Effect of additives on the susceptibility of zirconium alloys to nodular corrosion

Microstructural analysis and XPS investigation of nodular oxides formed on Zircaloy-4

“…Likhanskii and Evdokimov reported that nodular oxide growth on the cladding surface in BWRs is mainly related to large amounts of oxygen content in coolant caused by the boiling water and radiolysis. In the case of pressurized water reactors (PWRs) or heavy water reactors, on the other hand, uniform oxide layers are normally formed on the cladding surface because of suppression of water radiolysis and a decreased number of oxidizing radiolytic species caused by rather high contents of dissolved hydrogen in the coolants [4]. However, the authors also insisted that the nodular oxidation phenomenon could occur in cases when a steam phase is formed between the oxide and coolant and it could be a crucial problem for PWRs.…”

“…Representative models of the nodular oxidation process are well summarized in the research by Likhanskii and Evdokimov [4]. In Urquhart et al's report, it was suggested that nodular oxide morphology is commonly observed at sites of lower intermetallic particle concentration, which is related to the local enhancement of proton migration [11].…”

Overview of ageing and degradation issues in light water reactors (LWRs)

“…Though PWR and WWER structures are not prone to the nodular corrosion attack, nodular corrosion can be a problem if steam forms at the oxide-coolant interface. 54 1.29 Nodular corrosion on the fuel clad of a BWR fuel pin. 51 There is another type of localized corrosion in Zircaloys: the enhanced in-reactor corrosion when Zircaloy is placed close to a noble metal (under BWR conditions it is stainless steel or a nickel alloy), and where Zircaloy 'mimics' the noble metal corrosion.…”

Effect of Surface State on Nodular Corrosion Resistance of Zircaloy-4 Alloy

“…With the growth of nodular corrosion spots, the local cladding is rather quickly thinned [8], and hydrogen uptake increases, which shortens the service life of nuclear fuel cladding. Therefore, nodular corrosion of Zircaloy fuel claddings has to be concerned [9,10]. Several physical mechanisms involving the formation of nodular corrosion have been proposed, but it is still unclear how nodular oxide is formed.…”