Measurement of intra-cell thermal neutron flux distributions for plutonium fuel lattices; Experiments on 22.5cm pitch lattice

not registered; not registered; Fukumura, Nobuo*; Hachiya, Yuki*

Intra-cell thermal neutron flux distributions have been measured in plutonium fuels loaded in 22.5cm pitch lattice by means of dysprosium foil activation method. Coolant void fractions used in the experiment were 0%, 30%, 70% and 100% for the plutonium fuel lattice of 0.54w/o PuO-UO. And 0% and 100% void fractions were used in 0.87w/o PuO-UO fuel (standard grade) and 0.87w/o PuO-UO fuel (reactor grade). Experimental results were compared with the values calculated by NOAH-II code and LAMP-DCA code. Measurement positions were in the plutonium fuel pins, in the coolant, on both inside and outside surfaces of pressure tube and calandria tube, and in the DO moderator. Experimental errors for the resultant Dy activities were estimated as 2.0%. On the base of this accurate measurement, thermal neutron flux distributions became to be comparable in detail in each regions with results calculated by various codes. The experimental values agree with the calculated values by LAMP-DCA code better than the results by NOAH-II code.