Dr. Christina Mueller studied physics at the Technical University in Dresden and made her PHD in the field of theoretical solid state physics in 1982. After a phase of teaching and research at the university she worked in the practical development of material testing procedures in the electronic industry. Since 1985 she has been working in NDT, beginning with the develoment of ultrasonic probes for nuclear power plants. She works with BAM since 1988 in the division for NDT in the field of signal processing, modeling and 3D data reconstruction. In international co-opeartion she developed basic principles for reliability assessment of NDT and is since 1992 the head of a research group “Reliability of NDT”.

Since 2001 she was also concerned with the reliability of demining systems. She took part in test trials in Afghanistan in 2002 and contributed to the prescription for test and evaluation of metal dectors in the CEN BT 126 CWA07 and was engaged in international test trials for its practical verification. With her research group she developed a modular model investigating all possible influences on the reliability of NDT from the physics and industrial application factors up to the Human Factor including working psychology. The technical POD (Probability of Detection) was extended to multi parameter approaches suited to complex and thick components and especially applied to the NDT processes for canisters for radioactive waste in Scandinavian Nuclear Waste Programs. Dr. Mueller initiated and organized the international workshop series “European American Workshop on Reliability of NDT” which took place 4 times since 1997, leading to a comprehensive and interdisciplinary approach on reliability in NDT.

Abstract

Holistically Evaluating the Reliability of NDE Systems – Paradigm Shift

New methodologies for evaluating the reliability of NDE systems are discussed in accordance with the specific requirements of industrial application. After a review of the substantive issues from the previous decades, the go forward guidance is concluded.

At the beginning of any reliability analysis, the actual safety demands have to be defined in order to fit the investigation to the level of risk when the component would fail. All the essential influencing parameters need to be documented and transferred to an appropriate design of experiments (DOE) to determine the reliability in terms of a qualitative assessment for lower risk or in terms of a quantitative probability of detection (POD) created from hit miss experiments or signal response analysis or ROC (Receiver Operating Characteristics) curves for higher safety demands. The modular model distinguishes between the influence of pure physics and technique, industrial application factors and the Human Factor and helps to learn what factors are covered by modelling, open or blind trials. A new paradigm is offered to consider the POD or reliability of the system as a function of the configuration of input variables and use it for optimisation rather than for a final judgement. An advantage for the end user is also to sample all single PODs to an integral “Volume POD” of a part. New approaches are considered dealing with real defects in a realistic environment, affordable but precisely like the Bayesian approach or model assisted methods.

Among the influencing parameters, the human factor is of high importance. A systematic psychological approach helps to find out where the bottlenecks are and shows possibilities for improvement.  It will also provide best possible working conditions for the human inspectors. The new methodologies will be illustrated by industrial applications.