Transuranic contamination of stainless steel in nitric acid

Kerry, Timothy; Banford, Anthony; Thompson, Olivia R.; Carey, Thomas; Schild, Dieter; Geist, Andreas; Sharrad, Clint A.

doi:10.1016/j.jnucmat.2017.06.033

Cited by 9 publications

(12 citation statements)

References 14 publications

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“…Type 304L (1.4307) steel was received from Aalco (elemental composition in Table 1, production has been detailed elsewhere). 4 The material was ground with SiC paper (P120 to P2500) and polished (6 μm followed by 1 μm diamond paste) prior to investigation in this study. Uranyl nitrate was obtained from the Centre for Radiochemistry Research (University of Manchester) isotope stocks.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…It has previously been shown that radioactive material can be deposited on the surfaces of nuclear facility infrastructure leading to regions of contamination. − The presence of radioactive contamination on steel surfaces has numerous repercussions for the nuclear industry as a significant amount of stainless steel is used across the nuclear estate. In the UK alone, there is approximately 32 000 tonnes of contaminated stainless steel that is classified as intermediate level waste (ILW) .…”

Section: Introductionmentioning

confidence: 99%

“…As such, research has taken place to understand the binding mechanism/s of uranium species to stainless steel surfaces and ultimately define a decontamination methodology that most effectively removes the contaminant of concern. Previously reported studies on managing stainless steel from nuclear plants have predominantly focused on the latter subject with only limited work available on understanding fission product, uranium, and transuranic binding mechanisms. − Moreover, previous studies that have investigated solution based contamination processes with austenitic stainless steels have mostly taken place over relatively short time lengths (i.e., hours), in weakly acidic media. , Most nuclear processing plants that handle uranium in relatively concentrated nitric acid operate for more than 10 years. Furthermore, there will be limited, if any, opportunities to replace parts and components.…”

Section: Introductionmentioning

confidence: 99%

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Uranium Contamination of Stainless Steel in Nuclear Processing Plants

Kerry

Banford

Bower

et al. 2018

Ind. Eng. Chem. Res.

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Stainless steel coupons have been exposed to uranium-containing nitric acid solutions, in conditions similar to those found in various uranium handling nuclear facilities across the nuclear fuel cycle. Solid state analysis of the stainless steel samples and solution composition analysis were undertaken to gain a better understanding of the contamination process mechanisms. Stainless steel coupons were immersed in 12 M HNO 3 containing uranium (1 g/L), in the form of uranyl, for periods of up to 255 days. Uranium contamination was observed across all time lengths of exposure. Solution analysis indicated that the levels of contamination reached an equilibrium state after ∼14 days. Investigations using Raman microscopy, synchrotron microfocus X-ray fluorescence and X-ray absorption spectroscopy showed inhomogeneous localization of uranyl species associated with the oxide layer of the stainless steel surface. Over longer time lengths of exposure these contaminant species were predominantly found to locate within intergranular regions of the stainless steel. This finding should be taken into consideration when developing decontamination protocols for corroded stainless steel that has been exposed to uranium, to facilitate metal reuse/recycle and minimize hazardous waste volumes.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Uranium Contamination of Stainless Steel in Nuclear Processing Plants

Kerry

Banford

Bower

et al. 2018

Ind. Eng. Chem. Res.

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“…months to year time scale). The presence of others actinides in nitric acid such as plutonium [12,13], neptunium [12,14] or americium [12] were found to shift electrochemical potentials of studied systems and accordingly to modify the corrosion rate of stainless steel.…”

Section: Introductionmentioning

confidence: 96%

Corrosion studies of stainless steel 304 L in nitric acid in the presence of uranyl nitrate: effect of temperature and nitric acid concentration

Badet

Poineau

2020

SN Appl. Sci.

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In order to better understand the role of uranium on the corrosion behavior of stainless in aqueous nuclear fuel reprocessing and decontamination operations, 304L stainless steel coupons were treated with nitric acid media at 45 °C and 90 °C in the presence of 0.3 M of uranyl nitrate. The impact of time, temperature, nitric acid concentration and uranyl nitrate concentration has been studied over a 183 days period and corrosion rates determined. After 183 days, corrosion rates (μm y −1) at 90 °C are: 33.7 ± 3.4 for 8 M HNO 3 with [U] = 0 M; 39.7 ± 0.1 for 8 M HNO 3 with [U] = 0.3 M; 5.3 ± 0.1 for 3.5 M HNO 3 with [U] = 0 M and 5.9 ± 0.2 for 3.5 M HNO 3 with [U] = 0.3 M. After 183 days, the corrosion rates at 45 °C are all below 2 μm y −1 for the nitric acid concentration and uranyl nitrate concentration studied. Analysis of the data indicate that the corrosion domain remains passive, no uranium uptake onto stainless steel has been observed but only an increase of corrosion rate with temperature (major effect) and nitric acid concentration (minor effect) were reported. When both temperature and nitric acid concentration increased and drive the system into a transpassive corrosion domain, the presence of uranium promote the increase of corrosion rate after 3 months. Analyses of the coupon by scanning electron microscopy indicates that at the first stage low homogeneous dissolution of the steel occurs; intergranular corrosion appears at 10 days and finally grain loss is observed after 6 months treatment.

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“…Research has been carried out to explore the mechanism of binding radioactive element to SS surfaces and find out an environmentally friendly decontamination process that most effectively eliminates the hazardous contaminant. − Extensive efforts have been made to manage structural materials, that is, SS from nuclear facilities. Research has been focused predominantly on understanding the fission product and transuranic binding mechanisms on the SS surface. − However, most of the studies are carried out with a solution medium based on contamination processes with SS for short periods of exposure time (i.e., hours) under room temperature and a weakly acidic condition .…”

Section: Introductionmentioning

confidence: 99%

Understanding the Mechanism of Cs Accumulation on Stainless Steel Suspended in Nuclear High-Level Liquid Waste

et al. 2022

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In a nuclear facility, the surface of stainless steels (SS) was found to be contaminated during the processing of radioactive liquid waste. Their safe and secure disposal is highly challenging to the nuclear industry. If the fundamental property of steel corrosion could be evaluated, successful decontamination and effective decommissioning strategies could be planned. Although individual radionuclide contamination behavior on SS metal was studied, till date, SS contamination behavior under the exposure of high-level liquid waste (HLLW) was unexplored. In view of this, investigations were carried out to understand the nature of contamination in SS 304L alloy under the exposure of simulated HLLW (SHLLW). For understanding of radionuclide adsorption behavior on structural materials, scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy have been utilized for SS 304L. The solutions were analyzed using inductively coupled plasma optical emission spectroscopy to calculate the changes in the elemental composition of the solution and corrosion behavior of SS. The passivation of SS coupons was observed in the presence of HNO 3 due to enrichment of Cr at the surface. The deposition of Cs and Mo was noticed, while SS coupons were exposed to SHLLW. At 3 M HNO 3 and room temperature, the SS surface is mildly passivated by Cr enrichment by formation of a Cr oxide layer on the SS surface. However, the passive layer was not thick enough to attenuate the signal from the substrate below the passivated layer. Hence, Fe 0 and Cr 0 were also found along with Cr 3+ and Fe 3+ (in small quantity). When temperature was elevated to 70 °C, the SS surface was completely covered with the Cr oxide layer, and hence no Cr 0 signal was observed. The small signal of Fe 0 indicated that the signal from the substrate surface is present below the passive layer. During the passivation process, Cr diffused toward the passive layer, thereby producing a Cr-depleted layer below the passive layer (Cr 0 signal was not seen). In the case of SHLLW at 70 °C, the surface was fully covered by Cr 3+ , Mo 6+ , and Cs + . Fe and Ni were not observed at all. This finding will help to design an effective corrosion inhibitor and suitable decontamination agent. In addition to that, this information was found to be useful in designing high-performance novel and modern age reactor materials with improved characteristics.

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Transuranic contamination of stainless steel in nitric acid

Cited by 9 publications

References 14 publications

Uranium Contamination of Stainless Steel in Nuclear Processing Plants

Uranium Contamination of Stainless Steel in Nuclear Processing Plants

Corrosion studies of stainless steel 304 L in nitric acid in the presence of uranyl nitrate: effect of temperature and nitric acid concentration

Understanding the Mechanism of Cs Accumulation on Stainless Steel Suspended in Nuclear High-Level Liquid Waste

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