COMPARISON BETWEEN NDE QUALIFICATION STANDARDS AND PRACTICES IN DIFFERENT COUNTRIES. P. Jardet, M. Dib, EDF Qualification Body, France

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1 More Info at Open Access Database COMPARISON BETWEEN NDE QUALIFICATION STANDARDS AND PRACTICES IN DIFFERENT COUNTRIES ABSTRACT P. Jardet, M. Dib, EDF Body, France Nowadays NDE qualification is required for in service inspections of nuclear pressurized components in most countries where nuclear power plants are being exploited. But regulatory requirements, methodologies, and practices are more or less different. After a reminder of the origin and evolution of NDE qualification, the aims of this paper are to: - present and compare the main existing methodologies and standards such as ASME, ENIQ, RS-EM, - present the ISI qualification status in different countries, including regulatory requirements, applied standards, scopes of qualification, types of qualification body... - compare practices, - point out common areas but also the main differences - identify possible ways for harmonization. ORIGIN AND EVOLUTION OF NDE QUALIFICATION The reliability issue of ultrasonic testing for nuclear pressure vessels emerged in 1965 from the US Pressure Vessel Research Committee (PVRC), an NDE programme was therefore engaged. The Marshall Commitee, expert group in fracture mechanics established its recommendations about the size of the defects to detect on the Reactor Pressure Vessel welds, firstly in 1976, and then in International programmes were engaged to do blind comparisons of the results obtained by different teams on the same mock-ups containing induced defects. These programmes, PISC I ( ), PISC II & III ( ), UKAEA Defect Detection Trials ( ) and HSST showed significative differences between teams and techniques, and showed shortcomings as much as satisfactory pratices as these results were compared to the destructive results of the defects. The need to insure the reliability of NDE clearly appeared and different qualification approaches and associated referentials were launched and developped worldwilde : Recommendations in the UK 1982 LWRSG report; Appendix VIII of ASME Code Section XI from 1989 to present; US Perfomance Demonstration Initiative (PDI) from 1992 to present Creation of the European Network for Inspection (ENIQ) in 1992, which has established and updated the ENIQ qualification methodology since 1995; RSE-M french code has included the NDE qualification since 1997;... Meanwhile regulators have progressively required ISI qualification since the 1980s in different countries. MAIN EXISTING METHODOLOGIES AND STANDARDS As seen above, the main existing references for ISI qualification for nuclear pressurized components are the ASME code section XI (appendix VIII), the ENIQ Methodology and the RS-EM code (Appendix 4.3). One can also quote the IAEA Methodology for WWER NPP, which essentially follows the ENIQ Methodology, and the ASME section V (Article 14), followed in certain countries (e.g. Canada) to complete ASME section XI and/or ENIQ Methodology. A comparison on the main items between ASME XI Appendix VIII, ENIQ Methodology, and RSE-M Appendix 4.3 is given in the table 1. 28

2 item ASME XI Ap. VIII ENIQ Methodology RSE-M Ap. 4.3 Scope UT examination used to detect and size flaws (mainly fatigue craks) Input information Technical Justifications (TJ) - Component Type - NDE Procedure - Equipement description Any inspection method or technique used for detecting, sizing, locating a specified type of defect - objectives of the inspection qualification - full description of the component to be inspected - types, dimensions, orientations, location and morphologies of defects to be detected and/or sized - inspection performance to be achieved - qualification level - NDE procedure, equipment and personnel requirement No TJ required For providing convincing evidence that the inspection procedure is capable of meeting the requirements. TJ could include : - Measurement on practice or development test pieces - Physical reasoning - Feedback from field experience - Previous qualification - Results from modelling - Laboratory studies - Any inspection method or technique used for : - detecting, sizing, locating a specified type of defect, - or for surveillance purpose when no specified defects are postulated - objectives of the inspection - description of the component to be inspected - type of qualification: - Conventional (no defect suspected) - General (postulated defect situation) - Specific (defects observed) - General/Specific: types, dimensions, orientations, location and morphologies of defects to be detected and/or sized - Conventional: prescriptive standard to be applied, type of reflector used to express the sensitivity (Flat Bottom Hole, Notche ) -inspection performance to be achieved - NDE procedure, equipment and personnel requirement Distinction is made between the NDE Technique (instrumentation, probe..), and the in-the-field inspection (accessibilty, robotic if used ). TJ for NDE Technique provides evidence that the Technique is capable of meeting the requirements. TJ could include : - Measurement on practice or development test pieces - Physical reasoning - Feedback from field experience - Previous qualification - Results from modelling - Laboratory studies - TJ for implementation in field conditions include robot specifications, accessibility and geometric data. 29

3 Practical Trials, Test Pieces Type, Level of Equipment, NDE Procedure of Personnel Body Blind pratical trials are required. The Test pieces shall meet precise requirements in terms of dimensions, type of flaws (e.g. craks, semi-elliptic notches), and number and size of these flaws. These requirements are only depending on the component. The acceptance criteria are defined in terms of mimimum of flaws detected and maximum of false calls for detection, and RMS error for sizing. It is considered preferable to perform open practical tests for procedure/equipment qualification. Blind practical tests should be perform for personnel qualification. Test pieces may replicate the component in size and geometry, however simpler test pieces can also be used (results need to be extrapolated using justifications). No different type or level 3 defects situation are considered : specific (defects have been found), Equipement, NDE procedure and personnel are not qualified separately. See above Not specified. postulated and unspecified. Only specific and postulated situation are subject to qualification. level is determined by the utility. It is an input information for the qualification. NDE procedure and equipement can be qualified by TJ, open trials or both. If required, through one or combination of : - certification through a national NDE personnel certification scheme - theoretical and/or open practical examination - blind trials Required Three types of QB are possible : - An independant third party organisation - Part of a utility organisation set up on a long-term basis - An ad-hoc body set up for a particular inspection. Open pratical trials are required for General or Specific. The number and the type of defects contained in the Test pieces are justified case by case, in accordance with the TJ. The trials acceptance criteria are also defined cas by case in accordance with TJ. 3 types of qualification: conventional (no defect supected), general (postulated defect) and specific (defect have been found). No level defined, but TJ is sufficient for conventional qualification. Required Not required. The NDE procedure shall precise whether specific personnel qualification is required. If required, the content of the qualification is documented (training, tests ). Required The QB quality system is required to comply the ISO standard. Table 1: Comparison between ASME XI Ap.VIII, ENIQ Methodology, and RSE-M Ap. 4.3 To summarize and conclude, there are significative differences between ASME XI Ap. VIII requirements and both ENIQ Methodology and RSE-M Ap Furthermore, if we except the situation of unspecified defect, RSE-M Ap. 4.3 complies the ENIQ Methodology recommendations. 30

4 PRESENT ISI QUALIFICATION STATUS IN DIFFERENT COUNTRIES AND PRACTICES COMPARISON Based on the answers received from 14 countries (see figure 1) to a questionnaire sent in february 2012 to the ENIQ members or participants, elements are now available for a better knowledge of the ISI qualification status and practices in those countries. One should note that the following elements are only the results analysis of the answers by the authors and are subject to mistakes due to their understanding of the answers. Figure 1: countries ansewring to ENIQ questionnaire Hereafter presented in map form from figure 2 to figure 7, the main topics concerning ISI qualification in the different countries. Figure 2: Status of requirement 31

5 Figure 3: Codes & Standards followed Figure 4: NDT methods included in the scope of qualification Figure 5: Scope of the qualification 32

6 Figure 6: Different levels of qualication Figure 7: Type of Body The differences of qualification practices between countries are a consequence of the local regulations, the standards followed, and local cultures. Most countries have adopted the ENIQ Methodology, either as a complement to ASME XI (sometimes required by local regulation) or as the main reference. This success of the ENIQ methodology is probably due to its flexibility, which however leads to practice differences. As an example of topics of pratice differences : way to define the objective and input information such as performance target, defaults target, characteristics of the component, the levels/types of qualification, performance criteria for detection (POD, quantitative, deterministic ) 33

7 performance criteria for sizing (RMS, uncertainty ) balance between TJ and practical trials, basis for the design of the test pieces and the defects (imposed, justified, use of the concept of worst case defects ) WAYS FOR HARMONIZATION The final purpose in term of harmonization would be a straight transfer of qualifications between countries, but before reaching this objective different issues should be investigate. First of all tranfert of qualification supposes that the inspection requirements for a similar component are the same between countries. Perhaps, efforts could be made to standardize the contain of the inspection requirements (component description, defect characteristics ). Secondly, if a recognised way to conduct qualification was defined between QBs, it would then be easier for a vendor to submit part of a qualification dossier (e.g. TJ) from one country to an another one. A first step could be to identify the elements of qualification dossiers that could be easily transferred or used between countries (e.g. technical evidences, test pieces design, modelling ). CONCLUSION The overwiew of the current status of ISI qualification in different countries and practices comparison, shows that there are common areas but also significant differences. These differences are obstacles to be overcome to transfer qualification between countries. There is a real interest to find and develop ways of harmonization in order to facilitate, at least the use of elements of a qualification dossier from one country to another. REFERENCES 1) Allan Rogerson, A personal perspective on the early developments in inspection qualification and reliability assessment in the nuclear industry and comparison with similar developments in other industries, Proceedings of the 9 th International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components May 2012 Seatlle 2) ASME Section XI 2011a 3) ENIQ Methodology third edition ) RSE-M In-Service Inspection Rules for Mechanical Components of PWR Nuclear Islands - AFCEN,