No abstract available

[en] A one-day Seminar on Long Term Research into Liquid Waste Treatment was held at Harwell on 30th January 1986. The Seminar was sponsored by the Department of the Environment and was attended by ninety-five delegates representing industry, universities, DoE, CEGB and the AEA. The purpose of the meeting was to provide an opportunity for people working in the field of liquid effluent treatment to obtain up-to-date information on the nature and status of research being carried out in the United Kingdom. Nine presentations on research activity described work being undertaken on ultrafiltration and associated techniques, electrical processes and ion exchange. The presenters were from BNF plc, CEGB, Imperial College, University of Salford, University of Reading and from Harwell. (author)

[en] The use of seeded ultrafiltration for the treatment of radioactive waste streams arising from the nuclear industry has demonstrated its high potential as an efficient process for the removal of radionuclides present in the rad waste streams. The experimental data on simulated mining streams has given indications on the suitability of this technique for the treatment of mining waste streams. The results also show that proper choice of absorbers can reduce not only the radioactivity level but also remove most of the products of both the thorium and uranium decay series. Decontamination factors (D F) for the system using manganese dioxide (Mn O₂) are only slightly affected by the preparation method. On the contrary, the D F achieved using titanium hydroxide (HTiO) absorber was found to be dependent on the preparation method. The experimental data shows that total activity levels can be reduced to below to below detection limit (3 E-3 Bq/ml). The extent of decontamination of thorium containing waste streams was found to be dependent on the absorber used; in the order diuranate > HTiO> Fe(OH)₃> Mn O₂. The use of HTiO reduced the decay product activity of almost all the thorium daughters to nearly background levels. A D F of the order of 300 can easily be achieved using diuranate floe. 10 fig., 5 tab

[en] Six absorber materials supplied by Dr M J Hudson of the Department of Chemistry, University of Reading, have been tested in batch contact experiments to assess their effectiveness in removing radionuclides from simulated waste streams at pH 9 and 4. The absorbers were prepared at Reading University under a contract placed by Her Majesty's Inspectorate of Pollution. All the absorbers showed a good affinity for some of the radionuclides present in the waste streams. A modified goethite developed for the adsorption of the pertechnetate ion gave ∼ 80% removal in a twenty four hour contact. (Author)

[en] This invention concerns a process for decontaminating very radioactive liquid effluents from the dissolving of magnesium alloy fuel element claddings in a nitric medium. This process enables the treated effluents to be discharged into the sea and, at the same time, to concentrate into a solid phase the very radioactive elements and, among them, the actinides and the fission products. This concerns the precipitation of the bodies contained in the cladding digesting solutions. These are produced, one after the other, with decanting of the precipitates until a liquid phase suitable for removal to the sea is achieved

[en] Liquid radioactive effluents are decontaminated by stop-wise coprecipitation of sediments. These coprecipitates possess, in addition, the additional capacity for adsorption of further ions. They are added prior to the precipitation of fresh effluent to remove some of the radionuclides. Following separation of the precipitates the above procedure is followed. (WI)

[en] In the treatment of wastes, such as liquid radioactive effluents, it is known to remove radionuclides by successive in situ precipitation of cobalt sulphide, an hydroxide, barium sulphate and a transition element ferrocyanide, followed by separation of the thereby decontaminated effluent. In this invention, use is made of precipitates such as obtained above in the treatment of further fresh liquid radioactive effluent, when it is found that the precipitates have additional capacity for extracting radionuclides. The resulting supernatant liquor may then be subjected to a further precipitation treatment such as above. Decontamination factors for radionuclides of Ce, Ru, Sr and Cs have been considerably enhanced. (author)

[en] This report reviews the processes presently available for the decontamination of alpha-bearing waste effluents. Evaporation, chemical precipitation, organic and inorganic ion exchange, solvent extraction, ultrafiltration, electrical and microbiological processes are considered in turn. Each type of process and its applications in the nuclear industry are briefly described together with the results from any recent development studies. From the information available the advantages and limitations of the process for alpha removal to low-levels (10^-2-10^-3 Bq/msup(l)) are assessed. It is concluded that no single process is capable of removing the actinides to these very low levels but that this level of decontamination should be achieved by the use of two or more processes either sequentially or in combination; e.g. the use of ultrafiltration or precipitation processes in combination with finely divided inorganic ion exchange materials. Processes involving a good solid-liquid separation, such as ultrafiltration appear to be the most appropriate for actinides which show a tendency to hydrolyse and form colloids. However, there is very limited information available on the removal of actinides by such processes, particularly at levels < Bq/ml. Electrical and biological processes are not yet sufficiently developed for their potential to be properly assessed. (author)

[en] The use of seeded ultrafiltration for the treatment of waste streams arising from the nuclear research activities of the developing countries has demonstrated its high potential as an efficient process for the removal of radionuclides present in the rad waste stream. The results also show that the proper choice of absorbers can reduce the radioactivity levels to below the authorised discharge limits of most of these radionuclides. Decontamination factors (D F) for the system using titanium hydroxide (HTiO) absorber are in the order of 10 at PH 7. The combined effect of (HTiO) and preformed nickel hexacyanoferrate(II) (NiFCN) gave higher DFs of about 40 for Hg-203 and Cs-137, about 300 for Zn-65 but less than 10 for Co-60. The use of NiFCN prepared in-situ improved the D F, of Co-60 (higher than 300), while D F for Cs-137 was slightly reduced to about 30. The highest DFs for nearly all the radionuclides under investigation was achieved by using a combination of NiFCN prepared in-situ and NiFCN slurry. Key words: Decontamination, Co-60, Zn-65, Sr-90, Cd-109, Cs-137 and Hg-203, inorganic absorbers, ultrafiltration.1 fig., 1 tab

[en] Inorganic ion-exchange materials supplied by the Duratek Corporation, Maryland, USA have been tested in batch contact experiments to assess their effectiveness in removing radionuclides from aqueous solutions. The three absorbers tested, D10, D70 and D190, showed an affinity for all fourteen radionuclides present in the test solutions. (author)