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Steenkampskraal Thorium Limited (STL)

Development and design of nuclear fuel as well as
development of a new generation 'Pebble Bed'-type reactor

The HTMR-100/30 Reactor Building


Steenkampskraal Thorium Limited (STL) is a South African-registered company in the business of developing and commercialising thorium as a clean safe energy source for the future. The company is also designing the HTMR-100 and HTMR-30 High Temperature Gas-cooled Reactors (HTGRs). STL's business is therefore to develop the Thorium value chain from the point at which the thorium is mined to the production of thorium containing fuels and the modular reactors.

The HTMR-100 and HTMR-30

The HTMR-100 and HTMR-30 (High Temperature Modular Reactors) are Generation IV gas-cooled pebble-bed nuclear reactors that are graphite-moderated and cooled by forced helium flow. The HTMR-100 produces 35 MWe and the HTMR-30 produces 10 MWe of electric power from high-quality steam driving a high-pressure steam turbine/generator set. Steam could also be used in a wide range of cogeneration and process heat applications.

The power output of the reactors and the fuel cycles were chosen to suit the typical coverage areas required for energy and water in remote locations where a unit is deployed as a stand-alone power plant. Small intrinsically-safe modular units ensure simplified design and operational procedures; factory assembly and testing of skid-mounted sub-systems; easy road transportation; reduced construction schedules; and simplified licensing processes.

Deployment of the HTMR-100 and HTMR-30

The primary applications of the HTMRs are:

  1. Electricity
  2. Process heat (steam)
  3. Desalinated/purified water
  4. Medical and other isotopes
  5. Neutron beam research facility


The HTMR-100/30 Nuclear Power Plant Site Layout

In order to achieve this, STL has identified the following steps necessary to achieve a cost-effective beneficiation of thorium as a clean fuel:

  • The acquisition of thorium rights and resources
  • Know-how, design and manufacturing capabilities for PWR pellet fuel
  • Thorium fuel qualification and licensing for use in PWR reactors
  • Manufacture of thorium and uranium fuels for HTRs
  • Thorium fuel qualification and licensing for use in pebble-bed reactors
  • Design of the HTMR-100 and the HTMR-30 High-Temperature Modular Reactor (HTMR)

What STL Owns

STL owns:

  • The rights to the thorium at the Steenkampskraal monazite mine in South Africa
  • A significant share in THOR Energy in Norway, where an irradiation programme is underway to characterise and qualify thorium-based fuel for deployment in Light Water Reactors (LWRs)
  • A completed concept design of the HTMR-100, a 35 MWe (100 MWth) high-temperature gas-cooled reactor (HTGR) as well as a HTMR-30, a 10 MWe (30 MWth)

Process Heat Applications for the HTMRs

STL's High Temperature Modular Reactor is a gas-cooled, graphite-moderated pebble-bed reactor producing 100 MWth and 30 MWth. The design of the reactor is based on proven technology and therefore no new basic technology development is needed. The approach to small intrinsicly safe modular units ensures continuous production.

The HTMR-100/30 Nuclear
Power Plant Site Layout



STL's initiative is to develop a high temperature generation IV nuclear reactor that will supply high temperatures needed for industrial process heat applications as well as electricity production.


  • Intrinsic safety due to specific neutronic characteristics and passive residual heat removal, no safety-related active cooling systems needed

  • Due to the unique protection design of the plant it can be placed close to processing plants

  • Single or multiple 100 MWth and 30 MWth units is perfectly suited for industrial process applications in the petroleum, minerals processing and chemical industries

  • A primary coolant outlet temperature is 750C, higher temperatures are possible such as 900C

  • Exclusion of greenhouse gasses such as CO2 eliminate taxes

  • Short construction times, modular design for ease of expansion and small size for easy road transportability

  • On line fuelling

  • Once through then out OTTO cycle reduces capital costs dramatically and simplifies the process, the fuel passes slowly through the core and achieves extremely high burn-ups. This makes the reactor proliferation resistant

  • Ideal for co-generation applications such as process heat together with electricity

Process Heat Applications

The HTMRs are versatile reactors which are adaptable to industrial heat supply and electrical generation. These reactors produces high temperatures thus allowing them to supply many processes which need high temperature steam or process heat such as the following processes:


The HTMR is well suited to use its heat for multi effect distillation while producing electricity. The HTMR can also be used in a cogeneration application sharing electricity produce between electric users and reverse osmosis process producing potable water.

Petroleum, Coal and Natural Gas

The HTMRs can supply high temperature process heat needed by the petroleum refining industry for the indirect/direct coals to liquids processing and supply extremely high heat for gasification and steam methane reforming.


The reactors produces high temperature and pressure steam needed for the extraction of oils from tar sands as well as extraction of kerogen from oil shale.

Chemical Industry

  • Petrochemical products such as styrene and acrylonitrile
  • Ammonia for fertilizer
  • Plastics and rubbers

Hydrogen Production

In future large amounts of Hydrogen will be needed. The HTMRs can supply process heat and electrical energy needed for the various processes to produce hydrogen such as high temperature water electrolysis, steam methane reforming and thermochemical water splitting which includes the hybrid sulfur process, the sulfur-iodine process and the copper chlorine process.

Minerals Processing

Iron steel and aluminium account for the majority of metals produced and a HTMR is perfectly suited to supply process heat and electrical energy for processing these materials which include applications such as smelting and reduction processes. The HTMR produces the syngas which is used in the direct reduced iron process to produce iron. The HTMR is also well suited for aluminium oxide production. The lower temperature from the reactor helps with the extraction of aluminium hydroxide from the ore followed by high temperature calcination to aluminium oxide.

Non-Metallic Minerals Processing

Cement can be produced using the high temperature heat from the reactor together with a special catalyst.

The Thorium Refinery Plant

The beneficiation of thorium from the mining of raw materials containing thorium to the final fuel product is of utmost importance to STL. STL has embarked on a programme to develop the technology to extract thorium from a REE concentrate and then to purify the material to a nuclear grade powder for use in PWR fuel as well as HTR fuel.


The primary goal of the HTR fuel development programme at STL is to produce fuel spheres containing uranium for irradiation testing in the short term, thorium/uranium in the medium term as well as thorium and plutonium in the long-term. Thorium-based pellet fuels are being tested in the Halden Research Reactor in Norway with the aim of producing the data necessary for licensing of these fuels in the today's conventional Light Water Reactors (LWRs).
1st Floor, Soetdoring Building
7 Protea Street