1. Cementitious composite for immobilization of radioactive waste into final waste form Andrey P. Varlakov ( Moscow Scientific-Industrial Association RADON 2/14, 7 Rostovskij lane, Moscow, 119121, Russia) Second RCM Meeting- Romania, Nov.24-28, 2008

2. SIA“Radon” carries out a whole range of radioactive waste (RW) operations: collection, transportation, reprocessing and storage and radiological monitoring.collection, transportation, reprocessing and storage and radiological monitoring. collect and reprocessing of RW from 11 regions of central Russia.collect and reprocessing of RW from 11 regions of central Russia. deal with various radioactive waste from industry, science, medicine and other branches.deal with various radioactive waste from industry, science, medicine and other branches. Each type of the wastes requires application of a special cementation method and kind of binding materials and additives. Application of different binding materials, increase of quantity of various additives and their application in diverse aggregative state causes considerable increase of radioactive waste conditioning costs and complication of the technology. It is important that a special composite should be developed for the cementation both solid radioactive wastes and liquid ones having different and problem chemical composition. Problem wastes are defined as those wastes which are solidified with difficulty, have poor volumetric efficiencies or produce an unsatisfactory product.

3. Moscow SIA “Radon” has been created a special cementitious composite (SCC). Contents of special cementitious composition for RAW cementation Component Contents in additive, %wt. Purpose of use, modified properties of cement compound Special cement of 3-10  m particles in size 60-85 Strength, hardening terms, frost-resistance, water resistance, and penetrating ability. Fuel ash or ash after domestic waste incineration 10-30 Decreasing the quantity of hydration heat, сo- processing of toxic and radioactive wastes, reduction of binding material price. Bentonitic clay powder5-15Leaching rate, crack resistance. Hydraulic micro silica0,5-10 Bonding ash, stability of consistence, penetrating ability. Polymeric strengthening additive0,05-1 Strength, stability of consistence, vitality, penetrating ability, biological resistance. Defoamer0,1-1 Defoaming (suppression of air-entraining), decrease of porosity and leaching rate. Properties of materials MaterialSpecific surface, cm 2 /gNormal thickness Special cement6 000-12 0000,60 –0,70 Hydraulic micro silica12 000-15 0000,60 –0,70 Ash after domestic waste incineration7 000-10 0001,00 –1,10 Portland cement2 900 – 3 5000,18-0,23 The cementitious composite consists of 5-6 macro- and micro components. Eachcomponent improves simultaneously several properties of cement compound.(SCC). Each component improves simultaneously several properties of cement compound. (SCC).

4. At SIA “Radon”, the following different types of solid radioactive waste (SRW) are cemented with the use of SCC: lump SRW;lump SRW; fine-dispersed or close-packed SRW including ash residue after incineration of solid radioactive waste with average particle sizes 0,5-2 mm.fine-dispersed or close-packed SRW including ash residue after incineration of solid radioactive waste with average particle sizes 0,5-2 mm. Lump SRW are cemented by means of top filling of containers. Fine-dispersed and close packed SRW are cemented by means of bottom impregnation Cement grout on the basis SCC Fide pipe Cement grout on the basis SCC Cementation SRW with use SCC

5. Equipment for SRW impregnation with high penetrating grout. Container (100 liter) with ash residue after impregnation Equipment for ash residue impregnation with highpenetrating cement grout Equipment for SRW impregnation in 2,7 m 3 container with high penetrating cement grout Equipment for SRW impregnation in 100 and 200 liters container with high- penetrating cement grout

6. Properties of cement compound with ash residue prepared by impregnation method. Content of ash residue in the final product makes 65-75 % wt. Properties of cement compound with ash residue prepared by impregnation method. Content of ash residue in the final product makes 65-75 % wt..

7. Properties of cement compound with close packed SRW prepared by means of bottom impregnation method Properties of cement compound with close packed SRW prepared by means of bottom impregnation method.

8. LRW type Specific β-activity, Bq/l рН Density, g/cm 3 Salt, g/l SAS, g/l Fixed residue, g/l LRW3,65*10 3 7,01,107553 Concentrated LRW 5,70*10 4 7,97,91,151,15350<1120 LRW containing SAS 3,64*10 4 (α-) 5,1×10 4 11,01,301,30130700,20,2 Properties of LRW At SIA “Radon”, the following different compositions of liquid radioactive waste (LRW) are cemented: LRW high containing NaNO 3 ;LRW high containing NaNO 3 ; LRW additionally containing surface-active substances coming with detergents in decontaminating solutions in quantities up to 30-40 % wt.LRW additionally containing surface-active substances coming with detergents in decontaminating solutions in quantities up to 30-40 % wt. LRW containing oil.LRW containing oil.

9. Properties of cement compounds prepared of SCC and traditional Portland cement traditional Portland cement. At LRW cementation with the use of ordinary Portland cement without additives, the water cement ratio should not exceed 0,7-0,75. Increase of W/C ratio will cause demixing of cement grout (separation of water). Application of SCC allows increasing: W/C ratio up to 1 – 1,1 due to its stabilizing influence;W/C ratio up to 1 – 1,1 due to its stabilizing influence; contents of radioactive waste in the final product.contents of radioactive waste in the final product. At that all the regulated properties of cement compound do not worsen in comparison with the properties of cement compound prepared on the base of traditional Portland cement.

10. Properties of cement compounds containing SAS prepared of special cementitious composite and traditional Portland cement. Liquid radioactive waste containing a considerable quantity of SAS is very difficult for cementation because of forming a lot of foam. Cement compound is saturated with air and hardens very slowly forming a porous structure. Application of SCC allows obtaining the final product of higher quality which is not saturated with air Acceleration of hydration process is typical for these compounds because of a high dispersity of cement, ash and hydraulic micro silica.

11. Cement grout is placed into the containers and compartments of the repository can strongly warm up due to heat of cement hardening as well as radiation exposure. Volume of the containers for cementation waste can vary from 100 or 200 liters up to 2-3 m 3 and is not so great as the one of compartments of a repository, which can make 200-400 m 3. Warming up of cement can cause water evaporation from the cement monolith, stop hardening and lead to crystallization of salts within pores, that can lead to destruction of the final product while its long-term storage. For reduction of heating, it is necessary to use cement of mineral additives (fuel ashes, slag and hydraulic silica). Properties of ashes after domestic waste incineration can be similar to ones of fly fuel ashes. Utilization of secondary waste (slag and ash) of combustion plants is an important environmental approach to solving cities’ issues. But ash after domestic waste incineration is toxic industrial waste as it contains toxic elements Contents of most significant microelements in ashes after domestic waste incineration

12. Results of the research have shown that the special cement composition containing up to 10-30 % wt. of ash after domestic waste incineration allows: cementing waste by using higher water-cement ratio, what in turn allows increasing the amount of waste included into the final product and reducing the consumption of cement material; cementing waste by using higher water-cement ratio, what in turn allows increasing the amount of waste included into the final product and reducing the consumption of cement material; decreasing the amount of hydration heat, which is important for continuous cementation of waste and hardening of cement compound in compartments of a special repository or big containers. decreasing the amount of hydration heat, which is important for continuous cementation of waste and hardening of cement compound in compartments of a special repository or big containers. Co-processing of toxic and radioactive waste is ecological and economic efficiency. At SIA “Radon”, experimental batches of cement compositions are used for cementation of waste. Diagram of chemistry (A) and X-ray structure analysis (B) of ash after domestic waste incineration. 1- SiO 2, 2-CaO, 3-Al 2 O 3, 4-Fe 2 O 3, 5-Na 2 0+K 2 O, 6-MgO, 7-TiO 2, 8- microelements, 9-Cl, 10-SO 3, 11-P 2 O 5

13. Wastes containing technical oils are considerable problem. Oils can often be in repositories together with salt liquid radioactive waste (LRW), ion exchange resins, silicon lubricants and other wastes. Desired methods for treatment of such oil waste are incineration or cleaning. By many reasons, these methods are a serious technological and economic problem. Frequently, the only method for the radioactive oils treatment is their temporal storage in metal tanks. The simplest solution is them inclusion into a cement compound at cementing liquid salt radioactive waste. The experience of radioactive oils cementation at Moscow SIA "Radon" is five years. Radioactive oils are added into cement grout in quantity of 5-7 %wt. at cementing liquid salt radioactive waste. Disadvantages of the cementing way of technical oils and LRW: low contents of oils (about 5-7 wt.%) in cement grout depending on LRW salinity; low contents of oils (about 5-7 wt.%) in cement grout depending on LRW salinity; low (not more than 0,5) water-cement ratio; low (not more than 0,5) water-cement ratio; worsening of cement compound properties; worsening of cement compound properties; uneven distribution of oils in cement compound, which causes local decrease of its properties lower than determined values and degradation; uneven distribution of oils in cement compound, which causes local decrease of its properties lower than determined values and degradation; settling of oils during cement compound tempering; settling of oils during cement compound tempering; mixing of cement grout requires a special mixer because of cement grout disintegration; mixing of cement grout requires a special mixer because of cement grout disintegration; depending on type and state of waste it is possible air-inclusion at mixing cement grout, worsening all regulated properties of the final product; depending on type and state of waste it is possible air-inclusion at mixing cement grout, worsening all regulated properties of the final product; biological degradation of oils and consequently cement matrix.biological degradation of oils and consequently cement matrix.

14. Influence of the SCC on Properties Cement Compounds with Radioactive Oil. SIA”Radon” has been developed the new method for increasing contents of oils in cement compound up to 15 %. The new method offered for cementation of radioactive oil consists in the following. Stable to stratification a suspension is prepared on the base of oils and saline LRW. This suspension is introduced into the main cement grout, which allows evenly distributing oils in hardened cement compound. To increase the degree of oils inclusion into the final product SCC should be introduced in suspension. This suspension is introduced into the main cement grout, which allows evenly distributing oils in hardened cement compound. Ultra fine high mark quickly hardening cement improves all properties of the final cement compound.

15. Influence of the SCC on process of hydration cement compound with radioactive oil Influence of the SCC on process of hydration cement compound with radioactive oil. SEM of cement compounds containing 20 %wt. of oil received by traditional mixing with portland cement. Hardening time – 1 day. The oil film complicates reaction with water of initial cement minerals. SEM of cement compounds containing 20 %wt. of oil received by preliminary suspension with SCC. Hardening time – 1 day. The oil phase is submitted by the fine drops surrounded with "shell" bentonite. Products of hydration are observed. Components of SCC are able adsorbing oils and increasing the cement compound quality. SCC contains bentonite and ash, which are able to adsorb oils and decreases its contents in liquid phase. Influence of the SCC on process of hydration cement compound with radioactive oil is shown on of Scanning electron microscopy (SEM) picture. Where we can see that the oil film complicate reaction with water of initial cement minerals (a). The oil phase is submitted by the fine drops surrounded with "shell" SCC (b). Products of hydration are observed (b).

16. Nitrate-containing cement blocks. of nitrate-containing cement blocks without after 20 months of field tests in open container (samples №№ 2,4,10,12,14). The thin-porous “sponge-like” surface, wearing on sides, color changes can be seen. Appearance of nitrate-containing cement blocks without biocide after 20 months of field tests in open container (samples №№ 2,4,10,12,14). The thin-porous “sponge-like” surface, wearing on sides, color changes can be seen. Nitrate-containing cement blocks. Appearance of cement blocks with biocide additions after 20 months of field tests (open container) samples №№5 and 6 – cement blocks without nitrates; samples №№7 and 8 – cement blocks with nitrates. The structures are not changed. Oil in structure of cement is nutrient for development of bacteria. Gaseous products of activity of bacteria and also organic acids and aldehydes promote increasing of porosity cement compound and can lead to destruction it at long storage. On the research data biocide additive of a polyhexametylenguanidine class included in SCC can give protection from biodistruction preventing biogenic gas formation, which is important for long term storage.

17. А.А. С.С. В.В. D.D. Еxperimental-industrial cementation of radioactive oil. А - general view of plant of cementation of LRW. В - module for preparation of radioactive oil for cementation. С - Measuring tank. D - cement compound of radioactive oil in quantity of 10%wt. Hardening time – 1 day. In SIA"Radon" the module for preparation of radioactive oil for cementation is created. The module includes unit for preparation of suspension using liquid waste, oil and powder additives. The module includes unit for preparation of suspension using liquid waste, oil and powder additives. The main device of unit for preparation of suspension is disperser, which creates a turbulent stream and a pulsation of suspension with the help of special flanges. The prepared waste feed to the mixer of cementation installation. Tests have shown, that due to preparation of preliminary suspension and uniform distribution of oil in a cement grout, inclusion of radioactive oil in cement compound in quantity of 10-15 % wt. is possible. Properties of cement compounds obtained in experimental-industrial scale satisfied the meet requirements.

18. CONCLUSION As it can be seen from above data, SCC can be universal cementitious material at nuclear site like “Radon”. Were there are a lot of various waste, which requires different cements and additives. In having varied the quantity of SCC in mixture with traditional Portland cement, it can be used for different methods of cementation both various liquid radioactive waste and solid ones. SCC can be used for cementation difficult LRW like oil containing waste. At that SCC will allow improving the quality of final product and increasing its loading with radioactive waste and decreasing the final product volume. It is important that the cementitious composite can have been applied as an independent cement material or as an additive to the ordinary Portland cement changing properties of the cement compound in a required range depending on a technological process and wastes. SCC is used in dry form at cementation and introduced directly into the mixture as cement. Presence of components in macro quantities does not practically influence on cost of additive and makes free of necessity to complicate the RW cementation equipment by means of applying expensive and fragile dosing equipment in the installation. Besides, evenly distributed macro components in the additive make cementation simpler, increasing the productivity due to decreasing time for thorough mixing of cement compound components.

19. New technology for cementation of problem liquid radioactive wastes A new technology for cementation of problem liquid radioactive wastes has been developed at SIA”Radon”. These wastes are organic liquid (oil, solvents, extractants, scintillation cocktail and others); organic liquid (oil, solvents, extractants, scintillation cocktail and others); high containing surface-active substances LRW; high containing surface-active substances LRW; subacid aqueous saline LRW and high containing alpha nuclides LRW. subacid aqueous saline LRW and high containing alpha nuclides LRW. The technology can be used for conditioning of problem liquid radioactive wastes directly at nuclear sites without use stationary cementation plant. The technology consists in as follows: porous concrete is prepared by a special mixer and placed into a standard container 100 or 200 l. porous concrete is prepared by a special mixer and placed into a standard container 100 or 200 l. problem LRW is pumped into pore space of porous concrete matrix through previously positioned special feed tube at the age-hardening of concrete not less than 28 days. problem LRW is pumped into pore space of porous concrete matrix through previously positioned special feed tube at the age-hardening of concrete not less than 28 days. the wastes are effectively fixed in pores of the cement matrix. the wastes are effectively fixed in pores of the cement matrix. The final product has all the regulated properties. Compressive strength of porous concrete matrix at the age-hardening 28 days is 6-10 MPa. The average size pores makes 0,1-0,05 mm, density of concrete - 0,7-0,9 g/sm 3. Feed pressure of LRW makes 0,15-0,3 MPa. Capacity of impregnation depends on kind of LRW and makes 20-40 l/h. Impregnation of several containers can simultaneously be carried out.

20. Container and device for impregnation of porousconcrete by LRW Container and device for impregnation of porous concrete by LRW Structure of porousconcrete at 28 days of hardening Structure of porous concrete at 28 days of hardening At SIA “Radon”, an experimental-industrial tests of problem liquid radioactive wastes cementation in such way carry on. For impregnation various waste products have been used (oil, blend of tributylphosphate and sintin, subacid aqueous saline high containing alpha nuclides LRW). Properties of the final product have been corresponded to all the regulated requirements. Depending on kind of LRW contents of waste in final product has made 50-65 % vol. The new method of conditioning has the following advantages: the degree of inclusion of problem LRW into the final product can be up to 50-65 % vol.; the degree of inclusion of problem LRW into the final product can be up to 50-65 % vol.; the technology excludes negative influence of wastes on of cement hydration; the technology excludes negative influence of wastes on of cement hydration; there are no difficulties in mixing the cement grout and wastes; there are no difficulties in mixing the cement grout and wastes; small amounts of radioactive wastes are processing directly at nuclear sites; small amounts of radioactive wastes are processing directly at nuclear sites; equipment for conditioning radioactive wastes directly at nuclear sites can be mobile. equipment for conditioning radioactive wastes directly at nuclear sites can be mobile.