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Network for evaluation of structural components (NESC)

Objective

Specific Objectives
- To continue the successful operation of the NESC network and to pursue its further development for next framework programme, following ERA and Network of Excellence principles;
- To exploit the NESC-II project results on shallow flaws in an embrittled reactor pressure vessel material;
- To investigate the incidence of inter-granular cracking in the NESC-I and NESC-II sub-clad defects;
- To successfully complete the major test on a full-scale dissimilar weld assembly for the NESC-III project and to launch the associated inspection exercise;
- To rigorously pursue the post-test analyses and evaluation of the NESC-IV Project on shallow flaws in reactor pressure vessel welds, in collaboration with a US national laboratory;
- To support the development of a European Procedure for Thermal Fatigue assessment, with network actions linked to the THERFAT and the OECD/NEA projects;
- To continue to strengthen the Network Reference Laboratory, in particular focussing on fracture testing, structural analysis, residual stress analysis, thermal fatigue and advanced data management tools;
- To launch a NESC training-related initiative for structural integrity assessment procedures;
- To establish the NESC tests as international benchmarks and promote the results to standards bodies;
- To support the development of a European Fitness for Service for metallic structures code via the FITNET thematic network and CEN TC121 WG14;
- To continue to encourage participation in the network projects from candidate countries;
- To foster closer cooperation with DG RTD nuclear safety. activities.
Planned Deliverables

Specific deliverables to DGs:

- Evaluation reports for the NESC-II and NESC-IV large-scale projects as input to policy making;
- Technical reports on best practices for assessment of shallow flaws in ageing reactor pressure vessels and needs assessment for a European thermal fatigue assessment procedure;
- Technical report on regulatory aspects affected by the results of the NESC projects;
- Support to European best practice development and harmonisation of structural integrity assessment procedures;
- Expanded capabilities for the reference laboratory to support the network;
- "Clustering" of fracture assessment SCA's to improve dissemination.

As a result of the research:

- Final evaluation reports of the NESC-II and NESC-IV projects, covering the following aspects:
- adequacy of test methods to determine material parameters
- transferability of laboratory-generated materials data to plant integrity analysis and adequacy of current fracture mechanics codes (sensitivity to assumptions, inaccuracies).
- requirements for inspection and materials data in the integrated structural assessment process.
- safety margins with regard to defect sizing, materials characterisation, and fracture mechanics.

- Technical assessment of fracture assessment best practice for reactor pressure vessels based on the results of the NESC-I, II and IV projects
- JRC-IE reports on:
- non-destructive inspection performance for defects in dissimilar welds.
- causes of the integranular fracture at sub-clad defects in the NESC-I and NESC-II projects
- advanced fracture assessment for shallow defects using finite element analysis
- simulation and modelling of critical thermal fatigue processes

Summary of 2001 Deliverables: 31/12/2001

- Operation of the NESC network successfully continued

- Exploitation of the NESC I Project well advanced with the public release of the NESC-I Overview Report and the NESC-I Problem Definition Document.

- Evaluation report draft prepared for the NESC-II project on shallow flaws in a severely embrittled reactor pressure vessel material

- Successfully completed the major tests associated with the NESC-IV(biaxial loading effects) project

- Major new fracture testing machine installed for the Network Reference
Laboratory to support the NESC projects
-

Output Indicators and Impact

Objectives

Output indicators

(Specific actions taken)

Impact

(long term results)

Successful operation of the NESC network and its further development for FP6, following ERA and Network of Excellence principles.

- NESC strategy for FP6/ERA agreed by all stakeholders
- Maintain quality participation to the NESC network

- Strengthened JRC contribution to policy support in nuclear safety
- Optimised R&D efforts following the ERA concept

Encourage participation in the network projects from candidate countries

- Increased involvement of candidate country organisations (from 3 to 6)
- at least one new GH/DNE/VS for the NESC "team"

Support to integration of candidate countries in the EU R&D actions; promotion of implementation of acquis communautaire

Exploit existing results, complete ongoing tests, analyse and evaluate first results of the various NESC projects

Technical publications and presentations (major network reports for the projects, 2 journal publications, 6 conference publications)

Strengthened new profile of JRC/IE by representation at international committees

State-of-the-art Network Reference Laboratory, focussing on fracture testing, structural analysis, residual stress analysis, thermal fatigue, defect implantation and advanced data management tools

- At least one scientific publication or best practice for the noted areas.
- Integration of activities in Quality system

JRC/IE technical competence as integral part of operating agent role maintained

Establish the NESC tests as international benchmark references and promote the results to standards bodies.

- One new European best practice/harmonisation initiative
- External use of NESC benchmarks

Promotion of best practices leading to codes & standards

Promote training, maintenance of competence and dissemination to optimise the NESC results

- Launch of a training-related initiative for structural integrity assessment procedures
- Implement NESC data in a harmonised data dissemination and/or training system.

Improved network tool and enhanced JRC image

Foster closer cooperation with DG RTD nuclear safety activities

"Clustering" of fracture assessment related SCA's

Improved dissemination.
Summary of the project

NESC is an international, 90-member network set up to verify the overall structural integrity assessment process via selected large-scale experimental projects, designed as benchmarks. The network brings together operators, manufacturers, regulators, service companies and R&D organisations from 7 EU countries, 2 candidate countries and 2 third countries. At a technical level the present structure covers the disciplines of inspection, materials characterisation, fracture mechanics, residual stress measurement and instrumentation/monitoring.

In FP5 the completion of the NESC-I project has provided crucial insights into the behaviour of light water reactor vessels under pressurised thermal shock conditions. Three carefully selected new benchmark projects have been accepted in the network structure. NESC-II and NESC-IV are both concerned with the assessment of shallow defects, which typically dominate the assumed population density functions in reactor pressure vessel structural integrity assessments. NESC-III focuses on the testing of a full-scale dissimilar weld assembly representative of a critical primary circuit component. The support of the IE's Reference Laboratory is a key feature in all these projects, covering materials testing, data management, micro structural characterisation, residual stress analysis, defect simulation, non-destructive inspection and structural analysis.

See also the related EU enlargement process pre-accession (pa) project.

Rationale

How do we deal with the possibility of cracks occurring in large structures? This classical engineering problem takes on special significance for critical components in nuclear power plants. While regulators, utilities and plant manufacturers have developed effective procedures to assess structural integrity, a policy of continuous development is required to ensure that safety margins are maintained as plants accumulate many years of service.
NESC exploits the idea that the integrity of such components can be best-secured by grouping all the key players within a dedicated network designed to integrate fragmented R&D work, to accelerate, through consensus, harmonisation of European procedures and practices and to safeguard expertise. By actively encouraging the participation of candidate country organisations it supports implementation of the acquis communautaire.

The JRC's role as independent Operating Agent and its technical competence via the reference laboratory is a critical factor in ensuring the acceptance of the Network. NESC is also supported by the links to its sister networks AMES, ENIQ and EPERC. It acts as a focal point for several SCAs related to fracture assessment and is linked to a new Thematic Network designed to promote a European Fitness for Service Code.

Funding Scheme

JRC - Joint Research Centre research

Coordinator

Institute for Energy
Address

Petten
Netherlands