The core stability measurements were taken during the cycle-9 startup of the 1,300MWe BWR, Kernkraftwerk Kruemmel (KKK). The core contained advanced 9x9 type high burn-up design reload fuel with a higher enrichment than current 8x8 fuel. A design feature of the advanced 9x9 fuel assembly (FA) is a large square water channel for enhanced neutron moderation. The measurement data as a function of core flow and power showed almost the same stability characteristics as those of the past measurement during the cycle-3 startup of the KKK core with the 8x8 FA. The local power range monitors (LPRM) detected neutron flux oscillations in both core-wide in-phase and half-core out-of-phase modes.The frequency-domain stability analysis using the STAIF-PK code well reproduced the measurement result that the onset of unstable operation in KKK first occurs when about half of the reactor internal pumps are operating and the other half are stopped. The stability performance of the advanced 9x9 FA in the core was compared with the 8x8 FA by a design parameter analysis with respect to thermal-hydraulic and neutronic design. It has been demonstrated by the analysis that the stability performance of the advanced 9x9 FA is comparable with current 8x8 FA.
The isotopic exchange rate of cobalt ions between a hydrous tin(IV) oxide ion exchanger and aqueous solutions was radiochemically measured in order to obtain fundamental data which could be useful for elucidating the ion-exchange kinetics of the material for the transition metal elements. This rate can be understood by considering that the cobalt in an exchanger exists as three species: (A1) dissociated ions which can diffuse in the exchanger particles; (A2) weakly bound ions to the exchange sites, which are in local equilibrium with A1; and (B) covalently fixed ions to the exchange sites, which are exchanged very slowly with A1. At a small ratio of the amount of B to the total amount of cobalt sorbed on the exchanger, the rate is controlled by the diffusion of A1, with effective diffusion coefficient, \barDeff, a value which depends on the concentration ratio of A2 to A1. When B predominates over A, the concentration ratio of B to A1 greatly affects \barDeff. The values of \barDeff and their activation energy (20 kJ mol−1) were also estimated.
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