Thorium reactors and process heat applications



 

The Steenkampskraal Thorium Limited (STL) high temperature modular reactor (HTMR) is a Generation IV 100 MW helium-cooled power plant that features a thorium-based fuel cycle. The heat source is based on a fuel technology with intrinsic safety characteristics.

This article discusses the benefits of a HTMR compared to other types of nuclear reactor.

The power conversion is via a proven helical coil steam generator and the HTMR is a CO2-free nuclear thermal power source which can be used for power generation, process heat applications, water desalination and hydrogen production. The small size and modular construction results in a relatively low cost of construction and implementation.

Temperature Regions for various industrial processes

Steenkampskraal’s HTMR vs. other reactors

The HTMR has the broadest temperature range and is ideally suited to provide temperatures from 250 to 750°C. This is suitable to produce steam/heat/electricity or combinations thereof.

Fig. 1: Temperatures required per application.

The smaller reactor size provides for easier road transportability, while being modular enables more cost effective implementation and expansion. The
100 MW version is well suited to industrial processes. Since the HTMR is inherently safe, it enables placement close to processing plants to minimise energy losses.

No risk of core meltdown

The HTMR has a large mass/low power density which results in slow response after events. This means that it requires no nuclear safety-related diesel generators and no nuclear safety-related active systems. Residual heat is removed by active and passive means, and this type of reactor has a strong negative temperature coefficient, adding to its safety features.
It is small in size, extendable and, being a modular design, allows for the addition of extra modules, while the design facilities on-line fuelling. Small amounts of tritium are produced which makes inland operations possible. Spent fuel only needs simple dry cooling.

Fast construction (modular design, skid mounted)

The HTMR can be located above or below ground. High-level waste is in an acceptable form. No active cooling system is needed for spent fuel and no special facility is needed. There is only a low volume of medium and low level waste with blow-back filters used.

Process heat applications

The petrochemical industry is one of the largest consumers of primary energy in the form of diesel and jet fuel. Products include petrol and paraffin. Catalytic cracking and reforming requires temperatures of between 500 and 600°C.

Indirect coal to liquids

Gasification of coal with steam and oxygen to form syngas (CO + H2). The syngas is fed to the Fischer-Tropsch Process to obtain liquid hydrocarbon products (paraffins, methanol, etc.).

Fig. 2: Operating temperatures for different types of nuclear reactor.

Bitumen extraction

High temperature and high pressure steam is injected into the bitumen to make it less viscous for pumping. Steam at around 300°C and 15 MPa is needed for this purpose.

Kerogen upgrading (oil shale)

Heating oil shale releases kerogen which is used to produce liquid hydrocarbons.

Gasification

• Conversion of carbon-based materials into syngas
• Air/oxygen, steam and CO2
• Temperatures of between 700 and 950°C are needed

Steam methane reforming

• Methane and steam react to form syngas
• Temperatures of between 500 and 950°C are needed

Organic chemicals

Ethylene, propylene, benzene and xylene (300°C), Styrene, acrylonitrile (700°C)

Fertilisers

Ammonia production for nitrate fertilizers, at 400 to 600°C is needed. High temperature processing of phosphate rock (800°C for phosphate fertilisers).

Table 1: Comparison of various nuclear reactor technologies.
Reactor name Reactor description Reactor temperature
PWR Pressurised water reactor Up to 300°C
LWR Light water reactor Up to 300°C
BWR Boiling water reactor Up to 300°C
PHWR Pressurised heavy water reactor Up to 300°C
OCHWR Organic cooled heavy water reactor Up to 400°C
LMFBR Liquid metal fast breeder reactors Up to 540°C
AGR Advanced gas cooled reactors Up to 650°C
HTGR High temperature gas reactor Between 750 and 900°C
HTMR Steenkampskraal’s high temperature modular reactor Between 250 and 750°C

Plastics and rubber

Low-density polyethylene and rubber vulcanization requires temperatures between 300 and 500°C.

Cement

Pyro-processing, calcination using special catalyst (800°C)

Hydrogen production

Hydrogen is needed for vast amounts of applications. The HTMR is perfectly suited to produce H2 as it produces extremely high temperatures. Hydrogen production can be done in a variety of ways: High temperature steam electrolysis (high operating temperature reduces electrical input (800°C required). Steam methane reforming (500 to 950°C).

Thermochemical water splitting such as the hybrid sulfur process (HyS) (750 to 950°C required), a sulfur-iodine process (S-I) needs 850°C, and a copper-chlorine process (Cu-Cl) needs a temperature of 500°C.

A small size reactor is perfectly suited to supply electrical power at the mines.

Unconventional mineral resources

Processing of non-conventional sources usually require high-energy inputs (heat and/or electricity). HTGRs can supply base load heat and/or electricity for such processing. Certain minerals (U and Th) are usually seen as side waste steams during commodity processing.

HTGRs can be used to process minerals as well as wastes that can be used inside the reactor, creating a sustainable process. The HTGR’s inherent safety and transportability will allow construction close to processing plants that use advanced technologies to remove minerals that usually went to waste.

Desalination

Ninety-seven percent of the earth’s water is sea water. Fresh water at low cost is in increasingly short supply all over the world. Sea water contains around 3500 ppm of salt. The allowable salt concentration for human consumption is less than 500 ppm.

Benefits of desalination:

  • It addresses the shortage of potable water
  • It meets the demand for process water due to growth of technology and industry
  • It mitigates against the ongoing deteriorating quality of fresh water
  • Desalination is the only major unconventional source of water supply of economic significance
Table 2: Electrical energy requirements for the mining industry.
Type of operation Estimated kWh/t
Generalised processing technology (sizing)* 2 – 5 kWh/t
Total mining and processing FOB site** 1 – 7 kWh/t
Production of aluminium form bauxite ore*** 14600 kWh/t Al
Cement production 90 – 150 kWh/t cement
Chromite ore products 20 – 25 kWh/t ore produced
Production of coal-surface mine 18 – 37 kWh/t coal
Production of coal-underground mine 26 – 55 kWh/t coal
Recovery of cobalt cathode 3000 – 6500 kWh/t cobalt as cathode
Copper mining and generalised processing 2800 – 7000 kWh/t copper
Production of ferromanganese 2000 – 2600 kWh/t product
High carbon silicon manganese (average 27 MW furnace) 3500 – 4000 kWh/t product
Production of ferrovanadium 3200 kWh/t product
Production of ferrosilicon 6000 – 9000 kWh/t product
Production of ferrotitanium 7500 kWh/t product
Mining and production of gold (71 – 93) xl06 kWh/t gold
Mining and production of refined platinum (70 – 88) xl06 kWh/t refined Pt
Production of yellowcake (UJOa) 40000 kWh/t U30a
Electro-refining of zinc 3000 – 5000 kWh/t zinc metal
*Mining and producing aggregate (crushed rock)
**Mining and processing unconsolidated sand and gravel for construction
***Estimated annual capacity all of Africa = 2 Mt

There are three main sources of desalination that are best suited to the HMTR100 reactor:

  • Reverse osmosis
  • Multi-effect distillation
  • Multi-stage flash

Reverse osmosis (RO)

RO is a water purification technology that uses a semipermeable membrane to separate the solute (salt and minerals) from the solvent (water).

Multi-effect distillation (MED)

MED consists of multiple stages. In the first stage the feed water is heated by steam. Some of the water evaporates, and this vapour flows into the tubes of the next stage, heating and evaporating more water. Each stage essentially reuses the energy from the previous stage.

Multi-stage flash (MSF)

MSF is a water desalination process that distils sea water by flashing a portion of the water into steam in multiple stages of what are essentially counter current heat exchangers. Nuclear desalination is especially advantageous over fossil fuel processes as it is cost competitive and does not release greenhouse gases in the way the combustion of conventional fossil fuels do.

The electricity/heat produced by the HTMR100 reactor can be used for reverse osmosis and desalination. Heat from the HTMR100 reactor can be used for a multi-effect distillation or multi-stage flash desalination plant. The HTMR100 reactor is versatile and can be used in a cogeneration application producing both electricity and fresh water and/or high temperature steam for other process applications.

Contact David Boyes, Steenkampskraal Thorium, Tel 012 667-2141, david.boyes@thorium100.com

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