Corrosion of Stainless Steel in Acidic Nitrate Waste Solutions From Processing Stainless Steel Reactor Fuels

Abstract

Stainless steel tanks appear to be useful for long-term containment of acid wastes from the reprocessing of stainless steel fuel elements provided that; the temperature of the container is k.ept 5 50°C and that tanks are constructed so as not to expose grain ends to the solution. Chloride ions up to about 0.02 M and fluoride up to about 0.04 M produced no accelerating effect on the corroei,on. Certain organic compounds, for example, glycerol, acted as corrosion inhibitors, as did nitrite. Ferric iron in high concentrations was responsible for a grainboundary attack that increased in rate with increase in temperature and with increase in free acid concentration. Catastrophic end-grain attack was observed under the most aggressive conditions. In the usual case, true intergranular attack did not develop even after exposure times of 7000 hr. The presence of cr(111) appeared to accelerate the attack, but only when ~e(111) was also present. Polarization studies indicated that neither anodic nor cathodic protection would be markedly helpful. Appre-' ciable concentrations of C~(VI) were shown to be absent from the solution at temperatures as high as 80'~. Radiolysis of these solutions is expected to produce corrosion inhibitors (e.g. NO, NO2, H202) rather than accelerators.

The effect of acetohydroxamic acid on stainless steel corrosion in nitric acid

“…Thus, the corrosion accelerating behaviour of AHA is limited to situations where solution redox potential >+1.1 V. However, few studies exist on the solution potential that obtains in aqueous reprocessing streams. From the scant literature that does exist, the solution potential may potentially be up to 1.15 V, depending on actinide species present, acidity and temperature [33][34][35]. From our own studies on non-active thermodynamic simulants for Pu(IV) containing systems, potentials as high as 1.1V can be observed at simulant metal ion concentrations as low as 0.1 mmol dm -3 [36], a value that would only be expected to be higher at concentrations more typical of reprocessing streams (especially, as may occur in the near future, during the recycle of higher burnup fuels) and under certain maloperation conditions such as low pH excursions or high temperature.…”

Korrosion nichtrostender austenitischer Stähle in (kondensierender) chloridhaltiger Salpetersäure

“…Bei der Wiederaufarbeitung von I(ernbrenne1ementen nach dem Darex-Purex-und dem Darex-Thorex-Verfahren (2 bis 5 molare Salpetersaure) gelten 100 bzw. 300 ppm Chlorid als zulassig [28,29]. Nach [14] steigen die Abtragungsraten von X 4 CrNi 18 10 ab 0,3 g Chloridn und von X 6 CrNiTi 18 10 ab 0,5 g Chloridn rasch an.…”