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DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Designing Wasteforms for Technetium Anion sorption with precursors.

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Presentation on theme: "DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Designing Wasteforms for Technetium Anion sorption with precursors."— Presentation transcript:

1 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Designing Wasteforms for Technetium Anion sorption with precursors for ceramic phases Jonathan Phillips Centre for Advanced Structural Ceramics Department of Materials, Imperial College London Prince Consort Road, London, SW7 2AZ Supervisor Dr Luc Vandeperre

2 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Overview Problem Tc: The Problem Current Treatment Solution Layered Double Hydroxides Integrated solution Outcome Results Future Work

3 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Common form: 99 Tc with a half life of 2.13x10 5 years. Tc is a low energy beta emitter. It is produced with sufficient yield (6.1%) to be a concern for the environment. Technetium compounds generally do not bind well with soils and are highly mobile in the environment. Background

4 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Background In the UK, Tc was formerly discharged to the sea by BNFL however it is now separated using a process involving tetraphenylphosphonium bromide (TPPB). The TPPB enables Tc to be disposed of by cement encapsulation. In alkaline environments TPPB is known to degrade releasing the pertechnetate anion TcO 4 -.

5 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Aim The aim is to capture the pertechnetate anion from solution using layered double hydroxide materials with a suitable composition to be thermally converted to stable ceramic phases. LDH Production Anion Capture Thermal Conversion

6 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Ca cations: coordination 7 (with additional water/anion in interlayer) Edge sharing of octahedra forming large sheets Hydroxide Group Calcium Portlandite - Ca(OH) 2

7 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal M (II) + Isomorphous Substitution Al,Fe (III) M (III) Mg,Ca Layered Double Hydroxides

8 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal H2OH2O Anions M 2+ (1-x) M 3+ x (OH) 2 (A z+ ) x/z.nH 2 O Charge Balance

9 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Materials and Methods Phillips, J. and L.J. Vandeperre, Production of Layered Double Hydroxides for Anion Capture and Storage, in Materials Research Needs to Advance Nuclear Energy, Mater. Res. Soc. Symp. Proc., Vol. 1215, G. Baldinozzi, et al., Editors. 2010, MRS: Warrendale, PA. p. V NaOH + NaNO 3 pH >12.5 Stirrer bar Ca (1-x) (Al (1-y) Fe y ) x (OH) 2 (NO 3 ) x 1M Total Ca(NO 3 ) 2.4H 2 O Al(NO 3 ) 3.9H 2 O Fe 3+ (NO 3 ) 3.9H 2 O

10 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal X-Ray Diffraction Pattern and SEM

11 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Characterisation of product

12 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal LDH Production Anion Capture Thermal Conversion

13 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Topotactic Exchange Dissolution Reprecipitation Preference for to be intercalated therefore exchange with LDH dissolves, increasing the solution pH and then reprecipitates with new anion Anion Exchange Mechanism

14 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Anion Exchange Method 1g of LDH powder (NO 3 intercalated) was added to a solution containing the desired interlayer anions The composition of the anionic solution were varied in the following molar ratios (balanced for charge differences of the anions) 0.1 : : : 0.1 The exchange was allowed to occur for a period of 1hr and for 14 days. The solids were separated by vacuum enhanced filtration before being dried in an oven. 14

15 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Results : Anion Exchange Cl:NO3 J.D. Phillips, L.J. Vandeperre, J. Nucl. Mater.(2010),doi: /j.jnucmat Formation of two distinct interlayer spacings in the short term. Prolonged exposure to high [CO 3 ] solutions deleterious.

16 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Results : Anion Exchange NO 3 :CO 3 Cl:CO 3 CO 3 effect

17 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Untreated LDH Powder Calcined LDH Powder Rehydrated -Calcined LDH Powder B B x BB O O XRD- Memory effect B = Brownmillerite O = Calcium Oxide X = Calcium Carbonate CalcineCapture

18 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Wang Y. et al Jour. Coll and Int. Sci. 301 (2006) Competition with other anions. Capture of pertechnetate or other anions with calcined LDH, taking advantage of the memory effect Adsorption efficiency for surrogates of TcO ICP OES Anion Capture with LDHs

19 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal LDH Production Anion Capture Thermal Conversion

20 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Temperatures associated with the Tc system: Tc 2 O 7 = MP 119.5°C BP 311°C TcO 2 = sub ~900°C Conversion at as low a temperature as possible desirable. The aim is to convert these LDH phases to Brownmillerite Ca 2 (Fe,Al) 2 O 5 which are compositions commonly found in cements Thermal Conversion Ca 2 (Fe,Al) 2 O 5 *ICSD, Vanpeteghem et al, 2008 Ca Fe,Al O

21 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Theta(°) Intensity(a.u) 400°C B B x B B O O B = Brownmillerite O = Calcium Oxide X = Calcium Carbonate Thermal Conversion A sample of LDH-NO 3 was calcined to 400°C for 1 hour Browmillerite and Calcium Oxide have formed.

22 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Results : Thermal Analysis NO 3

23 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Thermal Product - NO 3 23 B: Brownmillerite Ca 2 AlFeO 5 P: Calcium Hydroxide Ca(OH) 2 C: Calcium Oxide CaO

24 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Results : Thermal Analysis Cl

25 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Thermal Product – Cl 25 B: Brownmillerite Ca 2 AlFeO 5 P: Calcium Hydroxide Ca(OH) 2 C: Calcium Oxide CaO

26 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Thermal Product – Cl 26 B: Brownmillerite Ca 2 AlFeO 5 P: Calcium Hydroxide Ca(OH) 2 C: Calcium Oxide CaO

27 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal Conclusions Layered double hydroxides with a composition suitable for thermal conversion to ceramic phases have been produced. The absorption capacity of these materials for the perhenate anion is significantly reduced due contamination with CO 3 from equilibrium with the atmosphere. Capture of Cl - is favourable even in the presence of CO 3, these materials may be applicable to the remediation of 36 Cl - from the processing of graphitic wastes. Thermal conversion product dependent on interlayer anion.

28 DIAMOND Decommissioning, Immobilisation and Management of Nuclear Waste for Disposal This project is funded by the UK Engineering and Physical Sciences Research Council through the DIAMOND consortium Thank you for your attention Acknowledgements


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