RIMIS

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RIMIS

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PROJECT ABSTRACT

Integrated Network for Structural Integrity Monitoring of Critical Components in Nuclear Facilities

        Contract No: 2-CEx 06-10-81/2006, Theme Area 10
        Program “Research of Excellence” 2005-2008”

        Based of the Romanian option to develop and operate nuclear facilities, using as model the networks created at European level and taking into account the international importance of the structural integrity assessments to extend the lifetime of the nuclear components a national Project has been launched since 2006 in the framework of the National Program “Research of Excellence”, Modulus I 2005-2008, managed by the Ministry of Education and Research.
        The Project “Integrated Network for Structural Integrity Monitoring of Critical Components in Nuclear Facilities”, with acronym RIMIS, had been focused on two main objectives:

To develop a procedure for structural integrity assessment of the critical components used in Romanian nuclear facilities;

to integrate the national networking in a similar one, at European level, to enhance the scientific significance of Romanian R&D organizations as well as to increase the contribution to solving one of the major issue of the nuclear field.

        Romanian R&D institutes, with activities in the structural integrity assessment of critical nuclear components, have developed an interdisciplinary research team, involving experimental, theoretical and modelling tasks. The Institute for Nuclear Research Pitesti, the Politehnica University from Bucharest, National R&D Institute, ICSI from Rm. Vâlcea and the University from Pitesti worked together in a partnership, developing specific and interdependent activities.
        The structural integrity assessment of a facility’s component is performed using the Failure Assessment Diagram methodology (acronym FADs), in the way which is described in British Procedure R6/rev4. This methodology consists of plotting the assessment points characterizing fracture - yielding mechanical state of flawed components under a certain set of operation loadings and strictly related on the mechanical properties and safety criteria. The levels of the assessment depend on the conservatism adopted and also on the ability to characterize the material stress - strain responses obtained in standard tests.
        In agreement with “R6/rev.4” procedure, a FAD diagram is described by the function: if Lr < Lrmax with f(Lr)=0 if Lr < Lrmax , where: represents the stress intensity factor to material toughness ratio and the is a ratio of nominal applied stress to flow stress representing a measure of the reaction of a structure with flaws against to the plastic collapse.
        For function, there are three assessment levels:

Assessment Level 1, known as “General Diagram of Failure Assessment”, useful for the analysis of materials with determined tensile stress and fracture strength values, but without a detailed stress-strain diagram;

Assessment Level 2, called also “Specific Diagram of material” designed for analyses with a determined stress-strain diagram of the material. This level requires high accurate measurements, especially for strain up to 1%.

Assessment Level 3, known as “J integral” for a particular material and specific geometry, can be obtained using the analysis of a structure with flaws, as function of the loading inducing the increase of the primary stress due to the external stresses.

Taking into account the steps involved to use the FAD diagrams, the project developed the experimental and theoretical methodologies based on numerical computing as follows:

The project was organized in four stages: the first stage with a basic research character, stage II, identified as experimental one, the last two stages include modeling and elaboration of the structural integrity procedure.
The project stages, estimated to meet the objectives of the project are shown in Figure 1.

Figure 1. Structure of RIMIS Project

        All the experimental results have been filled in two databases: one organized for the investigated structural component of CANDU reactor, fuel element sheath, pressure tube, steam generator tubing, entitled NUCMATPROP (Nuclear Material Properties Database), the other one for structural materials (austenitic/martensitic steel) operating in the nuclear facilities of hydrogen isotopes separation, called “SoftMat”.

        By using the experimental results, concerning mechanical properties measurements, structural materials containing defects are modeled, to assess theirs integrity, based on the R6 /R4 FAD diagrams concept.
        Finally, the Structural Integrity Analysis Procedure has been issued with a general character, useful for each type of material operating in the nuclear facilities.
        The complex character of the project and the network development at excellence level, enabled its integration in an European one. The objectives and activities which were achieved, offered the opportunities to sustain the participation in the “Lifetime Evaluation” and “Integrity Assessment” Working Packages of the European NULIFE Project. Romania has been involved as a associate contributor into the research activities, mainly based on the structural integrity assessments in the nuclear field. In the same time, the specific and characteristic degradation mechanisms and investigation procedures of the PHWR-CANDU reactor have been integrated and harmonized with those applied for the European PWR, BWR and RMBK reactors, Romania being the only CANDU type reactor owner in Europe.

Contact

Pentru detalii legate de acest proiect contactati-ne prin e-mail: maria.roth@nuclear.ro

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