Analysis of the magnetic corrosion product deposits on a boiling water reactor cladding

The buildup of corrosion product deposits (CRUD) on the fuel cladding of the boiling water reactor (BWR) before and after zinc injection has been investigated by applying local experimental analytical techniques. Under the BWR water chemistry conditions, Zn addition together with the presence of Ni and Mn induce the formation of (Zn,Ni,Mn)[Fe2O4] spinel solid solutions. X-ray absorption spectroscopy (XAS) revealed inversion ratios of cation distribution in spinels deposited from the solid solution. Based on this information, a two-site ferrite spinel solid solution model is proposed. Electron probe microanalysis (EPMA) and extended X-ray absorption fine structure (EXAFS) findings suggest the zinc-rich ferrite spinels formation on BWR fuel cladding mainly at lower pin.

Graphical AbstractAnalysis of spinels in corrosion product deposits on boiling water reactor fuel rod. Combining EPMA and XAFS results: schematic representation of the ferrite spinels in terms of the end members and their extent of inversion. Note that the ferrites are represented as a surface between the normal (upper plane, M[Fe2]O4) and the inverse (lower plane, Fe[MFe]O4).Actual compositionsred for the specimen at low elevation (810 mm),Figure optionsDownload full-size imageDownload as PowerPoint slideblue for the specimen at mid elevation (1800 mm).Figure optionsDownload full-size imageDownload as PowerPoint slideThe results have an impact on the properties of the CRUD material.Highlights► Buildup of corrosion product deposits on fuel claddings of a boiling water reactor (BWR) are investigated. ► Under BWR water conditions, Zn addition with Ni and Mn induced formation of (Zn,Ni,Mn)[Fe2O4]. ► X-Ray Adsorption Spectroscopy (XAS) revealed inversion of cations in spinel solid solutions. ► Zinc-rich ferrite spinels are formed on BWR fuel cladding mainly at lower pin elevations. Figure optionsDownload full-size imageDownload as PowerPoint slide