[en] Full text: The determination of H_eq values in the reactor operated zirconium alloy components with high degree of accuracy by various techniques is of prime importance, as it will be used in performance evaluation and life management of the components. Due to the inherent limitations in the techniques used for H_eq estimation, such as Inert Gas Fusion (IGF) technique, Differential Scanning Calorimetry (DSC) and Hot Vacuum Extraction and Quadrupole Mass Spectrometer (HVE and QMS), the H_eq values will have accuracy band. Therefore to compare and validate the H_eq estimation by different techniques, a systematic study was initiated which required H-charged and D-charged zirconium alloy samples. To cater such samples for the above said study, the samples of Zircalloy-2 material of different sizes were charged with Hydrogen (H) and Deuterium (D) separately at various levels of concentration and homogenized. The present paper explains the samples generated for IAEA CRR Round Robin programme, samples distribution and compares data generated in different laboratories by different techniques for validation of H_eq measuring techniques for pressure tube inspection and diagnostics

[en] Samples of Zircaloy-2, Zr-2.5Nb and Zr-2.5Nb-0.5Cu were subjected to Air oxidation at temperatures of 650 degC, 700 degC and 750 degC. For this study, the sample having size of 3mm x 2mm x 2mm were sectioned from zircaloy-2 pressure tube, Zr-2.5Nb pressure tube and garter springs by cutting in slow speed cut-off machine. These samples were ultrasonically cleaned, dried and chemically etched before exposure to air oxidation test. The samples were loaded in alumina crucible and placed on the thermo-balance of TGA unit. The weight gain data generated for Zircaloy-2 was analysed and the equation for air oxidation was derived. The samples were also observed under SEM to study the oxide morphology

[en] Zircaloy-2 pressure tubes pickup hydrogen species during in-reactor service. The hydrogen pickup leads to hydride precipitation and in the event of a contact between the pressure tube and the calandria tube, hydrogen migrates to the cold spot leading to the formation of hydride blister. One such hydride blister location in an operated Zircaloy-2 pressure tube of RAPS-2 was subjected to metallographic studies and mapping of the microstructure across the tube thickness

[en] India prepared samples from Zr-2.5%Nb pressure tube containing varying levels of hydrogen. These samples were sent to participating laboratories for analysis. The details of charging method employed and the number of samples generated for CRP are given in Annex 1. India analyzed the samples from Argentina for assessment of Hydrogen concentration. The analysis was carried out by three techniques: 1. Hot Vacuum Extraction Quadrupole Mass Spectrometer (HVE-QMS). 2. Inert Gas Fusion. 3. Differential Scanning Calorimetry. The results of hydrogen analysis on Indian and Argentinean samples by the above three techniques are given

[en] The hydrogen content in zirconium alloys is estimated by Differential Scanning Calorimetry (DSC) technique, non-destructively. The DSC cell compares the heat flux of the sample with an inert reference material. The Zirconium-H system has a sloping solvus. The solubility of Hydrogen in Zirconium alloys varies as a function of temperature. The Terminal Solid Solubility (TSS) temperature is governed by an Arrhenious type of equation. The hydrogen in the form of hydride platelets dissolve in Zirconium matrix as the temperature is raised. The DSC scan is obtained with a linear heating rate, under an inert atmosphere. The DSC technique was standardized using zircaloy-2 material with known amount of H, as estimated by Inert Gas Fusion technique. The derivative of the DSC scan is used to find out the point of inflexion and thus the TSS temperature from which the H-content is evaluated. (author)

[en] 40 MW (Thermal) Research reactor Cirus is located at Bhabha Atomic Research Centre, Mumbai, India. The reactor used natural Uranium metal fuel, heavy water moderator, light water coolant and graphite reflector. It was operated from year 1960 to 2010. From year 1997 to 2003, the reactor was under refurbishment. Currently the reactor has been defueled, spent fuels have been reprocessed and heavy water has been removed from the reactor. A deferred dismantling strategy has been selected for its decommissioning. Preliminary activities in this regard has been started. Various properties of irradiated graphite are being analysed to assess condition of graphite to select the best course of action during decommissioning which includes options such as re-use and/or disposal. (author)

[en] Neutron irradiation of graphite leads to storage of energy in graphite, called as Wigner energy. The stored Wigner energy gets released when the irradiated graphite is thermally activated. Uncontrolled release of Wigner energy could lead to a sudden temperature rise in the graphite, which may lead the graphite to burn under extreme conditions. Differential Scanning Calorimetry technique was used to assess the extent of stored Wigner energy in irradiated graphite. This paper presents the details of the sampling technique used for irradiated graphite material and the DSC measure the stored Wigner energy

[en] The paper discusses the sampling procedure and technique for estimation of the hydrogen content of the operating pressure tubes as hydrogen equivalent (H_eq). It gives the comparison of H_eq content in the Zircaloy-2 and Zr-2.5%Nb pressure tubes of PHWRs at different operating periods ranging from 6.7 to 11.45 hot operating years of reactor operation

[en] A detailed metallographic characterization and ring compression tests at ambient temperature were carried out on the oxidized clad tube pieces. The results of these experiments are presented in this paper

[en] Zircaloy-2 pressure tubes pickup Hydrogen species (H and D) during in-reactor service. The hydrogen pickup leads to hydride precipitation and in the event of a contact between the pressure tube and the calandria tube, hydrogen migrates to the cold spot leading to the formation of hydride blister. One such hydride blister location in an operated Zircaloy-2 pressure tube of RAPS-2 was subjected to metallographic studies and mapping of the microstructure across the tube thickness. Mapping of the hydrogen concentration across the tube thickness was carried out by careful sampling and H estimation by DSC technique. The H profile across the tube thickness, up to the blister boundary, was generated. The hydride blister region was found to be made up of microstructurally different regions starting from dense massive hydride at the outer surface and followed in sequence by a region with dense and thick platelets oriented parallel to the blister boundary and radial platelet region, which subsequently merged with the background platelet distribution appropriate for the average hydrogen content of the pressure tube. The equivalent blister depth corresponding to H content of 16,000 w/ppm has been estimated from the H profile at the blister location. In the case of a hydride blister with measured thickness of 0.4mm the equivalent blister thickness was found to be 0.414mm. Mapping of the hardness of the massive hydride and the adjoining microstructurally different regions was carried out by microhardness measurements at room temperature. (author)