The document analyzes monazite from the Steenkampskraal deposit in South Africa as a potential nuclear waste form for encapsulating actinides. Petrographic, SEM and electron microprobe analyses were conducted on samples. The analyses found evidence of alteration in the monazite. No uranium was detected. Due to the alteration, the thorium and uranium concentrations were depleted, indicating monazite cannot reliably encapsulate actinides over long time periods. Further study on unaltered samples is needed to fully evaluate monazite's potential.

1. Monazite as a nuclear waste form
for encapsulating actinides: a
mineralogical study of natural
monazite from Steenkampskraal
Supervisor: M. Knoper
Co-supervisor: D. Harlov
GABRIELLE FICQ
201300823

2. Introduction to Steenkampskraal
Steenkampskraal
Regional geology
Alteration
History and mining background
Introduction to nuclear waste
Why use thorium and not uranium?
Why use monazite?
Purpose of the research project
Data analysis
Petrographic analysis
Scanning Electron Microscope analysis
Electron Microprobe Analysis
Conclusion
Improvements
References
CONTENT

3. STEENKAMPSKRAAL
• Western Cape Province, South Africa
• Formed during the amalgamation of the Kaapvaal craton and the
Namaqua-Natal Belt (Bachmann et al., 2015)
• Namaqualand Metamorphic Complex (Andreoli et al., 1994)
• Mesoproterozoic (1600 – 1000 Ma) (McCarthy and Rubidge, 2005)
• Monazite ore is hosted within a metamorphic rock of amphibolite to
granulite facies (Spear and Pyle, 2002)
• Largest monazite deposit in terms of the REE, Th and U
concentration (Read and Williams, 2001; Read et al., 2002)

4. STEENKAMPSKRAAL
Adapted from Andreoli et al. (1994)

5. REGIONAL GEOLOGY
• Southern part of the Bushmanland sub-province (Andreoli
et al., 1994)
• Dominated by granite gneisses, granites and charnockite
gneisses (Andreoli et al., 1994; Andreoli et al., 2006)
• Best exposed along the Roodewal Suite (Andreoli et al., 1994)
• Radioactive terrains such as Steenkampskraal are
underlain by granulite-facies rocks (Andreoli et al., 2006)

6. ALTERATION
Three alteration theories:
•1st
- Intrusive granulite-facies (Andreoli et al., 1994)
• High temperature granulite-facies region
•2nd
- Greenschist-facies metamorphism (Read et al., 2002)
•3rd
- Hydrothermal alteration during metamorphism
(Wall. 2014)

7. HISTORY AND MINING BACKGROUND
• According to Steenkampskraal Thorium Limited (2016)
• Deposit discovered in the 1940’s
• Mined for the high thorium concentration
• Ore was processed for the full range of REE
• Mining took place from1952 – 1963
• Late 1960’s the mine closed due to mining of uranium
• Monazite ore is starting to make a comeback
• Higher demand for REE (Basson et al., 2016)
• Better understanding of Th (Basson et al., 2016)
Concerns regarding the encapsulation of Th as nuclear waste has
started to take place

8. WHY THORIUM AND NOT URANIUM?
According to Staff (2015)
•Safer radioactive element
•Produces a cleaner fuel source
•Produces a lower amount of nuclear waste
•Affordable fuel source
•Minimal water usage needed
•Environment and human health will improve
So why use phosphates to encapsulate actinides?

9. WHY USE MONAZITE?
• Durable phosphate mineral (Ewing and Wang, 2002)
• High chemical stability (Montel et al., 2006)
• High resistivity to radioactive damage (Montel et al., 2006)
• Immobilization of actinides (Ewing and Wang, 2002)
• Strong chemical structure, minimum damage through alpha decay
(Harrison et al., 2002)
• Resistant to strong alkaline and acidic solutions (Read and Williams,
2001)

10. PURPOSE OF THE STUDY
Determine the capability of monazite for the
encapsulation of actinides without mobilisation
during alteration

11. PETROGRAPHIC ANALYSIS

12. STK 108
• Granoblastic texture
• Monazite and apatite
surrounded by chalcopyrite
• Brown alteration
• Quartz vein
• Hydrothermal alteration

13. STK 091 FW
• Interlocking texture
• Granoblastic texture
• Triple point grain boundaries
• Internal zonation
• Brown alteration

14. NAM 1675 A
• Altered samples
• Granoblastic texture
• Associated with magnetite
and rutile

15. SCANNING ELECTRON
MICROSCOPE ANALYSIS

16. STK 79 HW
• Monazite associated with magnetite and rutile
• Figure B
• Monazite vein associated with lime (CaO)
• Thermal input through metamorphism (Betts, 1990)

17. STK 108 C 93.21 and STK 082 HW
• Monazite associated with magnetite and rutile
• Grid pattern

18. ELECTRON MICROPROBE
ANALYSIS

19. STK 108 STK 091 FW NAM 1675 A NAM 1675 C
Cry 5 Cry 6 Cry 1 C1 Cry 2 C1 Cry 1 C1 Cry 2 C1 Cry 1 C1 Cry 2 C1
Analysis Molar weight percentage
P2O5
28.80 29.30 29.10 28.80 28.70 28.90 28.00 24.10
SiO2
1.00 0.80 0.90 1.10 1.00 1.00 0.70 7.40
ThO2
8.30 8.40 8.90 8.80 8.50 8.30 3.40 7.30
U2O3
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Y2O3
2.30 2.20 2.20 2.10 2.30 2.30 0.40 0.50
La2O3
12.40 12.30 12.30 12.20 12.60 12.60 15.20 12.40
Ce2O3
27.10 27.10 26.80 27.00 26.60 27.10 32.50 26.40
Pr2O3
2.90 3.00 2.90 3.10 2.80 2.80 3.50 2.90
Nd2O3
11.00 11.10 10.70 11.00 10.80 10.60 12.30 10.90
SmO
1.80 1.80 1.70 1.90 1.70 1.80 1.60 1.80
EuO
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Gd2O3
0.60 0.60 0.60 0.60 0.60 0.60 0.00 0.00
Dy2O3
0.50 0.50 0.60 0.50 0.70 0.60 0.00 0.00
Al2O3
0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.60
FeO
0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.60
CaO
1.10 1.30 1.30 1.10 1.20 1.10 0.20 1.20
PbO
0.00 0.00 0.00 0.00 0.00 0.50 0.00 0.00
Total
97.80 98.40 98.00 98.20 97.50 98.20 97.80 101.10

23. Adapted from Andreoli et al. (1994)

24. CAN MONAZITE BE USED FOR THE
ENCAPSULATION OF ACTINIDES?

25. CONCLUSION
Monazite cannot be used for the encapsulation of actinides
No uranium was detected
All samples are slightly altered
Hydrothermal alteration
Thermal alteration
Due to the alteration of the monazite, the thorium and
uranium concentration became depleted

26. IMPROVEMENTS
• Fresh samples must be analysed
• Compare definite altered and unaltered monazite
samples
• Determine the alteration type and how the alteration took
place
• Improve the study to use all phosphates as a possible
method for the encapsulate of actinides

27. REFERENCES
Andreoli, M., Smith, C., Watkeys, M., Moore, J., Ashwal, L. and Hart, R. (1994). The geology of the
Steenkampskraal monazite deposit, South Africa; implications for REE-Th-Cu mineralization
in charnockite-granulite terranes. Economic geology, 89(5):994-1016.
Andreoli, M.A.G., Hart, R.J., Ashwal, L.D. and Coetzee, H. (2006). Correlations between U, Th
content and metamorphic grade in the western Namaqualand belt, South Africa, with
implications for radioactive heating of the crust. Journal of Petrology, 47(6):1095-1118.
Bachmann, K,. Schulz, B., Bailie, R. and Gutzmer, J. (2015). Monazite geochronology and
geothermobarometry in polymetamorphic host rocks of volcanic-hosted massive sulphide
mineralizations in the mesoproterozoic Areachap terrane, South Africa. Journal of African
Earth Sciences, 111:258-272.
Basson, I.J., Muntings, J.A., Jellicoe, B.C. and Anthoniesen, C.J. (2016). Structural interpretation of
the Steenkampskraal monazite deposit, Western Cape, South Africa. Journals of African Earth
Science. 121: 301-315.
Betts, J. (1990). Fine minerals: Lime mineral database. Accessed from:
http://webmineral.com/data/Lime.shtml#.V5d8zfl97IV Accessed on: 26/07/2016
Ewing, R.C. and Wang, L. (2002). Phosphates and nuclear waste forms. Reviews in Mineralogy and
Geochemistry, 48(1): 673-699.
Harrison, T.M., Catlos, E.J. and Montel, J.M. (2002). U-Th-Pb dating of phosphate minerals. Reviews
in Mineralogy and Geochemistry, 48(1): 523-559.

28. REFERENCES
McCarthy, T. and Rubidge, B. (2005). The story of earth and life. A southern African perspective on a
4.6- billion year journey. Struik Nature. Cape Town.
Montel, J.M., Glorieux, B., Seydoux-Guillaume, A.M. and Wirth, R. (2006). Synthesis and sintering of
a monazite-brabantite solid solution ceramic for nuclear waste storage. Journal of Physics
and Chemistry of Solids. 67: 2489-2500.
Read, D. and Williams, C.T. (2001). Degradation of phosphatic waste forms incorporating long-lived
radioactive isotopes. Mineralogical Magazine. 65 (5): 589-601
Read, D., Andreoli. M.A.G., Knoper, M., Williams, C.T. and Jarvis, N. (2002). The degradation of
monazite: Implications for the mobility of rare-earth and actinide elements during low-
temperature alteration. Eur. J. Mineral. 14: 487-497.
Spear, F.S. & Pyle, J.M. (2002). Apatite, monazite and xenotime in metamorphic rocks. Reviews in
Mineralogy and Geochemistry, 48(1):293-335.
Staff, W. (2015). Thorium could avert the energy crisis. Environmental Management.
Steenkampskraal Thorium Limited. (2016). Thorium refinery plant: Thorium refinery project ThRP.
Accessed from: http://www.thorium100.com/Thorium%20Refinery%20Plant.php Accessed on:
11/08/2016 and Historical and future operations for Steenkampskraal Monazite mine.
Accessed from: http://www.thorium100.com/SMM.php Accessed on: 11/08/2016.
Wall, F. (2014). Critical metals handbook. First Edition. John Wiley & Sons. United Kingdom p312-339