Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Unusual occurrences in fast breeder test reactor

Kapoor, R.P.; Srinivasan, G.; Ellappan, T.R.; Ramalingam, P.V.; Vasudevan, A.T.; Iyer, M.A.K.; Lee, S.M.; Bhoje, S.B. (Indira Gandhi Centre for Atomic Research, Kalpakkam (India))

Abstract

Fast Breeder Test Reactor (FBTR) is a 40 MWt.03.2 MWe sodium cooled mixed carbide fuelled reactor. Its main aim is to generate experience in the design, construction and operation of fast reactors including sodium systems and to serve as an irradiation facility for the development of fuel and structural materials for future fast reactors. It achieved first criticality in Ott 85 with Mark I core (70% PuC - 30% UC). Steam generator was put in service in Jan 93 and power was raised to 10.5 MWt in Dee 93. Turbine generator was synchronised to the grid in Jul 97. The indigenously developed mixed carbide fuel has achieved a burnup of 44,000 MW.d/t max at a linear heat rating of 320 W/cm max without any fuel clad failure. The commissioning and operation of sodium systems and components have been smooth and performance of major components, viz., sodium pumps, intermediate heat exchangers and once through sodium heated steam generators (SG) have been excellent. There have been three minor incidents of Na/NaK leaks during the past 14 years, which are described in the paper. There have been no incident of a tube leak in SG. However, three incidents of water leaks from water / steam headers have been detailed. The plant has encountered some unusual occurrences, which were critically analysed and remedial measures, in terms of system and procedural modifications, incorporated to prevent recurrence. This paper describes unusual occurrences of fuel handling incident of May 1987, main boiler feed pump seizure in Apr 1992, reactivity transients in Nov 1994 and Apr 1995, and malfunctioning of the core cover plate mechanism in Jul 1995. These incidents have resulted in long plant shutdowns. During the course of investigation, various theoretical and experimental studies were carried out for better understanding of the phenomena and several inspection techniques and tools were developed resulting in enriching the technology of sodium cooled reactors. FBTR has 36 neutronic and process parameters initiating reactor trip and has encountered large number of trips since first criticality. The paper also highlights several modifications affected in safety related systems for improved performance and safety reviews to reduce the parameters initiating reactor trip. The lessons learnt from the analysis of these incidents and safety reviews have been significant not only in improving FBTR performance but also as an important input for the design of future fast reactors.

view the full text of this article (23 pages, format: PDF, size= 1325kB)

key words: fbr type reactors; heat exchangers; leaks; materials handling; mixed carbide fuels; reactor shutdown; sodium; steam generators; test facilities; transients; turbines
Reference:
Technical committee meeting on unusual occurrences during LMFR operation. Vienna (Austria) 9-13 Nov 1998
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--1180, pp:146-168