CLEANING COMPOSITION FOR DECONTAMINATING SURFACES, IN PARTICULAR RADIOACTIVE SURFACES, AND RELATIVE DECONTAMINATION

Abstract

The present invention relates to a cleaning composition for the decontamination of surfaces, in particular radioactive surfaces, and the related decontamination method.

Claims

1. A method for decontaminating from radioactive residuals components or parts of a plant that come into contact with radioactive material, wherein said method comprises applying to said parts an aqueous composition (C) comprising: i. at least one of citric acid, oxalic acid, tartaric acid, malic acid and the respective sodium or potassium salts, ethylenediaminetetraacetic acid (EDTA), a bisodium salt, other synthetic complexing agents and mixtures thereof; and ii. at least one solvent selected from methanol, ethanol, ethyl acetate, propanol and isomers thereof, propylene glycol, butanol and isomers thereof, water soluble low molecular weight esters, methyl acetate, ethyl acetate, ethyl formate, dimethyl carbonate, esters of carbonic acid, and mixtures thereof.

2. The method according to claim 1, wherein said composition (C) further comprises: iii. at least one surfactant selected from coco-glucoside, alkyl polyglucoside, glyceryl oleate, a linear sodium alkylbenzene sulfonate, sodium lauryl sulfate, sodium lauryl ether sulfate, soy lecithin, soy lysolecithin and mixtures thereof.

3. The method according to claim 1, wherein said composition (C) further comprises: iv. at least one apolar solvent, from among limonene or another terpene analog thereof, tetrachloroethylene, carbon tetrachloride, other halogenated solvents, and mixtures thereof.

4. The method according to claim 1, wherein in said composition (C): the component i. is in a concentration that ranges from 12 to 45%, the component ii. is in a concentration that ranges from 1 to 6%; or the component iii. is in a concentration that ranges from 2 to 7%, the component iv. is in a concentration that ranges from 0.3 to 10%; where the percentages are by weight in relation to the total weight of the composition.

5. The method according to claim 1, wherein the acid i. is citric acid or the solvent ii. is ethanol or the apolar solvent iv., if present, is limonene, citral or a mixture of limonene and citral, or the surfactant iii., if present, is at least one from coco-glucoside, soy lecithin or lysolecithin, wherein the acid i. is citric acid, the solvent ii. comprises ethanol, dimethyl carbonate or a mixture thereof, the apolar solvent iv., if present, is a mixture of limonene and citral and the surfactant iii., if present, is at least one from among coco-glucoside, soy lecithin or lysolecithin.

6. The method according to claim 1, wherein said composition may further comprise at least one from acetic acid, sodium chloride and mixtures thereof, where the acetic acid is comprised in an amount from 3 to 8% by weight, the sodium chloride is comprised in an amount from 10 to 30% by weight, wherein all the percentages relate to the weight of the component with respect to the total weight of the composition.

7. The method according to claim 1 for the decontamination from radioactive residues of components or parts of a plant that come into contact with radioactive material that are valves, pumps, stirrers, flanges, tube sections or tools.

8. A cleaning/decontaminating composition (C) from radioactive residues comprising: i. at least one of citric acid, oxalic acid, tartaric acid, malic acid and the respective sodium or potassium salts, ethylenediaminetetraacetic acid (EDTA) a bisodium salt, other synthetic complexing agents and mixtures thereof in amounts from 12 to 45%, by weight with respect to the total weight of the composition; and ii. at least one solvent selected from methanol, ethanol, ethyl acetate, propanol and isomers thereof, butanol and isomers thereof, and other water soluble low molecular weight esters, preferably methyl acetate, ethyl acetate, ethyl formate, dimethyl carbonate, esters of carbonic acid and mixtures thereof, in an amount from 1 to 10%, by weight with respect to the total weight of the composition; iii. optionally, at least one surfactant selected from coco-glucoside, alkyl polyglucoside, glyceryl oleate, a linear sodium alkylbenzene sulfonate, sodium lauryl sulfate, sodium lauryl ether sulfate, soy lecithin, soy lysolecithin, and relative mixtures from 1 to 7%, by weight with respect to the total weight of the composition; and iv. optionally, at least one apolar solvent, such as limonene or another terpene analog thereof, citral, tetrachloroethylene, carbon tetrachloride, other halogenated solvents mixed with at least one surfactant iii, mixed with soy lecithin, soy lysolecithin, and possible mixtures thereof in an amount from 0.3 to 10%, by weight with respect to the total weight of the composition.

9. The composition according to claim 8, further comprising one from acetic acid, sodium chloride and mixtures thereof, where the acetic acid is comprised in an amount from 3 to 8% by weight, the sodium chloride is comprised in an amount from 10 to 30% by weight, wherein all the percentages relate to the weight of the component with respect to the total weight of the composition.

Description

EXAMPLE 1

[0059] 20 litres of cleaning composition according to the present invention comprising citric acid at the concentration of 20% by weight, ethyl alcohol at the concentration of 1-2% by weight, was tested on a machine of about 40 m.sup.3 volume, contaminated by radioactivity.

[0060] Through a cleaning treatment with an electropolisher, such composition allowed the removal of all the oxides formed during the operation of said machine located at the SORIN (now Livanova) nuclear waste storage site in Saluggia (Italy) and of all the carbonates, bringing the machine back to a “brilliant” polished state.

[0061] During such decontamination process, for each of the radioisotopes mentioned below, the following decontamination factors were reached after every single application with the electropolisher: [0062] .sup.137Cs>>60, .sup.60Co>>400, .sup.241Am>>50, .sup.90Sr>15, .sup.99Tc>20-100

[0063] At the end the machine was released, without radioactive prescriptions, as it complied with the following release limits:

TABLE-US-00001 Smear test Gamma spectrometry 1)Isotope Limits (Bq/cm.sup.2) Limits (Bq/g) .sup.137Cs 0.37 1 .sup.60Co 0.37 1 .sup.241Am 0.1 1 .sup.90Sr 0.37 1
and complied with the limit expressed by the following summation

[00001]${.Math.}_i.Math.\frac{\mathrm{Measurement}.Math..Math.\mathrm{of}.Math..Math.\mathrm{isotope}.Math..Math.i.Math..Math.\mathrm{Smear}.Math..Math.\mathrm{test}}{\mathrm{Limit}.Math..Math.\mathrm{of}.Math..Math.\mathrm{isotope}.Math..Math.i.Math..Math.\mathrm{Smear}.Math..Math.\mathrm{test}}\le 1$