GB1604371A - Treatment of solids with liquids - Google Patents

Treatment of solids with liquids Download PDF

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Publication number
GB1604371A
GB1604371A GB927077A GB927077A GB1604371A GB 1604371 A GB1604371 A GB 1604371A GB 927077 A GB927077 A GB 927077A GB 927077 A GB927077 A GB 927077A GB 1604371 A GB1604371 A GB 1604371A
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United Kingdom
Prior art keywords
acid
organic substance
reservoir
chamber
substance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB927077A
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UK Atomic Energy Authority
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UK Atomic Energy Authority
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Filing date
Publication date
Application filed by UK Atomic Energy Authority filed Critical UK Atomic Energy Authority
Priority to GB927077A priority Critical patent/GB1604371A/en
Publication of GB1604371A publication Critical patent/GB1604371A/en
Expired legal-status Critical Current

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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
    • G21F9/28—Treating solids
    • G21F9/30—Processing

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Processing Of Solid Wastes (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO THE TREATMENT OF SOLIDS WITH LIQUIDS (71) We, UNITED KINGDOM ATOMIC ENERGY AUTHORITY, London, a British Authority, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the treatment of solids with liquids and finds one application in the destruction of organic substances contaminated with radioactive materials.
According to one aspect of the present invention there is provided a method for digesting or dissolving an organic substance comprising locating the organic substance in a contacting region, directing onto the organic substance an acid capable of digesting or dissolving the organic substance thereby to contact the organic substance with the acid such that organic substance is digested or dissolved by the acid to give liquid containing digested or dissolved organic substance, and draining liquid containing digested or dissolved organic substance from the contacting region.
Preferably the organic substance is supported in a contacting region of a chamber, and liquid draining from the contacting region is collected in a reservoir.
In one embodiment the organic substance is supported by a grid arranged in the chamber so that liquid is removed from the substance by draining through the grid.
Acid for treating the substance may be contained in a reservoir and the reservoir may be in communication with a means for directing acid onto the organic material and also arranged to receive liquid removed from the substance when supported in the chamber.
Acid may be directed onto the organic substance by means of, for example, an air-lift pump incorporating an intake connected with the reservoir and an outlet above the support. The outlet may be in the form of a jet or spray for distributing acid over the substance to be treated.
As an alternative to an air-lift pump a fluidic pump, for example, may be used (e.g. to supply acid to an outlet for distributing acid over the substance to be treated). The fluidic pump may be a "reverse flow diverter".
Reverse flow diverter fluidic pumps are disclosed in British Patent Specification No.
1 480484 (UKAEA). A fluidic pump for use in accordance with the present invention may be, for example, one which operates in the manner of the system shown in Figure 6 of British Patent No. 1 480484.
The chamber may be a closed right circular cylindrical tube arranged with its longitudinal axis substantially vertical such that a lower portion of the tube provides the reservoir.
Thus, in one embodiment the present invention provides for the destruction, by digestion with acid of nuclear wastes comprising organic substances contaminated with a radioactive material or materials.
The digestion of such organic substances may be effected by use of acid comprising an acid such as sulphuric acid or nitric acid or a mixture of acids such as sulphuric acid and nitric acid.
The use of this mixture of sulphuric and nitric acids is well known for the decomposition of organic substances and in this context reference is made by way of example to Chapter 25 " Decomposition and dissolution of samples: organic" in part 1, vol. 2 of "Treatise on Ahalytical Chemistry" edited by I.M. Kolthoff et al (Interscience publishers New York and London). Conveniently the mixture of acids may be used at, for example, a temperature between 230 to 2800C.
According to another aspect of the present invention there is provided an apparatus for carrying out a method in accordance with the invention which apparatus comprises a chamber, a support located within a contacting region of the chamber for supporting an organic substance, access means for permitting introduction of organic substance to the support, a reservoir for containing acid, acid supply means for directing acid at the organic substance when supported in the chamber, said acid supply means including an intake connected with the reservoir, a pump and an outlet located for directing acid at the organic substance, and exhaust means for removing gaseous material from the chamber, the arrangement being such that liquid produced by contacting acid with the substance when supported in the contacting region of the chamber can be removed from the substance and such that liquid removed from the substance is received by the reservoir and the dimensions of the chamber being such as will prevent or discourage the formation of a critical assembly.
Clearly the parts of the apparatus in contact with the acid must be capable of resisting attack thereby and may, for example, be constructed of glass.
Examples of organic substances which may be digested by use of a mixture of sulphuric and nitric acids are naturally occurring substances such as cellulosic substances (e.g. paper) and synthetic substances such as polyvinyl chloride, polyethylene and ion exchange resins.
Where the organic substance is contaminated with a radioactive material which is a fissile radionuclide there is a risk of creating a "Critical assembly" capable of sustaining a nuclear chain reaction thus the dimensions of the chamber are chosen to prevent or discourage the formation of a critical assembly.
Accordingly, in accordance with an embodiment of the apparatus of the present invention for use in destruction of an organic substance contaminated with a radioactive material, the chamber is a right circular cylinder having dimensions such as will prevent or discourage the formation of a critical assembly.
Published data on the appropriate sizes of cylindrical vessels to prevent or discourage the formation of critical assemblies are, for example, to be found in " Engineering for Nuclear Fuel Reprocessing " by J. T.
Long (Gordon & Breach Science Publishers Inc., New York, London and Paris).
It will be appreciated that in accordance with the method of the present invention liquid having a relatively high concentration of digested or dissolved organic substance is removed from the organic substance and replaced by acid containing no, or at least a lower concentration of, digested or dissolved organic substance. Thus, a higher dissolution rate can be achieved as compared with an arrangement in which organic substance to be digested or dissolved is merely placed in a bath of acid.
It is to be understood that small portions of the organic substance may become detached from the main bulk of liquid organic substance being contacted with acid so that removed therefrom may contain organic substance in suspension. The substance in suspension may undergo dissolution or digestion.
The invention will now be further described by way of example only with reference to the single figure of the drawing accompanying the Provisional Specification which is a diagrammatic representation of an apparatus for carrying out a method in accordance with the present invention.
Referring now to the drawing there is provided a chamber 1 inside of which is located a grid support 2. Also there is provided an access port 3 for introducing substance to be treated to the grid support 2, and an air-lift pump 4 having an intake 5 and an outlet 6 for directing, in operation, acid at the substance supported on the support 2.
The chamber 1 is also provided with an outlet 7 for the removal of gaseous materials therefrom.
A lower portion of the chamber 1 provides a reservoir 8 for containing acid and the said lower portion is surrounded by a heater 9.
In operation the chamber 1 is arranged substantially vertically and a substance to be treated is introduced into the chamber 1 via the access port 3 to rest on the grid support 2 and the access port 3 is sealed to prevent egress of gaseous materials. A portion of substance to be treated is represented in the drawing as 10.
Acid contained in the reservoir 8 is heated to the desired temperature for carrying out the treatment by means of the heater 9 and is then drawn into intake 5 of the air-lift pump 4 and discharged through the outlet 6 thereby to fall onto the substance 10. Liquid produced by contacting acid with the substance 10 subsequently passes through the grid support 2 and falls mto the reservoir 8. Acid is recycled from the reservoir 8 over the substances 10 by means of the air-lift pump 4 intake 5 and outlet 6.
The invention will now be further illustrated by way of example only as follows: EXAMPLE An apparatus substantially as hereinbefore described with reference to the drawing was used to destroy, by means of digestion with acid, an organic substance contaminated with an inorganic material thereby to destroy the organic substance and give a solution or suspension containing the inorganic material.
The chamber 1 was a glass tube having a lower portion providing a reservoir (8) of approximately 7 litres capacity for containing acid.
Approximately 7 litres of concentrated sulphuric acid were introduced into the reservoir (8) and heated by means of an electrical heater to a temperature of approximately 250"C.
20 grams of paper tissues contaminated with inorganic material were placed on a PIPE grid support (2) located within the chamber and concentrated sulphuric acid at approximately 250"C was pumped from the reservoir by means of the air-lift pump (4) and sprayed over the paper tissues by means of the outlet (6).
Under the influence of the sulphuric acid the paper tissues were blackened and dissolved, a black carbonaceous material being washed down from the grid support (2) into the reservoir (8). 70% aqueous nitric acid was added at the bottom of the reservoir (8) to oxidise the carbonaceous material and large quantities of gas and vapour were evolved and removed from the chamber (1) via the outlet (7).
Circulation of acid over the grid support (2) and addition of nitric acid to the reservoir (8) were continued until all of the paper tissues had been digested and all carbonaceous matter in the reservoir (8) and been oxidised at which point the acid in the reservoir was pale yellow in colour.
The digestion and dissolution of the paper tissues took 4 minutes and required 25 ml of 70% aqueous nitric acid to be added to the concentrated sulphuric acid.
WHAT WE CLAIM IS: 1. A method for digesting or dissolving an organic substance comprising locating the organic substance in a contacting region, directing onto the organic substance an acid capable of digesting or dissolving the organic substance thereby to contact the organic substance with the acid such that organic substance is digested or dissolved by the acid to give liquid containing digested or dissolved organic substance and draining liquid containing digested or dissolved organic substance from the contacting region.
2. A method as claimed in claim 1 wherein the organic substance is supported in a contacting region of a chamber, and liquid draining from the contacting region is collected in a reservoir.
3. A method as claimed in claim 2 wherein the reservoir is in communication with a means for directing an acid onto the organic substance.
4. A method as claimed in claim 2 or claim 3 wherein the organic substance is supported by a grid arranged in the chamber so that liquid is removed from the substance by draining through the grid.
5. A method as claimed in claim 2, 3 or 4 wherein acid is directed onto the organic substance by means of a jet or a spray.
6. A method as claimed in any one of claims 2 to 5 wherein acid is supplied to a means for directing acid onto the organic substance by use of an air-lift pump.
7. A method as claimed in any one of claims 2 to 5 wherein an acid is supplied to a means for directing an acid onto the organic substance by use of a fluidic pump.
8. A method as claimed in claim 7 wherein the fluidic pump used is a reverse flow diverter.
9. A method as claimed in any one of the preceding claims wherein the acid is sulphuric acid or nitric acid.
10. A method as claimed in any one of the preceding claims wherein the acid comprises a mixture of acids.
11. A method as claimed in claim 10 wherein the mixture of acids is a mixture of sulphuric acid and nitric acid.
12. A method as claimed in any one of the preceding claims wherein the organic substance to be digested comprises a naturally occurring substance or a synthetic substance.
13. A method as claimed in any one of the preceding claims wherein the organic substance comprises an organic substance contaminated with a radioactive material.
14. Apparatus for carrying out a method as claimed in claim 1 comprising a chamber, a support located within a contacting region of the chamber for supporting an organic substance, access means for permitting introduction of organic substance to the support, a reservoir for containing acid, an acid supply means for directing acid at the organic substance when supported in the chamber, said acid supply means including an intake connected with the reservoir, a pump and an outlet located for directing acid at the organic substance, and exhaust means for removing gaseous materials from the chamber, the arrangement being such that liquid produced by contacting acid with the substance when supported in the contacting region of the chamber can be removed from the substance and such that liquid removed from the substance is received by the reservoir and the dimensions of the chamber being such as will prevent or discourage the formation of a critical assembly.
15. Apparatus as claimed in claim 14 wherein the outlet is in the form of a jet or spray for distributing acid over the substance to be treated.
16. Apparatus as claimed in claim 14 or 15 wherein the chamber is a closed right circular cylindrical tube for use with its longitudinal axis substantially vertical such that a lower portion of the tube provides the reservoir in use.
17. Apparatus as claimed in any one of the claims 14 to 16 for use in destruction of an organic substance contaminated with a
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (1)

  1. **WARNING** start of CLMS field may overlap end of DESC **.
    sulphuric acid were introduced into the reservoir (8) and heated by means of an electrical heater to a temperature of approximately 250"C.
    20 grams of paper tissues contaminated with inorganic material were placed on a PIPE grid support (2) located within the chamber and concentrated sulphuric acid at approximately 250"C was pumped from the reservoir by means of the air-lift pump (4) and sprayed over the paper tissues by means of the outlet (6).
    Under the influence of the sulphuric acid the paper tissues were blackened and dissolved, a black carbonaceous material being washed down from the grid support (2) into the reservoir (8). 70% aqueous nitric acid was added at the bottom of the reservoir (8) to oxidise the carbonaceous material and large quantities of gas and vapour were evolved and removed from the chamber (1) via the outlet (7).
    Circulation of acid over the grid support (2) and addition of nitric acid to the reservoir (8) were continued until all of the paper tissues had been digested and all carbonaceous matter in the reservoir (8) and been oxidised at which point the acid in the reservoir was pale yellow in colour.
    The digestion and dissolution of the paper tissues took 4 minutes and required 25 ml of 70% aqueous nitric acid to be added to the concentrated sulphuric acid.
    WHAT WE CLAIM IS: 1. A method for digesting or dissolving an organic substance comprising locating the organic substance in a contacting region, directing onto the organic substance an acid capable of digesting or dissolving the organic substance thereby to contact the organic substance with the acid such that organic substance is digested or dissolved by the acid to give liquid containing digested or dissolved organic substance and draining liquid containing digested or dissolved organic substance from the contacting region.
    2. A method as claimed in claim 1 wherein the organic substance is supported in a contacting region of a chamber, and liquid draining from the contacting region is collected in a reservoir.
    3. A method as claimed in claim 2 wherein the reservoir is in communication with a means for directing an acid onto the organic substance.
    4. A method as claimed in claim 2 or claim 3 wherein the organic substance is supported by a grid arranged in the chamber so that liquid is removed from the substance by draining through the grid.
    5. A method as claimed in claim 2, 3 or 4 wherein acid is directed onto the organic substance by means of a jet or a spray.
    6. A method as claimed in any one of claims 2 to 5 wherein acid is supplied to a means for directing acid onto the organic substance by use of an air-lift pump.
    7. A method as claimed in any one of claims 2 to 5 wherein an acid is supplied to a means for directing an acid onto the organic substance by use of a fluidic pump.
    8. A method as claimed in claim 7 wherein the fluidic pump used is a reverse flow diverter.
    9. A method as claimed in any one of the preceding claims wherein the acid is sulphuric acid or nitric acid.
    10. A method as claimed in any one of the preceding claims wherein the acid comprises a mixture of acids.
    11. A method as claimed in claim 10 wherein the mixture of acids is a mixture of sulphuric acid and nitric acid.
    12. A method as claimed in any one of the preceding claims wherein the organic substance to be digested comprises a naturally occurring substance or a synthetic substance.
    13. A method as claimed in any one of the preceding claims wherein the organic substance comprises an organic substance contaminated with a radioactive material.
    14. Apparatus for carrying out a method as claimed in claim 1 comprising a chamber, a support located within a contacting region of the chamber for supporting an organic substance, access means for permitting introduction of organic substance to the support, a reservoir for containing acid, an acid supply means for directing acid at the organic substance when supported in the chamber, said acid supply means including an intake connected with the reservoir, a pump and an outlet located for directing acid at the organic substance, and exhaust means for removing gaseous materials from the chamber, the arrangement being such that liquid produced by contacting acid with the substance when supported in the contacting region of the chamber can be removed from the substance and such that liquid removed from the substance is received by the reservoir and the dimensions of the chamber being such as will prevent or discourage the formation of a critical assembly.
    15. Apparatus as claimed in claim 14 wherein the outlet is in the form of a jet or spray for distributing acid over the substance to be treated.
    16. Apparatus as claimed in claim 14 or 15 wherein the chamber is a closed right circular cylindrical tube for use with its longitudinal axis substantially vertical such that a lower portion of the tube provides the reservoir in use.
    17. Apparatus as claimed in any one of the claims 14 to 16 for use in destruction of an organic substance contaminated with a
    radioactive material, wherein the chamber is a right circular cylinder having dimensions such as will prevent or discourage the formation of a critical assembly.
    18. Apparatus as claimed in any one of the claims 14 to 17 constructed of glass.
    19. Apparatus for use in digesting or dissolving an organic substance substantially as hereinbefore described with reference to the single figure of the drawings accompanying the Provisional Specification.
    20. A method for digesting or dissolving an organic substance substantially as hereinbefore described with reference to the single figure of the drawings accompanying the Provisional Specification or with reference to the Example.
GB927077A 1978-05-24 1978-05-24 Treatment of solids with liquids Expired GB1604371A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB927077A GB1604371A (en) 1978-05-24 1978-05-24 Treatment of solids with liquids

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Application Number Priority Date Filing Date Title
GB927077A GB1604371A (en) 1978-05-24 1978-05-24 Treatment of solids with liquids

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GB1604371A true GB1604371A (en) 1981-12-09

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4663085A (en) * 1984-05-25 1987-05-05 Kabushiki Kaisha Toshiba Apparatus for decontamination of radiation contaminated metallic waste

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4663085A (en) * 1984-05-25 1987-05-05 Kabushiki Kaisha Toshiba Apparatus for decontamination of radiation contaminated metallic waste

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