Spent nuclear fuel in the U.K. is stored within ponds dosed with NaOH in order to inhibit corrosion and, to ensure the efficiency of storage regimes, there is a need to define and quantify the corrosion processes involved during immersion of fuel cladding. In this project, state-of-the-art characterisation techniques were employed to image the corroding surfaces of two nuclear fuel cladding materials: stainless steel and Magnox. Advanced gas-cooled reactor fuel cladding consists of 20Cr-25Ni-Nb stabilised stainless steel and during irradiation the microstructure of the cladding undergoes significant changes, including grain boundary element depletion and segregation. High-speed atomic force microscopy with nanoscale resolution, enabled precipitates and pit initiation in stainless steel to be imaged. Magnox is a magnesium–aluminium alloy and during irradiation in a reactor the outer metal surface oxidises, forming an adherent passive layer which subsequently hydrates when exposed to water. Corrosion processes encompass breakdown of passivity and filiform-like corrosion, both of which were imaged in situ using the scanning vibrating electrode technique.
CoxB.A new model for the in-reactor corrosion of zirconium alloys. Vienna: IAEA; 1997.
2.
MottaATCouetAComstockRJ.Corrosion of zirconium alloys used for nuclear fuel cladding. Annu Rev Mater Res. 2015; 311–343. doi: 10.1146/annurev-matsci-070214-020951
3.
IAEA International working group on water reactor fuel performance and technology. Fundamental aspects of corrosion on zirconium base alloys in water reactor environments. IAEA; 1990.
4.
CoxB.Some thoughts on the mechanisms of in-reactor corrosion of zirconium alloys. J Nucl Mater. 2005; 336: 331–368. doi: 10.1016/j.jnucmat.2004.09.029
5.
NorrisDIRBakerCTaylorCRadiation-induced segregation in 20Cr/25Ni/Nb stainless steel. 15th Symposium on Effects of Radiation on Materials; 1990.
6.
ChanCMEngelbergDLWaltersWS.Performance characterisation of AGR fuel cladding relevant to long-term in-pond storage in pH-moderated aqeous environment. Top Fuel Reactor Fuel Performance 2015; Zurich ; 2015.
7.
ClarkRNWaltersWSWilliamsG.A scanning probe investigation of intergranular corrosion in sensitised stainless steel nuclear fuel cladding. NACE CORROSION 2016 Extended Abstracts; Vancouver ; 2016.
8.
PhuahCH.Corrosion of thermally-aged advanced gas reactor fuel cladding [thesis]. London: Imperial College; 2012.
9.
Al-ShaterAEngelburgDLyonSCharacterization of the stress corrosion cracking behavior of thermally sensitized 20Cr-25Ni stainless steel in a simulated cooling pond environment. J Nucl Sci Technol. 2017; 54: 742–751. doi: 10.1080/00223131.2017.1309305
10.
MorozovMPierceSGDobieGRobotic ultrasonic testing of AGR fuel cladding. Case Studies Nondestruct Test Eval. 2016; 6: 26–31. doi: 10.1016/j.csndt.2016.08.001
11.
BurrowsRHarrisSStevensNPC.Corrosion electrochemistry of fuel element materials in pond storage conditions. Chem Eng Res Des. 2005; 83 (A7): 887–892. doi: 10.1205/cherd.05023
12.
WilliamsGBirbilisNMcMurrayHN.Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte. Faraday Discuss. 2015; 180: 313–330. doi: 10.1039/C4FD00268G
13.
GodfreyHCannG.Effect of chloride on Magnox corrosion with respect to carbon-14 release post closure. 2016. (National Nuclear Laboratory, NNL (14) 13189).
14.
PaytonOPiccoLScottTB.High-speed atomic force microscopy for materials science. Int Mater Rev. 2016; 61: 473–494. doi: 10.1080/09506608.2016.1156301
15.
WarrenAMartinez-UbedaAPaytonOPreparation of stainless steel surfaces for scanning probe microscopy. Micros Today. 2016; 24: 52–55. doi: 10.1017/S1551929516000341
16.
International Atomic Energy Agency. Further analysis of extended storage of spent fuel. International Atomic Energy Agency; 1997 (IAEA-TECDOC-944).
17.
WilliamsGDafyddHALGraceR.The localised corrosion of Mg alloy AZ31 in chloride containing electrolyte studied by a scanning vibrating electrode technique. Electrochim Acta. 2013; 109: 489–501. doi: 10.1016/j.electacta.2013.07.134
18.
WilliamsGMcMurrayHN.Localized corrosion of magnesium in chloride-containing electrolyte studied by a scanning vibrating electrode technique. J Electrochem Soc. 2008; 155 (7): C340–C349. doi: 10.1149/1.2918900
19.
WilliamsGMcMurrayHN.Pitting corrosion of steam turbine blading steels: the influence of chromium content, temperature, and chloride ion concentration. Corrosion. 2006; 62 (3): 231–242. doi: 10.5006/1.3278269
20.
WilliamsGBirbilisNMcMurrayHN.The source of hydrogen evolved from a magnesium anode. Electrochem Commun. 2013; 36: 1–5. doi: 10.1016/j.elecom.2013.08.023
HosakaSEtohKKikukawaAMegahertz silicon atomic force microscopy (AFM) cantilever and high-speed readout in AFM-based recording. J Vac Sci Technol B Microelectron Nanom Struct. 2000; 18 (1): 94–99. doi: 10.1116/1.591157
23.
PalocziGTSmithBLHansmaPKRapid imaging of calcite crystal growth using atomic force microscopy with small cantilevers. Appl Phys Lett. 1998; 73 (12): 1658–1660. doi: 10.1063/1.122237
24.
AndoT.High-speed atomic force microscopy coming of age. Nanotechnology. 2012; 23 (6): 062001. doi: 10.1088/0957-4484/23/6/062001
25.
PaytonODPiccoLRobertDHigh-speed atomic force microscopy in slow motion – understanding cantilever behaviour at high scan velocities. Nanotechnology. 2012; 23 (20): 205704. doi: 10.1088/0957-4484/23/20/205704
26.
PaytonODPiccoLScottTB.High-speed atomic force microscopy for materials science. Int Mater Rev. 2016; 61 (8): 473–494. doi: 10.1080/09506608.2016.1156301
27.
AdamskaAMBrightELSutcliffeJCharacterisation of electrodeposited polycrystalline uranium dioxide thin films on nickel foil for industrial applications. Thin Solid Films. 2015; 597: 57–64. doi: 10.1016/j.tsf.2015.11.030
28.
AdamskaAMSpringellRWarrenADGrowth and characterisation of uranium-zirconium alloy films for nuclear industry applications. J Phys. 2014; 47 (31): 301–315.
29.
PopelAJAdamskaAMMartinPGStructural effects in UO2 thin films irradiated with U ions. Nucl Instrum Methods Phys Res B Beam Interact Mater Atoms. 2016; 386: 8–15. doi: 10.1016/j.nimb.2016.09.019
