Patent Number: 
Section: description

The invention is illustrated by the following Examples. A 1% solution (1 litre) of SDG3 (a decontaminant containing the chelators citric acid and EDTA) containing HNO3 to control pH had added to it 1 g of ferrous sulphate to give 1000 ppm of dissolved iron to act as Fenton""s reagent. The solution was dosed with Pu(NO3)4 (in an amount sufficient to give an activity concentration of 2600 Bq/ml), supplied with H2O2 and irradiated with UV light (254 nm). The operating parameters of the experiment were as set out in Table 1: The experiment was stopped when it was observed that bubbles were no longer forming, a sign that CO2 was no longer being produced. The liquor was sampled throughout the experiment and analysed for Total Organic Carbon (TOC) and total alpha activity. After 90 minutes, the liquor was allowed to stand over night and then passed through an ion exchange material before being flocculated by raising the pH to 9 and filtering out the resulting ferrous hydroxide floc. The remaining liquor was further irradiated and, after a further 80 minutes, passed again through the floccing procedure. The results obtained are shown in Table 2: The ion exchange material (polyantimonic acid, 5 g) was swamped by the large amount of ion present and thus was unable to achieve effective removal of the active Pu species from the solutions. Floccing, by raising the pH, however, demonstrated good decontamination factors for alpha emissions even before complete destruction of organic material had occurred; it is probable that this is because the chelating properties of the SDG3 were destroyed before the organic components were completely decomposed. This example was performed using a sample of the effluent from a laundry which washes clothing from the xe2x80x9cactivexe2x80x9d areas of a nuclear plant. The liquor contained an organic chelating agent and traces of alpha activity As with Example 1, HNO3 was added to control pH and the liquor had added to it ferrous sulphate to give 370 ppm of dissolved iron to act as Fenton""s reagent. The solution was supplied with H2O2 and irradiated with UV light (254 nm). The operating parameters of the experiment were as set out in Table 3: The experiment was performed for 10 hours and the liquor was sampled throughout the experiment and analysed for Total Organic Carbon (TOC) and total alpha activity. The results obtained are shown in Table 4: The experiment was performed on liquor from a washing process used to clean protective clothing from the plutonium handling areas of a nuclear plant. The decontaminant was a standard industrial detergent. As with Example 1, HNO3 was added to control pH and the liquor had added to it ferrous sulphate to give 1000 ppm of dissolved iron to act as Fenton""s reagent. The solution was supplied with H2O2 and irradiated with UV light (254 nm). The operating parameters are set out in Table 5 bellow: The alpha levels dictated use of a glove box, with the consequence that pH was determined with sticks instead of a meter, and so could not be determined so accurately as in the cases of Examples 1 and 2. The reaction was stopped by the formation of the ferric floe and consequent removal 10 of iron from solution. It was decided to re-acidify the liquor to below pH 0 and to attempt to improve the decontamination factor (DF). The following results were then obtained: It is apparent that the UV destruction and floccing steps have reduced the solution activity from 147,000 Bq/ml (the level achieved by floccing and filtration alone) to below 50 Bq/ml.