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RESULTS
    2006 - Stage I
    As part of the First Stage the Structural Integrity Assessment Methodology of Components operating in Nuclear Facilities has been finalized


        2007 - Stage II
        "Application of Experimental Investigation Methods and Procedures"
        In according to the requirements of the Structural Integrity Assessment Metodology, performed in the frame work of the first Stage of the Project, an Experimental Testing and Material Properties Analysis Program has been developed, necesarry for applying the integrity assessment evaluation levels used in the EU , for the nuclear field.
        The objective of this Stage was to finalize the experimental testing matrix concerning the material properties determination of the structural materials working in the Romanian nuclear facilities (CANDU reactor, hydrogen isotope separation installations).
 
        Macro and microscopic analysis and tests have been performed, including:
  • Mechanical tests under uniaxial state of stress as function of the structure geometry (fuel element sheath, pressure tube) and the specific operating conditions;
  • Tensile tests on samples in different conditions (material as-received, hydrided or oxidized); mechanical parameters like yield stress, UTS and the strain-stress curve have been measured, input values for the I and II Levels of assessment;

    • Tensile Test samples
    Zircaloy-4 Grain Size

    INSTRON Tensile test Systems     		Stress-Strain Diagram

  • Evaluation of the fracture mechanical parameters like toughness, J-integral, Jic and resilience – useful for the III. Level of assessment;


    • CT sample
    Resilience testing system

    Fracture Surface CT sample, toughness test
    Zr-2.5%Nb Toughness

  • Microscopic analysis based on metallographic, SEM and XRD techniques on the tested specimens.


    • Electronic Microscop
    Fracture Surface Zy-4

    XRD Spectrum oxidized Zy-4
    DRON Difractometer


        The existent testing equipments of the partner institutions (Instron Testing Systems, Reichert and Zeiss Optical Microscopes, Dron Diffractometer) or those acquired in the framework of the Project budget (Scanning Electronic Microscop, load cell, transducers/extensometers) have been used to carry out the experimental Program.

        The second Stage of the Project offers a consistent data base useful for the integrity assessment evaluation of the nuclear components under developing in 2008.

        2008 - Stage III
        "Simulation of nuclear components behavior"
        Stage III included two activities:
  • Activity III.1 – Data base elaboration;
  • Activity III.2 – Applying of finite element method.
        Applying of finite element method activity had as main objectve to evaluate the structural integrity of the nuclear components using the Failure Assessment Diagram concept. By running ANSYS, FEA-Flaw and FEA-Crack computer codes, the stress and strain field of a discrete structure, and of the fracture mechanics parameters at the tip of a postulated defect were described.
        Based on the British “R6/Revision 4 procedure „Assessment of the Integrity of Structures Containing Defects” requirements the curve of a FAD diagram has been drawn. The applications have been developed for CANDU Zr-2.5% Nb pressure tube, Zircaloy- 4 sheaths and Incoloy-800 tubing, containing postulated defects identical like those meet during the operation.
        The objective of the Data base elaboration activity was to summarized all the experimental results obtained in the framework of the II Project Stage, taking into account of the material type, testing conditions and experimental measured parameters. Two databases were filled in: NucMatProp and SoftMat . The Programs were organized for each investigated structural component: CANDU reactor fuel element sheath, pressure tube, steam generator tubing) and structural materials operating in the nuclear facilities of hydrogen isotope separation facilities. The Programs offer the opportunities to store new testing results, as a consistent database will be developed continuously.



        2008 - Stage IV
        "Structural integrity assessment of different critical components working in nuclear facilities "
        The IV-th Stage elaborated the procedure concerning structural integrity assessment of nuclear materials working in the CANDU type reactor (pressure tubes, fuel elements sheaths, tubing of steam generator).
        Based on the British “R6/Revision 4 procedure „Assessment of the Integrity of Structures Containing Defects”, Barnwood, 2001 published in the UK, British Energy Generation Ltd, applied in the nuclear field, the Romanian procedure presents en detail each working step and as an example how it could be applied for a postulated defect existing on the inner surface of a pressure tube.

Structural Integrity Assessment of a inner defect presents in the PT (2c=20 mm, a=1mm), using the elastic and elastic-plastic analysis, Option 1, Failure Assessment Curve, R6/ rev.4 British Procedure.
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