Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Sodium removal and decontamination process and decommissioning considerations for the PFBR components

Rajan, M.; Surendran, C.S.; Ganesan, V.; Sodhi, B.S.; Chetal, S.C.; Kale, R.D.; Indira, R.; Bhaduri, A.K. (Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam (India))

Abstract

The Prototype Fast Breeder Reactor (PFBR) of 500 MWe capacity using sodium as a coolant is designed at Indira Gandhi Centre for Atomic Research, Kalpakkam, India. The important components such as sodium pump, intermediate heat exchanger, safety rod drive mechanisms, fuel and other sub-assemblies etc. are to be cleaned and decontaminated before doing any maintenance work or disposal. The sodium removal process for PFBR components envisages reaction of water vapour with sodium in the presence of carbon-dioxide at temperature below 80 deg C or less. By varying the gas flow rate, the sodium-water reaction rate is controlled. The core subassembly is washed with steam and nitrogen mixture to remove sodium sticking on the surface. Detailed studies were carried out and the process was finalized. The choice of chemical decontamination process depends mainly on whether the component is to be reused or to be disposed. Sulphuric acid is planned for decontamination in the presence of phosphoric acid. The choice of hard facing material for different components of PFBR is aimed at keeping induced activity to the minimum for maintenance and decommissioning purposes, and also to reduce the shielding thickness required for the component handling. Based on the investigations, it has been decided to select nickel-base Colmonoy, in place of the cobalt-base Stellite, for hard facing of the NSSS components of PFBR. (author)

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key words: carbon dioxide; colmonoy; control rod drives; coolant cleanup systems; decontamination; gas flow; heat exchangers; kalpakkam lmfbr reactor; molten metal-water reactions; nitrogen; phosphoric acid; scram rods; sodium; steam systems; steam; stellite; breeder reactors; epithermal reactors; fast reactors; fbr type reactors; lmfbr type reactors; research and test reactors;
Reference:
Proceedings of a Technical Meeting held in Cadarache, France 11-15 March 2002
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--1405, pp:141-150