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INTRODUCTION OF THE NEW PROCESS AND QUALITY CONTROL
METHODS IN FUEL FABRICATION AT SIEMENS/ANF
K.T. ROGGE, H.H. FICKERS
A i j T. T i -i—i | I lllll mill llll Hill urn mil inn in n
Advanced Nuclear Fuels, XA0055763
Siemens AG, Unternehmensbereich KWU,
Lingen
W.DORR
Siemens AG, Unternehmensbereich KWU
Germany
Abstract
The central point of ANFs quality philosophy is the process of continuous improvements. With respect to
the causes of defects and the efforts needed for elimination, the importance of continuous impovements is
evident. In most of the cases, defects are caused in the initial stages of a product but the majority of the problems
will be only detected during fabrication and inspection and in the worst case when the product is already in use.
Goal of the improvement process is to assure a high product quality. Therefore, the efforts are focused on robust
and centered processes. A reasonable quality planning is the basis for achieving and maintaining the quality
targets. Quality planning includes prefabrication studies, inprocess inspections and final inspections. The
inspections provide a large amount of various quality data, process parameters as well as product properties. Key
data will be defined and subjected to a statistical analysis. In view of the effectiveness of the analysis, it is
important, that the process parameters which influence the characteristics of the product are well known and that
appropriate methods for data evaluation and visualization will be used. Main approach of the data visualization
is to obtain a tighter control of the product properties and to improve the process robustness by implementation
of defined improvements. With respect to the fuel safety and fuel performance, the presentation shows for
typical product quality characteristics some examples of visualized quality data. The examples includes the
integrity of the pellet column (rod scanner results), the spring force of PWR spacers (critical characteristic with
regard to rod fretting) and the spacer intersection weld size (thermo-hydraulical fuel bundle behaviour). The
presentation also includes an example for the statistical process control, the in-line surveillance of the fuel rod
weld parameters which assures the integrity of the welds within tight tolerance ranges. The quality system and
efforts assure products of high quality and contribute herewith to the safe and economical performance of the
fuel supplied by Siemens/ANF.
1. INTRODUCTION
The presentation provides an introduction of the new process and quality control methods which
are applied in the fuel fabrication at Siemens/ANF to assure a high product quality.
With respect to the main objectives of the meeting, that is the improvement of the fuel safety
and fuel reliability, the presentation is focused on the principle and the goals of the continuous
improvement process.
The presentation provides useful information to the content and structure of a reasonable quality
planning which can be considered as the driving force for continuous improvements.
The presentation explains the importance and the purpose of the analysis of quality data. The
visualization of quality data will be illustrated by practical examples.
2. THE CONTINUOUS IMPROVEMENT PROCESS
The continuous improvement process is the central point of ANF's quality philosophy.
A continuous control and a monitoring of processes will initiate preventive actions which
finally will result in further product improvements or process modifications. Any design or process
changes require a qualification. Based on the qualification, the changes will be introduced in the fuel
145
Customer benefit
Controlled Customer O Improved vendor assessment
Processes C~" Feed-back O Optimized product and/or process
surveillance
Process Q Realizecj^ciyallty expectations
Control Product _
Quality- Design Preventlve
Process System I I Action
Monitoring Process
Design Manufacturer benefit
Process O Improved product quality
Validation O Decreased failure costs
Continuous O Improved manufacturing capacity planning
Improvement O Staff and customer satisfaction
FIG. 1. Principles of continuous process improvement
fabrication and the controlled process continues. The sketch (Fig. 1) clarifies the principle of the entire
process.
The quality system provides the basis for the continuous improvement process, e.g. by
appropriate requirements with respect to the product and process qualifications and by a management
system for preventive actions. In addition to the QM system, there are also other factors contributing
to the efficiency of the continuous improvement process, especially the feedback of the customers.
Besides the fulfillment of quality expectations, the continuous improvement process provides
additional benefits to the customer such as an improved vendor assessment and an optimization of
product and process surveillances. Improved product quality, a decrease of failure costs and achieving
staff and customer satisfaction are the main benefits for the manufacturer.
The diagram (Fig. 2) explains the importance of improvements by showing the dependence on
the cause of defects and their elimination. In most of the cases, defects will be caused already in the
initial stages of the product research and development but the majority of the defects will be detected
much later, in most of the cases during inspection. In the worst case, defects which are already latent
during the product and process development will be detcted only during the performance of the
product. The costs to eliminate a defect depend on the phase of detection. Defects which appear
during final inspection or in the use of a product cause significantly higher costs than defects which
can be already settled during planning.
To meet a high product quality Siemens/ANF relies on robust and centered processes. The
diagrams shown in Fig. 3 illustrate the benefits of robust and centered processes. A process can be
considered as robust when relatively large variations of process parameters will have no significant
influence on the product properties. The centered process (Taguchi philosophy) can be evaluated by
means of the cpk-values. In order to achieve a robust and centered process it is necessarry to have an
adequate knowledge of the entire process.
3. QUALITY PLANNING
A systematic quality planning is the driving force for continuous improvements. Quality
planning includes:
Prefabrication studies with review of the design package,
Fabrication and inspection planning with review of qualifications,
Determination of key quality data for statistical evaluation,
Analysis and visualization of quality data,
Quality improvements (In view of the results of the statistical analysis).
Prefabrication studies are especially required in case of a new product design and or
manufacturing processes. The studies are mainly focused on:
Review of the suitability of the existing production and inspection equipment, including the
intended methods and techniques,
Review of the applicability and validity of present process and product qualifications,
Review of the process flow (sequence of operations, e.g. cleaning steps),
Review of the sufficiency of personnel qualification,
Review of the design package. Prior to the issue of a parts list, the specifications and
drawings will be reviewed by ANF key functions to verify the fabricabiltiy of the product
on the basis of the specified requirements. The design documents have to be agreed
between the design department and the manufacturer site. This procedure presents an
important part of the installed QM system and assures, that the design requirements and the
production experiences are brought together on the basis of a systematic process.
147
00
Elimination of Defects In most of the cases, defects are
caused in the initial stages of a
Cause of Defects product. A large amount of problems
is already latent during the product
and process development phases.
The majority of defects and problems
will be only detected during the
fabrication and inspection of the
product or later when the product is in
use.
mm The costs to eliminate a defect
JSBSL 1 depend on the phase of detection.
Defects which appear during
Product Process fabrication or in the use, cause
Definition Research and Research and Manufacturing Inspection Performance significant higher costs than defects
Development Development seen already during planning.
FIG. 2. The diagram of continuous process improvement - cause of defects and their elimination
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