ARIS-Status Report for Adva

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    Status report 75 - Advanced Passive pressurized water reactor (AP -600)

    1. Overview2. Description3. Technical data

    1. Overview

    Full name Advanced Passive pressurized water reactor

    Acronym AP-600

    Reactor type Pressurized Water Reactor (PWR)

    Coolant Light Water

    Moderator Light water

    Neutron spectrum Thermal Neutrons

    Thermal capacity 1940.00 MWthElectrical capacity 600.00 MWe

    Design status Basic Design

    Designers Westinghouse

    Last update 13-10-2010

    2. Description

    Introduction

    The Westinghouse Advanced Passive PWR AP-600 is a 600 MWe pressurized water reactor (PWR) withadvanced passive safety systems and extensive plant simplifications to enhance the construction,operation, and maintenance of the plant. The plant design utilizes proven technology which builds onapproximately 40 years of operating PWR experience. PWRs represent 74 percent of all Light WaterReactors around the world, and the majority of these are based on Westinghouse PWR technology.

    The AP-600 is designed to achieve a high safety and performance record. Safety systems maximize theuse of natural driving forces such as pressurized gas, gravity flow and natural circulation flow. Safetysystems do not use active components (such as pumps, fans or diesel generators) and are designed tofunction without safety-grade support systems (such as AC power, component cooling water, servicewater, HVAC). The number and complexity of operator actions required to control the safety systems are

    minimized; the approach is to eliminate a required operator action rather than to automate it. The netresult is a design with significantly reduced complexity and improved operability.

    The AP-600 standard design complies with all applicable U.S.NRC criteria. Extensive safety analysis hasbeen completed and documented in the Standard Safety Analysis Report (SSAR) and Probabilistic Risk

    Analysis (PRA) submittals to the NRC. An extensive testing programme has been completed, and verifiesthat the plants innovative features will perform as designed and analyzed. PRA results predict a very lowcore damage frequency which meets the goals established for advanced reactor designs and a lowfrequency of release due to improved containment isolation and cooling. The AP-600 design receivedFinal Design Approval from the U.S.NRC in September 1998 and Design Certification in December 1999.

    An important aspect of the AP-600 design philosophy focuses on plant operability and maintainability.These factors have been incorporated into the design process.

    The AP-600 design includes features such as simplified system design to improve operability whilereducing the number of components and associated maintenance requirements. In particular, simplifiedsafety systems reduce surveillance requirements by enabling significantly simplified technicalspecifications.

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    Selection of proven components has been emphasized to ensure a high degree of reliability with a lowmaintenance requirement. Component standardization reduces spare parts, minimizes maintenancetraining requirements, and allows shorter maintenance durations. Built-in testing capability is providedfor critical components.

    Plant layout ensures adequate access for inspection and maintenance. Laydown space for staging ofequipment and personnel, equipment removal paths, and space to accommodate remotely operatedservice equipment and mobile units have been considered as part of the plant design. Access platformsand lifting devices are provided at key locations, as are service provisions such as electrical power,

    demineralized water, breathing and service air, ventilation and lighting.

    The AP-600 design also incorporates radiation exposure reduction principles to keep worker dose as lowas reasonably achievable (ALARA). Exposure length, distance, shielding and source reduction arefundamental criteria that are incorporated into the design.

    Various features have been incorporated in the design to minimize construction time and total cost byeliminating components and reducing bulk quantities and building volumes. Some of these featuresinclude the following:

    The flat, nuclear island common basemat design effectively minimizes construction cost andschedule.Utilization of the integrated protection system, the advanced control room, distributed logiccabinets, multiplexing, and fiber optics, significantly reduces the quantity of cables, cable trays, and

    conduits.The stacked arrangement of the Class 1E battery rooms, the dc switchgear rooms, the integratedprotection system rooms, and the main control room. This stacked arrangement eliminates theneed for the upper and lower cable spreading rooms that are required in the current generation ofPWR plants.

    Application of the passive safety systems replaces and/or eliminates many of the conventionalmechanical safety systems that are typically located in the Seismic Category I buildings incurrent PWR plants.

    The AP-600 is designed with environmental consideration as a priority. The safety of the public, thepower plant workers, and the impact to the environment have all been addressed as specific design

    goals, as follows:

    Operational releases have been minimized by design features;Aggressive goals for worker radiation exposure have been set and satisfied;Total radwaste volumes have been minimized;Other hazardous waste (non-radioactive) have been minimized.

    The AP-600 Nuclear Power Plant was designed by Westinghouse under the sponsorship of the USDepartment of Energy (DOE) and the Electric Power Research Institute (EPRI). The design team includeda number of US and foreign companies and organizations, such as Bechtel, Burns & Roe, Initec (Spain),UTE (Spain), and Ansaldo (Italy) as architect engineers, Avondale Industries (module design), CBI

    Services, Inc. (containment vessel design), M-K Ferguson Co. (constructability, schedule, and costestimation), Southern Electric International (turbine island buildings and systems), ENEA EnergyResearch Center of Italy (tests of the automatic depressurization system), SIET, SPES Facility in Italy(full-pressure integral passive safety system tests), and Oregon State University (low-pressure integralpassive safety system tests).

    EPRI has, with a broad international participation of organizations from numerous countries, developeda Utility Requirements Document (URD) for ALWRs, taking into account the wealth of information relatedto nuclear power plant safety and operations that has been generated worldwide with commercialnuclear power. The purpose of the URD is to delineate utility desires for their next generation of nuclearplants, and to this end, it consists of a comprehensive set of design requirements for future plants.

    Incorporation of the ALWR URD has given the AP-600 a well-defined design basis that is confirmedthrough thorough engineering analyses and testing and is in conformance with the URD. Some of thehigh-level design characteristics, and operational and safety goals of the plant are:

    Net electrical power of at least 600 MWe; and a thermal power of 1940 MWt;Rated performance is achieved with up to 10% of the steam generator tubes plugged and with amaximum hot leg temperature of 600F (315.6C);

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    Core design is robust with at least a 15% operating margin on core power parameters;Short lead time (five years from owner's commitment to commercial operation) and constructionschedule (3 years);No plant prototype is needed since proven power generating system components are used;Major safety systems are passive; they require no operator action for 72 hours after an accident,and maintain core and containment cooling for a protracted time without ac power;Predicted core damage frequency of 1.7E-07/yr is well below the 1E-05/yr utility requirement, andfrequency of significant release of 3.0E-08/yr is well below the 1E06/yr utility requirement;Standard design is applicable to anticipated US sites;

    Occupational radiation exposure expected to be below 0.7 man-Sv/yr (70 man-rem/yr);Core is designed for a 24-month fuel cycle assuming an 87% capacity factor; capable of an18-month cycle;Refuelling outages can be conducted in 17 days or less;Plant design life of 60 years without replacement of the reactor vessel.Overall plant availability greater than 93%, including forced and planned outages; the goal forunplanned reactor trips is less than one per year.

    Description of the nuclear systems

    2.1. Prim ary circuit and its m ain characteristics

    The primary circuit of the AP-600 reactor has retained most of the general design features of currentdesigns, but some evolutionary features that enhance the safety and maintainability of the system havebeen adopted. The coolant loops (Figure 2.1-1) consist of two hot leg and four cold leg pipes, and thereactor coolant pumps are installed directly onto the steam generators, eliminating the primary pipingbetween pumps and steam generator; these features significantly contribute to safety and main-tainability. Also, a simplified support structure for the primary systems reduces in-service inspections andimproves accessibility for maintenance.

    The reactor coolant system pressure boundary provides a barrier against the release of radioactivitygenerated within the reactor and is designed to provide a high degree

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