The extensive technology transfer of Framatome ANP design codes and methods formed the basis for the justification studies for an increase to 18-month fuel cycles and for the new AGA-3G fuel. These codes and methods were successfully applied by Guangdong Nuclear Power Joint Venture Company Limited (GNPJVC) and Nuclear Power Institute of China (NPIC) and were licensed by the National Nuclear Safety Administration (NNSA). The technology transfer enables Framatome ANP's Chinese partners to further improve plant performance and availability, and to reduce production costs.

In accordance with international trends towards optimized fuel management in reactor cores, the Daya Bay operator, GNPJVC, made the decision to change from 12-month to 18-month fuel cycles using improved fuel management performance that could lead to better fuel reload and plant operation economy. GNPJVC wanted to implement the 18-month fuel cycles from cycle 9 at both Daya Bay units, beginning in early 2002, after obtaining the required NNSA licensing permit. All requirements were successfully met. The project's technical requirements meant increasing cycle length up to 500 equivalent full power days (EFPD) using higher fuel enrichment (4.45%) with increased core peaking factors (FQ=2.45). Such long cycle operation leads to a maximum fuel assembly burn-up of 52 MWd/kgU.

Strategy

Therefore, a new fuel with improved cladding material and enhanced thermal-hydraulic performance was needed. The fuel selected for this advanced fuel management strategy was AFA-3G with mid span mixing grids (MSMG) and M5^® alloy as cladding material, one of Framatome ANP's advanced and proven designs. To obtain the Final Safety Analysis Report (FSAR) approval on time (to be ready for cycle 9 reload related activities), the licensing strategy was to apply for approval of new codes and methods at an early stage of the project and to submit the safety studies for NNSA review and approval, using a step-by-step approach. New codes and methods were indeed necessary to obtain the required core margins that result from accident analyses, documented in the FSAR.

The Scope of Design and Safety Studies Covered

• fuel management analysis and the core nuclear design
• fuel assembly mechanical design verification with increased burnups
• core thermal-hydraulic design and core power capability analyses
• FSAR accident analyses (LOCA and non-LOCA)
• impacted plant systems verification
• radiological consequences
• update of plant documentation(Technical Specifications, System Design manuals and Procedures)

Technology Transfer

A change from 12- to 18-month fuel cycle requires higher fuel enrichment

The expertise required to perform these justification studies was transferred in parallel by Framatome ANP to GNPJVC and NPIC engineers via a concrete Technology Transfer Program that dovetailed with the project schedule objectives. These engineers thus learned in France (through courses and on-the-job training) and in China (in NPIC Chengdu offices) to apply advanced design tools, including the Science codes, for core nuclear design and the Cathare code for LOCA analyses, together with their associated methodologies.

These design tools have been fully transferred and actually implemented in China, including 70 computer codes (main and auxiliary codes), design procedure manuals and project specific guidelines. At the same time, the manufacturing process of the AFA-3G fuel product also was transferred to the Yibin Fuel Factory, in line with the overall Framatome ANP policy.

Project Success

The project is a success after three years and is on schedule. The plant justification file was licensed and plant documentation for 18-month cycle operation was completed. The thermal-hydraulic critical heat flux correlation (FC) fitted to AFA-2G and AFA-3G/ MSMG performance was approved by NNSA in May 2001.

The large core margins (>15%) obtained from the FSAR DNB accidents also were approved which met one of GNPJVC's safety objectives. The LOCA analyses performed with the advanced Deterministic Realistic Method using Cathare also were successfully licensed.

The project reached its conclusion with the restart of both Daya Bay Units at cycle 9 in early 2002. The agreement between the measurements and calculations for this first transition cycle confirms the applicability of the Science codes and the new expertise of the GNPJVC and NPIC engineers to apply these codes in their reload design activities.

This project demonstrated the ability of integrated teams of Chinese and French engineers, working together, to achieve the ambitious objectives of performing advanced design justification studies. The high performance fuel management implemented, as a result of the 18-month fuel cycle project, will result in economical benefits, both in terms of fewer fuel reloads and outage frequency, and enhance GNPJVC's competitiveness for tomorrow's energy supply.

The successful technology transfer and licensing of the design codes and methods for this project positions Framatome ANP for further fruitful collaboration with GNPJVC and the Chinese institutes and factories.