Thorium

Content maintained by Yanis Miezitis

• Thorium
• Resources
• Thorium resources in heavy mineral sand deposits
• Thorium resources in vein-type deposits
• Thorium resources in alkaline rock complexes
• Thorium resources associated with carbonatite intrusions
• Exploration
• Production
• World Ranking

Thorium oxide (ThO₂) has one of the highest melting points of all oxides (3300°C) and has been used in light bulb elements, lantern mantles, arc-light lamps and welding electrodes, as well as in heat resistant ceramics.

Currently, there is no large scale demand for thorium resources. Thorium can be used as a nuclear fuel through breeding to ²³³U and any large-scale commercial demand for thorium is expected to be dependant on the future development of thorium fuelled nuclear reactors. Several reactor concepts based on thorium fuel cycles are under consideration, but a considerable amount of development work is required before it can be commercialised.

India has been developing a long-term three stage nuclear fuel cycle to utilise its abundant thorium resources. The construction of a 500 megawatt electric (MWe) prototype fast breeder reactor at Kalpakkam, near Madras, was about 66% complete in early 2011. It will have a blanket with thorium and uranium to breed fissile ²³³U and plutonium respectively. This project will take India’s thorium program to stage 2.

In stage 3 Advanced Heavy Water Reactors (AHWRs) burn ²³³U and plutonium with thorium to derive about 75% of the power from thorium. For each unit of energy produced, the amount of long-lived minor actinides generated is nearly half of that produced in current generation Light Water Reactors. Importantly, a high level of radioactivity in the fissile and fertile materials recovered from the used fuel of AHWR, and their isotopic composition, preclude the use of these materials for nuclear weapons. In mid 2010 a pre-licensing safety appraisal had been completed by the Atomic Energy Regulatory Board (AERB) and site selection was in progress. The AHWR can be configured to accept a range of fuel types including enriched U, U-Pu MOX, Th-Pu MOX, and ²³³U -Th MOX in full core.

However, full commercialisation of the AHWR is not expected before 2030. In September 2009, India announced an export version of the AHWR – the AHWR-Low Enriched Uranium (LEU) version. This design will use LEU plus thorium as a fuel, dispensing with the plutonium input. About 39% of the power will come from thorium (via in situ conversion to ²³³U). This version can meet the requirement also of medium sized reactors in countries with small grids along with the requirements of next generation systems (World Nuclear Association 2011¹ ; Kakodkar 2009)².

The China Academy of Sciences, in January 2011, launched a research and development program on Liquid Fluoride TR, known at the academy as the thorium-breeding molten-salt reactor (Th-MSR or TMSR). A 5 MWe MSR is apparently under construction at Shanghai, with a target of being operational by 2015.

Atomic Energy of Canada Ltd (AECL) has reported that some countries are assessing the use of thorium fuels in existing CANDU 6 (700MWe class) reactors. In July 2009, AECL signed a second phase agreement with four Chinese entities to develop and demonstrate the full-scale use of thorium fuel in the CANDU 6 reactors at Qinshan in China³.

A company in the USA, Lightbridge Corporation, is developing thorium-uranium fuel for the existing Russian Vodo-Vodyanoi Energetichesky reactors (VVER-1000) and for use in existing Pressurised Light Water Reactors (PWR).

The thorium fuel design program for the VVER-1000 reactors is aimed primarily at the Indian market, which has two VVER-1000s under construction, with four more planned and another four having received environmental approval.

On 24 July 2009 it was reported in World Nuclear News (accessed on 26 July 2009) that the French public multinational industrial conglomerate, Areva, and Thorium Power (now Lightbridge Corporation) signed an initial collaborative agreement on 23 July to investigate the potential use of thorium in Areva’s Evolutionary Power Reactor (EPR). This was followed by a five year consulting agreement signed on 3 August 2009 (Lightbridge Corporation presentation to Deutsche Bank Conference 11 May 2010).

Australia’s total indicated and inferred in-situ resources of thorium amounts to about 527 000 tonnes. Because there is no publicly available data on mining and processing losses for extraction of thorium from these resources, the recoverable resource of thorium is not known. However, assuming an arbitrary figure of 10% for mining and processing losses in the extraction of thorium, the recoverable resources of Australia’s thorium could amount to about 474 000 tonnes.

Because there is no established large scale demand and associated costing information, there is insufficient information to determine how much of Australia’s thorium resources are economically viable for electricity generation in thorium nuclear reactors.

There are no comprehensive detailed records on Australia’s thorium resources because of the lack of large-scale commercial demand and a paucity of the required data.

Most of the known thorium resources in Australia are in the rare earth-thorium phosphate mineral monazite within heavy mineral sand deposits, which are mined for their ilmenite, rutile, leucoxene and zircon content. Prior to 1996, monazite was being produced from heavy mineral sand operations and exported for extraction of rare earths. However, in current heavy mineral sand operations, the monazite is generally returned to the pit in dispersed form, as stipulated in mining conditions, to avoid the concentration of radioactivity when returning the mine site to an agreed land use. In doing so, the rare earths and thorium present in the monazite are negated as a resource because it would not be economic to recover the dispersed monazite for its rare earth and thorium content. The monazite content of heavy mineral resources is seldom recorded by mining companies in published reports.

Most of the known resources of monazite are in Victoria and Western Australia (WA). Heavy mineral sands are being mined in the Murray basin deposits at Ginkgo and Snapper in New South Wales (NSW) and at Douglas in Victoria. In WA, mining of heavy minerals is taking place at Eneabba, Cooljarloo, Dardanup and Gwindinup.

Using available data, Geoscience Australia estimates Australia’s monazite resources in the heavy mineral deposits to be around 6.1 million tonnes (Mt). The data on monazite and the thorium content in the monazite in the mineral sand resources is very variable, but the available sources include:

• analyses for monazite and thorium in published and unpublished reports;
• published and unpublished analyses of thorium content in exported monazite concentrates; and
• monazite and thorium analyses on heavy mineral sand deposits in company reports on open file available at some State Geological Surveys.

Information from these sources was applied to resource data on individual heavy mineral sand deposits to estimate the thorium resources in these deposits. Where local data on the monazite and thorium was not available, regional data were applied to individual deposits to estimate their monazite and thorium resources. Using this information, Australia’s inferred thorium resources in the mineral sands were estimated to be around 372 000 tonnes.

Apart from heavy mineral sand deposits, thorium can be present in other geological settings such as alkaline intrusions and complexes, including carbonatites, and in veins and dykes. In these deposits, thorium is usually associated with other commodities such as rare earths, zirconium, niobium, tantalum and other elements. The more significant deposits are described in the following paragraphs.

Arafura Resources Ltd: Nolans Bore rare earth-phosphate-uranium-thorium deposit is located 135 kilometres (km) northwest of Alice Springs in the Northern Territory (NT). The mineralisation is hosted in fluorapatite veins and dykes. This deposit contains about 81 810 tonnes of Th in 30.3Mt of Measured, Indicated and Inferred Resources grading 2.8% rare earth oxides (REO), 12.9% P₂O₅, 0.02% U₃O₈ and 0.27% Th. Arafura is currently considering processing the rare earth-phosphate-uranium-thorium ore concentrate from the Nolans Bore deposit at Whyalla in South Australia. The thorium content in the concentrate will be separated as an iron thorium precipitate and transported back to the Nolans Bore mine site in NT for long-term storage as a possible future energy source.

Alkane Resources Ltd: The Toongi zirconium-niobium-rare earth deposit occurs within an alkaline trachyte plug about 30km south of Dubbo in NSW. The deposit has a Measured Resource of 35.7Mt and 37.5Mt of Inferred Resources grading 1.96% ZrO₂, 0.04% HfO₂, 0.46% Nb₂O₅, 0.03% Ta₂O₅, 0.14% Y₂O₃, 0.745% total REO, 0.014% U₃O₈, and 0.0478% Th, giving a total of about 35 000 tonnes contained Th. A demonstration pilot plant (DPP) was constructed and commissioned in May 2008 at the Australian Nuclear Science and Technology Organisation (ANSTO) in the Sydney suburb of Lucas Heights. The DPP is designed to test the flowsheet for ore from Toongi and provide the various products for distribution to potential end users. Alkane reported that two trial runs of the DPP were completed in 2008 and one more in the first quarter of 2009. The plant operated efficiently during this period with no significant issues and in the latter half of the run produced high quality zirconium and niobium products. On 19 September 2011, Alkane announced a Proved Reserve for the deposit of 8.07Mt grading 1.91% ZrO₂, 0.04% HfO₂, 0.46% Nb₂O₅, 0.03% Ta₂O₅, 0.14% Y₂O₃, and 0.75% total REO. At the same time the company released results of a definitive feasibility study for the project that excluded the production of thorium. The financial analysis indicated a nett present value for the project of $181 million at a processing rate of 400 kilotonnes per annum (ktpa) and $1.207 million at a processing rate of 1000ktpa.

Hastings Rare Metals Limited: Other alkaline complexes with known rare earth and thorium mineralisation include Brockman in WA. It is a large low-grade zirconium-niobium-rare earth element (Zr-Nb-REE) deposit hosted in altered trachytic tuff of Paleoproterozoic age. On 8 September 2011, Hastings reported 36.2Mt of Indicated and Inferred Resources grading 8.86 parts per million (ppm) ZrO₂, 3.55ppm Nb₂O₅, 182ppm Ta₂O₅, 110ppm Ga₂O₅, 318ppm HfO₂, 186ppm Dy₂O₅, 1120ppm Y₂O₃, 2102ppm total REO and 1802ppm heavy REO. Historic company reports on open file on the Geological Survey of Western Australia WAMEX database show analyses for thorium in six separate drill hole intersections (in tuffs) of 16 metres (m) to 28m averaging from 259-371ppm Th (Western Australia Geological Survey WAMEX database report A 40991).

Capital Mining Limited: The peralkaline granitic intrusions of the Narraburra Complex 177km northwest of Canberra contain anomalous amounts of zirconium, REO and low concentrations of Th (55Mt at 1000 grams per tonne (g/t) ZrO₂, 60g/t Y₂O₃, 300g/t REO, 40g/t HfO₂, 80g/t Nb₂O₅, and 50g/t ThO₂, Capital Mining Limited Prospectus 2006). The thorium oxide (ThO₂) content amounts to 2750 tonnes (2420 tonnes Th). In the March quarterly report in 2010, the owners of the project, Capital Mining Limited, reported that it was conducting metallurgical test to recover hafnium (Hf), Th, tantalum (Ta), Nb, Nd and Ce.

Data on the thorium content of carbonatite intrusions in Australia is sparse. Mount Weld and Cummins Range in WA have the most significant rare earth resources reported for carbonatites in Australia to date, with both having some thorium content.

Lynas Corporation Ltd: The Mount Weld deposit in WA occurs within a lateritic profile developed over an alkaline carbonatite complex. On 6 September 2010 Lynas reported Measured, Indicated and Inferred REO resources for the Central Lanthanide Deposit at a cut-off of 2.5% REO of 9.88Mt at 10.7% REO including 990ppm Y₂O₃. The ThO₂ content of the deposit is estimated to be 712ppm which equates to 626ppm Th (personal communication B Shand, Lynas Corporation Ltd (Lynas) 17 June 2009).

On 6 September 2010, Lynas also announced additional REO resources in the Duncan Deposit, of the carbonatite complex of 7.620Mt of Measured, Indicated and Inferred Resources at 4.8% REO including 2570ppm Y₂O₃. The ThO₂ content is estimated to be 441ppm (388ppm Th). In another part of the carbonatite complex there are 37.7Mt of mostly Inferred Resources grading 1.07% Nb₂O₅, total lanthanides at 1.16% and 0.09% Y₂O₃, 0.3% ZrO₂, 0.024% Ta₂O₅, 7.99% P₂O₅ and a ThO₂ content of 479ppm (421ppm Th).

Navigator Resources Ltd: In their annual report for 2010, Navigator Resources reported Inferred Resources for Cummins Range in WA carbonatite deposit of 4.17Mt at 1.72% REO, 11.0% P₂O₅ 187ppm U₃O₈ and 41ppm Th. In other parts of the deposit however, sample analyses recorded in open file report A16613 in the Geological Survey of Western Australia WAMEX database averaged about 500ppm Th in the top 48m of weathered zone in one drill hole. Thorium-rich zones of 200-400ppm Th were intersected in two drill holes in fresh carbonatite and carbonated magnetite amphibolite to depths of 400m.

Artemis Resources Ltd: The Yangibana ferrocarbonatite-magnetite-rare earth bearing dykes in WA (termed ironstones) crop out over an area of 500 square kilometres and form part of the Gifford Creek Complex. The dykes are part of a carbonatitic episode which intrudes the Proterozoic Bangemall Group. The ferrocarbonatite-magnetite-rare earth bearing dykes occur as lenses and pods and are typically the last stage of carbonatite fractionation and are enriched in REEs, fluorite and uranium-thorium mineralisation. The Yangibana prospect has a recorded resource of 3.5Mt at 1.7% REO. The rare earths are in coarse grained monazite containing up to 20% Nd₂O₅ and 1600ppm Eu₂O₃. Whole rock chemical analyses of 21 ironstone samples collected from five prospects in the Yangibana area recorded more than 1000ppm Th for 10 of the samples (1062ppm to 5230ppm Th).

Capital Mining Limited: Similarly the peralkaline granitic intrusions of the Narraburra Complex 177km northwest of Canberra contain anomalous amounts of zirconium, REO and low concentrations of Th (55Mt at 1000g/t ZrO₂, 60g/t Y₂O₃, 300g/t REO, 40g/t HfO₂, 80g/t Nb₂O₅, and 50g/t ThO₂, Capital Mining Limited Prospectus 2006). The ThO₂ content amounts to 2750 tonnes (2420 tonnes Th). In the March quarterly report in 2010, the owners of the project, Capital Mining Limited, reported that it was conducting metallurgical test to recover hafnium (Hf), Th, tantalum (Ta), Nb, Nd and Ce.

There has been no widespread exploration for thorium in Australia. However thorium is a significant component of some deposits being explored for other commodities. Thorium is present in the Nolans Bore deposit in the NT and in the Toongi intrusives complex in NSW. Heavy mineral concentrations within the King Leopold Sandstone and the Warton Sandstone, which constitute the Durack Range uranium project in WA, also contain up to 2% thorium in the heavy mineral concentrate (Northern Mining Ltd – announcement to the Australian Securities Exchange, 21 March 2007). Western Desert Resources Ltd reported that thorium was one of the commodities being explored for at Blueys and Cloughs Dam prospects near Alice Springs in the NT with 599-1400ppm Th being reported in rock chip samples from the Blueys rare earth, zirconium, thorium prospect. In April 2011 Centius Gold reported low altitude airborne thorium and uranium anomalies over the northern rim of its Bethungra Caldera prospect which was claimed to resemble similar airborne radiometric anomalies over Alkane's Dubbo (Toongi) zirconium-rare earth project to the north.

There is no production of thorium in Australia, but it is present in monazite currently being mined with other minerals in heavy mineral beach sand deposits.

Between 1952 and 1995, Australia exported 265 kilotonne (kt) of monazite with a real export value (2008 dollars) of $284 million (Australian Bureau of Statistics 2009)⁴. Most of the monazite was exported to France for extraction of REE, but the monazite plant in France was closed because its operators were unable to obtain a permit for the radioactive disposal site.

In current heavy mineral sand operations, the monazite fraction is returned to mine site and dispersed to reduce radiation as stipulated in mining conditions.

The Organisation for Economic Cooperation and Development/Nuclear Energy Agency OECD/NEA & International Atomic Energy Agency (IAEA) (2009)* have compiled estimates of thorium resources on a country-by-country basis. The OECD/NEA report notes that the estimates are subjective as a result of the variability in the quality of the data, a lot of which is old and incomplete. Table 6 has been derived by Geoscience Australia from information presented in the OECD/NEA analysis. The total identified resources refer to Reasonably Assured Resources (RAR) plus Inferred Resources recoverable at less that US$80/kilogram Th. With increasing cost of production, the upper limit for these costs categories may have to be raised to US$130/kilogram.

OECD/NEA & IAEA (2009) have grouped thorium resources according to four main types of deposits as shown in Table 7. Thorium resources worldwide appear to be moderately concentrated in the carbonatite type deposits, accounting for about 30% of the world total. The remaining thorium resources are more evenly spread across the other three deposit types in decreasing order of abundance in the placers, vein type deposits and alkaline rocks. In Australia, a larger proportion of resources are located in placers where the heavy mineral sand deposits account for about 70% of the known thorium resources.

*Sources: Data for Australia compiled by Geoscience Australia; estimates for all other countries are from: OECD/NEA & IAEA, 2009: Resources, Production and Demand. OECD Nuclear Energy Agency & International Atomic Energy Agency.
**See Uranium chapter for definitions of resource categories

1. World Nuclear Association 2011, Nuclear Power in India. Country briefings, September 2011, 31pp.
2. Kakodkar A, 2009, Statement by Dr Anil Kakodkar, Chairman of the Atomic Energy Commission and leader of the Indian delegation, IAEA 53rd General Conference, Vienna, 16 September 2009.
3. World Nuclear Association 2011, Nuclear Power in China. Country briefings, September 2011, 12pp
4. ABS, 2009. International trade, Cat. No.5465.0, Canberra