Steam generator test facility—A test bed for steam generators of Indian sodium cooled fast breeder reactors

Second stage of India's three stage nuclear power programme consisting of the development and operation of fast breeder reactors (FBRs) commenced with the construction, commissioning and operation of fast breeder test reactor (FBTR) at Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam. FBTR operating experience and better understanding of the technologies involved has enabled India to design a 500 MWe prototype fast breeder reactor (PFBR). Construction of PFBR is in advanced stage at Kalpakkam. Steam generator (SG) is one of the critical components of a fast reactor power plant. It is a once-through SG housing both water at high pressure and sodium at low pressure separated by a tube wall. Any defect to this barrier resulting in an internal leak allowing sodium and water to react could severely affect the plant availability. A 5.7 MWt capacity steam generator test facility (SGTF) has been set up in Indira Gandhi Centre for Atomic Research (IGCAR) to test a 5.5 MWt sodium heated once through SG of 19 tubes similar to the indigenously designed 157 MWt, 547 tube SG of PFBR. The test programme includes the evaluation of thermal hydraulic performance of SG, instability mapping, measurement of tube bundle vibrations etc. Most of the planned experiments have been completed successfully. The heat transfer experiment has proved that the SG has a heat transfer area margin of 12.25%. This experiment has also helped in validating the design codes and reducing the area margin for SGs of future FBRs. Experiment on flow induced vibration of tube bundles has shown that the bending stress due to vibration is much less than the endurance limit of the material. The results of the experiments and the valuable lessons learnt from the operating experience have been successfully applied to PFBR and will be applied to future commercial fast breeder reactors. The facility is also planned as a test bed for SGs of Indian FBRs and to assess improved designs of auxiliary equipment used in FBRs. This paper brings out various experiments conducted and the experience gained during the operation of the facility.

► Performance testing of a 5.5 MW capacity once through straight tube steam generator.
► 5000 h of endurance test has demonstrated the steam generator design.
► Heat transfer experiment revealed the extra area margin as 12.25%.
► Flow instability observed at 20% power below 130 kg/cm2.
► Acoustic method of steam generator leak detection was tested and qualified.