Insights into the zinc effect on radio-cobalt deposition on stainless steel piping surfaces under BWR conditions from experiment guided 1st principles modelling

Reactivity of Zn+aq in high-temperature water radiolysis

“…5,6 Zn 2+ ions have been reported to replace Ni, Fe, and Co ions in spinel-type oxides formed on nickel-based alloys and stainless steels. 7 Zinc-incorporated oxides are thermodynamically more stable and corrosion release rates are significantly mitigated, resulting in a substantial reduction of structural material corrosion. However, continuous zinc injection is necessary to maintain the suppression of corrosion products over the long term.…”

“…Rate constants of the reactions listed(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) applied in the kinetics model for Zn + aq decay at room temperature at zero ionic strength À ) aq + Zn 2+ -Zn + 1.3 AE 0.06 (this work); 1.6; 8 1.8;22 1.5;20,26,27 0.95; 23 1.0 28 2 Z n + + OH -Zn 2+ + OH À 11.8 AE 0.6 (this work); 20; 21 15 29 3 Z n + + H 2 O 2 -Zn 2+ + OH + OH À 2.2 AE 0.05 (this work); 2.4; 23 2.3; 30 1.8 25 4 Z n + + H (+H + ) -Zn 2+ + H 2…”

Experimental Investigation of Cobalt Deposition on 304 Stainless Steel in Borated and Lithiated High-Temperature Water

“…In fact, nonradioactive corrosion or abrasion products on the surfaces of metal components in the primary loop system of a PWR nuclear power plant are activated by neutrons in the core and form radioactive corrosion products (ACPs) ( 51 Cr, 54 Mn, 58 Co, 59 Fe, 60 Co, 110m Ag, 122 Sb), which are transferred outside the core by the coolant and deposited on the inner surfaces of the equipment, forming radiation fields [ 1 , 2 ]. Among them, 60 Co and 58 Co are the main radioactive products formed in the primary loop and the main sources of irradiation doses for power plant maintenance personnel; approximately 90% or more of the collective dose comes from the deposited corrosion products [ 3 , 4 , 5 ]. Therefore, it is important to explore the deposition behaviors of ACPs on the metal surfaces of PWRs under normal conditions.…”

“…In addition, Fuse et al [ 9 ] studied radioactive contamination by cobalt by simulating the water environment of a boiling water reactor based on the Gibbs free energies of the reactions between metal ions and oxides; the cobalt on the surfaces of carbon and stainless steel was mainly deposited as CoFe 2 O 4 and CoCr 2 O 4 , and there was a direct link between the concentration of cobalt and the formation of oxide films on the metal surface. Cantatore et al [ 4 ] explained the formation of two cobalt contamination layers on a metal surface by using 1st principles modeling, and the addition of zinc to the solution inhibited the deposition of cobalt on the metal surface. Many experimental or simulation studies have been conducted for boiling water reactors, but there are not enough studies of cobalt deposition in the water cooling circuits of PWRs.…”