density, and other electrochemical process variables for the passivation of SS. The surfaces were analyzed using Laser InducedBreakdown Spectroscopy (LIBS), Auger Electron Spectroscopy (AES), Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM). Novel techniques to characterize the passive layers are also being developed. In future experiments, gas sample bottles will be loaded with protium and deuterium to determine the relative exchange characteristics of the treated vessels. Previous work has indicated that if little protium ingrowth occurs or few contaminant species form, e.g., methane or ammonia, and little hydrogen exchange occurs in a protium and deuterium gas mixture the treatment is suitable for maintaining the tritium stability. This statement is not intended to imply that tritium, deuterium, protium mixes will not exchange, only that these results are useful as a screening tool prior to tritium exposure.

Laser-induced breakdown spectroscopy; nuclear safeguards; pyroprocessing; molten salts;LIQUIDS

In the pyrochemical separation of used nuclear fuel (UNF), fission product, rare earth, and actinide chlorides accumulate in the molten salt electrolyte over time. Measuring this salt composition in near real-time is advantageous for operational efficiency, material accountability, and nuclear safeguards. Laser-induced breakdown spectroscopy (LIBS) has been proposed and demonstrated as a potential analytical approach for molten LiCl-KCl salts. However, all the studies conducted to date have used a static surface approach which can lead to issues with splashing, low repeatability, and poor sample homogeneity. In this initial study, a novel molten salt aerosol approach has been developed and explored to measure the composition of the salt via LIBS. The functionality of the system has been demonstrated as well as a basic optimization of the laser energy and nebulizer gas pressure used. Initial results have shown that this molten salt aerosol-LIBS system has a great potential as an analytical technique for measuring the molten salt electrolyte used in this UNF reprocessing technology.

IN-SITU ANALYSIS

Laser induced breakdown spectroscopy (LIBS) has been tested to diagnose impurity elements on a Korea Superconducting Tokamak Advanced Research (KSTAR) divertor tile. Spectral lines of various impurity elements such as iron, chromium, and nickel were detected from the divertor surface. The variation of spectra with consecutive laser pulses demonstrates the potential for depth profiling analysis for the deposited impurity layer. The LIBS plasma parameters have been qualitatively determined from analysis of the relative line intensities and linewidths for each element. The validity of this analysis has been checked with atomic spectral simulations. (C) 2017 Elsevier B.V. All rights reserved.

LiSn alloy; CF LIBS; Surface analysis; Fusion; Liquid metal;LASER-INDUCED-BREAKDOWN; LIQUID LITHIUM; SPECTROSCOPY; DIAGNOSTICS; PLASMAS; LEAD

The difference between the composition of the surface and the inner part of the LiSn sample was studied using Calibration Free Laser Induced BreakdownSpectroscopy (CF-LIBS) method. The sample was analysed under the low pressure (1330 Pa) in Ar atmosphere. The spectra were record using Echelle spectrometer (Mechelle ME5000). Gate delay and gate width was optimised and set to 300 ns. In order to analyse depth profile the LIBS spectra was recorded after each laser shot. The electron density analysed by laser induced plasma was determined separately for each laser shot, which means for each ablated layer of investigated sample. The difference between the individual shots taken at distinct sites of the sample are shown. The CF-LIBS method was used to determine the elemental composition near the surface and in the central part of the LiSn sample. (C) 2016 Published by Elsevier B.V.

Optical isotopic analysis; Uranium; Laser ablation molecular isotopic spectrometry; Laser induced breakdown spectroscopy; Isotope shift;INDUCED BREAKDOWN SPECTROSCOPY; LEAST-SQUARES REGRESSION; EMISSION-SPECTROMETRY; QUANTITATIVE-ANALYSIS; ELECTRONIC-STRUCTURE; COMPUTER-SIMULATION; ENERGY-LEVELS; UO; FEMTOSECOND; RATIO

Through computer simulation on experimentally acquired optical spectra, uranium isotopic analysis by laser ablation molecular isotopic spectrometry and laserinduced breakdown spectroscopy were studied. The use of only one spectral feature, either the strong UO band at 593.55 nm or the nearby U I 593.382 nm line, are similar in precisions (similar to 1.5% in absolute U-235 abundances). Precision improves to 0.72% with the use of a group of U atomic lines from 591.6 to 596.5 nm. The use of both molecular bands and atomic lines further advances the precision to 0.42% and compares well with the U II 424.437 nm single-line benchmark (0.48% precision).

INDUCED BREAKDOWN SPECTROSCOPY; EMISSION-SPECTROSCOPY; PLASMA; PULSES; RATIO; AIR; PROPAGATION; GENERATION

The ability to perform not only elementally but also isotopically sensitive detection and analysis at standoff distances is important for remote sensing applications in diverse ares, such as nuclear nonproliferation, environmental monitoring, geophysics, and planetary science. We demonstrate isotopically sensitive real-time standoff detection of uranium by the use of femtosecond filament-induced laser ablation molecular isotopic spectrometry. A uranium oxide molecular emission isotope shift of 0.05 +/- 0.007 nm is reported at 593.6 nm. We implement both spectroscopic and acoustic diagnostics to characterize the properties of uranium plasma generated at different filamenturanium interaction points. The resulting uranium oxide emis-sion exhibits a nearly constant signal-to-background ratio over the length of the filament, unlike the uranium atomic and ionic emission, for which the signal-to-background ratio varies significantly along the filament propagation. This is explained by the different rates of increase of plasma density and uranium oxide density along the filament length resulting from spectral and temporal evolution of the filament along its propagation. The results provide a basis for the optimal use of filaments for standoff detection and analysis of uranium isotopes and indicate the potential of the technique for a wider range of remote sensing applications that require isotopic sensitivity.

Fiber optics; irradiation; transmission rate;INDUCED BREAKDOWN SPECTROSCOPY; FUEL CONDITIONING PROCESS; SILICA-CORE FIBERS; WAVE-GUIDES; ABSORPTION; DESIGN

The performance and eligibility of the fiber optic laser-induced breakdown spectroscopy (FO-LIBS) instrument will be primarily evaluated at the Advanced Spent Fuel Conditioning Process Facility (ACPF), where spent nuclear fuel is processed in a high-temperature molten salt bath using electrochemical methods. The damage incurred by the optical fiber cable due to radiation should be addressed to ensure the reliability of FO-LIBS measurements. High-level and low-level gamma ray and neutron irradiation experiments were conducted to measure the effect of radiation on the optical transmission rate of the optical fiber cable. Conclusively, we determined the dependence of the transmission rate of the cable on the radiation dose rate as a function of the wavelength.

LIBS; Hydrogen isotopes; Plasma-facing-components; ITER; Laser diagnostics; Fusion reactors;EMISSION; PLASMA; ENHANCEMENT; TUNGSTEN; SAMPLES; LIBS; ABLATION; SPECTRA; TRITIUM; SPARK

The amount of hydrogen isotopes retained in plasma facing components (PFCs) and the determination of their surface layer composition are among the most critical issues for the next generation fusion device, ITER, under construction in Cadarache (France). Laser Induced Breakdown Spectroscopy (LIBS) is currently under evaluation as a technique suitable for quantitative, in situ, non-invasive measurements of these quantities. In order to detect traces of contaminant in metallic samples and improve its limit of detection (LOD), the Double Pulse LIBS (DPLIBS) variant can be used instead of the standard Single Pulse LIBS (SP-LIBS), as it has been proven by several authors that DP-LIBS can considerably raise the analytical performances of the technique. In this work Mo samples coated with a 1.5-1.8 mu m thick W-Al mixed layer, contaminated with co-deposited deuterium (D) were measured by SP- and DP-LIBS under vacuum (p similar to 5 x 10(-5) mbar), with an experimental set-up simulating conditions that can be found in a real fusion device between plasma discharges. A partial Calibration Free procedure (pCF) was applied to the LIBS data in order to retrieve the relative concentration of W and Al in the mixed layer. The amount of deuterium was then inferred by using tungsten as internal standard, accounting for the intensity ratio between the D alpha line and nearby W I lines. The results are in satisfactory agreement with those obtained from preliminary Ion Beam Analysis measurements performed immediately after the specimen's realization. (C) 2017 Elsevier B.V. All rights reserved.

Deposition; PFC tile; HL-2A; LIBS; QMB;DIVERTOR TILES; ASDEX UPGRADE; CARBON; JET; EROSION/DEPOSITION; CODEPOSITION; EROSION; WALL

Since the divertor geometry of a tokamak has a strong impact on the material erosion and deposition on the wall and HL-2A has a unique divertor configuration, it is necessary to investigate the material deposition pattern in HL-2A although a few results on other tokamakS have already been published. In this paper, tiles retrieved from the vessel are analyzed ex-situ by sIMS, SEM and laser-induced breakdown spectroscopy (LIBS). And deposition behind the lower divertor is in-situ measured by a quartz crystal microbalance (QMB). The deposition in HL-2A displays a complex pattern and clear localization characteristic. The thickness of the deposition layer varies in the range of 0-4 mu m. And in-situ diagnostic of QMB indicates that the average thickness of the deposition layer per pulse is over ten nanometers. In addition, the results imply that Si, Fe and D have different behaviors during the material deposition in HL-2A. (C) 2016 Elsevier B.V. All rights reserved.

tokamak; laser-induced breakdown spectroscopy; impurity deposition; fuel retention; plasma wall interaction;ADVANCED SUPERCONDUCTING TOKAMAK; PLASMA-FACING COMPONENTS; CO-DEPOSITED LAYERS; FUSION-REACTORS; RETENTION; REMOVAL

Post-mortem methods cannot fulfill the requirement of monitoring the lifetime of the plasma facing components (PFC) and measuring the tritium inventory for the safety evaluation. Laser-induced breakdown spectroscopy (LIBS) is proposed as a promising method for the in situ study of fuel retention and impurity deposition in a tokamak. In this study, an in situ LIBS system was successfully established on EAST to investigate fuel retention and impurity deposition on the first wall without the need of removal tiles between plasma discharges. Spectral lines of D, H and impurities (Mo, Li, Si, ...) in laser-induced plasma were observed and identified within the wavelength range of 500-700 nm. Qualitative measurements such as thickness of the deposition layers, element depth profile and fuel retention on the wall are obtained by means of in situ LIBS. The results demonstrated the potential applications of LIBS for in situ characterization of fuel retention and co-deposition on the first wall of EAST.

LIBS; Chemometrics; PLSR; Nuclear fuel; AHWR;INDUCED BREAKDOWN SPECTROSCOPY; NANOSECOND 266 NM; WAVELENGTH DEPENDENCE; GLASS; THORIUM; URANIUM; SPECTROMETRY

The determination of uranium with composition varying from 0% to 35 wt% in (Th-U)O-2 mixed oxide fuel using laser induced breakdown spectroscopy (LIBS) utilizing partial least square regression (PLSR) has been demonstrated. Good agreement between expected and experiment results using 266 nm, 532 nm and 1064 nm was shown. The analytical results at 266 nm of 2-3% precision and similar to 1% accuracy (bias) satisfy the acceptance criteria range for chemical analysis in the nuclear industry. (C) 2016 ElseVier B.V. All rights reserved.

INDUCED BREAKDOWN SPECTROSCOPY; STAINLESS-STEEL CANISTER; CONCRETE; CHLORINE

Extended dry storage of spent nuclear fuel makes it desirable to assess the structural integrity of the storage canisters. Stress corrosion cracking of the stainless steel canister is a potential degradation mode especially in marine environments. Sensing technologies are being developed with the aim of detecting the presence of chloride-bearing salts on the surface of the canister as well as whether cracks exist. Laser induced breakdown spectroscopy (LIBS) methods for the detection of Chlorine are presented. Detection of a notch oriented either parallel or perpendicular to the shear horizontal wave vector is demonstrated using the pulse-echo mode, which greatly simplifies the robotic delivery of the noncontact electromagnetic acoustic transducers (EMATs). Robotic delivery of both EMATs and the LIBS system is necessary due to the high temperature and radiation environment inside the cask where the measurements need to be made. Furthermore, the space to make the measurement is very constrained and maneuverability is confined by the geometry of the storage cask. In fact, a large portion of the canister surface is inaccessible due to the presence of guide channels on the inside of the cask's overpack, which is strong motivation for using guided waves for crack detection. Among the design requirements for the robotic system are: to localize and track where sensor measurements are made to enable return to those locations, to avoid wedging or jamming of the robot, and to tolerate high temperatures and radiation levels.

Laser-induced breakdown spectroscopy (LIBS); Microwave-assisted laser-induced breakdown spectroscopy (MA-LIBS); Effect of ambient gas; Analysis of Ca impurity in Gd2O3;INDUCED BREAKDOWN SPECTROSCOPY; ATOMIC EMISSION-SPECTROMETRY; URANIUM; ENHANCEMENT; IMPURITIES; EXTRACTION; ABLATION

The effect of ambient gas on measurements with microwave-assisted laser-induced plasma in microwave-assisted laser-induced breakdown spectroscopy(MA-LIBS) was studied with relevance for the analysis of nuclear fuel. A pelletized gadolinium oxide (Gd2O3) sample, which was used as a simulated nuclear fuel, was irradiated by a pulsed Nd:YAG laser (532 nm, 5 mJ) coupled with microwaves (2.45 GHz, 400 W) under various gases of air, Ar, and He. Microwaves can be effectively used to enhance laser-induced plasma emissions. The emission spectrums of Gd obtained by MA-LIBS in Ar and He gases are much better than those of the air case. Namely, the spectral lines can be clearly identified and are far from molecular bands. Furthermore, the emission intensity is highest with low background emissions. Linear calibration curves of Ca in the concentration range between 0 and 500 mg/kg as an impurity in Gd2O3 have been successfully obtained in all gases. The detection limits of Ca impurity in air, Ar and He gases were 2, 0.8 and 0.6 mg/kg, respectively, which are much lower than the required limits of Ca impurity in nuclear fuels.