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Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Volumes per year:

various

Year 2006

DOI: 10.1615/IHTC13.p7

THERMAL HYDRAULIC ANALYSIS OF SPENT FUEL SUBASSEMBLY DURING TRANSPORTATION FROM FBTR TO REPROCESSING FACILITY

D. Sujish
Indira Gandhi Centre for Atomic Research, Kalpakkam

C. Meikandamurthy
Indira Gandhi Centre for Atomic Research, Kalpakkam

T. R. Ellappan
Indira Gandhi Centre for Atomic Research, Kalpakkam

M. Rajan
Indira Gandhi Centre for Atomic Research, Kalpakkam

G. Vaidyanathan
Indira Gandhi Centre for Atomic Research, Kalpakkam

ABSTRACT

Fast Breeder Test Reactor (FBTR) commissioned at Kalpakkam, India in 1985, is a 40MW(t) sodium cooled fast reactor. Fuel used is U-Pu carbide and it has seen a peak burn up of 148GWd/t. Fuel after irradiation is kept initially in the internal storage position within the reactor and subsequently taken out at a power level of 400W and transferred to an air cooled storage. From here after 300 days of cooling, the decay power drops to 160W after which it is taken to the reprocessing plant. The transportation of the spent fuel is carried out in a lead shielded shipping cask in horizontal position. Each cask is designed to carry one fuel subassembly. Irradiated fuel subassembly in argon atmosphere is put in a pot and sealed and loaded into the cask. It is essential to know the temperatures of the fuel within the cask to decide the acceptability and to see if any forced cooling in the cask is essential during the time it is transported to the reprocessing site.
Removal of decay heat from the spent fuel during transportation is essential to prevent clad failure due to high temperatures. Also the pot, which is provided with a special cap, can withstand a maximum pressure of 0.4 bars with respect to the cask. A theoretical estimation of the maximum clad temperatures and argon pressure in the pot was carried out using PHOENICS (3.5). The results of the analysis indicate that for a decay power of 160W and with natural convection of air in the cask, the maximum clad temperature would be 595°C and the maximum argon pressure in the pot would be 0.17 bar (g). Since these values are less than the permissible limits of 700°C and 0.4 bars, it can be concluded that forced cooling of the pot is not essential during transportation of the spent fuel.