Corrosion film solubility and suspended particle behaviour of corroding SS316L surfaces in simulated nuclear plant coolant

Hewett, John M. (2018). Corrosion film solubility and suspended particle behaviour of corroding SS316L surfaces in simulated nuclear plant coolant. University of Birmingham. Ph.D.

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Abstract

A once-through flowing rig built entirely from 316L stainless steel (SS316L) was used to study dissolution and particulate release behaviour of corrosion films on SS316L surfaces in simulated PWR primary coolant.

Coolant of pH25C 9-11 was prepared using LiOH in nitrogen-sparged ultrapure water, and pumped at 0.1-2 g/min, under ~100 bar pressure and temperatures up to 300 °C. Flow velocity was at most 6.4 mm/s in ¼” tubing, and 0.13 mm/s in 1” bore tubing where the bulk of the volume resided.

Levels of the five most prevalent alloying elements – Fe, Cr, Ni, Mo, Mn – were analysed in rig effluent samples using ICP-MS. Nitrocellulose filters (0.05-3.0 μm) were used at the point of sampling to assess the contribution from particulate and colloidal matter. In most runs, SS316L surfaces of the rig acted as the sole source of corrosion products.

Levels of Fe, Cr, and Ni were generally in the low ppb range, consistent with solubility, though transients to higher levels occurred.

Levels of Mo and Mn varied with time and flow rate, sometimes exceeding 100 ppb, and cumulative release, particularly of Mo, appeared to be greater than could be accounted for by non-selective oxidation, suggesting leaching from the SS316L subsurface.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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