GB2116355A - Bitumenisation of radioactive wastes - Google Patents
Bitumenisation of radioactive wastes Download PDFInfo
- Publication number
- GB2116355A GB2116355A GB08206321A GB8206321A GB2116355A GB 2116355 A GB2116355 A GB 2116355A GB 08206321 A GB08206321 A GB 08206321A GB 8206321 A GB8206321 A GB 8206321A GB 2116355 A GB2116355 A GB 2116355A
- Authority
- GB
- United Kingdom
- Prior art keywords
- wax
- bitumen
- weight
- process according
- blend
- 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.)
- Granted
Links
- 239000002901 radioactive waste Substances 0.000 title claims abstract description 17
- 239000010426 asphalt Substances 0.000 claims abstract description 68
- 239000000203 mixture Substances 0.000 claims abstract description 47
- 239000002699 waste material Substances 0.000 claims abstract description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000001993 wax Substances 0.000 claims description 67
- 238000000034 method Methods 0.000 claims description 33
- 238000005538 encapsulation Methods 0.000 claims description 13
- 239000000945 filler Substances 0.000 claims description 12
- 239000000463 material Substances 0.000 claims description 9
- 239000002002 slurry Substances 0.000 claims description 9
- 239000010409 thin film Substances 0.000 claims description 9
- 239000000080 wetting agent Substances 0.000 claims description 8
- 239000007864 aqueous solution Substances 0.000 claims description 7
- 239000004568 cement Substances 0.000 claims description 7
- 230000007774 longterm Effects 0.000 claims description 7
- 239000012188 paraffin wax Substances 0.000 claims description 6
- 230000035515 penetration Effects 0.000 claims description 6
- 239000012169 petroleum derived wax Substances 0.000 claims description 5
- 235000019381 petroleum wax Nutrition 0.000 claims description 5
- 239000011230 binding agent Substances 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 230000002285 radioactive effect Effects 0.000 claims description 4
- 238000001704 evaporation Methods 0.000 claims description 3
- 230000008020 evaporation Effects 0.000 claims description 3
- 239000003063 flame retardant Substances 0.000 claims description 3
- 238000002386 leaching Methods 0.000 claims description 3
- 239000000243 solution Substances 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 239000004215 Carbon black (E152) Substances 0.000 claims description 2
- 239000000654 additive Substances 0.000 claims description 2
- 230000000694 effects Effects 0.000 claims description 2
- 229930195733 hydrocarbon Natural products 0.000 claims description 2
- 150000002430 hydrocarbons Chemical class 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 claims description 2
- 239000004576 sand Substances 0.000 claims description 2
- 239000004094 surface-active agent Substances 0.000 claims description 2
- 150000003839 salts Chemical class 0.000 abstract description 6
- 230000008961 swelling Effects 0.000 abstract description 3
- 238000001179 sorption measurement Methods 0.000 abstract 1
- 239000002910 solid waste Substances 0.000 description 2
- 229910000288 alkali metal carbonate Inorganic materials 0.000 description 1
- 150000008041 alkali metal carbonates Chemical class 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- AYJRCSIUFZENHW-DEQYMQKBSA-L barium(2+);oxomethanediolate Chemical compound [Ba+2].[O-][14C]([O-])=O AYJRCSIUFZENHW-DEQYMQKBSA-L 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000005202 decontamination Methods 0.000 description 1
- 230000003588 decontaminative effect Effects 0.000 description 1
- 150000004985 diamines Chemical class 0.000 description 1
- 238000011038 discontinuous diafiltration by volume reduction Methods 0.000 description 1
- 239000008394 flocculating agent Substances 0.000 description 1
- -1 for example Chemical class 0.000 description 1
- 150000008282 halocarbons Chemical class 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920003303 ion-exchange polymer Polymers 0.000 description 1
- 239000002925 low-level radioactive waste Substances 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 230000003204 osmotic effect Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
- 239000003760 tallow Substances 0.000 description 1
- 235000013311 vegetables Nutrition 0.000 description 1
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
- G21F9/04—Treating liquids
- G21F9/06—Processing
- G21F9/16—Processing by fixation in stable solid media
- G21F9/167—Processing by fixation in stable solid media in polymeric matrix, e.g. resins, tars
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Processing Of Solid Wastes (AREA)
- Paints Or Removers (AREA)
Abstract
Radioactive wastes, particularly water wet wastes, are encapsulated, prior to disposal, in bitumen/wax blends. Such blends are less prone to swelling due to water adsorption by encapsulated water-sensitive salts.
Description
SPECIFICATION
Bitumenisation of radioactive wastes
This invention relates to the bitumenisation of radioactive wastes.
Encapsulation in bitumen has become an established method of treating low and medium level radioactive wastes from a variety of sources prior to disposed, e.g. long term storage.
Bitumenisation is particularly practised on aqueous or water-wet wastes from nuclear power generating plants, these include ion exchange resins in bead and powder form, decontamination solutions and filter sludges etc. With such wastes encapsulation is carried out at an elevated temperature such that any water present in the waste is driven off by evaporation leaving the substantially dry solid waste encapsulated in the bitumen. The encapsulated solid waste is then fed into storage drums and the encapsulating bitumen allowed to solidify. The drums containing the solid bitumenised wastes are then disposed of or sent to long term storage. Encapsulation may conveniently be carried out in a twin screw mixer or, more preferably, in a thin film evaporator.
In order to be commercially and environmentally acceptable the bitumenised wastes have to show long term physical stability and resistance to leaching, for example, by surface water, and it is here that problems can arise in the bitumenisation of aqueous and water wet radioactive wastes. Frequently such wastes contain substantial proportions of water-soluble or water-sensitive inorganic salts, for example, alkali metal carbonates, permanganates and sulphates specifically added for example as decontaminating agents or as flocculating agents and filter aids, and the presence of such watersensitive salts in the bitumenised waste has been found to lead to considerable swelling and possibly cracking and disintegration of the bitumenised waste during leach tests.This is believed to be the result of increased osmotic pressure initiated by the presence of watersensitive salts within the bitumen. In comparison, leach tests with bitumenised non-water-sensitive salts, such as barium carbonate, have not shown any appreciable swelling even after several months of immersion in water.
In some cases, aiso the relatively high viscosity of the encapsulating bitumen restricts the amount of waste that can satisfactorily be encapsulated.
In accordance with the present invention it has been found that the tendency of bitumenised wastes containing water-sensitive salts to swell when in contact with water or moisture can be substantially reduced or eliminated altogether by incorporating a wax into the bitumen. Moreover, the presence of wax in the bitumen not only greatly reduces its viscosity, but also provides a very considerably improved compressive strength in the bitumenised product. Thus the incorporation of wax leads to lower viscosities, easier handling, significantly reduced cold flow, higher compressive strength and greater volume reduction of the radioactive waste, i.e. a larger amount of waste can be encapsulated in the same amount of bitumen.
The proportions of wax and bitumen may be varied over a wide range, for example, wax/bitumen mixtures may be used containing from 1 to 99% by weight wax and
correspondingly 99 to 1% bitumen. If desired, optional ingredients may be incorporated into the wax/bitumen mixture such as wetting agents, e.g.
long chain fatty amines such as tallow diamine, fillers e.g. cement, flame retardants, e.g.
halogenated hydrocarbons, etc.
A typical mixture used in the present invention comprises: on a weight basis:
Bitumen 1-99%, preferably 5090%, based on bitumen/wax
mixture
Wax 199%, preferably 1050%, based on bitumen/wax
mixture
Wetting Agents 0-5%, based on total
composition
Filler 0--509/0, based on total
composition
A suitable bitumen for use in the present invention is a penetration grade bitumen, having a penetration (ASTM D5-73) at 250C of 50+10.
Other grades of bitumen will be suitable provided that they have a sufficient viscosity not to give rise to cold flow problems in the product, and
subject to compatibility with the wax component.
As the wax component there may be used waxes of animal, vegetable or mineral origin, but preferred are petroleum waxes and in particular
paraffin wax.
Since the wax greatly reduces the viscosity of the molten bitumen, the above described mixtures can be used to encapsulate low-level radioactive waste material at relatively low temperatures; for example, using three particular grades of bitumen and paraffin wax described above in 60:40 weight ratio, encapsulation may be effected simply by stirring the waste into the molten mixture, e.g. at about 850C, and then allowing the mixture to solidify. Higher temperatures can be used, but to no substantial advantage. Also, of course, the optimum encapsulation temperature will depend upon the particular bitumen/wax blend being used. A more preferred encapsulation technique, particularly in the case of aqueous solutions and slurries, is by encapsulation in a thin film evaporator.In this known technique, the molten waxibitumen mixture and waste are fed to the upper end of a vertically disposed tubular evaporator internally fitted with a paddle or stirrer. In the evaporator, the waxibitumen mixture flows as a thin film down the internal walls of the evaporator which is appropriately heated by an external jacket. In the evaporator, water present in the waste feed is evaporated off, and the residue emerges from the bottom of the evaporator as a homogenous dispension in the wax/bitumen mixture. The encapsulated waste can then be fed into drums in the customary manner in preparation for disposal or long term storage.
In a further development of the invention it has also been found that, using the same techniques as above, i.e. by mixing at an elevated temperature in a twin screw mixer, or in a thin film evaporator, water-wet radioactive wastes can be encapsulated satisfactorily in a binder consisting essentially of wax, i.e. without any bitumen, to provide encapsulated products of long term stability and high resistance to leaching. Preferred waxes for this technique are hydrocarbon waxes, and particularly petroleum waxes, such as paraffin wax. As in the case of the bitumen wax blends, other additives may be incorporated into the wax binder to achieve particular objects, such as fillers, e.g. sand or cement, surface active or wetting agents, and flame retardants etc.
Claims (filed on 24/2/83)
1. A process for the treatment of radioactive wastes prior to disposal, which comprises encapsulating the waste in a bitumen/wax blend comprising from 1-99% by weight of bitumen and from 991% by weight of wax, based on the combined weight of the bitumen and wax components.
2. A process according to claim 1, wherein the bitumen/wax blend contains from 5090% by weight bitumen and from 5010% by weight of wax, based on the combined weight of the bitumen and wax.
3. A process according to claim 1 or 2, wherein the bitumen is a penetration grade bitumen having a penetration (ASTM D5-73) at 250C of 50+10.
4. A process according to any one of the preceding claims, wherein the wax is a petroleum wax.
5. A process according to claim 4, wherein the wax is a paraffin wax.
6. A process according to any one of the preceding claims, wherein the radioactive waste is encapsulated by stirring the waste into a molten blend of said bitumen and wax, and allowing the bitumen/wax blend to set.
7. A process according to any one of claims 1-5, wherein the radioactive waste is a radioactive aqueous solution or slurry.
8. A process according to claim 7, wherein the encapsulation is effected by mixing the radioactive aqueous solution or slurry with a molten blend of said bitumen and wax in a thin film evaporator in which the aqueous solution or slurry is formed into a thin film with said molten bitumen/wax blend and simultaneously heated to effect the concomitant evaporation of the water from the solution or slurry and encapsulation of the dry residue in the bitumen/wax blend.
9. A process according to any one of the preceding claims, wherein the bitumen/wax blend additionally contains up to 5% by weight, based on the total composition of a wetting agent and/or up to 50% by weight based on the total composition of a finely divided filler.
10. A process according to claim 9, wherein the bitumen/wax blend contains up to 50% by weight of cement as said filler.
11. A process according to any one of the preceding claims, wherein after encapsulation the bitumen/wax encapsulated waste is fed into drums and allowed to solidify therein prior to disposal.
12. An encapsulatory material for radioactive wastes comprising a blend containing 199% by weight bitumen and 9910% by weight wax,
based on the combined weight of the bitumen
and wax components.
13. A material according to claim 12 containing 5090% bitumen and 1050% wax.
14. A method according to claim 12 or 13, wherein the bitumen is as required by claim 3.
1 5. A material according to claim 12, 13 or 14, wherein the wax is as required by claim 4 or 5.
1 6. A material according to any one of claims
12 to 1 5 additionally containing up to 5% by weight based on the total composition of a wetting agent and/or up to 50 ,0 by weight based on the total composition of a finely divided filler.
1 7. A method according to claim 16, which contains up to 50% by weight of cement as said filler.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (14)
1. A process for the treatment of radioactive wastes prior to disposal, which comprises encapsulating the waste in a bitumen/wax blend comprising from 1-99% by weight of bitumen and from 991% by weight of wax, based on the combined weight of the bitumen and wax components.
2. A process according to claim 1, wherein the bitumen/wax blend contains from 5090% by weight bitumen and from 5010% by weight of wax, based on the combined weight of the bitumen and wax.
3. A process according to claim 1 or 2, wherein the bitumen is a penetration grade bitumen having a penetration (ASTM D5-73) at 250C of 50+10.
4. A process according to any one of the preceding claims, wherein the wax is a petroleum wax.
5. A process according to claim 4, wherein the wax is a paraffin wax.
6. A process according to any one of the preceding claims, wherein the radioactive waste is encapsulated by stirring the waste into a molten blend of said bitumen and wax, and allowing the bitumen/wax blend to set.
7. A process according to any one of claims 1-5, wherein the radioactive waste is a radioactive aqueous solution or slurry.
8. A process according to claim 7, wherein the encapsulation is effected by mixing the radioactive aqueous solution or slurry with a molten blend of said bitumen and wax in a thin film evaporator in which the aqueous solution or slurry is formed into a thin film with said molten bitumen/wax blend and simultaneously heated to effect the concomitant evaporation of the water from the solution or slurry and encapsulation of the dry residue in the bitumen/wax blend.
9. A process according to any one of the preceding claims, wherein the bitumen/wax blend additionally contains up to 5% by weight, based on the total composition of a wetting agent and/or up to 50% by weight based on the total composition of a finely divided filler.
10. A process according to claim 9, wherein the bitumen/wax blend contains up to 50% by weight of cement as said filler.
11. A process according to any one of the preceding claims, wherein after encapsulation the bitumen/wax encapsulated waste is fed into drums and allowed to solidify therein prior to disposal.
12. An encapsulatory material for radioactive wastes comprising a blend containing 199% by weight bitumen and 9910% by weight wax,
based on the combined weight of the bitumen
and wax components.
13. A material according to claim 12 containing 5090% bitumen and 1050% wax.
14. A method according to claim 12 or 13, wherein the bitumen is as required by claim 3.
1 5. A material according to claim 12, 13 or 14, wherein the wax is as required by claim 4 or 5.
1 6. A material according to any one of claims
12 to 1 5 additionally containing up to 5% by weight based on the total composition of a wetting agent and/or up to 50 ,0 by weight based on the total composition of a finely divided filler.
1 7. A method according to claim 16, which contains up to 50% by weight of cement as said filler.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08206321A GB2116355B (en) | 1982-03-04 | 1982-03-04 | Bitumenisation of radioactive wastes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08206321A GB2116355B (en) | 1982-03-04 | 1982-03-04 | Bitumenisation of radioactive wastes |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2116355A true GB2116355A (en) | 1983-09-21 |
| GB2116355B GB2116355B (en) | 1985-07-31 |
Family
ID=10528770
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08206321A Expired GB2116355B (en) | 1982-03-04 | 1982-03-04 | Bitumenisation of radioactive wastes |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2116355B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1987001502A1 (en) * | 1985-08-30 | 1987-03-12 | Hoeglund Lars Olov | An encapsulated ion-exchange resin and a method for its manufacture |
-
1982
- 1982-03-04 GB GB08206321A patent/GB2116355B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1987001502A1 (en) * | 1985-08-30 | 1987-03-12 | Hoeglund Lars Olov | An encapsulated ion-exchange resin and a method for its manufacture |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2116355B (en) | 1985-07-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |