1. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH L. Ionascu, M. Nicu, F. Dragolici, C. N. Turcanu, Gh. Rotarescu L. Ionascu, M. Nicu, F. Dragolici, C. N. Turcanu, Gh. Rotarescu

2. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  Portland cement matrix  good mechanical properties : handling, storage, transport and long term stability  monolith with acceptable mechanical, chemical and physical properties  release of radioactivity from the waste form in the environment is minimized.

3. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  XRD application for the phase identification of matrix that simulates the conditioned radioactive waste and the correlation with mechanical performance  selected matrices for the study are normal cement with iron precipitates.  information about the chemical reactions between the radioactive precipitates and the hydrates, hydrolysis products of the cement.

4. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  the chemical nature and proportion of the precipitation products affect : - the hydrolysis of the initial cement components - the reactions of metastable hydration constituents - mechanical strength and the chemical resistance of the hardened cement system

5. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  Solidification of radioactive wastes with hydraulic cement either with or without admixtures  the wastes produced by nuclear activities are very diverse and under certain circumstances affect the rate of hydration on cement and/or reduce the quality of product  IFIN – HH - multiple precipitation based on iron hydroxide and calcium phosphate formation  data basis necessary for the approach the medium and long term assessment of the safety and performance for final packages disposed in Radioactive Waste National Repository Baita-Bihor

6. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  Medium term programme (1997-2010) was implemented : - study of iron precipitates obtained during LLAW treatment; - cementation of sludge chemical components; - durability of cemented waste in repository and under simulated conditions.

7. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  Method : - precipitation of the insoluble compounds - LLAW having iron hydroxides and iron phosphates - microstructure analysis on some samples obtained through methods that simulate conditioning of the iron hydroxide and iron phosphate precipitate.

8. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH There were prepared two types of iron precipitates:  the addition of the neutralization agents NaOH concentrated to the diluted solution of FeCl 3 ;  the Na 3 PO 4 addition to the diluted solution of FeCl 3.

9. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH The precipitates obtained were conditioned through cementation as it follows:  cement + iron hydroxide (5g cement + 2.5g wet precipitate);  cement + iron phosphate (5g cement + 2.5g wet precipitate).

10. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  The X-ray investigation was performed with a Dron 2 diffractometer, using Ni-filtered Cu-K radiation (λ=1.5418 Ǻ), for diffraction angles 2 theta ranged between 5 and 65˚.  Calculating interplanar distance “d” parameters for all diffraction maxima which appears in the polycrystalline mixture spectrum and comparing with “d” values from ASTM cards can be obtained a qualitative analysis for crystalline phases.  For each phase there is a certain minimal proportion of it in a mixture in order to be identified. This minimal proportion depends on the particular phase nature and also on the other present phases nature. In the same time with the growth of the phase content in mixture, the intensity of specific lines increases.

11. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  The basic information on the waste matrix is obtained by mechanical strength tests.  The selected matrices for characterization are normal concrete composition as reference samples and the conditioned matrices prepared with non-active precipitate compounds (iron hydroxides and iron phosphate) simulating the real radioactive sludge.  Samples were positioned in five points (from 1 to 5) of Radioactive Waste National Repository Baita-Bihor and kept 1, 3, 5, and 7 years before mechanical characterization.

12. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH Steps assumed for the conditioned waste matrix characterization in simulated and real conditions:  - preparation and mechanical characterization of reference cemented matrices:  Portland Cement + water, with a cement/water ratio 2:1;  - preparation of iron precipitates such as to:  addition of the neutralization agents, NaOH(20%), to the diluted solution of FeCl3(40%);  addition of Na3PO4 to the diluted solution of FeCl3(40%);  - preparation and mechanical characterization of simulated sludge cemented matrices containing iron precipitates:  Portland cement + iron phosphate precipitate with cement / iron phosphate ratio 1:0.5;  Portland cement + iron hydroxide precipitate with cement / iron hydroxide ratio 1:0.5  - selection of real and simulated disposal conditions for cemented matrices;  - emplacement of cemented matrices in Radioactive Waste National Repository Baita Bihor for real disposal characterization;

13. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  After the preparation, the samples of cemented matrices were kept 24 hours in pattern, then in tight plastic bag for 7, 14 and 28 days for reinforcement.  After 28 days, the samples of cemented matrices were introduced in distillate water (laboratory conditions) and in the Radioactive Waste National Repository Baita-Bihor (real condition).  For the mechanical characterization tests the size of the samples was 20x20x20 mm (tested at compression).  The compression tests, performed on five samples, were done in a construction material laboratory using an digital press machine type MATEST, with loading rates 1.2 MPa/s

14. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH No. The point of disposal in real condition Temperature [◦C] Humidity [%] 1 Position 1 1198 2 Position 2 1092 3 Position 3 1092 4 Position 4 11.585 5 Position 5 1085 Table 1 – The temperature and humidity conditions in the Radioactive Waste National Repository Baita- Bihor

15. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH The results for samples disposal in real conditions will be compared with the results obtained for the same type of samples kept in laboratory conditions.

16. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH 1. XRD Analysis Figure 1 - The x-ray diffractogram of hydrated cement The XRD diffractogram of the hydrated cement emphasizes crystalline hydrated compounds as: -tricalcium hydrosulfataluminate similar to the natural ettringite - Ca3Al2O6·3CaSO4·31H2O (2θ: 15.8; 19.2; 21.8; 35; 41), -calcium hydroxide – Ca(OH)2 well crystallized from the intergranular solution (2θ: 18; 34.2; 47.2; 50.6; 54.6), -the hexagonal calcium hydroaluminate - Ca4Al2O7·13H2O (2θ: 11.6; 33.6; 36) -tricalcium silicate – Ca3SiO5 (2θ: 29.5; 32.3; 51.8), -dicalcium silicate – Ca2SiO4 (2θ: 29.5; 32; 32.3) -tricalcium aluminate – Ca3Al2O6 which remain unreacted (2θ: 21.8; 32)

17. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  Due to the precipitates low crystallized, a part of the iron compounds present low and large lines.  The measurement done through XRD on the iron precipitate Fe(OH)3 confirmed the existence of two types spinelic structures corresponding to magnetite (Fe3O4) and γ Fe2O3 as well as to β Fe2O3·H2O and αFe2O3 compounds.  From the Fe(OH)3 x-ray diffractogram one can notice the appearance of a crystallized phase being present through well underlined peaks and of a amorphous phase presenting very large and low peaks. Figure 2 - The x-ray diffractogram of iron hydroxide

18. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH At the precipitate FePO4 x-ray diffractogram one can notice that the iron phases present a better crystalline namely there are presented more sharped peaks and with the higher intensities especially: - iron hydrate orthophosphate - FePO4·2H2O, - iron metaphosphate – Fe(PO2)2 - iron hydrate phosphate – Fe4(PO4)2(OH)6·H2O. In the case of this iron precipitate can be noticed in the x-ray diffractogram the appearance of amorphous phase. Figure 3 - The x-ray diffractogram of iron phosphate

19. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH The peaks characteristic of the hydrated cement compounds do not disappear, they presenting a very small decreasing of intensity of the lines specific to these compounds (Ca(OH)2, tricalcium hydrosulfataluminate – Ca3Al2O6·3CaSO4·31H2O, calcium hydroaluminate – Ca4Al2O7·13H2O and calcium hydrosilicates like tobermorite gel – Ca2SiO4·H2O). In this x-ray diffractogram appeared new compounds during the hardening of cement paste as a consequence of the chemical reactions between iron hydroxide and the hydrated cement compounds: calcium iron oxide – β-Ca4Fe14O25 (2θ: 34.55; 34.21; 33.30; 29.92), calcium iron silicate – Ca3Fe2(SiO4)3 (2θ: 33; 29.59; 36.45; 20.8), calcium aluminium iron oxide - Ca4Al2Fe2O10 (2θ: 34.09; 32.31; 47.34; 33.56). These compounds belonging to the hydrated cement present an important role concerning the hardening structure of the cement and the mechanical strength of the concrete. Figure 4 - The x-ray diffractogram of cement - iron hydroxide

20. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH Emphasizes the existence of some new compounds which appear after the chemical reactions between the cement and iron precipitate namely: phosphate hydroxide double of iron and calcium - Ca2Fe(PO4)2(OH)1½H2O (its diffraction angle being: 29.2; 32.8; 34.6; 25.6). Beside these new compounds, lower quantities of iron hydrate orthophosphate -FePO4·2H2O unreactioned, can be identified. It is also emphasize the important presence of compounds from the hydrated cement, but presenting a diminution of the Röentgen interferences intensities specific to these compounds. Figure 5 - The x-ray diffractogram of cement - iron phosphate

21. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH 2. Mechanical tests  The compression tests were done on the samples of cemented matrices with sizes 20x20x20 mm.  The samples were submitted of the mechanical tests after 28 days and 1, 3, 5, 7 years disposal in the real and laboratory conditions.  Preliminary results show that iron hydroxide and iron phosphate precipitate have a negative influence on the mechanical performances of cemented matrices.  In table 2 are presented values obtained for the compressive strength on the cement: water matrices after 28 days, 1, 3, 5and 7 years of disposal in real and laboratory conditions.

22. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH NoSamplePosition Rcomp. (N/mm2 ) 1. Cement - water after 28 days 26.0 2. Cement – water after one year disposal under distillate water (laboratory conditions) 28.3 3. Cement – water after one year disposal in National Repository of Radioactive Waste (real conditions) 13539.543.537.6 4. Cement – water after three years disposal under distillate water (laboratory conditions) 51.3 5. Cement – water after three years disposal in National Repository of Radioactive Waste (real conditions) 13555.35956 6. Cement – water after five years disposal under distillate water (laboratory conditions) 61.0 7. Cement – water after five years disposal in National Repository of Radioactive Waste (real conditions) 13563.572.063.0 8. Cement – water after five years disposal under distillate water (laboratory conditions) 64 9. Cement – water after five years disposal in National Repository of Radioactive Waste (real conditions) 135697366.7

23. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH The behaviour in time of the compressive strength for cement- water matrices is presented in figure 6.

24. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH In table 3 are presented values obtained for the compressive test on the cement: iron hydroxide precipitate matrices after 28 days, 1, 3, 5and 7 years of disposal in real and laboratory conditions. Figure 7 - The behaviour in time of compressive strength on the cement – Fe(OH)3 matrices

25. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH NoSamplePositionRcomp.(N/mm2) 1 Cement – iron hydroxide precipitate after 28 days 22 2 Cement – iron hydroxide precipitate after one year disposal under distillate water (laboratory conditions ) 23.41 3 Cement – iron hydroxide precipitate after one year disposal in National Repository of Radioactive Waste(real conditions) 13525.326.324.2 4 Cement – iron hydroxide precipitate after three years disposal under distillate water (laboratory conditions) 25.375 5 Cement – iron hydroxide precipitate after three year disposal in National Repository of Radioactive Waste(real conditions) 13527.4528.6523.53 6 Cement – iron hydroxide precipitate after five years disposal under distillate water (laboratory conditions ) 29.1 7 Cement – iron hydroxide precipitate after five years disposal in National Repository of Radioactive Waste(real conditions) 13531.3733.528.0 8 Cement – iron hydroxide precipitate seven years disposal under distillate water (laboratory conditions) 37.6 9 Cement – iron hydroxide precipitate after seven years disposal in National Repository of Radioactive Waste(real conditions) 13554.9542.6230.5

26. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH In table 4 are presented values obtained for the compressive test on the cement: iron phosphate precipitate matrices after 28 days, 1, 3, 5and 7 years of disposal in real and laboratory conditions The behaviour in time of the compressive strength for cement-water matrices is presented in figure 8.

27. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH NoSamplePositionRcomp.(N/mm2) 1 Cement – iron phosphate precipitate after 28 days 23.5 2 Cement – iron phosphate precipitate after one year disposal under distillate water (laboratory conditions) 25.2 3 Cement – iron phosphate precipitate after one years disposal in National Repository of Radioactive Waste (real conditions) 13529.331.235.7 4 Cement – iron phosphate precipitate after three years disposal under distillate water (laboratory conditions) 38 5 Cement – iron phosphate precipitate after three years disposal in National Repository of Radioactive Waste (real conditions) 13539.540.843 6 Cement – iron phosphate precipitate after five years disposal under distillate water (laboratory conditions) 42.3 7 Cement – iron phosphate precipitate after five years disposal in National Repository of Radioactive Waste (real conditions) 13545.3746.7548.0 8 Cement – iron phosphate precipitate seven years disposal under distillate water (laboratory conditions) 44.6 9 Cement – iron phosphate precipitate after seven years disposal in National Repository of Radioactive Waste (real conditions) 13552.6452.4554.2

28. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH  Concluding remarks : XRD analysis  The analyses of the simulated radioactive waste processing products by x-rays diffraction proved that, despite of the investigated systems complexity, the main phases could be identified.  This study allowed the identification of the compounds that appear after the interaction between the cement and the iron precipitates.  The new results obtained concerning the embedding of the iron compounds in cement offered large possibilities for a detailed characterization of the mechanism during the cementation process.  The XRD proved to be useful in the establishing of the composition and structure of the iron compounds used in the chemical treatment of the radioactive waste.  In the future these data will be the reference data for structural and mechanical characterization of the long term behaviour of these matrices kept in condition simulating the final disposal.

29. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH Mechanical tests The compressive strength obtained for the samples which contain cement - iron hydroxide and cement-iron phosphate are smaller than the reference samples which contain cement-water but they are included in the accepted limits for the embedding matrix with cement (above 5N/mm2).  The compressive strength for system with iron precipitates increase in time and they are not influenced on the disposal conditions.  The results obtained by mechanical tests will be correlated with the structural modifications (after three, five and seven years of disposal).

30. Long term behaviour evaluation of cement conditioning matrices used for management of radioactive wastes at IFIN-HH Thank you !