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Thorium in Australia

Research Paper no. 11 2007–08

Thorium in Australia

Greg Baker

Statistics and Mapping Section

17 September 2007

Contents

Executive summary

Introduction

Thorium

Sources of thorium

Thorium resources

Thorium as a nuclear fuel

The future of thorium in Australia

Conclusion

Glossary

Endnotes

Executive summary Thorium is a radioactive element that can be used in a new generation of nuclear reactors as an alternative source of fuel for the generation of electricity.

A thorium-based fuel cycle is more proliferation resistant than conventional uranium-based reactors though there is still a degree of risk.

A thorium-based fuel cycle is less accident prone and is more energy efficient than conventional uranium-based reactors.

Thorium-based fuel cycle waste products are not as long lived as those from conventional nuclear reactors.

Thorium is abundant in Australia.

There are technical issues still needing resolution before a thorium-based fuel cycle can become common.

Even if the technical issues can be resolved there are still residual environmental concerns in the mining, handling and storage of radioactive materials.

Introduction Thorium is a naturally-occurring radioactive element that can be used in a new generation of nuclear reactors as an alternative source of fuel for the generation of electricity. Thorium has several advantages as a nuclear fuel:

it produces less of the nuclear by-products normally used to make nuclear weapons and less of the long-lived radioactive products of conventional nuclear power

its use in suitable nuclear reactors can reduce the hazard of nuclear accidents

unlike natural uranium, its energy content can be used almost in its entirety, and

thorium ore minerals are abundantly available in Australia.

There are, however, some technical issues to be resolved before thorium can be considered as a fuel for Australia s future. If these technical issues can be resolved, residual environmental concerns of mining, handling and storage of radioactive materials will still make the decision to use any thorium-based fuel cycle a political one. This research paper discusses thorium and the implications of its use, particularly in the Australian context. Thorium Thorium is a naturally-occurring radioactive element. [1] It was discovered in 1828 by the Swedish chemist and mineralogist J ns Jakob Berzelius who named the element after Thor, the Norse god of thunder. [2] In 1898 Gerhard Carl Schmidt and Marie Curie independently found that thorium was radioactive. [3] In its natural state thorium is composed almost entirely of an isotope called thorium-232. Isotopes of an element, although chemically the same as each other, have different nuclear structures. [4] Thorium-232 has a half-life of 14 050 million years, meaning that half of any given mass will decay disintegrate into other nuclear products in that time; 14 050 million years is over three times the age of the earth. This means that thorium-232 is not particularly radioactive, although its decay products are. From its natural state, thorium-232 decays through a number of stages finishing with lead-208, which is stable. [5] Thorium is used for some industrial purposes, including bringing the intense white colour to gas-lamp mantles. However, its principal modern interest is as a nuclear fuel. Sources of thorium Thorium is found in small quantities in the earth s upper crust where, at 6 10 parts per million, it is about three times more abundant than uranium. [6] The main source of thorium in Australia and worldwide is the mineral monazite which is a reddish-brown rare-earth phosphate mineral. [7] Monazite contains 8 10 per cent thorium. [8] Other minerals containing thorium include thorite (thorium silicate), a thorium uranium mineral which is also an important ore of uranium and thorianite which contains around 70 per cent thorium dioxide. [9] In Australia monazite is usually found as a component of heavy mineral sand deposits. [10] Because there is no market for the mineral, monazite is not extracted during mining for heavy mineral sands but dispersed back through the original host material when a mining site is returned to its agreed post-mining land use. [11] This dispersal of monazite is done to prevent concentrations of radioactivity in rehabilitated mine sites. [12] However, in doing so, the thorium and rare earths present in the monazite are negated as a resource as it is unlikely to be economic to recover the dispersed monazite for its rare earth and thorium content. Thorium resources Because there has been little commercial demand for thorium there are few detailed records on Australia s, or the world s, thorium resources. [13] However, Geoscience Australia estimates that Australia s monazite resources amount to 5.2 million tonnes. At an estimated average thorium content of 7 per cent, this is calculated to mean thorium resources of around 364 000 tonnes from this source. In addition, Geoscience Australia notes that the resources at Nolans Bore, 135 kilometres northwest of Alice Springs, contain 60 600 tonnes of thorium dioxide amountint to 53 300 tonnes of thorium; another deposit, Toongi, 30 kilometres south of Dubbo in New South Wales contains about 35 000 tonnes of thorium. Summing these three figures yields an estimate for Australia s total identified thorium resources of 452 300 tonnes which Geoscience Australia estimates are extractable at less than US$80 per kilogram of thorium. [14] Other countries with thorium resources include India, Norway, the USA and Canada. Table 1 shows estimates of world thorium resources derived by Geoscience Australia. [15] The identified resources in the table are those resources considered to be extractable at less than US$80 per kilogram. The figure for Australia is the Geoscience Australia estimate discussed above. The remaining figures are from the OECD s Nuclear Energy Agency (NEA) reproduced by Geoscience Australia. [16] Undiscovered resources are resources which are believed to exist and to be exploitable using conventional mining techniques; they have not yet been physically confirmed. Data for China and for central and eastern Europe are not available. [17] These figures show that Australian thorium resources are significant on a world scale.

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Thorium

Yanis Miezitis (yanis.miezitis@ga.gov.au)

Thorium oxide (ThO 2 ) 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.

Thorium can be used as a nuclear fuel through breeding to 233U. There is no significant demand for thorium resources currently and any large-scale commercial demand 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 81% complete in November 2011. It will have a blanket with thorium and uranium to breed fissile 233U and plutonium respectively. Six more such fast breeder reactors have been announced for construction and 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. In mid 2010, a pre-licensing safety appraisal had been completed by the Atomic Energy Regulatory Board (AERB) and site selection was in progress. Construction of the AHWR is anticipated to commence in 2014, but full commercialisation of thorium reactors is not expected before 2030. 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.

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 2011; Kakodkar 2009).

In January 2011, the China Academy of Sciences 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 5MWe MSR is believed to be under construction at Shanghai, with an operational target date of 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 China. This was supported in December 2009 by an expert panel appointed by CNNC and comprising representatives from China’s leading nuclear academic, government, industry and research and development organisations. The panel also recommended that China consider building two new CANDU units to take advantage of the design’s unique capabilities in utilising alternative fuels. A demonstration ‘High Temperature Reactor-Pebble Modules’ (HTR-PM) of 210MWe (two reactor modules) is being built at Shidaowan in Shandong province. A further 18 units of 210MWe each are planned and followed by increases in the size of the 210MWe unit modules including the introduction of thorium in fuels.

Resources

At end of December 2011, Australia’s total indicated and inferred in-situ resources of thorium amounted to about 532 000 tonnes. Because there is no publicly available data on mining and processing for 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 478 800 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.

Thorium resources in heavy mineral sand deposits

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 required by mining regulations. This dispersion is carried out to avoid a concentration of radioactivity when rehabilitating 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. However, in June 2012, Astron Corporation Ltd noted in an investor presentation that it intends to export 10 000 tonnes of monazite per year to China from its Donald heavy mineral sand deposit in Victoria.

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 7.4 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.

Figure 12. Reported regional monazite content in heavy mineral concentrates of heavy mineral sand deposits in Australia. 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 were not available, regional data were applied to individual deposits to estimate their monazite and thorium resources. Using this information, Australia’s inferred in situ thorium resources in the mineral sands were estimated to be around 371 000 tonnes. The regional distribution of monazite in heavy mineral sands is shown in Figure 12 and the location of various types of deposits containing thorium and the regional distribution of estimated thorium resources is shown in Figure 13. Resources for a new type of placer deposit, the Charley Creek deposit, containing zircon, monazite and xenotime was reported on 15 May 2012 by Crossland Uranium Mines Ltd. The Charley Creek deposit was reported by the company as an alluvial outwash with comprises an Indicated Resource of 387 Mt containing 27 000 tonnes of xenotime, 161 000 tonnes of monazite and 196 000 tonnes of zircon. The xenotime and monazite were stated to contain about 114 000 tonnes of total rare earth oxides. In addition, another 418 Mt of Inferred Resources was reported to hold about 121 000 tonnes of rare earth oxides in about 31 000 tonnes of xenotime and 167 000 tonnes of monazite as well as 220 000 tonnes of zircon. The thorium content in the xenotime and monazite was not stated. 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 sections. Figure 13. Distribution of thorium resources (in situ) in heavy mineral and other types of deposits.

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The long-term goal of India’s nuclear program has been to develop an advanced heavy-water thorium cycle.The first stage of this employs the PHWRs fuelled by natural uranium, and light water reactors, which produce plutonium incidentally to their prime purpose of electricity generation.

Stage 2 uses fast neutron reactors burning the plutonium with the blanket around the core having uranium as well as thorium, so that further plutonium (ideally high-fissile Pu) is produced as well as U-233.

Then in stage 3, Advanced Heavy Water Reactors (AHWRs) will burn thorium-plutonium fuels in such a manner that breeds U-233 which can eventually be used as a self-sustaining fissile driver for a fleet of breeding AHWRs. An alternative stage 3 is molten salt breeder reactors (MSBR), which are now being evaluated for possible large-scale deployment.

In 2002 the regulatory authority issued approval to start construction of a 500 MWe prototype fast breeder reactor at Kalpakkam and this is now under construction by BHAVINI. It is expected to be operating in 2014, fuelled with uranium-plutonium oxide (the reactor-grade Pu being from its existing PHWRs). It will have a blanket with thorium and uranium to breed fissile U-233 and plutonium respectively. This will take India’s ambitious thorium program to stage 2, and set the scene for eventual full utilisation of the country’s abundant thorium to fuel reactors. Six more such 500 MWe fast reactors have been announced for construction, four of them by 2020. This fleet of fast reactors will breed the required plutonium which is the key to unlocking the energy potential of thorium in AHWRs. This will take another 15-20 years, and so it will still be some time before India is using thorium energy to any extent.

So far about one tonne of thorium oxide fuel has been irradiated experimentally in PHWR reactors and has reprocessed and some of this has been reprocessed, according to BARC. A reprocessing centre for thorium fuels is being set up at Kalpakkam.

Design is largely complete for the first 300 MWe AHWR (920 MWt, 284 MWe net), which is now planned to be built in the 12th plan period to 2017, for operation about 2022, though no site has yet been announced. It will have vertical pressure tubes in which the light water coolant under high pressure will boil, circulation being by convection. A large heat sink – “Gravity-driven water pool” – with 7000 cubic metres of water is near the top of the reactor building. In April 2008 an AHWR critical facility was commissioned at BARC “to conduct a wide range of experiments, to help validate the reactor physics of the AHWR through computer codes and in generating nuclear data about materials, such as thorium-uranium 233 based fuel, which have not been extensively used in the past.” It has all the components of the AHWR’s core including fuel and heavy water moderator, and can be operated in different modes with various kinds of fuel in different configurations.

In 2009 the AEC announced some features of the 300 MWe AHWR: It is mainly a thorium-fuelled reactor with several advanced passive safety features to enable meeting next-generation safety requirements such as 72-hour grace period for operator response, elimination of the need for exclusion zone beyond the plant boundary, 100-year design life, and high level of fault tolerance. The advanced safety characteristics have been verified in a series of experiments carried out in full-scale test facilities. Also, per 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*. By mid-2010 a pre-licensing safety appraisal had been completed by the AERB and site selection was in progress. The AHWR can be configured to accept a range of fuel types including low-enriched U, U-Pu MOX, Th-Pu MOX, and U-233-Th MOX in full core. Steam temperature is 285ºC and thermal efficiency 30.9%. There are 452 fuel assemblies, with burn-up of 38 GWd/t.

At the same time the AEC announced an LEU version of the AHWR. This will use low-enriched uranium plus thorium as a fuel, dispensing with the plutonium input. About 39% of the power will come from thorium (via in situ conversion to U-233, cf two thirds in AHWR), and burn-up will be 64 GWd/t. Uranium enrichment level will be 19.75%, giving 4.21% average fissile content of the U-Th fuel. While designed for closed fuel cycle, this is not required, and the used fuel, with about 8% fissile isotopes can be used in light water reactors. Plutonium production will be less than in light water reactors, and the fissile proportion will be less and the Pu-238 portion three times as high, giving inherent proliferation resistance. The design is intended for overseas sales, and the AEC says that “the reactor is manageable with modest industrial infrastructure within the reach of developing countries”.

A third variety is the AHWR-Pu, which will have Pu-Th MOX and Th-U-233 MOX fuel.

An NPCIL presentation early in 2012 had LEU AHWRs being fueled with LEU-thorium, while U-233 and thorium from fast reactors, along with used fuel from those AHWRs, fueled accelerator-driven molten salt reactors. Thorium was evidently the main fuel for both these types.

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