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.

Liquid lithium corrosion; Corroded layer; Depth profiling; LIBS; Refined grains enhanced;INDUCED PLASMA; QUANTITATIVE-ANALYSIS; SURFACE-TOPOGRAPHY; MASS-SPECTROMETRY; EUTECTIC PB-17LI; ABLATION; BEHAVIOR; SAMPLES; HELIUM; CURVES

Liquid metal lithium cause severe corrosion on the surface of metal structure material that used in the blanket and first wall of fusion device. Fast and accurate compositional depth profile measurement for the boundary layer of the corroded specimen will reveal the clues for the understanding and evaluation of the liquid lithium corrosion process as well as the involved corrosion mechanism. In this work, the feasibility of laser-induced breakdown spectroscopy for the compositional depth profile analysis of type 316 stainless steel which was corroded by liquid lithium in certain conditions was demonstrated. High sensitivity of LIBS was revealed especially for the corrosion medium Li in addition to the matrix elements of Fe, Cr, Ni and Mn by the spectral analysis of the plasma emission. Compositional depth profile analysis for the concerned elements which related to corrosion was carried out on the surface of the corroded specimen. Based on the verified local thermodynamic equilibrium shot-by-shot along the depth profile, the matrix effect was evaluated as negligible by the extracted physical parameter of the plasmas generated by each laser pulse in the longitudinal depth profile. In addition, the emission line intensity ratios were introduced to further reduce the impact on the emission line intensity variations arise from the strong inhomogeneities on the corroded surface. Compositional depth profiles for the matrix elements of Fe, Cr, Ni, Mn and the corrosion medium Li were constructed with their measured relative emission line intensities. The distribution and correlations of the concerned elements in depth profile may indicate the clues to the complicated process of composition diffusion and mass transfer. The results obtained demonstrate the potentiality of LIBS as an effective technique to perform spectrochemical measurement in the research fields of liquid metal lithium corrosion. 2017 Elsevier B.V. All rights reserved.

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.

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.

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.