Deposition of nickel and cobalt ions on heated surface under nucleate boiling condition.

Abstract

The deposition of Ni and Co ions on a heated surface of simulating fuel rods has been studied in water at atmospheric and 70 atm pressures during nucleate boiling.The effects of various factors, including heat flux of the heated surface, concentration of coexisting iron oxide (a-Fe.0 3 ) and concentration of Ni and Co ions, on their deposition rate have been investigated. The model for iron oxide deposition which is based on microlayer evaporation and drying out phenomena in the nucleate boiling bubble was shown to be applicable to the deposition of Ni and Co ions. That is, dWjdt=K·Q·C/L, where dWjdt is the deposition rate, K the deposition rate coefficient, Q the heat flux, C the ion concentration, and L the latent heat of vaporization. The K value of Ni ion is about 0.1 and independent of iron oxide concentration. On the other hand, the K value of Co ion increases with iron oxide concentration and seems to approach that of iron oxide (0.3). The Co ion deposited with iron oxide forms Co ferrite. Solubility of Co ferrite is small compared with that of Co deposits without iron oxide (CoO or Co (OH)2). The increase in the K value of Co ion with iron oxide concentration is attributed to the change in chemical form of Co deposits into more stable species not favoring Co release.

Corrosion and deposition on the secondary circuit of steam generators

“…Ni ion deposition rate has been found to be influenced by Ni ion concentration and heat flux, displaying linear relationship (Figure 7). The study also found that Ni ion deposition rate was independent of iron oxide concentration when taking 1.0 mg/L Ni ion and 0-5 mg/L iron oxide under 280°C, 7 MPa (boiling condition) [63].…”

Water chemistry technology – one of the key technologies for safe and reliable nuclear power plant operation

“…Typical patterns of crud and ionic species deposition on the fuel surface are summarized in Table 5 [58]. The results were used to develop the microlayer evaporation and drying out model, which was applied not only to crud and ion deposition on BWR fuels but also to boron deposition under subcooled boiling and boron accumulation on PWR fuel to evaluate axial offset anomaly phenomena [59].…”

Zinc Isotope Fractionation on Benzo-15-crown-5 Resin by Liquid Chromatography

“…Injection of trace amount of soluble zinc has recently been proved effective to suppress 60 Co contamination to the primary coolant of a boiling water reactor and to reduce the gamma ray dose from the piping system carrying the coolant. 12,13) So far, most boiling water reactor plants in American have initiated zinc injection to reduce radiation build-up on the surface of recirculation piping. However, natural occurring zinc contains 48.6% 64 Zn and the thermal neutron cross section of 64 Zn is 0.46 barn.…”