16-05-2013, 03:47 PM
Case study of Kaiga Atomic Power Projects
Case study of Kaiga.docx (Size: 691.94 KB / Downloads: 41)
Kaiga project - Location:
Kaiga Project is one of the most advanced plants in the series of 220MWe Pressurized Heavy Water Reactors (PHWRs) in India. The rich experience acquired by the Nuclear Power Corporation over the years has gone into the making of Kaiga, right from sitting to its completion.
Kaiga is situated upstream at the left bank of the Kali River upstream of the Kadra Dam. The Kadra reservoir provides sufficient water to meet the total plant water requirement. While finalizing the location of Kaiga, the safety aspects relating to the unlikely event of dam failure and flooding of the site have been considered. The grade level of the Kaiga site has been chosen considering the above. The accessibility and maintainability of the plant is also ensured during such an event at all times. Kaiga is situated in Seismic Zone-III as per the Indian Standards. The nearest epicenter is 20 km. from the site. There are no capable faults within 5 km. The design of the plant has been based on peak Ground Acceleration (PGA) of 0.2g for Safe Shutdown Earthquake (SSE) and 0.1g for Operating Basis Earthquake (OBE). Kaiga normally has a very heavy monsoon - rainfall up to approximately 4600mm spread over June to September. The atmospheric temperature varies from around 15°C to 42°C, with relative humidity (RH) varying from 66 to 80%.
A detail construction report of Kaiga 2 inner containment structure: The Inner Containment (IC) is a pre-stressed concrete shell type structure, consisting of a circular wall and a dome on the top. The diameter of the inner containment is 42 m. It is designed to withstand a pressure of 1.73 kg/sq.cm during postulated rupture of the main steam line. It also acts as a biological shielding during normal operation and the worst case of postulated Loss of Coolant Accident (LOCA) condition. The Outer Containment (OC) is a reinforced concrete shell type structure, also consisting of a circular wall and a dome. Both the domes are torispherical in shape, having four circular openings of 4.10m.dia to facilitate any replacement of the steam generators during operational stage of the reactor. The complete work from fabrication of the formwork supporting structure to the concreting of IC dome took a mere 16 months, including 4 months of monsoon, when the work practically came to a halt. This was an achievement in the field of civil engineering.
IC Dome formwork supporting structure:
Owing to the large diameter of the IC dome and the self-weight of concrete, the formwork required a strong supporting structure. Much before the finalization of the engineering of the IC dome, the design of the formwork supporting structure was taken up by M/s. Larsen & Toubro Ltd., Chennai. The work of fabrication and erection of the formwork supporting structure started in November 1996. It consisted of 32 numbers of plate girders in the radial direction, inter-connected with 22 numbers of pin jointed trusses in the circumferential direction. This formed a space frame structure. The complete structure weighed 580 MT. The load from the supporting structure was transferred to 32 numbers of brackets on the IC wall and 10 numbers of intermediate supports resting on the internal walls. The fabrication and erection work was completed in 90 days, thus achieving another milestone.
IC Dome Formwork:
The formwork consisted of 12mm plywood with 100 x 150 mm (4"x6") backing wooden members, resting and the steel supporting structure through adjustable spindles. The complete IC dome formwork covering an area of 2000 sq.m was divided into a number of panels and each panel was fabricated to curvature in all the three directions at the carpentry shop.