Study on Volume Reduction of Contaminated Soil by Radioactive Cesium Using Magnetic Separation
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This study intends to develop a new volume reduction method of the soil that is contaminated by radioactive cesium. The volume reduction process by the magnetic separation method is described as follows. First, the soil constituent particles with different particle sizes such as gravel, sand and clay are separated by classification. In this method, the clay, which mainly adsorbs cesium, is separated from the soil. Then, the magneto-Archimedes method is applied to the clay, that utilizes the difference of magnetic susceptibility of substances. The clay minerals consist of two principle types, 1 : 1 and 2 : 1 type. The 1 : 1 type clay mineral is diamagnetic and weakly adsorbs small amount of cesium, whereas the 2 : 1 type clay mineral is paramagnetic and strongly adsorbs a large amount of cesium. The recovery of paramagnetic 2 : 1 type clay mineral by superconducting magnet enables selective separation of high-dose soil. It will reduce the volume of contaminated soil. In this study, the separation of 1 : 1 and 2 : 1 type clay mineral by the magneto-Archimedes method was investigated. It was confirmed that it was possible to separate between 1 : 1 and 2 : 1 type clay mineral effectively. Based on the result, the magneto-Archimedes method was applied to the actual contaminated soil in Fukushima. It was shown that there was a possibility that the volume reduction of contaminated soil could be reduced.Keywords:
Caesium
Magnetic separation
Human decontamination
Diamagnetism
Three decontamination solutions of beta-cyclodextrines were prepared. Their abilities to decontamine rat skin contamined with nerve agent soman were tested. Decontamination efficacy of the tested cyclodextrine solutions was compared with the same decontamination means but without the cyclodextrines. The efficacy of tested decontaminants was evaluated by the assessment of the ID50 values. Two decontamination prescriptions with cyclodextrines (tetraborate buffer and tetraborate buffer with acetone) do not show significantly better decontamination efficacies in comparison with prescriptions without cyclodextrines. Only in case of aqueous solution of 2-aminoethanol the addition of beta-cyclodextrine resulted in significant increase (32%) in decontamination efficacy.
Human decontamination
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Living 4-6 week-aged San Yuan white pigs (Suzhou,China) were used in skin decontamination experiments. Following a standard procedure, SM series of decontamination agents were used for decontamination of liquid nuclides. The results of immediate decontamination were as follows: K (decontamination efficiency) =97. 7% (decontamination factor DF = 43. 5) for 131I;K99% (DF100) for 90Sr/90Y,MFP and U+TRU; K =99. 9% (DF = 1000) for 137Cs.In 3 h-delayed decontamination,DF = 27-67 ( K = 96. 3%-98.5%) for the nuclides mentioned above. When the initiatory MFP contamination increased from 20 to 300 s-1 ?cm-2,the value of DF by immediate decontamination increased from 20 to 173 with the remaining activity not higher than 10 Bq ?cm-2,and no additional decontamination was needed. For radioactive ash contamination of skin,DF = 57-1000 ( K=98. 2% - 99. 9%) in 4 h-delayed decontamination. SM series of decontamination agents are neutral liquid or cream without any irritative effect on skin. They are effective and easy to use in skin decontamination.
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The preliminary experiment was performed to obtain the operating conditions of soil washing decontamination process such as decontamination agent, decontamination temperature, decontamination time and ratio of soil and decontamination agent. To estimate decontamination efficiency, particle size of soil was classified into three categories; ≥ 2.0 mm, 2.0 ~ 0.21 mm and ≤ 0.21 mm. Major target of this experiment was decontamination of Cs-137. The difference of decontamination efficiency using water and neutral salts as decontamination agent is not high. It is concluded that the best temperature of decontamination agent is normal temperature and the best decontamination time was about 60 minutes. And the best ratio of soil and decontamination agent is 1:10. In case of Cs decontamination for fine soils, the decontamination results using neutral salts such as Na2CO3 and Na3PO4 shows some limits while using strong acid such as sulfuric acid or hydrochloric acid shows high decontamination efficiency(≥ 90%). But we conclude that decontamination using strong acid is also inappropriate because of the insufficiency of decontamination efficiency for highly radioactive fine soils and the difficulty for treatment of secondary liquid waste. It is estimated that the best decontamination process is to use water as decontamination agent for particles which can be decontaminated to clearance level, after particle size separation.
Human decontamination
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Living 4-6 week-aged San Yuan white pigs (Suzhou, China) were used in skin decontamination experiments. Following a standard procedure, SM series of decontamination agents were used for decontamination of liquid nuclides. The results of immediate decontamination were as follows: K(decontamination efficiency) = 97. 7% (decontamination factor DF = 43. 5) for 131I; K 99% (DF100) for 90Sr/90Y, MFP and U+TRU; K =99. 9% (DF = 1000) for 137Cs. In 3 h-delayed decontamination,DF = 27-67 ( K =96. 3%-98. 5%) for the nuclides mentioned above. When the initiatory MFP contamination increased from 20 to 300 s-1 . cm-2, the value of DF by immediate decontamination increased from 20 to 173 with the remaining activity not higher than 10 Bq . cm-2, and no additional decontamination was needed. For radioactive ash contamination of skin, DF=57-1000 ( K =:98. 2%-99. 9%) in 4 h-delayed decontamination. SM series of decontamination agents are neutral liquid or cream without any irritative effect on skin. They are effective and easy to use in skin decontamination.
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This chapter contains sections titled: Introduction Animal Washing Dehairing Spot-Carcass Decontamination Treatments Pre-Evisceration Decontamination Final Carcass-Washing Thermal Decontamination Chemical Decontamination Multiple Decontamination Interventions Chilling Post-Chilling Decontamination Treatments Overview of Practical Improvements Achieved by Decontamination Potential Concerns and Risks Associated with Decontamination Legislative Aspects of Decontamination Future Trends References
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This article analyzes the data on chemical decontamination methods dealing with radioactively contaminated surfaces. It considers the composition of solutions most commonly used for decontamination purposes. Numerical data are presented to illustrate the effectiveness of various decontamination methods. The paper considers an experiment on the decontamination of stainless steel samples with water following a cavitation treatment. The study reveals a dependence between the decontamination efficiency and the treatment time of the contaminated surface with a decontamination solution based on cavitation-activated water, which appears to be comparable with the results of the one involving an alkaline solution.
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In previous work on diamagnetism the author has brought forward evidence that the magneton may prove to be a constituent of diamagnetic as well as of paramagnetic and ferro-magnetic matter. Certain properties of diamagnetic crystalline media can be interpreted as due to the effects of intense local intermolecular forces which if interpreted magnetically are comparable with the Weiss molecular field in ferro-magnetic substances. This suggests the possibility that in the molecules of diamagnetic substances there may be elements of magnetism arranged in such a way that the molecule is self-compensated, so that experimentally the effect of applying an external magnetic field gives a diamagnetic effect only.
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This report documents the results of a test of the New Calcining Facility (NWCF) process decontamination system. The decontamination system test occurred in December 1981, during non-radioactive testing of the NWCF. The purpose of the decontamination system test was to identify equipment whose design prevented effective calcine removal and decontamination. Effective equipment decontamination was essential to reduce radiation fields for in-cell work after radioactive processing began. The decontamination system test began with a pre-decontamination inspection of the equipment. The pre- decontamination inspection documented the initial condition and cleanliness of the equipment. It provided a basis for judging the effectiveness of the decontamination. The decontamination consisted of a series of equipment flushes using nitric acid and water. A post-decontamination equipment inspection determined the effectiveness of the decontamination. The pre-decontamination and post-decontamination equipment inspections were documented with photographs. The decontamination system was effective in removing calcine from most of the NWCF equipment as evidenced by little visible calcine residue in the equipment after decontamination. The decontamination test identified four areas where the decontamination system required improvement. These included the Calciner off-gas line, Cyclone off-gas line, fluidizing air line, and the Calciner baffle plates. Physical modifications to enhance decontamination were made to those areas, resulting in an effective NWCF decontamination system.
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This report documents the results of a test of the New Calcining Facility (NWCF) process decontamination system. The decontamination system test occurred in December 1981, during non-radioactive testing of the NWCF. The purpose of the decontamination system test was to identify equipment whose design prevented effective calcine removal and decontamination. Effective equipment decontamination was essential to reduce radiation fields for in-cell work after radioactive processing began. The decontamination system test began with a pre-decontamination inspection of the equipment. The pre-decontamination inspection documented the initial condition and cleanliness of the equipment. It provided a basis for judging the effectiveness of the decontamination. The decontamination consisted of a series of equipment flushes using nitric acid and water. A post-decontamination equipment inspection determined the effectiveness of the decontamination. The pre-decontamination and post-decontamination equipment inspections were documented with hotographs. The decontamination system was effective in removing calcine from most of the NWCF equipment as evidenced by little visible calcine residue in the equipment after decontamination. The decontamination test identified four areas where the decontamination system required improvement. These included the Calciner off-gas line, Cyclone off-gas line, fluidizing air line, and the Calciner baffle plates. Physical modifications to enhance decontamination were made to those areas, resulting in an effective NWCF decontamination system.
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The paper presents research of the process of decontamination of chemical protection suits. The results of the research show the effectiveness of selected decontamination techniques. In experiments took into account the influence of the contaminant, the time of decontamination, the type of the decontamination agent and the use of mechanical support in removing the contaminant. The research has shown how to minimize the negative action of hazardous substances on protective clothing and show the problem of the possibility of secondary contamination. They demonstrate the impact of each factors on the quality of decontamination and showed that small changes in the process of decontamination significantly affect the safety of the rescuer. The key to effective decontamination is the synergy effect of the studied parameters. This approach will allow efficient and effective execution of the decontamination process, minimize the risk of contact between rescuers and the contaminant and prevent secondary contamination.
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