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CHARACTERISATION, IMPROVEMENTS AND LONG TERM EVALUATION OF CEMENTITIOUS WASTE PRODUCTS

CHARACTERISATION, IMPROVEMENTS AND LONG TERM EVALUATION OF CEMENTITIOUS WASTE PRODUCTS – AN INDIAN SCENARIO. by R.G. Yeotikar*, R.R. Rakesh, Biplob Paul, T.P. Valsala, Ajay Shirole and Dilip Kumar Chaudhari Bhabha Atomic Research Centre, INDIA *E mail- yeotikar@barc.gov.in.

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CHARACTERISATION, IMPROVEMENTS AND LONG TERM EVALUATION OF CEMENTITIOUS WASTE PRODUCTS

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  1. CHARACTERISATION, IMPROVEMENTS AND LONG TERM EVALUATION OF CEMENTITIOUS WASTE PRODUCTS – AN INDIAN SCENARIO by R.G. Yeotikar*, R.R. Rakesh, Biplob Paul, T.P. Valsala, Ajay Shirole and Dilip Kumar Chaudhari Bhabha Atomic Research Centre, INDIA *E mail- yeotikar@barc.gov.in

  2. Layout of presentation • Aims and objectives of CRP • Works planning in details & future works to be carried out for CRP • Practices followed for cementation • Some of the results of cementation work • Expected result / outcome of CRP

  3. Aim & objectives of CRP-1 • Preparation of cement waste products (CWP) on laboratory and plant scale with different cement formulation from : • Sluges from treatment of LLW • Intermediate level liquid waste • Ion exchange resins • Miscellaneous wastes • Improvement of CWP

  4. Aim & objectives of CRP-2 Long term evaluation • Cement Waste Products (CWPs) for • Chemical durability • Compressive strength • Homogeneity • Micro structure • Biological interaction • Back fill material • Site specific material / parameter • Engineering barriers

  5. Aim & objectives of CRP-3 • Study of cementation and hardening of CWP in presence of • Various wastes • Different cement compositions • Role of additives during cementation

  6. Work planning • Development of CWP having better leaching characteristics and which can have more activity loading. • Preparation of CWP • Laboratory scale • Plant scale • Characterization of CWP • Laboratory • Field • Evaluation of backfill material

  7. Preparation of CWP on Lab. Scale Variable • Waste, cement and admixtures • Waste to cement ratio • Admixture to cement ratio • Water / waste to cement ratio Method • Preparation of number of blocks for each variable at a time • Casting in moulds • Curing : 28 days • Leaching for 6 to 12 months as per ANSI 16.1 in DM Water • Leachant vol. /block vol.= 10

  8. Preparation of CWP on Plant Scale • CWP on 20 liter scale • CWP on 200 liter scale • Taking the sample of CWP during in-situ cementation • Core drilling of few samples from in-situ cementation

  9. TYPES OF CEMENTS • Ordinary Portland cement (opc) • ASTM type 1. OPC • Slag based cement (SBC) • Fly ash cement • High alumina cement • Blended cements OPC clinker + gypsum + admixtures - ground together

  10. General composition of the different cements

  11. ADMIXTURES • Inorganic admixtures • Backfill material • Bentonite • Vermiculite • Silica fumes • Precipitated silica • Clay • Rock powder • Organic admixtures- water reducing chemicals such as • Platilcisers • Super plasticisers

  12. Characterization of CWP • Leaching characterization • Mechanical properties • Compressive strength • Homogeneity • XRD analysis • Pore size distribution • Microscopy –optical & SEM • Others • Hydraulic conductivity • Accelerated diffusion test • Instrumental methods

  13. Instrumental methods of characterisation of CWPS • Aim • To correlate the compressive strength, • porosity, diffusion coefficient, permeability • and leaching characteristics with respect to • composition • To shortlist CWP for leaching test • To track the mineralogical changes with time • after simulated disposal in NSDF • To identify mechanisms of hardening, • strength development/ deterioration etc.

  14. Field test characterization • Disposal of CWPs in earth trench in NSDF • Removal of CWPs periodically (once in two years) and examination for : • Surface for cracks, chip off, color change etc. • Rebound hammer test • Homogeneity • Compressive strength • Hydraulic conductivity • Porosity • Mineralogical changes • Chloride penetration • Depth of carbonation • Change in diffusion coefficient

  15. Long term Leaching characterization of CWP • Laboratory scale CWP blocks in DM water • Leaching of 200 lit CWP block • Dynamic leaching of CWP • Simulation of radiolysis of water - leaching

  16. LID LIFTING HOOKS 400 LITRE STEEL CONTAINER WITH AND WITHOUT DECAYING WOO 200 LITRE CWP LEACHANT 200 L;ITRES SUPPORTS LONG TERM LEACH TEST OF 200 LITRE CWP PROPOSED SET UP collector

  17. Field test characterization-disposal CWP in NSDF • At one such location – Trombay • Simulated CWPs of different sizes have been disposed in 2001. • The location is having sandy silt with appreciable content of montmorillonite clay • Similar experiments have been planned in other locations having different strata such as black cotton soil and sandy soil.

  18. Field test characterization-disposal CWP in NSDF

  19. Clay degraded basalt basalt 20 litre blocks 0.2 litre blocks • CHARACTERISATION OF CWPs BY AFTER EXCAVATION IN 2008 • COMPRESSIVE STRENGTH, • MIP, XRD, SEM, ANALYSIS OF SOIL ADHERING TO CWP • REBOUND HAMMER TESTS

  20. Characterization of CWPs after excavation • Compressive strength, • MIP, XRD, SEM, • Analysis of soil adhering to CWP • Rebound hammer tests • Ultrasonic tests

  21. Geological Succession of the area

  22. A typical geological section of the RSMS area Ref. : Rakesh, R. R., Yadav, D. N., Narayan, P. K. and Nair, R. N. (2005). – “Post Closure Safety Assessment of Radioactive Waste Storage and Management Site, Trombay”, BARC library report. BARC/2005/I/010.

  23. PHYSICAL AND GEO-CHEMICAL PROPERTIES OF THE SITE The representative physical properties such as density and porosity has been presented in Table 1. The distribution coefficient values of soil samples obtained from RSMS site[2] were analysed and are presented in Table 2. Table 2: Distribution coefficient of the soil Table 1: Physical Properties of the soil Ref: Rakesh, R. R., Yadav, D. N., Narayan, P. K. and Nair, R. N. (2005). – “Post Closure Safety Assessment of Radioactive Waste Storage and Management Site, Trombay”, BARC library report. BARC/2005/I/010.

  24. Properties of soil of RSMS, Trombay Ref: Rakesh R.R. 2005. Simulation of radioactive contaminant transport in unsaturated soils, Ph. D. Thesis. Dept. of Civil Engineering, Indian Institute of Technology, Bombay, India.

  25. LONG TERM EVALUATION OF CWPs- Non-Destructive Test (NDT) Procedures • Ultrasonic Tests • Ultrasonic pulse velocity can be used to determine homogeneity, presence of voids, cracks of CWP • Basic data correlating ultra sonic pulse velocity with density, • porosity and strength will be generated by preparing and testing • number of blocks. • Rebound Hammer Test • Simple and quick method of obtaining correlation between compressive strength and rebound number • The force and pulse duration are critical parameters & will be used on various CWPs of 20 and 200 litre CWPs as quality control measure • Will be used for disposed CWPs after their removal

  26. Evaluation of admixture and clay • Distribution coefficient • Composition • Physical properties, • Chemical properties

  27. TYPICAL SPECIFICATIONS OF VERMICULITE AND BENTONITE

  28. Evaluations of admixtures for their sorption characteristics

  29. Evaluation of bentonite for particle size distribution Majority of particles are in the range of 100- 500 microns

  30. Evaluation of bentonite for swelling behavior

  31. Evaluation of bentonite for swelling behavior • Swelling is complete in 8-10hrs. • The swelling is of the order of 200-280 %. • The swelling is more in distilled water than in service water : due to replacement of Ca ions from bentonite in the distilled by water molecule • The swelling is more in case of calcium bentonite than sodium bentonite : Replcement of bigger Ca ions by water molecule • Swelling gets enhanced due to exchange of Ca and Na ions with water molecule

  32. Evaluation of bentonite for thermal stability • The heat treated and un-heat treated bentonites in the range 300-500 oC show comparable swelling. • In DTA run there are two major endo peaks at 100 and 450oC corresponding to free and bound water loss.

  33. Evaluation of bentonite for water equilibration Water gets saturated very fast and thereafter no marked change

  34. Evaluation of vermiculite for particle size distribution About 90 % of the particle size distribution is in the range of -16 to +80 ASTM mesh.

  35. Evaluation of vermiculite for Cs loading There is structural change in the vermiculite due to Cs loading.

  36. Evaluation of vermiculite for thermal stability DTA runs of as such and heat treated vermiculite indicate that the vermiculite is thermally quite stable.

  37. Bio-degradation of CWP • Identification of cement degrading bacteria in NSDF soils • 2. Flow test on 60 ml size CWP & • 3. Characterization of degraded CWP Micro organisms of interest for degradation Study on cement waste products

  38. Practices followed for Cementation of various types of Radioactive Waste in India • Cementation is carried out at various locations for immobilization of • Sludge generated due to LLW treatment • Intermediate level wastes • Ion exchange resins • Miscellaneous wastes • Techniques of Cementation at plant scale • In drum mixing • Conical Mixture Equipment and pouring the CWP in 200 lit drum. • In-situ cementation in 4000 lit capacity in CS tank in RCC trenches. • Admixtures used - Vermiculite

  39. In-situ Conditioning of ILW and Sludge of LLW in Cement Matrix at Tarapur

  40. CONE MIXER ASSEMBLY USED FOR CEMENTATION

  41. CURRENT CWPs FOR IMMOBILISATION OF NUCLEAR WASTES

  42. AVAILABLE FACILITIES • Cementation techniques • Near surface disposal facility (NSDF) • Radiological lab. • Compressive strength testing unit • Accelerated diffusion test unit • XRD & XRF • Optical microscope & SEM-EDX • Ion chromatograph & AAS • Mercury intrusion porosity (MIP) unit • Pore water analysis • FTIR • Impedance spectroscopy • Gas chromatograph

  43. Some of the results of cementation • Evaluation of cement composition • Optimization of waste to cement ratio • Sampling of CWP during plant scale • Evaluation of CWP from plant scale and comparison of result with laboratory

  44. Cement composition evaluation for immobilization of ILW* * Specific activity of ILW : 1000 MBq/l Ref : A.S. Pente, U.S. Singh, C. P. Kaushik, R.G. Yeotikar, A. Mishra and S.S. Ali., “Cementation study of Intermediate Level radioactive liquid waste stored at Tarapur”, Proc.: Nuclear and Radiochemistry Symposium (NUCAR-2001), Department of Chemistry, University of Pune, Pune, India, Feb. 7-10, 2001, pp 540-541 .

  45. Properties of CWPs of immobilisation of various types of nuclear waste

  46. Cementation of IX resins • Different Waste to cement ratio • Properties of cement matrix • Homogeneity • Pore size distribution • Diffusion phenomenon • Leaching evaluation • Mineralogical examination

  47. Mineral phases detected by XRD analyses of CWP using SBC incorporating IX resins

  48. PORE SIZE DISTRIBUTION OF CWP a b (b) ILW IN BLENDED CEMENT (a) IX RESINS IN SBC

  49. OPTICAL MICROSCOPY Void* CWPs incorporating IX resin * FORMED DUE TO SHRINKING OF RESIN CAUSED BY LOSS OF WATER TO CEMENT HYDRATION

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