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Cementation of waste resins by calcium sulfoaluminate cement Junfeng Li

Cementation of waste resins by calcium sulfoaluminate cement Junfeng Li Institute of Nuclear and New Energy Technology Tsinghua University, P.R.China. Outline. Introduction of Resin cementation in China Introduction of SAC system Researches carrying out

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Cementation of waste resins by calcium sulfoaluminate cement Junfeng Li

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  1. Cementation of waste resins by calcium sulfoaluminate cement Junfeng Li Institute of Nuclear and New Energy Technology Tsinghua University, P.R.China

  2. Outline • Introduction of Resin cementation in China • Introduction of SAC system • Researches carrying out • Resin cementation by SAC and zeolite system • Long term stability study

  3. 1. Resin cementation in China

  4. Radioactive Waste Resins • Boride contained Generated from nuclear power plant • No-boride contained From nuclear facilities

  5. Techniques for Radioactive resins treatment • Incineration Problems of high temperature and gases release • Wet oxidation Difficult to operate • Direct Solidification Plastic, Pitch ，Cement and Organic Polymer

  6. Resins treatment in China • There is no suitable technique • Tons of radioactive resins were stored temporarily • These resins are difficult to retake for permanent treatment

  7. Flaws of resins cementation • Low loading of spent resins • Low compressing strength, • Cracking or demolishing of the matrix • High leaching rates of radionuclides • Cracks from hydration heat

  8. Cracks in the matrix

  9. Prescriptions in references • Furnace slag 24 wt.%, fly ash 24 wt.%, and OPC 8 wt.% , wet resin 24 wt.% , water 20 wt.% resin: base material =43:100 (wt./wt.) compressing strengh is 7 Mpa • Resins 24ml, OPC 55.9g, zeolite 37.3g resins:base material = 20:100(wt./wt.)

  10. Volume change in resin cementation • About 300L resins will come into a 2000 L waste solid when cemented, • Wastes were enlarged 6-7 times 2000 L solid 300L resin cementation

  11. 2. Calcium Sulfoaluminate Cements system

  12. Calcium Sulfoaluminate Cements • Quick setting • Expansive • High hydration heat release rate • Good resistance to conventional sulfate attack and corrosion • Good resistance to freezing, - 10 ~ - 20oC • Low alkalinity, pH 10 ~ 12

  13. Calcium Sulfoaluminate Cements Main clinker phases yeelimite(3CaO.3Al2O3.CaSO4), Belit(2CaO.SiO2), iron phase (4CaO.Al2O3.Fe2O3), 12CaO.7Al2O3, CaO.Al2O3 Main hydration phases ettringite (3CaO.Al2O3.3CaSO4.32H2O), Al(OH)3 monosulfate (3CaO.Al2O3.CaSO4.12H2O)

  14. SEM of OPC and SAC OPC SAC

  15. Physical Properties of the Cements

  16. 3. Researches carrying out

  17. Controlling cracks from hydration temperature • Reducing ratio of cement in the products • Using cement of lower hydration heat • Adding ice into binders, or pre-cooling part or all of the materials • Improving heat emit conditions • Minimizing temperature grads in the products • Using fibers

  18. Supplementary materials used • Zeolite, • Quenching slag, • Furnace slag • Fly ash

  19. Impaction of additives on compressing strength

  20. Impaction of zeolite on compressing strength

  21. Impacts of zeolite addition on Cs+ leaching rate ■—ASC ；●—ASC with 10％ zeolite；▲—ASC with 20％ zeolite； ▼—ASC with 30％ zeolite；—ASC with 40％ zeolite

  22. Impact of zeolite addition on Cs+ retard ■—ASC ；●—ASC with 10％ zeolite；▲—ASC with 20％ zeolite； ▼—ASC with 30％ zeolite；—ASC with 40％ zeolite

  23. Impacts of zeolite on microstructure 10% zeolite 20% zeolite 30% zeolite 40% zeolite

  24. Prescription we used resin: base material =100:100 (wt./wt.) the 28d compressing strength is 12-13 MPa

  25. Temperature curve of 200L matrix

  26. Experiment of 200L

  27. Long term stability • Compressing strength lost in water • Radioactive decomposition of the matrix

  28. Compressing strength lost in water • In the near surface treatment system, although many Engineering measures had been taken to provide water immersion, it can not be avoid totally. • Erosive components in water are normally chloride,carbonate, and sulphate. • In Northwest treatment plant of medium and low level radioactive waste are mainly sulphate

  29. Quick Immersion test • 1. Water contain 2.1% Na2SO4 were used of immersion • 2. Put the samples into the Na2SO4 contained water for 16 hours • 3. Put the samples in (54±1)℃ airs for 7 hours and 40 minutes • 4. Cool the samples for 20 minutes； • 5. Do steps 1-4 for 4 circles

  30. Immersion results

  31. Compressing strength lost

  32. Radioactive decomposition(106 Gy) 图6‑3 ASCTZ树脂固化体辐照前后的抗压强度对比

  33. Gas generate (105Gy)

  34. Conclusion • SAC cement is a promising candidate as an alternative cement for radioactive spent resins treatment. • The SAC and zeolite system can reducing leaching rate of radionuclides greatly, and with good strength. • Controlling the cracks from temperature should be concerned in SAC cementation of resins

  35. Thanks For Your Attention

  36. Interaction of cement and resins • The resins and cement hadn’t solidified together, the resins were only physically encapsulated

  37. Advantages of cementation • Requiring simple equipment • Low working temperature • No trouble of gas cleaning • Low cost

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