304.1
THE EUROPEAN NETWORK FOR INSPECTION AND QUALIFICATION (ENIQ)
Oliver Martin
European Commission, Joint Research Centre (JRC) – Institute for Energy & Transport (IET) Westerduinweg 3
1755LE Petten, The Netherlands oliver.martin@ec.europa.eu
Etienne Martin
EDF - Direction Production Ingénierie Ceidre, 2 rue Ampère
93206 St Denis Cedex 01, France etienne.martin@edf.fr
Russ Booler
AMEC Clean Energy Europe Walton House, Birchwood Park, Risley
Warrington WA3 6GA, UK russ.booler@amec.com
Tony Walker Rolls-Royce Submarines
Derby, UK
tony.walker@roll-royce.com
ABSTRACT
The European Network for Inspection and Qualification (ENIQ) is a utility driven network dealing with the reliability and effectiveness of non-destructive testing (NDT) for nuclear power plants (NPP). ENIQ is recognised as one of the main contributors to today’s global qualification codes and guidelines for in-service inspection (ISI) and has published nearly 50 documents. Among them are the “European Methodology for Qualification of Non- Destructive Testing”, the first qualification methodology based on technical justifications, the
“European Framework Document for Risk-Informed In-Service Inspection (RI-ISI)”, and various recommend practices. In addition ENIQ has carried out two pilot studies and a number of surveys. In 2012 ENIQ joined the European based R&D association on Gen II &
III reactors, NUGENIA, making ENIQ its 8th technical area. Following the entry into NUGENIA, ENIQ members have re-written the ENIQ roadmap and included a number of technical challenges facing its members in the near future. ENIQ will perform projects to tackle these challenges and new recommended practices and reports are likely to evolve from these projects, which will enable ENIQ to maintain its role as one of the main contributors to today’s global qualification codes and guidelines for ISI. This paper describes the development of ENIQ since its establishment in 1992 and the technical challenges facing its members in the coming years.
1 OBJECTIVES AND STRUCTURE OF ENIQ
The European Network for Inspection and Qualification (ENIQ) is a network dealing with the reliability and effectiveness of non-destructive testing (NDT) for nuclear power plants (NPP). ENIQ is driven by European nuclear utilities and is working mainly in the areas of qualification of NDT systems and risk-informed in-service inspection (RI-ISI). Since its establishment in 1992 ENIQ has performed two pilot studies and has issued nearly 50 documents. Among them are recommended practices, technical reports, discussion documents and the two ENIQ framework documents, the “European Methodology for Qualification of Non-Destructive Testing” [1] and the “European Framework Document for Risk-Informed In- Service-Inspection” (RI-ISI) [2]. ENIQ is recognized as one of the main contributors to today’s global qualification guidelines for in-service inspection (ISI). By co-ordinating expertise and resources, ENIQ aims at supporting licensees (utilities) and stakeholders in:
Addressing issues where the practice and implementation of NDT will ensure the safe and reliable operation of NPPs through inspection qualification, the application of RI approaches, and other processes.
Providing recommendations and guidance to optimise and harmonise processes.
Continually improving the processes for inspection qualification and RI-ISI for increased effectiveness and efficiency.
Responding to the new challenges resulting from plant life extension and new build.
Promoting ENIQ approaches outside Europe and in non-nuclear industries.
To achieve its goals ENIQ has three task groups in which the technical work is performed, the Task Group for Qualification (TGQ), the Task Group for Risk (TGR) and the Task Group for Inspection Qualification Bodies (TGIQB). Their members come from utilities, ISI vendors, IQBs or research organisations in Europe with additional members from Canada and the USA. Beside the TGs ENIQ has a steering committee (SC), which is the decision making body of ENIQ. The SC approves all the documents drafted inside the TGs, but also serves as an exchange forum for ISI related issues in NPPs. The SC has twelve voting members who are entirely coming from European utilities with one vote per country. Voting members come from Belgium, Czech Republic, Finland, France, Germany, Hungary, The Netherlands, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Additionally the SC has non-voting members (observers) from Canada, USA, the chairpersons of the three task groups and additional representatives of European utilities, ISI vendors, IQBs or research organisations.
In 2010, the SC recognised that the European nuclear industry was entering a period of significant change and thus initiated an internal discussion to determine its vision and objectives regarding ENIQ's future role and activities. This exercise resulted in the issuing of a strategy document, entitled the "ENIQ 2020 Roadmap" [3] and the decision of ENIQ voting members to integrate ENIQ into NUGENIA (www.nugenia.org), which is an European based R&D association on Gen II & III reactors founded in November 2011. NUGENIA combines the activities of previous networks and technical working groups (TWG) like SARNET (www.sar-net.eu), a network on severe nuclear accidents, NULIFE (plant life management), and the TWG on Gen II & III reactors of the Sustainable Nuclear Energy Technology Platform (SNETP, www.snetp.eu). NUGENIA has now 70 members with all major European nuclear organisations among them. ENIQ joined NUGENIA as its 8th Technical Area (TA) in 2012 and has recently updated its roadmap [4] and has included a number of technical challenges facing its members in the near future.
2 THE DEVELOPMENT OF ENIQ 2.1 NDT Qualification
ENIQ started in 1992 with the TGQ and its first milestone was the publication of the first issue of the “European Methodology for Qualification of Non-Destructive Testing” in 1995. It contains guidelines for the qualification of NDT systems and is often referred to as the “European Qualification Methodology Document (EQMD)”. In contrast to the qualification guidelines laid down in the ASME codes & standards, which are based mainly on practical trials on mock-ups and real tests, EQMD assembles theoretical (physical reasoning, technical justification (TJ), numerical simulation) and experimental evidence (past ISI experience, open practical trials). When firstly published the EQMD contained a number of innovative proposals such as the use of technical justifications (TJ), the separation between procedure/equipment and personnel qualification and the use of open trials for procedure and equipment qualification. The EQMD was updated two times to account for the rapid progress of ISI qualification in Europe and the ENIQ Recommended Practices (RPs) that have been published in the meantime. The latest version of the EQMD, Issue 3 [1], was published in 2007. In 2010 the TGQ published a short version of the EQMD for the non-specialist [5].
In 1998 and 1999 TGQ issued a number of ENIQ RPs, which all have been updated recently. “ENIQ RP1: Influential / Essential Parameters” [6] explains the concept of influential / essential parameters and how the concept could be used in inspection qualification according to the EQMD, gives advice on the classification of influential parameters and provides two practical examples. “ENIQ RP2: Strategy and Recommended Contents for Technical Justifications – Issue 2” [7] provides assistance in the use of TJs and explains their purposes. RP2 also provides assistance in drafting TJs by giving recommendations on the content of TJs. “ENIQ RP4: Recommended Contents for the Qualification Dossier” [8] provides guidance on the material to be included in the qualification dossier, which assembles all the information that is relevant for the definition and execution of the qualification. “ENIQ RP5: Guidelines for the Design of Test Pieces and Conduct of Test Piece Trials” provides guidelines for the design of test pieces and the conduct of open and blind test piece trials. In 2011 Issue 2 of RP5 [9] has been published together with a corresponding report on practical examples for manufacturing of test pieces for inspection qualification [10]. “ENIQ RP6: The Use of Modelling in Inspection Qualification”
[11] provides guidance on the types and range of available models, how models can be used for generating evidence for a TJ, important considerations and constraints in the use of models and validations of models.
Following the publication of the first six RPs TGQ performed its first pilot study. The aim of the pilot study was to investigate the feasibility of the EQM in practice and to explore the details of its implementation. The task of the pilot study was to qualify the inspection of an austenitic pipe-to-pipe weld through a combination of TJ and practical trials and then applying the qualified inspection to test pieces representing the actual component. The latter inspections simulated the ISI. Comparison of the obtained data during the qualification with that from the ISI provided evidence for the effectiveness of the qualification. The results of the first ENIQ pilot study were published in a final report [12].
The first ENIQ pilot study proved that the EQM provides a satisfactory framework for the development of detailed qualification schemes for ISI of NPP components, but also showed the need for additional guidance. As a result additional RPs were issued by TGQ.
“ENIQ RP7: Recommended General Requirements for a Body operating Qualification of Non-Destructive Tests” [13] provides guidance on the requirements for an IQB, i.e. the
minimum criteria it should meet, so that it is recognised as an independent, competent and reliable IQB. “ENIQ RP8: Qualification Levels and Approaches” [14] provides guidance on deciding on the level of qualification and on determining the qualification approach based on the chosen level. In practice inspection qualification can be performed with varying degrees of complexity and cost, depending among others on the structural integrity significance of the NPP component involved and difficulty of the ISI involved. The aim of this RP is to provide guidance on how inspection qualification might be applied according to the purpose and nature of the inspection.
Despite the success of the first ENIQ pilot study the use of TJ could not fully be explored. The technical component chosen for the study was an austenitic weld and the modelling software at that time was only fully applicable to isotropic materials (e.g. ferritic steels). As a consequence TGQ carried out a second pilot study using a ferritic BWR-type nozzle to shell weld as the technical component under investigation this time. The objective of the second pilot study was to demonstrate how to fully exploit the potential of TJs in the qualification of inspection procedures and thereby reduce the number of test piece trials on full-scale components. The second pilot study has met its objective and has also proved the availability of models that give large conservative predictions of defect response when used within their regimes of validity. But the second pilot study has also emphasised the importance of ensuring that all models used in TJs should be experimentally validated. The results of the second pilot study were published in a final report [15].
In 2010 TGQ issued a RP on personnel qualification [16], which provides recommendations for the qualification of inspection personnel. Currently TGQ is drafting a discussion document providing guidance on the parameters that should be considered or assessed when specifying inspection qualification objectives and also how to adequately define such parameters. Another recent task of TGQ was a survey on mutual recognition of inspection qualifications. The aim of this survey was to identify the obstacles in transferring inspection qualifications between countries. A questionnaire was issued and was sent to one organisation (utility or IQB) per country. The received answers from the individual countries were summarized in tables and based on these TGQ is currently preparing a pilot study on mutual recognition (see Challenges).
2.2 Risk-Informed In-Service Inspection
With more widespread use of RI-ISI in Europe since the mid 1990s an own task group on RI-ISI, TGR was established in ENIQ. One of the first tasks of TGR was the publication of a discussion document on RI-ISI for NPPs in Europe. The document was the first step in the development of a common European methodology on RI-ISI and in the document TGR members expressed their views on the content of such a methodology. In 2005 the European methodology on RI-ISI [2] was published and its purpose is to provide guidelines to utilities for developing their own RI-ISI approaches or for using or adapting already existing approaches in Europe while taking into account utility-specific characteristics and national regulatory requirements.
Around the same time TGR published two RPs and a number of discussion documents.
The scope of “ENIQ RP9: Verification and Validation of Structural Reliability Models and associated Software to be used in Risk-Informed In-Service Inspection Programmes” [17] are structural reliability models (SRMs). They are commonly used to evaluate failure probabilities and RP9 summarizes the verification and validation requirements, which SRMs and associated software should meet. “ENIQ RP11: Guidance on Expert Panels in RI-ISI”
[18] gives guidance on how to form, prepare and facilitate an expert panel for a RI-ISI process.
The discussion documents issued by TGR are on the role of in-service inspection for defence in-depth [19], on how to apply RI-ISI concepts onto reactor pressure vessels [20] and on how to maintain and update a RI-ISI program [21].
From 2006 to 2010 TGR members participated in the joint EC/JRC – OECD-NEA benchmark project RISMET [22]. The aim of this benchmark project was to compare different RI-ISI methodologies and to investigate to what extent they deliver different results.
From 2010 to 2012 TGR carried out a research project on probability of detection (PoD) curves. PoD is a measure to quantify the reliability of ISI. A number of publications evolved from this project starting with a state-of-the-art report on the use of PoD curves [23], followed by a study on the influence of the sample size and other factors on the hit/miss PoD curves [24] [25]. TGR has recently issued a simpler version of the European Framework Document on RI-ISI for the non-specialist [26] and is currently drafting a technical report on the lessons learned from the application of RI-ISI to European NPPs [27].
2.3 Task Group for Inspection Qualification Bodies
IQBs provide advice to licensees (utilities) on the processes and application of inspection qualification to ensure a high level of confidence in NDT results. In 2012 the utilities represented in ENIQ have decided to set up a separate task group for IQBs to improve qualification practices and to provide a consensus view to licensees. The role of TGIQB is to provide a forum for the exchange of information between IQBs and to identify and conduct surveys and other activities that are targeted at improving the efficiency and effectiveness of approaches for establishing confidence in NDT. TGIQB had its inaugural meeting in March 2013 and is in the process of defining its future tasks.
3 CHALLENGES 3.1 NDT Qualification
After joining NUGENIA ENIQ re-wrote its roadmap published in early 2011 and added a number of new challenges. These are briefly explained in the following paragraphs.
Computed radiography (CR) is used extensively to replace film based industrial radiography and there is a need to understand the relative performances of CR and film based radiography. One aspect that makes CR attractive is its linear detection characteristics and the resulting ability to reduce the radiation exposure, which in turn reduces inspection times and the potential radiological hazard. As the detection, processing and interpretation of both methods differ considerably, there are many technical aspects that need to be explored. TGQ is currently preparing a comprehensive study on the performance of CR aiming to identify the essential parameters that affect the performance of CR thereby providing a consistent approach to inspection design and the production of TJs.
Ultrasonic phased array provides significant improvements for a wide range of applications compared to conventional ultrasonic testing (UT). These range from the ability to generate several fixed beam angles from within a single probe, beam focussing and the provision of detailed defect characterisation through signal processing. The current approach for qualifying ISI using phased arrays is to apply the same principles and processes as for conventional methods on a case by case basis. With the increasing use of phased array there is substantial benefit to be gained through a more formalised approach. The essential parameters for phased array are more numerous and complex than for conventional UT and extensive studies are required to ensure inspection reliability in practice.
Guided waves UT (GWUT) is seen as a promising ISI method, but an independent assessment of this method has not been performed yet. Such an evaluation would be useful for an informed decision making process on the relevance of deployment of this technique.
The European Methodology for inspection qualification [1] was initially designed as a framework that would enable each country to establish its own detailed practices that matched the specific national requirements (regulatory, plant type, resources, etc.). Whilst being extremely successful in achieving this objective, the inevitable specific nature of the qualification processes has introduced significant obstacles in the ability to transport qualifications between countries. ISI vendors that have qualified their inspection systems in one country are then required to repeat the qualifications in another country even if the plant is similar. Consequently, one of the major tasks faced by ENIQ is to understand the technical barriers that preclude the transport of qualifications between countries and to overcome these.
To identify these barriers TGQ has previously carried out the above mentioned survey and is currently preparing a pilot study on mutual recognition of ISI qualifications.
NDT inspection simulation software is widely used as a first step in the development of inspection procedures and sometimes as the final step in verifying inspection capabilities of a technique for defect detection, because of the relatively little costs involved compared to experimental verification using mock-ups. An independent assessment to verify the accuracy of existing NDT inspection simulation software would be useful in evaluating the relevance of simulation software output for the qualification of NDT Systems.
High density polyethylene (HDPE) is a promising alternative to cast iron for piping systems of tertiary cooling systems of NPPs, since HDPE is not subject to corrosion and erosion degradation discovered among cast iron piping. The greatest challenge concerning HDPE is its accurate and reliable ISI.
With long term operation of NPPs becoming reality the integrity and ageing of concrete structures of NPPs, in particular the containments, is receiving more attention inside the nuclear community. This includes ISI of concrete, which is more complex compared to the ISI of metallic components. TGQ considers the development of an evaluation process for the reliability of commercially available inspection techniques and to implement a qualification process for these techniques for concrete components.
3.2 Risk-Informed In-Service Inspection
One of the challenges concerning RI-ISI is the use of Probability of Detection (PoD) curves. As mentioned in Chapter 2.2 PoD curves are a tool to quantify the reliability of NDT systems and they are slowly finding their way into the nuclear industry. The need to quantify the output of inspection qualification has become more important, especially as structural reliability modelling and quantitative RI-ISI methodologies become more common and the PoD provides a metric for quantifying ISI reliability. Despite recent progress in the development of PoD methodologies adequate guidance on the use of PoD for practitioners is still missing. TGR is currently preparing a project on PoD curves, which includes the issuing of specifications on the use of PoD curves, but also a study on the application of the Monte Carlo approach for generation of PoD curves and defining the role of PoD in risk reduction.
Despite RI-ISI is well established an analysis on its role for defence-in-depth and an assessment on the achievable level of risk reduction with RI-ISI is still missing. A study which addresses these issues is currently under preparation by TGR. Another challenge related to RI-ISI is RI pre-service inspection (PSI) for new build in view of the on-going and planned new build of NPPs in Europe.
3.3 Inspection Qualification Bodies
The main challenges for TGIQB are the mutual recognition of qualified inspections and the improvement of inspection qualification practices, in particular the development of a consensus on the design of practical trials and production of test pieces for qualification of ISI procedures and personnel, an investigation on the wider aspects of NDT model validation, the establishment of a consistent approaches for the re-qualification of NDT personnel and provision of a consistent approach to the assessment of NDT simulation.
4 CONCLUSIONS
ENIQ is a utility driven network dealing with the reliability and effectiveness of NDT for NPPs. ENIQ is recognised as one of the main contributors to today’s global qualification codes and guidelines for ISI. As such, ENIQ has always been playing a first order role on qualification state-of-the-art, creating the first qualification methodology based on TJs, an European methodology on RI-ISI, issuing various RPs and carrying out pilot studies and surveys resulting in the publication of nearly 50 documents since its establishment in 1992.
With the entry into NUGENIA as its 8th TA ENIQ has re-written its roadmap and included a number of challenges facing its members. The ENIQ TGs are currently preparing surveys and pilot studies to tackle these challenges and new RPs and reports are likely to evolve from these projects. With these new future publications ENIQ will maintain its role as one of the main contributors to today’s global qualification codes and guidelines for ISI.
REFERENCES
[1] ENIQ, European Methodology for Qualification of Non-Destructive Testing – Issue 3, ENIQ Report no. 31, EUR 22906 EN, 2007.
[2] ENIQ, European Framework document for Risk-Informed In-Service Inspection, ENIQ Report no. 23, EUR 21581 EN, 2005.
[3] ENIQ, The ENIQ 2020 Roadmap, ENIQ Report no. 43, EUR 24803 EN, 2011.
[4] NUGENIA, The NUGENIA Roadmaps, to be published.
[5] ENIQ TGQ Discussion Document: European Methodology for Inspection Qualification – An Overview for the Non-Specialist, ENIQ Report no. 40, EUR 24428 EN, 2010.
[6] ENIQ RP1: Influential / Essential Parameters – Issue 2, ENIQ Report no. 24, EUR 21751 EN, 2005.
[7] ENIQ RP2: Strategy and Recommended Contents for Technical Justifications – Issue 2, ENIQ Report no. 39, EUR 24111 EN, 2010.
[8] ENIQ RP4: Recommended Contents for the Qualification Dossier, ENIQ Report no. 13, EUR 18685 EN, 1999.
[9] ENIQ RP5: Guidelines for the Design of Test Pieces and Conduct of Test Piece Trials, ENIQ Report no. 42, EUR 24866 EN, 2011.
[10] ENIQ TGQ Technical Document: Practical Examples for Manufacturing of Test Pieces for Inspection Qualification, ENIQ Report no. 44, EUR 24878 EN, 2011.
[11] ENIQ RP6: The Use of Modelling in Inspection Qualification – Issue 2, ENIQ Report no. 45, EUR 24914 EN, 2011.
[12] ENIQ, Final Report of the 1st ENIQ Pilot Study, ENIQ Report no. 20, EUR 19026 EN, 1999.
[13] ENIQ RP7: Recommended General Requirements for a Body operating Qualification of Non-Destructive Tests, ENIQ Report no. 22, EUR 20395 EN, 2002.
[14] ENIQ RP8: Qualification Levels and Approaches, ENIQ Report no. 25, EUR 21761 EN, 2005.
[15] ENIQ, Final Report of the 2nd ENIQ Pilot Study, ENIQ Report no. 27, EUR 22539 EN, 2006.
[16] ENIQ RP10: Personnel Qualification, ENIQ Report no. 38, EUR 24112 EN, 2010.
[17] ENIQ RP9: Verification and Validation of Structural Reliability Models and associated Software to be used in Risk-Informed In-Service Inspection Programmes, ENIQ Report no. 30, EUR 22228 EN, 2007.
[18] ENIQ RP11: Guidance on Expert Panels in RI-ISI, ENIQ Report no. 34, EUR 22234 EN, 2008.
[19] ENIQ TGR Discussion Document on the role of In-Service Inspection within the Philosophy of Defence in Depth, ENIQ Report no. 29, EUR 22230 EN, 2007.
[20] ENIQ TGR Discussion Document on the role of In-Service Inspection of the Reactor Pressure Vessel, ENIQ Report no. 35, EUR 23419 EN, Luxembourg, 2008.
[21] ENIQ TGR Discussion Document on Updating of Risk-Informed Inspection Programmes, ENIQ Report no. 37, EUR 23929 EN, 2009.
[22] L. Gandossi et al., EC-JRC/OECD-NEA Benchmark Study on Risk Informed In Service Inspection Methodologies (RISMET), OECD-NEA Report no. NEA/CSNI/R(2010)13, Paris, 2010.
[23] C. Annis, L. Gandossi, ENIQ TGR Technical Report: Probability of Detection Curves:
Statistical Best Practices, ENIQ Report no. 41, EUR 24429 EN, 2010.
[24] C. Annis, L. Gandossi, ENIQ TGR Technical Report: Influence of Sample size and other Factors on the Hit/Miss Probability of Detection Curves, ENIQ Report no. 47, EUR 25200 EN, 2012.
[25] C. Annis, L. Gandossi, O. Martin, "Optimal Sample Size for Probability of Detection Curves ", Nuclear Engineering and Design, 262, 2013, pp. 98-105.
[26] ENIQ TGR Discussion Document on Risk-Informed In-Service Inspection: An Overview for the Non-Specialist, ENIQ Report no. 46, EUR 25199 EN, 2012.
[27] ENIQ TGR Technical Report: Risk-Informed In-Service Inspection: Lessons Learned from Application to European Nuclear Power Plants, ENIQ Report no. 48, in draft.
