Conceptual design of fresh fuel pebble storage for RGTT using MCNPX code

RGTT is a high temperature reactor type helium-cooled nuclear reactor with graphite moderator. The reactor is very suitable adopted as a co-generation reactors because its ability to produce outlet temperature of 900-1000 °C. RGTT's fuel is ball-shaped which is called pebble made of pyrolytic graphite which serves as a moderator. Each fuel pebble contains thousands of TRISO coated fuel particles with U²³⁵ enriched 7 % UO₂ kernel. Every day RGTT is estimated to require 347 fuel pebble taken from the fresh fuel pebble storage tank. This paper discusses effective multiplication factor as a function of radius and height of the fresh fuel pebble storage tank. The MCNPX Monte Carlo transport program utilized in the calculation with the continuous energy nuclear cross-section data library ENDF/B-VI. The results of the analysis concluded that the geometry of the fresh fuel pebble storage tank with a radius of 110 cm and height of 900 cm meet criticality safety standard criteria. (author)