Waste container durability: monitoring of a stainless steel 4 metre box over 12 years

Abstract

In the UK, most intermediate level radioactive waste is packaged in stainless steel containers. It is important that containers should maintain their integrity for extended periods of storage prior to final disposal. A prototype 4 metre box fabricated from 304S11 stainless steel was monitored at an inland rural building for over twelve years to gain experience in monitoring environmental conditions and corrosion during storage. A wide range of different types of aerosol particles were observed on the surfaces and in the air. They contained corrosive ions such as chloride, as well as other anions such as sulfate and nitrate. The chloride deposition rate was between 0.1 and 4 mg cm À2 yr À1 depending on the orientation and location of the surface, with a chloride/sulfate ratio ranging from~0.3À2. The temperature and relative humidity typically ranged from 0À30ºC and 40À90%, respectively. The greatest degree of corrosion developed on the base of the box, which had elevated chloride concentrations (10À140 mg cm À2 ). However, there was little evidence of corrosion propagation on the surface of the box and no evidence of stress corrosion cracking. The average pit propagation rates on a 316L coupon mounted next to the 4 m box were <1 mm yr À1 .

Overview of anaerobic corrosion of carbon steel radioactive waste packages in alkaline media in support of the Belgian supercontainer concept

“…The results from the cells containing steel wires are adjusted by deducting any pressure fluctuations that occur in the control cells and are normalised to standard temperature and pressure. [26][27][28][29][30] The setup of the barometric gas cell measurements is shown in Figure 2.…”

“…Carbon steel wire (1017 grade), with a diameter of 0.4 mm and a total exposed surface area of 0.1 m 2 , is F I G U R E 2 Setup of the barometric gas cell measurements [30] [Color figure can be viewed at wileyonlinelibrary.com] KURSTEN ET AL.…”

“…The autoclaves are flooded entirely to ensure that the steel is permanently wetted by the test solution. [26,30] The setup of the autoclave experiments is shown in Figure 3.…”

“…And also, irradiation (25 Gy h −1 ) appears to have a limited effect on both the initial and long-term corrosion rate (Figure 9). [30] Experimental data for P355 QL2 grade carbon steel obtained by monitoring hydrogen gas generation using sealed autoclaves equipped with pressure transducers for unirradiated and irradiated conditions is shown in Figure 10. This plot displays the cumulative hydrogen production rate together with the corresponding smoothed integrated corrosion rate.…”

“…Preparation of the test solutions, together with filling and sealing of the test cells is conducted in an argon-purged glove box to ensure initial anoxic conditions in the cells. [26,30] Gas cell experiments are carried out to study the effects of temperature (25°C and 80°C), dose rate (0 and 25 Gy h −1 ), chloride concentration (0 and 100 mg L −1 ), sulphide concentration (0 and 500 mg L −1 ) and thiosulphate concentration (0 and 100 mg L −1 ). The studied ranges of concentration are chosen based on measurements and modelling calculations.…”