Experimental studies on the coolant mixing effect in a "Joyo" irradiated fuel Assembly; Experimental results for the 7-pin bundle in the A-Type irradiation fuel assembly

not registered; not registered; not registered; Okada, Toshio; Yamaguchi, Katsuhisa; Aoki, Tadao

The subchannel coolant mixing effect in the "Joyo" A-Type irradiated fuel assembly, has been experimentally investigated by using the sodium test 100p, the mixing test loop, and a mockup test section (7 heater pin-bundle; pin diameter=6.5 mm, wire diameter=0.9 mm, pin pitch=7.45 mm, wire wrapping pitch=209 mm). The radial and axial temperature profiles were measured with calibrated Chromel-Alumel thermocouple (6.5 mm in outer diameter) attached on the pin and rapper tube surfaces. The experiments were performed under the following conditions: (Inlet sodium temperature 370C) (Linear power of heater pin 40520W/cm) (ReynoldS number 5,70041,000) The subchannel sodium temperature profiles measured were compared with the calculated results by the SWIRL and COBRA-IV codes, while the cladding temperature profiles measured were compared with the results by the SPOTBOW code. These analyses led to the following conclusion: (1)The mixing coefficients Cs(1), Cs(2) and Cs(3) of the SWIRL code were fitted satisfactorily by the data and the values for the 7-pin bundle were 0.55, 2.30 and 0.74 in order at the Reynolds number of 30,000. The mixing coefficient Cs(1) was less sensitive to the calculated subchannel temperatures than the others, Cs(2) and Cs(3). The mixing coefficient Cs(3) decreased with the increasieng Reynolds number, while the others kept almost constant. (2)The forced cross flow parameters DUR1, DUR2 and DUR3 of the COBRA-IV code were also fitted wen and the following values were obtained for the 7-pin bundle at the Reynolds number of 30,000: DUR1=0.012, DUR2=0.05 and DUR3=0.08. The sensitive forced cross flow parameters DUR(1) was less sensitive to the calculated subchannel temperature than the others, All of them decreased with increasing Reynolds number. (3)The circumferential temperature distribution caluculated by the SPOTBOW code for the cladding of a specified heater pin was higher than that measured. However, there was ...