Best Practice for Risk Based Inspection

a) A Technical Justification, and
b) A Practical Assessment (carried out using a representative test piece(s))
Two documents are in existence that can be used as a basis for the development of
inspection qualification programmes. One is a European document (8.9) developed
by ENIQ, the European Network for Inspection Qualification. This document is
widely used within the nuclear industry both in the UK and in Europe. The other is
a BSI document (8.10) that used the ENIQ document as a basis for its development.
This document is aimed at the non-nuclear industry.
8.4.2. Technical Justification
A Technical Justification is a collection of information that provides evidence of
inspection capability. The Technical Justification might include physical reasoning
(inc. identification and discussion of the essential parameters of the inspection),
mathematical modelling and inspection results.
The Technical Justification should identify ‘worst-case’ defects, i.e. defects judged
to be the most difficult to detect and size at specific locations.
8.4.3. Practical Assessment
A Practical Assessment involves the conduct of trials on a test piece(s)
representative of the component, and provides a demonstration of inspection
capability. Material composition, size/geometry and the defective condition of the
component should be represented. The population of the test piece(s) should include
‘worst-case’ defects.
Test piece trials to prove the capability of the inspection procedure should normally
be carried out ‘open’, i.e. the personnel involved in the trials having specific
knowledge of the defects contained in the test piece(s).
Test piece trials to assess the capability of the inspection personnel, to apply the
proven procedures correctly under realistic conditions, should normally be carried
out ‘blind’, i.e. the personnel involved in the trials having no specific knowledge of
the defects contained in the test piece(s).
The combination of theoretical evidence and practical demonstration provides
powerful confirmation that the inspection is capable of achieving the required
performance. The mix of the two depends on the inspection being qualified and the
level of qualification (see Section 8.4.4). In general, the more straightforward the
inspection the more practically biased the mix; the more complicated the inspection
the more equal the mix.
8.4.4. Qualification Level
The level of rigour is a matter to be agreed between the different parties involved
(plant owner/operator, regulatory body etc). More often than not, the safety and/or
economic consequences of component failure are the major factors in determining
the level of rigour required.
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