COMPARISONS OF DESIGN PROVISIONS OF FRENCH CODE RCC-G AND AMERICAN CODE ASME SECTION-Ⅲ, DIVISION-2, WITH RESPECT TO THE DESIGN OF INNER CONTAINMENT STRUCTURE IN 700MWe INDIAN PHWR

摘要

In its current 700 MWe series of PHWRs, being the first of its kind in Indian PHWR programme, numbers of improvements have been implemented with respect to earlier Indian nuclear power plants (NPP). These improvements are based on experience gained over years on analysis, design, operation and maintenance of Indian PHWR based power projects/plants. The inner containment (IC) structure, which houses the reactor, the primary coolant and moderator system and other systems related to steam generation, is the most important structure of a nuclear power plant (NPP). The IC structure consists of a prestressed concrete cylindrical wall capped with pre-stressed concrete segmental dome. Two circular openings are provided in IC dome to facilitate the erection of steam generators (SG) as well as replacement of the same if need arises at later date. Two airlock openings viz., main airlock (MAL) and auxiliary airlock (AAL) are provided in the wall portion of IC structure for equipment and personnel movement. In general, the thickness of IC wall and dome is uniform in nature, except at discontinuous region where thickness has been increased suitably with appropriate transitions to cater for the higher stress resultant due to discontinuity effects. For the first time in Indian PHWR, metallic liner has been used on the inner surface of inner containment structures. Higher capacity of prestressing cables is used. Earlier for 220 MWe & 540 MWe series of reactor, the IC structure was designed based on the provisions of French code RCC-G applicable for unlined double containment. The analysis and design of IC structure of present 700 MWe series of power plant is carried out based on the requirements of section Ⅲ Division 2 of ASME code (2010 ASME Boiler and Pressure Vessel Code SECTION Ⅲ: Rules for Construction of Nuclear Facility Components DIVISION 2: Code for Concrete Containments). It may be noted that RCC-G is applicable for both lined and unlined structure, where as ASME specifically deals with lined containment only. In RCC-G code limit state design philosophy is adopted, whereas ASME is based on allowable stress methodology, with provisions which allow for the higher strains in case of secondary load under factored load combinations. A brief review of the analysis and design approach of inner containment structure according to both the standards i.e RCC-G and ASME code has been summarized in this paper and major differences have been brought out. In some specific cases, the direct comparison between the provisions of the two standards has been attempted in a quantified manner.