Performance test using modified (6000rpm type) centrifugal clarifier (II); Vibration characteristic test(I)

; Yasu, Takami; Kawata, Tomio

PNC TN8410 91-325, 68 Pages, 1991/11

PNC-TN8410-91-325.pdf:2.12MB

[Purpose] We confirmed modified (6000rpm type) centrifugal clarifier happened unstable vibration in the downward rotation on the condition of including undissolved residue after the clarification operation. This report describes the cause of unstable vibration and the measurement results of vibration characteristic after taking countermeasure for vibration decrease. [Method] It was considered that the cause of unstable vibration was four items in the following. (1)Unbalance between damping force of lower bearing damper and vibration force arisen by rotational bowl (2)Effect of feed condition (3)Effect of self-excited vibration on the free surface (4)Effect of frame strength that be set modified. This test is for take countermeasure to each item (13 item) in the upper items, and for quantitative measure of vibration characteristic (amplitude of rotational bowl and shaft) in the downward rotation on the condition of including undissolved residue after the clarification operation and for select best countermeasure, that is most effective to vibration damping, and does not arise the fall of clarification performance (capture efficiency), the increase of leak rate of feed solution and the fall of sludge washing performance. [Results] (1)We could not confirme vibration damping, compared with spring constant k=9 kgf/cm, damping constant c=20㎏fs/cm and the former condition (k=600 kgf/cm, c=0.3 kgfs/cm). (2)In case of countermeasure that operate as balance ring by sludge cohering height on the inside wall of rotational bowl, we could confirm that the amplitude in the downward rotation is about 1/3, the leak rate of feed solution is about 1/6, compared with the case of feed solution 55㎜ in height from the lower plate of rotational bowl and the former condition (25mm in height from the lower plate of rotational bowl). (3)Compared with the case of setting the side baffle plate 150㎜ in height from the lower plate of rotational bowl for decreasing ...

Evaluation of labile Cs in Fukushima rivers by diffusive gradients in thin films (DGT), 3; Relations between geochemical parameters

Tanaka, Takuro*; Saito, Takumi*; Toda, Kanako*; Fujiwara, Kenso; Terashima, Motoki; Nakanishi, Takahiro; Kobayashi, Natsuko*; Tanoi, Keitaro*; Kato, Hiroaki*

no journal, , 

Cs dispersed by the Fukushima Daiichi Nuclear Power Plant accident deposited in Fukushima area, that are not decontaminated in mountainous areas, may migrate through river water to animals and plants. Most of Cs in river are fixed in clay minerals, but there are some Cs that can be easily desorbed, named as labile components. It has been suggested that labile components affect the bioavailability of Cs. In this study, the labile Cs was sampled in situ from upstream to downstream in several rivers of Fukushima using a passive sampler called diffusive gradients in thin films (DGT). The desorption behavior of the labile component and factors affecting it will be discussed by examining the relationship with particulate Cs and geochemical parameters in river water.