Contact Author:
Mr Sumit Ray
rays@westinghouse.com
P:1-412-374-2101
F:1-412-374-3670
Westinghouse Electric Company
Nuclear Fuel
Post Office Box 355
Pittsburgh, PA 15230
USA
AP1000 Fuel Design and Core Operations
S. Ray (Westinghouse - USA)
AP1000 Fuel Design and Core Operations
Sumit Ray, Director
New Reactor Fuel Engineering, Westinghouse Electric Corporation, Pittsburgh, PA, USA
The Westinghouse AP1000 plant significantly simplifies the approach to reactor design and construction. This simplicity is achieved through the use of passive safety systems that eliminate the need for many existing components in the current generation of reactors, thereby substantially reducing Capital as well as O&M costs. Consistent with its functional requirements, the design characteristics of this reactor provide large margins to safety limits, while utilizing proven and previously tested technologies.
The Fuel Design of the AP1000 reactor utilizes a similar approach. The basic fuel design that will be utilized has seen significant operating experience in reactors worldwide. AP1000 Core Design and Operating margins will remain within the experience base of similar Westinghouse fuel designs. The basic fuel design will be further enhanced to provide additional margins, both thermal and mechanical.
The AP 1000 system uses 69 total control rods, thereby providing a high level of reactivity control, including significantly enhanced shutdown margins. One characteristic of this system is the use of “Gray Rods” to control core reactivity related to power changes. The use of these rods significantly simplifies the requirements on the Chemical and Volume Control System.
Another feature of the AP1000 reactor will be the use of the Westinghouse BEACON software system to provide core related Technical Specification monitoring and operational support.
This paper will:
- Discuss the key core design requirements and thermal parameter summary for the AP1000 core, and compare core margins to those of existing reactors.
- Provide a description of the AP1000 fuel design and details on the operational experience of this design. The fuel assembly design has an active fuel length of 4.267 meters, which is similar to fuel assemblies that have seen significant exposure at EdF 1300Mwt plants, in the Doel reactor and at the South Texas Units in the USA. Is utilizes the 17X17 RFA grid design which has had extensive experience in Westinghouse plants. It includes state of the art debris resistant features, and adds Intermediate Flow Mixing grids (IFMs) to significantly increase thermal as well as mechanical design margins.
- Discuss the details of the AP1000 control rod functions and how three different sets of control rods are utilized for different functions. These include a bank of rods whose primary function is to provide rapid shutdown capability, a bank of rods that is utilized specifically for axial power distribution control, and a bank that includes both gray and black rods whose primary function is to provide reactivity control associated with temperature, power level and transient Xenon changes.
- Discuss the Core Monitoring and Operational Support provided by the BEACON system. The AP1000 BEACON system utilizes multi-section fixed incore detectors with long life Vanadium emitters. This system monitors core thermal margins such as DNBR and Peak linear Heat rate. It also provides predictive simulation capability for the reactor core to aid in operational optimization and to help in the avoidance of limiting plant configurations.