DEVELOPMENT FOR FUTURE

The quality control and assurance system shall be modified adequately and timely according to the requirement of quality. It is considered that the inspection procedures should be developed in future on the following viewpoints.

The existence of hold point is important for quality control and assurance. It is necessary to stop the process operation until the result of inspection is obtained. From the viewpoint of process control, if the timeliness of inspection or analysis is secured, the flexibility, efficiency of process operation and productivity will be improved because of the rapid feedback and reduction of waiting

time. Therefore, it should be considered that the speed-up of evaluation of inspection, such as speed-up of analysis with high accuracy, or introduction of new analysis and in-line analysis on the assumption of high accuracy would be necessary. It should be considered that XRFAandNDAare used for process control besides for material accountancy. In future it will be desirable to improve the accuracy and precision of such measurement methods for rational process control. About the introduction of in-line analysis, it should be considered that the relationship between requirements from the process operation and performance of analysis is important.

Rationality and cost effectiveness should be considered in inspection procedures. Analysis is necessary for each lot and the size of lot of MOX fuel is small rather than that of UOX fuel fabrication. The number of analysis in MOX fabrication plant is extremely large and effects the cost.

It is necessary to develop the analysis methods with low cost and to introduce automated process.

5. CONSIDERATION

It is concluded that concept of the quality control and the procedure adopted in MOX fuel fabrication process in JNC should be correct and reasonable in fuel safety aspect. Based on the experience, the present quality control and assurance system is satisfied to the requirement of quality.

It is, however, considered that the current procedure for quality control may have a conservative margin for fuel safety and seems to lose rationality in economic point of view. Therefore, it will be requested that the more rational procedure and the inspection method should be developed and established for the future. The direction of quality control in the future is also discussed mainly based on the improvement of economy with maintaining the safety confidence level.

In future the necessity of MOX fuel fabrication should be increased and capability of the MOX fuel plant should be increased. The experience of UOX fuel fabrication plant, the capability of that is huge rather than that of MOX plant, should be taken in quality control scheme of MOX fuel fabrication for the improvement of the rationality.

"QUALITY AT THE SOURCE" (QATS) SYSTEM XA0055751 DESIGN UNDER SIX SIGMA METHODOLOGY

F. AGUIRRE, I. BALLASTEROS, J. MARICALVA Emperesa Nacional del Uranio, S.A. (ENUSA), Nuclear Fuel Manufacturing Plant,

Juzbado, Salamanca, Spain Abstract

One of the main objectives in the manufacturing of fuel assemblies, is to fulfill the customer expectations with a product that assures its reliability during its stay in the NPP.

By mean of the QATS System design under 6-Sigma methodology, all the customer requirements are included in the product specifications and drawings.

Product characteristics and process variables are classified and process capability is evaluated. All this information permits to identify CTQ's (Critical to Quality) product characteristics and process variables, and to define a quality system (QATS) based in the process and on-line characteristics control handled by the manufacturing workers.

At the end, this system ensures a continuous product quality improvement, and a strong commitment with the customer requirements.

1. INTRODUCTION

Continuing with its Quality Policy, ENUSA has taken the leadership of a project of Quality Assurance system for pellets, based on the "Quality at the Source" (QATS System). According to this system, the manufacturing worker is responsible for the quality of the product. He becomes involved with process control and its variables. He carries out inspections of the product on line checking the process and stopping, if necessary. Quality organization carries out process and product verifications, analyses periodically process capability and certifies the product.

2. METHODOLOGY

For the implementation of this project a continuous improvement methodology called 6-Sigma has been applied. This project has been developed in working teams. Experts in 6-6-Sigma, Quality, Manufacturing Process and Fuel Assembly Design have participated in it. The project has been implemented the following steps:

• 2.1. Define

• ELABORA TION OF THE DESIGN QFD

The design QFD ("Quality Function Deployment") evaluates:

• The importance of Functional Requirements. (First House of Quality)

• The importance of Product Characteristics. (Second House of Quality)

It starts with a deployment of Functional Requirements of the fuel rod. These are: energy production, integrity (the existence of a barrier to prevent fission products to pass on the primary

circuit), growth (compatibility with the fuel assembly) and traceability.

Evaluation of the importance of Functional Requirements is made by means of one

"Comparison Matrix" (Requirements vs Requirements) The results are shown m Figure 1

QFD- U0? PWR PELLET - COMPARISON MATRIX (REQUIREMENTS VS REQUIREMENTS)

fUNCJIONAL REQUIREMENTS

'-Fue/ Rod Funct onal Ftequ rements

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Tube Fatgue ^ 8

Tub ng Collapse f 12 Plenum Co lapse

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F/G 7 Comparison matrix - Requirements vs Requirements

It starts with a deployment of Functional Requirements of the fuel rod These are energy production, integrity (the existence of a barrier to prevent fission products to pass on the primary

circuit), growth (compatibility with the fuel assembly) and traceability.

Evaluation of the importance of Functional Requirements is made by means of one

"Comparison Matrix" (Requirements vs Requirements) The results are shown in Figure 1

Once the functional requirements have been evaluated, the evaluation of the dimensional and visual characteristics of the pellets selected to be put in QATS is done according to the degree of expected improvement in the Functional Requirements, as a result of the direct modification of the characteristics The functional requirement "z" is a function of the product characteristics "y", z = f (y^t, y²,..., yⁿ) The results are shown in Figure 2

Once the product characteristics have been evaluated a "Pareto Chart" is made and the design CTQs ("Critical to Quality Characteristics") are selected bearing in mind that the whole of the CTQs implies a high percentage in importance of the total number of the characteristics evaluated It must also be considered that there is a big gap in importance between CTQ and NON-CTQ characteristics The results obtained can be shown in Figure 3

QFD - UQ2/PWR Pellet (2nd Level) (Requirements vs Characteristics External Co ros on/Hyd/yd ng 4 Internal Hydndng 3

Instantaneous Collapse i5 fl|?N>J^|

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FIG 2 Matrix for UO2 pellets - Requirements vs Characteristics