Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/001—Decontamination of contaminated objects, apparatus, clothes, food; Preventing contamination thereof
  • G21F9/002—Decontamination of the surface of objects with chemical or electrochemical processes
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/28—Treating solids
  • G21F9/30—Processing

Definitions

• This invention relates to a method of separating radionuclides from contaminated material, for example construction debris.
• the method according to the invention is suitable for isolating material which is not or only slightly contaminated with high selectivity from the total volume of the contaminated material, ie for removing contaminants (radionuclides) or contaminated material phases almost completely.
• the volume of such material which requires a particularly complex and thus particularly cost-intensive disposal and storage, can be significantly reduced, which is also very advantageous in view of the very limited storage reserves.
• the no longer or only slightly contaminated material can be disposed of under less stringent safety requirements or recycled and reused accordingly.
• radioactive material such as rubble or graphite
• Strict safety regulations must be adhered to, so that the requirements for containers and deposits of radioactive material cause very high costs.
• the object of the invention to provide a method which makes it possible to release radionuclide-contaminated material, for example building rubble, from the contaminants (radionuclides) with high selectivity. s.
• the term "contaminated” is used according to the invention synonymously with the term "contaminated with radionuclides".
• the contaminated material contains Cs-137 and / or Co-60 and / or Sr-90 + and / or Pu-239 and / or U-235 and other radioactive isotopes of uranium and / or Th-232 and other radioactive isotopes of thorium, and / or Pb-203 and other radioactive isotopes of lead, and / or C-14 and / or CI-36.
• radionuclides there may be any other radionuclides in the material. If one of the aforementioned radionuclides is present in the material, it may be a single one. It is also conceivable that mixtures comprising at least two or more of said radionuclides are present in the material. Moreover, such mixtures may also comprise other radionuclides which are not explicitly mentioned here.
• the present radionuclides are especially CI-36 and / or C-14. Also conceivable are radionuclides selected from one or more of Cs-137, Co-60, and Sr-90 +.
• Contaminated graphite may include radionuclides of uranium, thorium and / or plutonium.
• the method described herein and claimed for the separation of radionuclides from contaminated material achieves the above object.
• the term "removal of radionuclides” it is meant according to the invention that the contaminated material isolates a material which is not or only slightly contaminated according to the invention as decontaminated, ie the contaminated material is separated by the process according to the invention into decontaminated material and contaminated residue, which usually occupies a relatively small volume.
• the person skilled in the art knows what is meant by uncontaminated, slightly contaminated and contaminated. He will consider his general expertise and relevant rules known to him. Such a set of rules is, for example, an applicable radiation protection ordinance with installations.
• total activities of ⁇ 40 Bq / g are a value that may correspond to a low level of contamination. It is also known to those skilled in the art that the values of the total activity and the classification based thereon are highly dependent on the particular radionuclide causing the contamination.
• weak contamination examples are ⁇ 10 Bq / g, ⁇ 7 Bq / g, ⁇ 6 Bq / g, 1 Bq / g, ⁇ 0.6 Bq / g, 0.5 Bq / g, ⁇ 0, 1 Bq / g, ⁇ 0.04 Bq / g, ⁇ 0.004 Bq / g, -S 0.003 Bq / g.
• the contaminated residue comprises the contaminants (radionuclides) in isolated form.
• the contaminated residue may additionally comprise contaminated material phases.
• the contaminated residue may also include fractions of contaminated material phases with differing contamination.
• the method according to the invention makes possible an almost complete separation of the contaminated material into decontaminated material and contaminated residue, ie an almost complete removal of the radionuclides according to the invention.
• Typical contaminated material is, for example, graphite, in particular as obtained in the dismantling of nuclear power plants. In this material, the content of radionuclides compared to the total volume of the material is relatively low. To date, however, the total volume of a proper disposal must be supplied as nuclear waste.
• Graphite is commonly used in nuclear reactors in a high density form.
• rubble comes into question as contaminated material.
• this contains material phases which are contaminated to different degrees, that is to say they are loaded to different degrees with contaminants, namely a gravel phase which is not or only slightly contaminated and a contaminated cement phase.
• the contaminated material is preferably selected from graphite, rubble or mixtures thereof.
• Contaminated construction waste in particular profits from the process according to the invention, because with the process according to the invention, in the case of contaminated construction waste, the amount of material which is to be stored under strict safety precautions can be reduced particularly markedly.
• the method according to the invention makes it possible to isolate the material phases that are not or only slightly contaminated, in particular the gravel phase, from the contaminants and contaminated material phases, in particular the cement phase.
• rubble is used as contaminated material.
• the contaminated material is, in particular, building rubble, as is the case in the dismantling of nuclear power plants or nuclear facilities for the open handling of radionuclides.
• the building rubble may also contain other phases and / or components, such as metals. These can likewise be separated off effectively by the process according to the invention.
• the method according to the invention it is possible to separate the small volume of radioactive residue, ie of contaminants and optionally contaminated material phases, from the total volume of the contaminated material with high selectivity and thus to isolate decontaminated material. As a result, only the usually relatively small volume of contaminated residue needs to be disposed of in a costly manner.
• the decontaminated material that is, the not or only slightly contaminated material can be fed to a less expensive disposal.
• the process according to the invention is a process for the separation of radionuclides from contaminated material, for example building rubble, with the steps
• the contaminated material into at least one contaminated material phase and at least one non-contaminated or only slightly contaminated material phase; for example, cement phase and gravel phase in the case of rubble as contaminated material;
• the fact that the container has a first and a second electrode does not mean that the electrodes are a component of the container. They can also be designed so that they are hung in the liquid or otherwise in the Protrude container.
• the container preferably comprises a non-conductive material, in particular plastic. Polyethylene has proven to be particularly suitable.
• the container is preferably located in a reactor.
• the separation of the radionuclides from contaminated material thus according to the invention comprises a step in which at least one voltage pulse is generated between the electrodes, so that the contaminated material is comminuted in the liquid, with contaminants (radionuclides) accumulate in the liquid.
• a separation of the contaminated material in at least one contaminated and at least one or only weakly contaminated material phase followed, in particular a separation in not or only slightly contaminated gravel and contaminated cement phase, for example, if the contaminated material is rubble.
• a separation in not or only slightly contaminated gravel and contaminated cement phase for example, if the contaminated material is rubble.
• the entirety of the constituents of a material is referred to, which shows the same physical and chemical properties and differs from other material components of a material.
• Material phases are, for example, gravel and cement, which are contained in rubble.
• Contaminated building rubble as a preferred contaminated material thus includes the material phases gravel and cement, which have a different degree of contamination due to the different properties.
• the radionuclides from the cement phase are often not released sufficiently into the liquid in the process according to the invention can.
• the process of the invention preferably comprises the process step of separating the contaminated material into contaminated and non-contaminated or slightly contaminated material phases, more preferably into contaminated cement phase and unimpacted or poorly contaminated gravel phase.
• the process of the invention further comprises the step of separating solid and liquid components, preferably by separating off the liquid constituents.
• the liquid components according to the invention comprise the liquid and radionuclides from the contaminated material.
• the solid constituents comprise the material which is not or only slightly contaminated, for example gravel or decontaminated graphite.
• the solid constituents further contain the contaminated material phase, for example cement.
• the separation of the solid and liquid constituents is preferably followed by a step for separating the non-contaminated or only weakly contaminated material phase from the contaminated material phase, preferably by sieving. If the contaminated material is rubble, the solid constituents contain gravel and cement phase, wherein after separation of the solid and liquid constituents, the gravel phase is preferably separated from the cement phase, ie material phase which is not or only slightly contaminated is separated from contaminated material phase. This is preferably done by sieving.
• the method according to the invention further comprises, after the step of separating the solid from the liquid constituents, a step comprising isolating the radionuclides from the liquid constituents. After isolation of the radionuclides, proper disposal of the radionuclides may be followed as radioactive waste.
• the inventive method uses the technique of electrodynamic fragmentation, as described in DE 195 34 232 A1.
• the application DE 195 34 232 A1 is hereby incorporated by reference completely in this description.
• a shock wave is generated in the contaminated material by the voltage pulse generated between the electrodes. This shock wave ensures that the contaminated material is crushed.
• the use of the technique of electrodynamic fragmentation is particularly advantageous and allows almost complete separation of the radionuclides from the contaminated material.
• lower discharge currents and energy consumption are required, which on the one hand enables a cost-effective process management and on the other hand protects the components.
• the comminution of the contaminated material with high selectivity first takes place at grain or phase boundaries.
• the method according to the invention provides for the comminution of the contaminated material by electrodynamic fragmentation leads to selective comminution of the material along the grain boundaries.
• the radionuclides can be released and accumulate in the liquid.
• the liquid ingredients can then be easily separated from the solid ingredients and the radionuclides can be isolated from the liquid ingredients.
• selective separation in material phases can be made possible, in particular in a not or only slightly contaminated coarse gravel phase and a contaminated fine-grained cement phase, for example when the contaminated material is rubble. It is inventively preferred that the contaminated material is rubble.
• the liquid used has to meet some requirements: it has to have only a very low conductivity and, in addition, a sufficient solubility for radionuclides.
• Water, halogenated hydrocarbons and silicone oils and mixtures thereof have proven to be suitable liquids. Consequently, the liquid preferably comprises water, halogenated hydrocarbons and / or silicone oils.
• the halogenated hydrocarbons are preferably chlorinated and / or fluorinated alkanes. Particularly preferred is water, because water is inexpensive and the disposal of the water causes no major problems.
• the liquid should have as few dissolved ions as possible otherwise the conductivity could rise too high.
• the use of deionized water has proved to be particularly advantageous.
• solubilizers can be added to the liquid.
• solubilizers preferably complexing agents, surfactants or mixtures thereof are used.
• the complexing agents directly increase the solubility of the radionuclides by complex formation, while the surfactants improve the wettability of the contaminated material. In addition, they reduce the conductivity.
• the surfactants can promote foaming. This is normally not desired.
• a possible fine fraction, in particular a cement phase are removed from the liquid.
• the flotation step preferably follows the comminution of the contaminated material and the optional separation of the material into the material phases.
• Another preferred additive to the liquid is a further water-immiscible liquid phase, in particular an organic oil or a mixture of organic oils.
• This further phase preferably contains a
• Silicone oil and / or an alkane having a chain length of at least 6 and at most 18 carbon atoms e.g. Dodecane, which forms an emulsion through the added surfactants and extracts the complexed ions from the aqueous phase, thus further reducing the conductivity of the liquid.
• the further liquid phase is preferably added to the liquid in a concentration of not more than 50% by volume, more preferably a maximum of 20% by volume.
• the minimum content of the further liquid phase in the liquid is preferably at least 1% by volume, more preferably at least 5% by volume and particularly preferably at least 0% by volume.
• the liquid can thus be two-phase, in particular an emulsion.
• Preferred complexing agents are organic complexing agents, in particular nitrilotriacetic acid (NTA), ethylene glycol bis (aminoethyl ether) -N, N'-tetraacetic acid (EGTA), ethylenediamine disuccinic acid (EDDS),
• NTA nitrilotriacetic acid
• EGTA ethylene glycol bis (aminoethyl ether) -N
• EGTA N'-tetraacetic acid
• EDDS ethylenediamine disuccinic acid
• Ethylenediaminetetraacetic acid citric acid, polycarboxylates, oxalic acid, carbamoylmethylphosphine oxide (CMPO), crown ethers, and mixtures thereof.
• CMPO carbamoylmethylphosphine oxide
• Particularly preferred complexing agents are CMPO, crown ether, oxalic acid and mixtures thereof.
• the surfactants are preferably organic molecules, in particular they are nonionic surfactants.
• the complexing agents are preferably used in a concentration of at least 0.0001 mol / l, more preferably at least 0.001 mol / l, and particularly preferably at least 0.01 mol / l. Below these values, the effect is not very pronounced. Nevertheless, the content of these substances should not exceed values of preferably not more than 1 mol / l and more preferably not more than 0.1 mol / l. If too much complexing agent is used, the conductivity of the liquid increases.
• the surfactants are preferably used in a concentration of at least 0.00005 mol / l, more preferably at least 0.002 mol / l, and particularly preferably at least 0.01 mol / l. Below these values, the effect is not very pronounced. However, the content of these substances should not exceed values of preferably at most 1 mol / L, and more preferably at most 0.05 mol / L. If too much surfactant is used, the liquid tends to foam very heavily, which can lead to contamination of other parts of the system.
• oxidizing substances Another preferred additive in the liquid is oxidizing substances.
• the oxidizing substances increase the cleaning effect, because the surface of the contaminated material is partially oxidized and thus chemically bonded elements are better detached.
• the oxidizing substances are preferably used in concentrations of at least 0.0001 mol / l, more preferably at least 0.01 mol / l and particularly preferably at least 0.05 mol / l. Below these values, the effect is not very pronounced. However, the content of these substances should not exceed values of preferably at most 2 mol / l, and more preferably at most 0.1 mol / l. If too high a concentration of oxidizing substances is used, the container is attacked, which reduces the life of the system.
• Preferably used oxidizing substances are organic peroxides, chromates, manganates and mixtures thereof. Organic peroxides are particularly preferred oxidizing substances because the conductivity of the liquid is only slightly affected.
• the cleaning efficiency is particularly high when the pH of the liquid is chosen to be either very high or very low.
• the pH is in a range of 0.5 to 3 or in a range of 9 to 12.
• the liquid consists of water, more preferably deionized water, and most preferably does not contain any additives such as solubilizers, oxidizing substances or substances for pH adjustment. This is additionally advantageous since the process can then proceed more cost-effectively and the resulting liquid constituents can also be easily disposed of and recycled after isolation of the radionuclides without further processing.
• the number of voltage pulses used depends on the material to be decontaminated. Typically, at least 5 voltage pulses will be necessary, preferably even at least 50 or at least 100 voltage pulses, and more preferably at least 600 voltage pulses. In order not to crush the material too much, that is across the grain boundaries, the voltage pulses should be limited to a number of at most 10,000, more preferably at most 5,000, and most preferably at most 1,500 his. If the material is comminuted across the grain boundaries, the particle size of the material becomes so small that these particles, when separated into liquid and solid components, enter the liquid constituents. This affects the cleaning efficiency.
• the duration of a voltage pulse is preferably at least 1 ns and at most 1 ms, in particular at least 100 ns and at most 100 ⁇ .
• the voltage pulses preferably act on the material at a frequency of at least 0.5 Hz, more preferably at least 1 Hz and more preferably at least 3 Hz.
• this frequency is at most 1 kHz, more preferably at most 500 Hz, more preferably at most 100 Hz and particularly preferably at most 50 Hz.
• the comminution is preferably carried out with an energy of at least 10 and at most 300 J / cm.
• the voltage pulses have average voltages of preferably at least 50 kV, more preferably at least 100 kV, and most preferably at least 140 kV. Otherwise, depending on the material often does not take place sufficient comminution. At the same time, the average stress should not be too high, otherwise crushing will take place beyond the grain boundaries of the material and the equipment will also be severely affected. Therefore, the average voltage is preferably at most 1 MV, and more preferably at most 400 kV.
• the liquid components contain radionuclides from the contaminated material.
• the radionuclides are isolated from the liquid constituents in one process step. Possible methods for isolating the radionuclides from the liquid components are selected from Evaporating the liquid,
• Combinations of these methods can also be used.
• the precipitation and evaporation can then be followed by a filtration step.
• the radionuclides isolated from the liquid components can then be sent for proper disposal.
• the embedding in hollow body made of graphite comes into question.
• waste packages as described in WO 201/17354 A1 and WO 2010/052321 A1 are suitable. Both applications will be fully incorporated into this description by this reference.
• the method according to the invention has the advantage that the comminution of the contaminated material does not take place in the dry state. This prevents dust formation.
• the liquid fulfills the task of preventing the formation of dust and to absorb radionuclides for further processing.
• the method according to the invention provides for the separation of the contaminated material into contaminated and not or only slightly contaminated material phases, in particular into a cement phase and a gravel phase
• these phases of matter can be introduced and disposed of separately in waste packages.
• waste packages as described in WO 2011/17354 A1 and WO 2010/052321 A1 are suitable.
• the number and amplitude of the voltage pulses are chosen so that the contaminated material is comminuted along its grain boundaries.
• no comminution should take place, in particular essentially no CC bonds are split.
• Example 1 437 g of building rubble were treated with a cement and a gravel fraction having a grain size of between 2 cm and 5 cm with a total ⁇ / ⁇ activity of 187 Bq by the method according to the invention.
• the average voltage was 130 kV, the number of pulses was 16 at a frequency of 5 Hz.
• the following table shows that the rubble was separated into decontaminated material and contaminated residue.
• the fractions of the contaminated residue show different activity.
• the decontaminated material is essentially gravel phase, which has very little activity.
• the mass of the high activity material has been greatly reduced and the unimpaired or only slightly contaminated material can be fed to a simplified disposal.
• Powder had a grain size of 20 to 50 pm.
• Table shows some experimental data:
• a graphite granule with a grain size of 500 pm to 2 mm was placed in a container.
• the graphite granules were loaded with the radionuclide CI-36 in a proportion of 5 pg / kg. It was crushed in water. Thereafter, the water was separated and the present in 10 to 50 pm crushed granules present CI-36 determined quantitatively.
• the CI-36 content was only ⁇ 0.1 pg / kg.
• the following table shows some experimental parameters:

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• 2013
  • 2013-02-13 RU RU2014137171A patent/RU2014137171A/ru not_active Application Discontinuation
  • 2013-02-13 EP EP13703825.3A patent/EP2798645A1/de not_active Withdrawn
  • 2013-02-13 US US14/375,268 patent/US20150025294A1/en not_active Abandoned
  • 2013-02-13 KR KR1020147025007A patent/KR20140135183A/ko not_active Application Discontinuation
  • 2013-02-13 JP JP2014556105A patent/JP2015511316A/ja active Pending
  • 2013-02-13 WO PCT/EP2013/052912 patent/WO2013120919A1/de active Application Filing

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