Constructibility Assessment of APR1400

Transcription

1 Constructibility Assessment of APR1400 Sung Jae Cho, Yong Chul Kang, Jae Gon Lee and Woo Sang Lim Engineering Center, Korea Hydro & Nuclear Power Co,. LTD P.O.Box 149, Yuseong Daejeon, , KOREA Phone : Fax : yongkang@khnp.co.kr APR1400(formerly KNGR) development is one of national G-7 projects sponsored by government and KHNP(Korea Hydro & Nuclear Power Co., LTD). It is an evolutionary standard reactor with the thermal output of 4000MWt and has been adopted for Shin-Kori Unit 3&4. The government organizations, research institutes, universities and industries have participated in the project since 1992 along with KHNP, and the standard design certification program was issued in May The project set up the top-tier requirements about the safety, economy, operability and maintainability, and constructibility in the early design stage. The requirements have been evaluated periodically during the design process, and the results were reflected to the design. This paper describes the methods for constructibility enhancement and the results of schedule analysis to assure meeting construction duration target, which is set to 48 months from the first concrete pouring to the commercial operation on the condition that learning effects are maximized at Nth plant. To meet the target schedule, the design characteristics and constructibility studies such as new construction methods and construction schedule analysis were performed. The new construction methods presented here are over the top method for NSSS components, deck plate and steel form for concrete wall and slab, automatic welding for large bore piping, and modularization of components and structure, etc. KEYWORDS: constructibility, construction schedule analysis, APR1400, improvement of the constructibility for Nuclear Power Plants I. Introduction The construction duration of the nuclear power plant is an important factor for construction projects affecting construction capital interest which is one of the most important cost factors, and capability to come up with the growing electrical power demand. Therefore, utilities are striving to shorten the construction duration. Acknowledging that the efforts only during the construction stage bear limiting results, they are trying to review constructibility during the early design stage. In this regard, every effort is made to improve the constructibility of APR1400 in the beginning of the basic design phase. The standard construction duration of 1,000MWt output pressurized water reactor plant in Korea is 60 months from the first concrete pouring to the commercial operation. Actual accomplishments of construction duration are ranging from 58 to 64 months for Yonggwang unit 3, Ulchin unit 3 and Yonggwang unit 5 as shown in Table 1. In case of other countries, there are few deployments of nuclear power plant but Japanese 1350MWe ABWR with 51 months of construction duration. Target of EPRI URD is 54 months. The construction schedules were developed in three steps. A 64-month Basic schedule, a 54-month Reducible Schedule and a 48-month Target Schedule were developed accordingly at every step. The 64-month Basic Schedule was developed based on the experience of domestic nuclear power plants (1000MW KSNP) and the design characteristics of APR1400; common base-mat, quadrant arrangement of the safety-related system, wrapped-around containment building, the in-containment refueling water storage tank(irwst), radial arrangement of turbine building and introduction of compound building, etc. Table 1. Status of construction duration in Korea Plant Dur. Capacity Type (Mth) (MWe) Ulchin #1 68 PWR 900 Yonggwang #3 64 PWR 1,000 Actual Ulchin #3 61 PWR 1,000 Yonggwang #5 58 PWR 1,000 Ulchin #5 56 PWR 1,000 Shin-Kori # 1 54 PWR 1,000 Plan Shin-Wolsong #1 54 PWR 1,000 Shin-Kori # 3 58 ALWR 1,400 Some studied items to improve constructibility for the APR1400 were reflected in the 54-month Reducible Schedule. Finally, the 48-month Target Schedule was

2 developed by application of the enlarged scope of the modularization and the learning effects to the 54-month Reducible Schedule. The construction schedule includes about 500 elementary activities for two units and the construction period of Sin-Kori Unit 3&4, the first construction project of APR1400, is planned to complete in 58 months considering project uncertainties. Turb. SWGR. Turb. SWGR. All the items of the detailed construction sequences and duration were evaluated by many specialists of design and construction companies, and then the review results were reflected in the basic design and construction schedules of APR1400. For APR1400, the target is established as 48 months at the Nth(the third or forth) unit. This paper presents how it can be accomplished and introduces construction methods and technical issues resulted from the constructability evaluation in order to confirm meeting the goal. II. Design Aspects of APR1400 APR1400 is aimed at being one of the most compatible nuclear power plant through safety and economy enhancement. To improve safety, the SIS is a type of direct vessel injection and safety features are designed to mitigate severe accidents as well as design base accidents. To enhance economic viability, it is designed to increase electrical output, to optimize building volumes and construction material and to facilitate applying new construction methods. Major performance features are; generation cost : Equal to coal-fired plant or less capacity : 1,450 Mwe plant lifetime : 60 years Power Block of APR1400 consists of nuclear island(ni) and turbine island(ti). The NI includes the containment building, the auxiliary building and the compound building. TI includes the turbine building and the switchgear building. Figure 1 shows the building arrangement of APR1400. Concepts of the building arrangement are 2-unit basis, radial arrangement of the turbine building and slide-along arrangement of the two units. The compound building is located between two units. Cylindrical, pre-stressed concrete containment building contains a refueling water storage tank and improved reactor cavity. Foundations of the containment building and the auxiliary building are integrated into common base-mat. Steel concrete auxiliary building accommodates the main control room, a quadrant arrangement of safety-related systems including auxiliary feed water tanks, fuel handling area and emergency diesel generators. In concrete and steel turbine building, there are turbines, condensers, generator and switchgear building. Access control building, radwaste treatment building, radiation hot machine shop, sampling room and laboratory are located in steel concrete compound building for APR1400. DG Aux. DG DG Comp. Cont. Fig. 1 Building arrangement of APR1400 III. APR1400 Constructibility Enhancement Method 1. Common base-mat work Power block foundation of APR1400 is seismically enhanced with 0.3g SSE(safety shutdown earthquake) compared to the existing plants with 0.2g SSE. And it is a common base-mat integrating containment building and auxiliary building. They require highly increased mat size and the concrete quantity. So some methods are needed for this massive concrete structure to come up with the target duration. The common base-mat foundation is simplified as a flat type as shown in Fig. 2 so that it may have benefits for the concrete works; (a) KSNP (b) APR1400 Cont. DG Fig. 2 Comparative view of KSNP and APR1400 foundation Fuel

3 GENES4/ANP2003, Sep , 2003, Kyoto, JAPAN establishing broader vertical 3-stage concrete filling segments easier to modularize re-bars and to erect at the construction sites placing re-bars simply and thus making it possible to shorten construction duration Figure 3 shows layout of the lower re-bar module of the common base-mat in which the re-bars are arranged in a lattice form. It reduces need of various radius re-bars. Figure 4 shows layout of the upper re-bar module in which ring-shaped re-bars are arranged in radial and cylindrical directions. are two ways to bring big components like steam generators into the containment building and to seat them at their own places. One is the Over the TOP Method in which massive equipment come into the containment building in vertical direction from top of the building by large capacity crane. Figure 5 shows its concept. The other is a conventional concept of Side Method in which major components are brought into the containment building passing through equipment hatch as shown in Fig. 6 and seated by using the polar crane. Fig. 5 Over the Top Method Fig. 3 Lower rebar module of the common base-mat Fig. 6 Side Method Fig. 4 Upper rebar module of the Common Base-mat 2. Containment Building Work The containment building is wrapped around the auxiliary building and has bigger and heavier components in it than those of former nuclear power plants. These can incur significant inconvenience and schedule delay. There With the Side Method, components can enter the containment building only after providing the polar crane and the area around the equipment hatch on the auxiliary building roof. These may cause serious schedule delay. To avoid this, the Over the TOP Method is adopted after a comparative study and assessment as shown in Table 2. It

4 is anticipated to reduce the construction duration by 2 months compared to that of the Side Method. Detail installations were simulated using 3-D CAD models. Table 2 Comparison between over the top and side method Description O.T.T Side Method Preceding works Weight of S/G(Ton) Lifting crane Effect ㅇ Containment building inner structure ㅇ Containment wall and polar crane ㅇ Containment building inner structure ㅇ Equipment hatch area of Aux LTL-2600 Manitiowoc M1200 ㅇ O.T.T can shorten duration by about 2 months compared to side method Fig. 7 Cross section of area around IRWST Internal structures of the containment building provide space to accommodate major components such as reactor, steam generators, pressurizer, and thick re-enforced concrete walls to shield radiation as shown in Fig. 9. A noticeable finding in the construction experiences of former nuclear power plants is that most of time is spent in fabricating rebar and concrete forms and removing them. Especially, the works in the steam generator room and pressurizer room should be done in such high and small spaces that they have low productivity and limit to reduce construction duration. Unlike the existing nuclear power plants, a refueling water storage tank is located in the containment building; so it is called In-containment Refueling Water Storage Tank (IRWST). As a result of reviewing its design scheme as shown in Fig.7 and impacts on the construction schedule, it was anticipated that its installation works would be on the critical path of the schedule. Followings were identified for efficient construction; The stainless steel liner plate (SSLP) of the IRWST is pre-fabricated and assumes the role of concrete forms to eliminate their erecting and removing works. It consists of several modules as shown in Fig. 8. Steam Generator Fig. 8 Steel plate module layout WALL Reactor WALL SSLP IRWST IRWST

5 Fig. 9 Containment building layout; operating floor The internal structure works are also important for APR1400 in that they had to proceed before installation of steam generators and reactor. To resolve these problems, steel plates for inner walls of steam generator and pressurizer rooms are designed so that they can play a role of permanent concrete forms without need of their fabricating and removing works. Additionally, rebars are modularized to them. Figure 10 shows a concept of modular steel plate for the steam generator room. Fig.11 Slab deck plate layout 4. Turbine Building Work For the turbine building, turbine pedestal and deck have composite structure that has benefits of facilitating to modularize re-bar using steel structure and reducing re-bar quantity. Its steel frame can be used for temporary construction supports. A pre-assembled turbine roof truss, a re-bar module in the main turbine/generator, and a condenser module are also applicable to simplify the works and reduce construction duration. Fig. 10 Steel plate module layout of the inner steam generator room 3. Auxiliary building and compound building work For the auxiliary building and the compound building, the Deck Plate Method was adopted not to affect the critical path of the construction schedule. Identified building design aspect and detailed application of the Deck Plate Method are; Sufficient height between building floors Use of both composite and non-composite module; at the specific area, many parts such as deck plate, re-bar, piping, HVAC and cable tray are integrated into a composite deck plate module Integrating deck plates and girders into one module as shown in Fig. 11 Modularizing wall re-bar Applying the method to all slabs of auxiliary building and compound building 5. Electrical and Mechanical Works For mechanical and electrical equipment and piping installation, it is recommended to increase the fabricating portion in the manufacture s shop. Approximate 80 modularizing items including auxiliary and containment building water chillers and pumps, feed water pumps and turbine drives, charging pumps, turbine building component cooling water heat exchangers, and condenser were identified. For example, condenser module of APR1400 requires minimum installation work such as condenser hydro test and installation of necks and expansion joints. Lifting and access plan was also provided. Figure 12 shows the modularized condenser shells and transitions. Low pressure feed water heaters and water box are still fabricated at the shop of construction site. Fig. 12 Condenser module

6 Assembling reactor internals at the construction site is complicated and requires much time. Therefore, most of their wok items are on the critical path of construction schedule. Performing mock-up test in addition to extending the fabricating portion at manufacture s shop is recommended to contribute meeting the target schedule. As one of such efforts, core support barrel(csb) and lower support structure(lss) and core shroud(cs) are integrated into one module. Figure 13 shows CSB and LSS/CS module and upper guide structure(ugs). It increases manufacturing period by 8 weeks, on the other hand reduces by about 28 weeks. Consequently, total period reduces by about 20 weeks. IV. Construction Schedule Development 1. Methodology Construction schedule is generally developed through estimating required material quantity and identifying available resources during the detailed design phase. In case of APR1400, since its development began at early design phase, following methods are used to minimize uncertainties. Critical Path Method was used at the simplified level of approximate 500 elementary works. Three kinds of schedules such as Basic Schedule, Reducible Schedule and Target Schedule were developed in turn. Continuous comparative studies were performed to identify ways in which the Reducible Schedule makes it possible to meet the Target Schedule. Turb. Main Road Turb. Concrete Boom (schwing : DVMK50) Main Road Aux. Cont. Temporary Opening SWGR. JETTY Compound Aux. Cont. Tower Crane (Cornell 2300B) Main Crane (LTL V) Fig. 13 CSB and LSS/CS module and UGS For Reactor Coolant System piping, main steam system piping and main feed water system piping, automatic welding will be applied rather than manual welding which spends much time. 6. Accessibility and Construction Crane In APR1400, the auxiliary building wraps around containment building and the compound building is located between two plants. This can incur inconvenience for access between buildings. Therefore, temporary platforms are installed during the construction to pass through the main buildings as shown in Fig. 14. The figure also shows the reaching area and location of the main crane and the tower crane, and the location of concrete pouring facilities. : Crane : Concrete pouring facility Fig. 14 Temporary platforms and construction crane location Layout 2. Results of Development A 64-month Basic Schedule was developed from reviewing the actual schedule of Yonggwang Unit 3 and Ulchin Unit 3 and assessing constructibility of APR1400. As a result of the Target Schedule development, appropriate construction duration of every elementary work was established to achieve the aggressive 48-month schedule. Results of the Reducible Schedule development suggest that it can meet the Target Schedule by applying the

7 design countermeasures and construction methods as shown in Table 3. Figure 15 shows the Basic Schedule versus the Reducible Schedule. V. Conclusion In conclusion, the constructibility aspects of APR1400 are as followings. Even though APR1400 has new design aspects such as IRWST and quadrant arrangement of the safety-related systems, has seemed to have adverse effects to the constructibility, even has the target of shorter construction duration, it is expected to meet its construction target. Major ways are to apply the Over the Top Method for major NSSS equipment and large modules, Deck Plate Method for concrete structure slabs, automatic welding for reactor coolant system piping, extensive use of the concrete forms of steel plate, and extensive use of complex modularization for auxiliary components. Although a new shipping skid design is required and has some other cost increase factors, it has little impacts on economic viability. Table 3. Items for the target schedule Description Major Items Civil works ㅇ Deck Plates for auxiliary & compound building ㅇ Broad use of steel liner plate module - SSLP of IRWST - CLP of containment wall - Steel form of S/G & PZR wall - SSLP of spent fuel storage pool - SSLP of AFWST ㅇ Broad use of pre-fabrication & structure module - Pre-fabrication modularization of base-mat re-bar - Modularization of deck plate and structural steel - Composit structure modularization of turbine pedestal ㅇ Over the top method for NSSS major components ㅇ Automatic welding of RCS piping ㅇ Modularization of reactor internals Mech./Elec. worksㅇ Broad use of pre-fabrication and modularization - Polar crane girder module - Condenser tube module - Composite module of BOP components As the results of the construction schedule development, a 64-months Basic Schedule was established. In case of applying the reducible items to the maximum extent, it suggests that even 48-month target is also achievable. However, since the schedule analysis was based on not the detailed design but the basic design and on the level of accordingly simplified schedule, reassessing the schedule is needed to minimize uncertainties and to confirm it. Above all, it is remarkable for APR1400 that constructibilty analysis was performed in the early design phase unlike the former nuclear power plants. It makes possible for APR1400 to accomplish better constructibility by assessing periodically and feeding their results back to the design during whole the design period. F/C Rx set CHT F/L 64 M (Base) (26) (22) (8) (8) 58 M (1 st UNIT) 54 M 48 M (Nth) Fig. 15 Basic Schedule versus Reducible Schedule Nomenclature SIS : Safety Injection System CLP : Containment Liner Plate (22) (21) (8) (7) (20) (19) (8) (7) (17) (17) (7.5) (6.5) C/O References 1) Korea Electric Power Corporation, Korea Electric Power Research Institute Korean Next Generation Reactor(II), KNGR Design Development, Final Report, ) Korea Electric Power Corporation, Korea Electric Power Research Institute Korean Next Generation Reactor(II), KNGR Constructibility Assessment Report, ) Korea Electric Power Corporation & Korea Power

8 Engineering Company, A Study on the Reducing Methods of Construction Duration for Yonggwang Unit 3&4, ) Korea Electric Power Corporation, Construction Experiences for Yonggwang Unit 1&2, 3&4, 5&6 and Ulchin Unit 3&4, 1981~2000 5) Tokyo Electric Power Company, Construction Methods for ABWR Nuclear Power Plants, Kashiwazaki Kariwa Nuclear Power Station Construction Project, ) EPRI, Advanced Light Water Reactor Utility Requirements Document, Rev.1, ) ABB-CE, ABB-CE s Advanced LWR Technology for System 80+, An Integrated Design Approach for System 80+, 1992