Optimization of Integrity Testing of Piping System in a Nuclear Fuel Cycle Facility

Abstract

Abstract Nuclear fuel cycle facility under construction at Kalpakkam houses more than 200 process vessels and equipments of different capacity and configurations and about 62 Kms of piping of varying sizes from 8 DN to 250 DN in about 5000 m3 of concrete cell volume. Austenitic stainless steel 304L has been widely used as work horse material for this plant due to its resistance to corrosion in acidic environment. The fabrication works of this facility involves more than 70000 weld joints for interconnecting various vessels, equipment and associated piping system. Pneumatic pressure testing and soap bubble leak testing are the two methods effectively used to assess the final integrity of the system after fabrication and erection. Physical verification of entire piping system as per the approved as-built drawing is a pre pneumatic test requirement. During physical verification, entire piping system will be physically scanned by visual inspection methods for orientation, gradient and also to identify any surface imperfections. Even though all surfaces of the piping system are examined before giving clearance for welding, the surfaces will be re-examined prior to integrity testing to ensure that piping system orientation is as per approved design and its surfaces are free from damages. Orientation and slope plays an important role in nuclear fuel cycle facility. Because nuclear fuel cycle facility is designed in such a way that gravitational force is effectively used to transfer process fluid to avoid the usage of moving mechanical parts. This is one of the zero maintenance design feature of nuclear fuel cycle facility. Based on experience many procedures are developed to ensure the intended design requirements. Before proceeding to the integrity testing, one has to verify the completion of all quality control stage inspection activities during fabrication by way of documents verification pertaining to the weld joints and loop involved in the testing. All inspection documents right from raw material identification, fabrication and inspection of components are to be verified prior to integrity testing. Verification of large number of inspection related documents posses a very big challenge. To meet this herculean task in time, an asset management system is designed and developed in house. Asset management system plays a key role in storage and retrieval of all inspection credentials and NDE images involved in the system, and with least amount of time these can be retrieved and verified. The asset management system also plays a constructive role during the pre commissioning activities of the plant. This paper emphasis the optimization methodologies adopted during integrity testing.