STP1332

    The Use of Local Approach to Fracture in Reactor Pressure Vessel Structural Integrity Assessment: Synthesis of a Cooperative Research Program Between EDF, CEA, Framatome and AEA Technology

    Published: Jan 1999


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    Abstract

    A cooperative research program on the field of the local approach to cleavage fracture applied to reactor pressure vessels is conducted between Electricité de France, CEA, Framatome and AEA Technology. The purpose of this program is to have a better knowledge of this kind of approach for reactor pressure vessels fracture mechanics integrity assessments regarding the risk of brittle fracture. This program includes both an experimental part on the A508 C13 steel and numerous 2D and 3D numerical computations.

    The identification of m and σu parameters of Beremin model (local approach to cleavage fracture) is studied on the A508 C13 steel using mechanical tests on axisymmetrical notched tensile specimens AE2. The tests are performed at several temperatures (-100 °C, -130 °C and -170 °C) by three laboratories (EDF, CEA and AEA Technology). There are 120 specimens tested in total. The experimental results from different laboratories are compared and analyzed, the effect of temperature on m and σu parameters of Beremin model is discussed and a standard procedure to identify these parameters is proposed.

    Within the framework of this program, numerous two-dimensional numerical calculations using the Beremin model have been performed by different partners on several cracked specimens (CT specimen, cladded vessels with flaws in cladding or in base metal under thermal loading…). Some comparisons between finite element programs (Aster, Castem 2000, Systus and ACaretbaqus) are made on reference specimens in order to evaluate and validate finite element programs in the field of local approach to cleavage fracture. These comparisons show a rather good agreement on main parameters, notably on Weibull stress σw calculation for mechanical or thermal loading.

    The “shallow flaw effect” is examined from these computations. The effect of the “a/W” ratio on the probability of cleavage failure is clearly underlined with the Beremin model using the “Weibull stress σw versus Stress intensity factor KJ” curves. Significant differences between cracked specimens are observed, related to the “a/W” ratio : for a given level of the stress intensity factor KJ, the probability of cleavage failure increases with increasing values of flaw depth. These results show that the Beremin model is able to predict an influence of crack tip constraint on fracture toughness.

    Finally, first three-dimensional applications of the Beremin model are presented regarding the interpretation of large-scale tests performed on cladded specimens containing subclad flaws.

    Keywords:

    fracture mechanics, fracture toughness, local approach, cladding, cleavage, structural integrity, shallow flaw, subclad flaw


    Author Information:

    Moinereau, D
    Electricité de France (EDF), Les Renardières, Moret-sur-Loing,

    Frund, JM
    Electricité de France (EDF), Les Renardières, Moret-sur-Loing,

    Brochar, J
    Commissariat à l'Energie Atomique (CEA), Saclay, Gif-sur-Yvette

    Valeta, MP
    Commissariat à l'Energie Atomique (CEA), Saclay, Gif-sur-Yvette

    Marini, B
    Commissariat à l'Energie Atomique (CEA), Saclay, Gif-sur-Yvette

    Joly, P
    Framatome, Tour Framatome, Paris La Défense,

    Guichard, D
    Framatome, Tour Framatome, Paris La Défense,

    Bhandari, S
    Framatome, Tour Framatome, Paris La Défense,

    Sherry, A
    AEA Technology, Risley, Warrington, Cheshire,

    France, C
    AEA Technology, Risley, Warrington, Cheshire,

    Sanderson, DJ
    AEA Technology, Risley, Warrington, Cheshire,


    Paper ID: STP14955S

    Committee/Subcommittee: E08.04

    DOI: 10.1520/STP14955S


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