Investigation of structural and electronic properties in Ru perovskite oxides by XAFS measurements

Mizumaki, Masaichiro*; Yoshii, Kenji; Hinatsu, Yukio*; Doi, Yoshihiro*; Uruga, Tomoya*

Physica Scripta, T115, p.513 - 515, 2005/00

The electronic and structural properties of Ru oxides were investigated by utilizing X-ray absorption spectroscopy (XAS). We estimate the valence of Ru in perovskite ruthenium oxides by XAS measurements. XAS measurements were carried out at room temperature around Ru K-edge. The valence of Ru in ( = Ba, Sr)LnRuO and ( = Ca, Ba, Sr)RuO was 4+. The valence of Ru in LnRuO was 5+. The valence of Ru in PbRuO showed an intermediate value between 4+ and 5+. Theoretical calculation reproduced the experimental spectra. We analyzed XAS spectra and obtained information of local structure. The bond length between Ru and O was consistent with the results of neutron diffraction.

Investigation of analytical method in thermal stratification analysis; Evaluation of flow rates through flow holes for normal and scram conditions of 40% power operation with AQUA code

Doi, Yoshihiro; Muramatsu, Toshiharu

PNC TN9410 97-083, 106 Pages, 1997/08

PNC-TN9410-97-083.pdf:12.18MB

Thermal stratification phenomena are observed in an upper plenum of liquid metal fast breeder reactors (LMFBRs) under reactor scram conditions, which give rise to thermal stress on structural components. Therefore it is important to evaluate chracteristics of phenomena in the design of the internal structure in an LMFBR plenum. To evaluate flow rates through flow holes of the prototype fast breeder reactor, MONJU, numerical analyses were carried out with AQUA code for normal and scram conditions with 40% power operation. Through comparison of analysis results and measured temperature, thermal stratification phenomena in 300 second period after the scram was evaluated. During the post-scram condition, the fluid from core flows to the lower part of the upper plenum. The hot-cold transition area inside the inner barrel could be seen around the level of upper flow holes at 120 seconds after the scram. After the period, the transition area was risen to the upper part of the plenum with accumulation of the cold fluid at the lower part of the plenum. The rising of the transition area was not affected with the flow that impinged bottom surface of UIS because the fluid flew horizontally in 300 second period. Flow rate through the upper flow holes, the lower flow holes and annular gap between the inner barrel and the reactor vessel were evaluated with the measured temperature and the analysis results individually. With the evaluation of the measured temperature, the ratio to total flow rate was about 7% that through the lower flow holes at 30 seconds after the scram. The ratio was about 30% that through the annular gap at 360 seconds after the scram. The analysis results showed that the ratio was in 17% to 31% that through the upper and lower flow holes and the flow flew the annular gap dominantly in the normal operation. In the post-scram condition, the ratio of flow rate that through the flow holes was increased with the time. The ratios of flows for the upper flow ...

Direct numerical analysis of turbulent mixing in a thermally stratified flows; Turbulent mixing in isothermal field

Doi, Yoshihiro; Muramatsu, Toshiharu

PNC TN9410 97-033, 66 Pages, 1997/04

PNC-TN9410-97-033.pdf:3.09MB

Thermal stratification phenomena are observed in an upper plenum of liquid metal fast breeder reactors (LMFBRs) under reactor scram conditions, which give rise to thermal stress on structural components. Therefore it is important to evaluate chracteristics of phenomena in the design of the internal structure in an LMFBR plenum. The phenomena is a stable stratified flow and shear layer is formed by bringing two streams of fluid. Previous many experiments and numerical simulations have the layer is dominated by large, spanwise coherent vortex structures and the structures have an important effect on mixing. In this study, to evaluate numerical model and its constants for the thermal stratification phenomena, numerical analyses were carried out for a shear flow test with water. The test that had no temperature difference was analyzed with direct numerical simulation code. The numerical results could indicate the large spanwise coherent vortex structures with vortex growing and pairing. The analyses with different mesh arrangement, inlet velocity distribution and two dimensional and three dimensional arrangement were carried out and the numerical velocity, velocity fluctuation and Reynolds stress were compared with the experimental results. Through the comparison, the difference of mesh arrangement or the velocity distribution inlet boundary not caused distinction of the velocity, velocity fluctuation and Reynolds stress at 0.9 meter away from separator. Velocity fluctuations in the depth was very small in the three dimensional analysis and no difference was found in the comparison of the results with two dimensional analysis. The numerical velocity and velocity fluctuation in horizontal direction were well agreed with measured velocity, but the velocity and fluctuation in vertical direction were higher than measured value.

Thermal stratification tests in Monju upper plenum, 1; Temperature distributions under normal and scram conditions with 40% power operation

Doi, Yoshihiro; Muramatsu, Toshiharu; Kunogi, Kosuke

PNC TN9410 96-117, 60 Pages, 1996/05

PNC-TN9410-96-117.pdf:1.94MB

Thermal stratification phenomena are observed in an upper plenum of liquid metal fast breeder reactors (LMFBRs) under reactor scram conditions, which give rise to thermal stress on structural components. Therefore it is important to evaluate chracteristics of phenomena in the design of the internal structure in an LMFBR plenum. To evaluate the thermal stratification characteristics of the prototype fast breeder reactor, MONJU, axial temperature distributions were measured with a thermocouple tree installed into the upper plenum for normal and scram conditions with 40% power operation. The axial temperature distribution for the normal operation showed thermal stratification phenomena that temperatures were about 410C under the level of the fuel subassembly top, about 480C around the level of the flow holes and about 490C above the level of the upper flow holes. Temperature fluctuations were observed at the levels of the lower flow and upper flow holes. RMS (Route Means Square) of functuation at the lower and upper flow holes were 1.6 C and 1.5C, respectively. Based on the temperature histories of the upper plenum during scram conditions, temperature decreasing rate, temperature gradient and rising rate of stratification interface were evaluated. The temperature decreasing rates were about 5.0 C/sec at the core outlet, 2.0 C/sec around the level of flow holes and from 0.3 to 0.4C/sec at the top of the inner barrel. The temperature gradients were about 160 C/m, 90C/m, 45C/m and 170 C/m at the time of 120 sec, 180 sec, 600 sec and 4800 sec from the reactor scram, respectively. The rising rate of stratification interface is about 1.0 m/h for the period from 120 sec to 600 sec with the onset of reactor scram. On the other hand, the rising rate is about 0.6 m/h after 600 sec from the scram. The rising rate at the top of the inner barrel is 0.2 m/h ...