IL30424A - Process for decontaminating radioactive objects - Google Patents

Description

Process for objects 30424 2 2 Linen and other material used in nuclear equipments must be cleaned and decontaminated very thoroughly in order to be employed The washing effluents must then be purified before being The usual detersives do not appear efficient enough for this It has therefore been proposed to use products containing very strong for of under the action of these the lose their properties and the washing effluents containing them cannot be subjected to Neither is their treatment by evaporation p raotically because the presence of substances considerably decreases the output of the The invention consists in a process for the tion of radioactive the washing effluents of which are easily This process uses the completing properties of acids and in particular those of the acid commercialised under the name of by Monsanto Chemical These acids form with the ions having a valency equal or higher complexes su iciently s table to maintain them in solution in a slightly neutral or alkaline but le enough to permit of the for by an excess of precipitating The invention consists in for the mination of wherein the objects to be in deionized of a mixture of a preferably entirely for a heavy alcohol with a straight ethoxylated and a nearly neutral sodium salt of an and the effluent is purified after the addition of calcium by or by treatment with zeolites The s ur substances most suitable in the process according to the invention are preferably biodegradable products such ethoxylation products of higher alcohols having straight such as commercialized by the Alcohol sulphates and also give good Surf substances which are or only partially biodegradable can also be Such substances are the sulphates or ethoxylated derivatives of polypropylene such as commercialis ed by the ethoxylated and also the ethoxylated and projoxylated derivatives of such as also by the A starting solution is prepared from deionized containing from 5 to 500 g of acid and from 10 to 500 of substance per liter of This solution is neutralized with sodium hydroxide to a pH of from 7 to and constitutes the mother The washing solution is obtained by dilution to about of the mother liquor preferably with deionized if such as optical are The concentration of the washing liquid is evidently adapted to the degree of staining of the objects to be The soaking of the objects may accompanied by a strong The of decontamination obtained by this process is very After the of the decontaminated controlled with conventional control is no longer discernible from the radio activity of the background by the The activity the effluents resulting from the washing has generally a low or medium value of 10 to the effluent there is added calcium in the form of nitrate or chloride up to concentration sufficient for displacing the rare earths and the strontium from their complexes with the amount of calcium ion introduced is generally smaller than gram equivalent per liter of solution but this amount is not The solution is purified in the usual for by coprecipitation by treatment with this latter treatment having a high The following examples relate to the decontamination of two kinds of objects used in nuclear installations and to the treatment of the resulting EXAMPLE 1 Washing of linen A starting solution in deionized water containing 50 g of Plurafac 20 alcohol and 50 g of acid per liter of solution was prepared and neutralized by addition of sodium This mother liquor was then diluted ten t imes heated to a temperature of 80 to and used for the washing of At the end of the washing Decontamination of laboratory material This comprised stainless nylone polyvinyl porcelai and glass As concerns care been taken dip it inaaediately after a condition ofefficient The starting solution in contained 40 g of Plurafac alcohol and 70 of acid per liter of solution and was neutralized with sodium hydroxide to give a mother liquor of a pH between 7 and The mother liquor was washing to concentration with water to form which was heated to The soaking was accompanied by damp brushing of After this the control instruments did indicate a of the decontaminated the of the Decontaminatio of the resulting effluent The effluent solution obtained in had a im apparent activity of was measured with device having a very lew background counting fitted with a large gas flow ani small g of calcium of were and the solution was divided into three each which purified The first after treatment b precipitation of calcium had an apparent activity o The decontamination factor obtained was The second after treatment by precipitation She third after treatment with a and had an apparent activity of 128 decontamination factor obtained was insufficientOCRQuality

Claims (3)

1. CLAIMS 1. A process for the decontamination of radio-active objectsf xfherein the objects to be decontaminated are washed with a aqueous solution, preferably in deionised water, of a mixture of a surface-active substance and a nearly neutral salt of an o-amino-(alkyl-phosphonic) acid, and the effluent is purified, after the addition of calcium ions, by coprecipitation or by treatment with zeolites.
2. 2. A process according to Claim 1, wherein the ffi-amino-(alkyl-phosphonic) acid used is anino-tri (methyl-phosphonic) acid or one of its homologues.
3. 3. A process according to Claim 1, wherein the surface-active s bstance used is biodegradable. 4· A process according to Claim 3, wherein the surface-active substance used is a higher alcohol with a straight ethoxylated chain. 5· A process according to any of the preceding claims wherein a solution in deioniaed water, containing 10 to 500 g/l each of α-amino (alkyl-phosphonic) acid and a surface-active substance, is neutralized w ith sodium hydroxide to a pH of from 7 to 7o5? then diluted, preferably with deionized vrater, to a concentration of 10$; the objects to be decontaminated are washed with this solution and the effluent is prified. β· A process according to Claim 5, wherein disinfectants and/or optical brighteners are added to t he w shing solution prior to washing. 7. A process according to Claim 1, wherein the amount of calcium ions added is below or equal to 1/100 gram-equivalent per liter of effluent. 8. A process for the decontamination of radio-active objects, substantially as cbsnribed herein with reference to the Examples. For the Applicants ND:BH