| NDT.net - August 2002, Vol. 7 No.08 |
3nd International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, Nov 14-16, 2001, Seville Spain
Non-destructive testing (NDT) is used by many industries to provide confidence in the quality or structural integrity of components. Experience from round robin trials has demonstrated that the capability of Non-destructive testing is does not always meet the requirements made of it. Inspection Qualification, sometimes known as Validation or Performance Demonstration, has been developed as a method for demonstrating the capability of NDT. In the nuclear industry NDT is often used to demonstrate the structural integrity of safety critical components and the European nuclear utilities have set up a network to develop the ENIQ methodology for inspection qualification. The ENIQ network and its documents are suitable for the nuclear industry but the requirements in these documents were considered too much of a burden for some other industries. Hence there was seen a need for a broader based document that would be appropriate for all industries and as a result a European Standards Working Group (TC138 WG 9) has been established which is responsible for developing a European Methodology for the qualification of inspections for all industries. This paper describes the main features of the two documents (the ENIQ Methodology and the TC138 WG9 Methodology) and makes a comparison between them and discusses important issues associated with inspection qualification.
Inspection Qualification is now being used to demonstrate that non-destructive inspections are capable of meeting the requirements placed on them. One of the problems associated with qualification is that it is not always easy to decide how to qualify an inspection or find helpful advice on how to carry out the qualification process. The nuclear industry in Europe with assistance from the European Commissions Joint Research Centre (JRC) set up the European Network for Inspection Qualification (ENIQ). This group consists of NDT experts from nuclear utilities, inspection vendors and qualification bodies in Europe. The main task of ENIQ has been to produce a methodology [1] for carrying out inspection qualification that provides guidance on how qualification should be carried out. The aim was to produce a document that was flexible enough to be used in each country and that would provide a framework for qualification that could be agreed by all nuclear utilities and would be accepted by the nuclear regulators throughout Europe. A similar document has been prepared by the International Atomic Energy Agency - Methodology for Qualification of In-Service Inspection Systems for WWER Nuclear Power Plants [2]. For the purposes of this paper the ENIQ and IAEA documents are considered to have the same basic principles.
Non-destructive testing (NDT) is used in a wide range of industries outside nuclear and it has become clear that a guidance document on qualification was required for this broader range of industries. The ENIQ methodology was used a basis for this new document which was intended to provide a simpler approach to qualification that could be used for all industries. This document [3] has been developed through the European Committee for Standardization (CEN/TC 138 WG9). This group has members from Denmark, France, Finland Germany, Italy, Spain, Sweden and the UK. The challenge for the committee was to develop useful practical guidelines that would be acceptable to all the European countries and a wide range of industries.
This paper will describe the main features of these methodologies and discusses some of the important issues associated with inspection qualification.
The European nuclear utilities combined under the aegis of the European Commission’s Joint Research Centre at Petten to establish a European Network for Inspection Qualification (ENIQ). The ENIQ network also includes qualification bodies such as the Inspection Validation Centre (IVC) and others with relevant expertise
The main task of ENIQ was to prepare the European Methodology for Inspection Qualification. The second issue of this document was published in 1997 and has been used as the basis for many qualifications world-wide. ENIQ has also produced a series of Recommended Practice documents [4, 5,6, and 7] which provide more detailed guidance on qualification.
Further assistance on qualification is being provided by ENIQ through two pilot studies. The first pilot study involved using the methodology to develop and then implement a qualification system for austenitic pipework welds. The objective was to provide an illustration of how qualification can be carried out in practice within the ENIQ methodology. The second pilot study, which is currently ongoing, will explore the role and extent technical justification can play in effective inspection qualification. The components involved are BWR nozzle to shell welds.
The European Committee of Standardization (CEN) technical committee TC138 set up a working group with the mandate to write a technical report containing a methodology for qualification of NDT. The working group, whose convenor is Michel Bièth of the European Commission’s JRC Petten, is made up of NDT specialists from a wide range of industries in France, Germany, Italy, Denmark, Finland, Spain, Sweden and the UK.
There was too much resistance in CEN TC138 to make the document a European Standard, so the objective of the working group was to prepare a technical report. The technical report has a lower legal status than a standard but may be upgraded at a later date depending on the documents use.
A first draft has been prepared and is just about to be issued by CEN. It is intended that a final approved document will be issued in June 2002.
| ENIQ Methodology |
CEN TC138 WG9 Methodology | |||
| Point for comparison | Advantages | Disadvantage | Advantage | Disadvantage |
| Scope | Main focus on qualification of nuclear inspections all types of NDT | Too specific and requirements too heavy for many industries | Intended to coverall types of NDT in all industries | Not enough detail for specific applications |
| Framework | Flexible approach that can be tailored to requirements | Sometimes used as a set of rules in a rigid inflexible way | Flexible approach that can be tailored to requirements | |
| Glossary | ENIQ Glossary available to all revised and agreed by European nuclear utilities | Those involved in qualification do not always consult the Glossary | Brief Glossary included in document to aid understanding | Definitions do not always agree with ENIQ Glossary |
| Use of new concepts | Use of TJ saves on test pieces. TJ provides additional confidence not achieved through practical trials | TJ relatively new concept not well understood | Use of TJ saves on test pieces. TJ provides additional confidence not achieved through practical trials | TJ relatively new concept not well understood |
| Authors | Document prepared by NDT specialists from nuclear utilities, Qualification bodies & Inspection Vendors | Document not fully understood by those outside specialist NDT field | Document prepared by a team of NDT experts representing a wide range of industries | Document not fully understood by those outside the NDT field |
| Responsibilities | Defined | Defined | ||
| Acceptance by Industry | Accepted by nuclear utilities in Europe | Simplified structure should lead to acceptance by industry | ||
| Acceptance by Regulators | Accepted by European nuclear regulators working group | |||
| Experience of using the document | Widely used in Europe | Some difficulties experienced in practical application experienced in understanding and applying the document | New document not issued | |
| Feedback from experience | Feedback from experience will be used to improve documents in future through ENIQ | Experience from use should be fed back to CEN via WG9 so that improvements can be made | No feedback because it is a new document still to be issued | |
Authors
Both documents have been produced by international committees made up of technical specialists in the field of NDT. The technical specialists represent plant owners, manufacturers, inspection vendors and qualification bodies.
Scope and Use
Because the countries in Europe are subject to different regulatory and legal requirements it was not possible or desirable to produce a detailed set of requirements for qualification. Both ENIQ and CEN/TC138 WG9 have produced documents which set out a framework for qualification. The objective is to describe the principles which should be applied and the organisational responsibilities of the different involved parties. The principles include the following:
The aim of both documents is to promote a uniform approach throughout Europe without being prescriptive in the detail.
Glossary
Both documents contain a section on terms and definitions used, where possible the ENIQ terms and definition have been used in both documents but this has not always been possible. Inspection qualification is a relatively new subject and it is important that there is a common understanding of the terms used.
Scope and Use
The ENIQ methodology has been primarily developed for use in the nuclear industry where there is a strong reliance on NDT to ensure the structural integrity of safety critical components.
To assist those developing detailed systems for qualification on the basis of the methodology, ENIQ has developed a series of recommended practices which provide more detailed advice such as the material which could be included in technical justifications and the way in which practical trials should be conducted.
The ENIQ methodology has been in use since 1997 and has formed the basis for many qualifications carried out in the nuclear industry world-wide.
The CEN TC138/WG9 document has been written to be applicable to all industries. The document provides more specific advice that the ENIQ methodology on when there is a need for qualification. The CEN TC138/WG9 document is in its final draft stage and should be issued early in 2002 hence there is currently no experience or feedback from the practical application of the document.
Feedback from experience of using the documents is probably one of the most important issues associated with developing better guidelines for the future. It is important that CEN TC138 sets up an effective system for feedback to make improvements to the document. ENIQ provides and effective forum where improvements to the ENIQ methodology and recommended practices can be made.
Acceptance by Industry and Regulators
The European nuclear regulators have considered their own position on qualification through the Nuclear Regulators Working Group on Reactor Safety. They established a task force to study the essential elements of the ENIQ methodology and in April 1996 produced a report on the subject. The report is, in general, in good agreement with the ENIQ methodology.
Several of the important issues associated with the successful implementation of cost effective inspection qualification are not necessarily dealt with in the two documents. The intention here is to discuss some of these issues for consideration and possible inclusion in future versions of the documents.
One of the main benefits of qualification is to start a process where those who are using non-destructive testing consider why it is being used and what requirements are being made of it. For example, qualification often brings to light issues such as the defects that the NDT is intended to detect have not been adequately specified. Another common example is that the role the NDT has in the safety case for the component may not be fully understood because there is not an adequate knowledge of the inspection capabilities in terms of detecting, sizing and characterising defects.
Good communication between all the interested parties involved in the qualification process is an essential at all stages of the process. It is particularly important that, for example, the plant owner, regulator, the qualification body and the inspection vendor discuss and thoroughly understand the qualification process. Many of the important documents associated with qualification such as the technical specification, the technical justification, the inspection procedure and the qualification procedure will probably require revision during the qualification process. Hence it is important to set up efficient methods of communication so that documents and changes to documents can be revised quickly. Most important is that those involved talk to each other on a regular basis to make sure there is a common understanding of any changes that may be required.
Inspection qualification is a relatively new subject and there is a shortage of expertise in this specialist area. Hence, it is important that those involved in qualification receive suitable training in the subject.
Two useful documents have been prepared that will provide advice and guidance to those wishing to carry out inspection qualification. These documents will provide a sound basis for the qualification of any NDT method used in a wide range of industries. If you wish to be successful in developing an appropriate qualification it is recommended that the following steps be considered:
Finally be creative in your thinking and approach to qualification, the documents described here are only guidance and provide a framework for you to build upon.
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