Nuclear Desalination

 (Updated October 2011) 

•  Potable water is in short supply in many parts of the world. Lack of it is set to become a constraint on development in some areas. 
•  Nuclear energy is already being used for desalination, and has the potential for much greater use. 
•  Nuclear desalination is generally very cost-competitive with using fossil fuels. 

It is estimated that one fifth of the world's population does not have access to safe drinking water, and that this proportion will increase due to population growth relative to water resources. The worst-affected areas are the arid and semiarid regions of Asia and North Africa. A UNESCO report in 2002 said that the freshwater shortfall worldwide was then running at some 230 billion m³/yr and would rise to 2000 billion m³/yr by 2025. Wars over access to water, not simply energy and mineral resources, are conceivable.

Fresh water is a major priority in sustainable development. Where it cannot be obtained from streams and aquifers, desalination of seawater or mineralised groundwater is required.  An IAEA study in 2006 showed that 2.3 billion people live in water-stressed areas, 1.7 billion of them having access to less than 1000 m³ of potable water per year.  With population growth, these figures will increase substantially.  Further demand in the longer term will come from the need to make hydrogen from water.

Desalination

Most desalination today uses fossil fuels, and thus contributes to increased levels of greenhouse gases. Total world capacity is approaching 40 million m³/day (14,600 GL/yr) of potable water, in some 15,000 plants. Most of these are in the Middle East and north Africa, using distillation processes.  The largest plant produces 454,000 m³/day (166 GL/yr).  Two thirds of the world capacity is processing seawater, and one third uses brackish artesian water.

The major technology in use and being built today is reverse osmosis (RO) driven by electric pumps which pressurise water and force it through a membrane against its osmotic pressure*.  A thermal process, multi-stage flash (MSF) distillation process using steam, was earlier prominent and it is capable of using waste heat from power plants.  With brackish water, RO is much more cost-effective, though MSF gives purer water than RO.  A minority of plants use multi-effect distillation (MED) or multi-effect vapour compression (MVC) or a combination of these.  MSF-RO hybrid plants exploit the best features of each technology for different quality products.

* About 27 Bar, 2700 kPa.  Therefore RO needs compression of much more than this. 

Desalination is energy-intensive. Reverse Osmosis needs up to 6 kWh of electricity per cubic metre of water (depending on its original salt content), hence 4 MWe will produce about 16,000 to 24,000 m³ per day from seawater.   MSF and MED require heat at 70-130°C and use 25-200 kWh/m³,  though a newer version of MED (MED-MVC) is reported at 10 kWh/m³ and competitive with RO.  A variety of low-temperature and waste heat sources may be used, including solar energy, so the above kilowatt-hour figures are not properly comparable.  For brackish water and reclamation of municipal wastewater RO requires only about 1 kWh/m³.  The choice of process generally depends on the relative economic values of fresh water and particular fuels, and whether cogeneration is a possibility.

Some 10% of Israel's water is desalinated, and one large RO plant provides water at 50 cents per cubic metre. Malta gets two thirds of its potable water from RO. Singapore in 2005 commissioned a large RO plant supplying 136,000 m³/day - 10% of needs, at 49 cents US per cubic metre.  Malta gets two thirds of its potable water from RO, and this takes 4% of its electricity supply. Singapore in 2005 commissioned a large RO seawater desal plant supplying 136,000 m³/day - 10% of needs, at 49 cents US per cubic metre, and has contracted for a 318,500 m³/d RO plant on a build-own-operate basis, costing US$ 700 million, to provide water at US 36 c/m³. The same company is building a 500,000 m³/d seawater desal plant in Algeria.

Small and medium sized nuclear reactors are suitable for desalination, often with cogeneration of electricity using low-pressure steam from the turbine and hot seawater feed from the final cooling system. The main opportunities for nuclear plants have been identified as the 80-100,000 m³/day and 200-500,000 m³/day ranges.

A 2006 IAEA report based on country case studies showed that costs would be in the range ($US) 50 to 94 cents/m³ for RO, 60 to 96 c/m³ for MED and $1.18 to 1.48/m³ for MSF processes, with marked economies of scale.  Nuclear power was very competitive at today's gas and oil prices.  A French study for Tunisia compared four nuclear power options with combined cycle gas turbine and found that nuclear desalination costs were about half those of the gas plant for MED technology and about one third less for RO.  With all energy sources, desalination costs with RO were lower than MED costs.

The Kwinana desalination plant near Perth, Western Australia, has been running since early 2007 and produces about 140,000 m³/day (45 GL/yr) of potable water, requiring 24 MWe of power for this, hence 576,000 kWh, hence 4.1 kWh/m³ overall, and about 3.7 kWh/m³ across the membranes. The plant has pre-treatment, then 12 seawater RO trains with capacity of 160,000 m³/day which feed six secondary trains producing 144,000 m³/day of water with 50 mg/L total dissolved solids. The cost is estimated at A$ 1.20/m³. Discharge flow is about 7% salt. Future WA desalination plants will have more sophisticated pre-treatment to increase efficiency.  In August 2011 the state government decided to double the size of its new Southern Water Desal Plant at Binningup plant near Perth to 100 GL/yr, taking the cost to about $1.45 billion.  Stage 1 of 50 GL/yr was within the A$ 955 million budget.

At the April 2010 Global Water Summit in Paris, the prospect of desalination plants being co-located with nuclear power plants was supported by leading international water experts.

 Complementary wastewater treatment for irrigation

In the Middle East, a major requirement is for irrigation water for crops and landscapes. This need not be potable quality, but must be treated and with reasonably low dissolved solids.

In Oman, the 76,000 m3/day first stage of a submerged membrane bioreactor (SMBR) desalination plant was opened in 2011. Eventual plant capacity will be 220,000 m3/day. This is a low-cost wastewater treatment plant using both physical and biological processes and which produces effluent of high-enough quality for some domestic uses or reinjection into aquifers.

Desalination: nuclear experience

The feasibility of integrated nuclear desalination plants has been proven with over 150 reactor-years of experience, chiefly in Kazakhstan, India and Japan.  Large-scale deployment of nuclear desalination on a commercial basis will depend primarily on economic factors. Indicative costs are US$ 70-90 cents per cubic metre, much the same as fossil-fuelled plants in the same areas.

One obvious strategy is to use power reactors which run at full capacity, but with all the electricity applied to meeting grid load when that is high and part of it to drive pumps for RO desalination when the grid demand is low.

The BN-350 fast reactor at Aktau, in Kazakhstan, successfully supplied up to 135 MWe of electric power while producing 80,000 m³/day of potable water over some 27 years, about 60% of its power being used for heat and desalination. The plant was designed as 1000 MWt but never operated at more than 750 MWt, but it established the feasibility and reliability of such cogeneration plants. (In fact, oil/gas boilers were used in conjunction with it, and total desalination capacity through ten MED units was 120,000 m³/day.)

In Japan, some ten desalination facilities linked to pressurised water reactors operating for electricity production yield some 14,000 m³/day of potable water, and over 100 reactor-years of experience have accrued. MSF was initially employed, but MED and RO have been found more efficient there. The water is used for the reactors' own cooling systems.

India has been engaged in desalination research since the 1970s. In 2002 a demonstration plant coupled to twin 170 MWe nuclear power reactors (PHWR) was set up at the Madras Atomic Power Station, Kalpakkam, in southeast India. This hybrid Nuclear Desalination Demonstration Project (NDDP) comprises a reverse osmosis (RO) unit with 1800 m³/day capacity and a multi-stage flash (MSF) plant unit of 4500 m³/day costing about 25% more, plus a recently-added barge-mounted RO unit. This is the largest nuclear desalination plant based on hybrid MSF-RO technology using low-pressure steam and seawater from a nuclear power station. They incur a 4 MWe loss in power from the plant. In 2009 a 10,200 m³/day MVC plant was set up at Kudankulam to supply fresh water for the new plant. It has four stages in each of four streams. An RO plant there supplies the plant's township. A low temperature (LTE) nuclear desalination plant uses waste heat from the nuclear research reactor at Trombay has operated since about 2004 to supply make-up water in the reactor.

Pakistan in 2010 commissioned a 4800 m³/day MED desalination plant, coupled to the Karachi Nuclear Power Plant (KANUPP, a 125 MWe PHWR) near Karachi. It has been operating a 454 m³/day RO plant for its own use. 

China Guangdong Nuclear Power has commissioned a 10,080 m³/day desalination plant at its new Hongyanhe project at Dalian in the northeast.

Much relevant experience comes from nuclear plants in Russia, Eastern Europe and Canada where district heating is a by-product.

Large-scale deployment of nuclear desalination on a commercial basis will depend primarily on economic factors. The UN's International Atomic Energy Agency (IAEA) is fostering research and collaboration on the issue.

 Small nuclear reactors suitable for desalination

SMART: South Korea has developed a small nuclear reactor design for cogeneration of electricity and potable water. The 330 MWt SMART reactor (an integral PWR) has a long design life and needs refuelling only every 3 years. The main concept has the SMART reactor coupled to four MED units, each with thermal-vapour compressor (MED-TVC) and producing total 40,000 m³/day, with 90 MWe.

CAREM: Argentina has designed an integral 100 MWt PWR suitable for cogeneration or desalination alone.

NHR-200: China's INET has developed this, based on a 5 MW pilot plant.

Floating nuclear power plant (FNPP) from Russia, with two KLT-40S reactors derived from Russian icebreakers, or other designs for desalination. (If primarily for desalination the twin KLT-40 set-up is known as APVS-80.) ATETs-80 is a twin-reactor cogeneration unit using KLT-40 and may be floating or land-based, producing 85 MWe plus 120,000 m³/day of potable water. The small ABV-6 reactor is 38 MW thermal, and a pair mounted on a 97-metre barge is known as Volnolom floating NPP, producing 12 MWe plus 40,000 m³/day of potable water by reverse osmosis. A larger concept has two VBER-300 reactors in the central pontoon of a 170 m long barge, with ancillary equipment on two side pontoons, the whole vessel being 49,000 dwt. The plant is designed to be overhauled every 20 years and have a service life of 60 years. Another design, PAES-150, has a single VBER-300 unit on a 25,000 dwt catamaran barge.

See also: Small Nuclear Power Reactors paper.

New desalination projects

 Algeria has undertaken a study on nuclear power generation and desalination using RO and MED. The country is also considering a 150,000 m3/day MSF desalination plant for its second-largest town, Oran (though nuclear power is not a prime contender for this).  It is also building a 500,000 m³/d plant at Magtaa to start in 2012, and commissioned a 120,000 m3/d plant at Fouka near Algiers in 2011.

 Australia: In Victoria, a 410,000 m³/day (150 GL/yr) RO desalination plant is being built near Wonthaggi, to supply Melbourne. It claims to use renewable energy, and is expandable to 200 GL/yr.  Adelaide's 100,000 m³/d (36 GL/yr) plant started operation in 2011 and will reach capacity in 2012, with plans to expand it to 100 GL/yr.  A 200 - 280,000 m³/d desalination plant to serve the expanded Olympic Dam mine in South Australia has environmental approval.

 China is looking at the feasibility of a nuclear seawater desalination plant in the Yantai area of Shandong Peninsula, producing 80-160,000 m³/day by MED process, using a 200 MWt NHR-200 reactor. Another project is for a 330,000 m³/day plant near Daya Bay.

A 50,000 m³/day Aqualyng plant was completed in October 2011 at Caofeidian in Hebei province. A second stage will double this in 2012, and possibly lead to a 1 million m³/d set up, or maybe three times this, to supply Beijing through a 230 km pipeline.

 Dubai has invited bids for constructing a 450,000 m³/d (165 GL/yr) seawater desalination plant as part of its Hassyan project.

 Egypt has undertaken a feasibility study for a cogeneration plant for electricity and potable water at El-Dabaa, on the Mediterranean coast. In 2010 plans were being formed for four 1000 MWe-class reactors to be built there and coming on line 2019-25, with significant desalination capacity.

In India, further plants delivering 45,000 m³Â per day are envisaged, using both MSF and RO desalination technology, and building on the extensive experience outlined above.  The 100,000 m³/d Nemmeli desalination plant is due for completion in December 2011, and a 200,000 m³/d plant is planned for Pattipulam nearby, both serving Chennai.

 Indonesia: South Korea investigated the feasibility of building a SMART nuclear reactor with cogeneration unit employing MSF desalination technology for Madura Island, and later studies have been on larger-scale PWR cogeneration in Batan.

 Iran: A 200,000 m³/day MSF desalination plant was designed for operation with the Bushehr nuclear power plant in Iran in 1977, but appears to have lapsed due to prolonged construction delays.

 Jordan has a "water deficit" of about 1.4 million m³Â per day and is actively looking at nuclear power to address this, as well as supplying electricity.

 Kuwait has been considering cogeneration schemes up to a 1000 MWe reactor coupled to a 140,000 m³/day desalination plant.

 Libya: in mid 2007 a memorandum of understanding was signed with France related to building a mid-sized nuclear plant for seawater desalination.  Areva TA would supply this.  Libya is also considering adapting the Tajoura research reactor for a nuclear desalination demonstration plant with a hybrid MED-RO system.

 Mexico has awarded a contract for the 21,000 m³/day El Salitral plant to be in operation from the end of 2013.

 Morocco has completed a pre-project study with China, at Tan-Tan on the Atlantic coast, using a 10 MWt heating reactor which produces 8000 m³/day of potable water by distillation (MED).  The government has plans for building an initial nuclear power plant in 2016-17 at Sidi Boulbra, and Atomstroyexport is assisting with feasibility studies for this.

 Qatar has been considering nuclear power and desalination for its needs which are expected to reach 1.3 million m³Â per day in 2010.

 Saudi Arabia has contracted with Doosan to build a 68,000 m³/day MED plant in its Yanbu region, the $80 million Yanbu II plant. It will be the world's largest MED plant and due for completion early in 2014.

 Spain is building 20 RO plants in the southeast to supply over 1% of the country's water. Spain has 40 years of desalination experience in the Canary Islands, where some 1.1 million m³/day is provided.

 Tunisia is looking at the feasibility of a cogeneration (electricity-desalination) plant in the southeast of the country, treating slightly saline groundwater.

In the UK, a 150,000 m³/day RO plant is proposed for the lower Thames estuary, utilising brackish water.

Most or all these have requested technical assistance from IAEA under its technical cooperation project on nuclear power and desalination. A coordinated IAEA research project initiated in 1998 reviewed reactor designs intended for coupling with desalination systems as well as advanced desalination technologies.  This programme, involving more than 20 countries, is expected to enable further cost reductions of nuclear desalination.

Other CO2-free desalination

Renewable energy sources are able to be used for desalination more readily than for most electricity supply, since the product can be stored on any scale, unlike electricity. A new A$ 387 million RO plant near Perth, Western Australia is powered by electricity ostensibly from a wind farm. Its capacity is 130,000 m³/day in optimal wind conditions.

Main Sources:
IAEA 1997, Nuclear Desalination of Sea Water, proceedings of 1997 Symposium.
IAEA 1998, Nuclear heat applications: design aspects and operating experience, IAEA-TECDOC-1056.
Konishi & Misra, Freshwater from the Seas, IAEA Bulletin 43, 2; 2001.
IAEA Nuclear Desalination, paper on web.
International J of Nuclear Desalination, 2003, vol 1, 1.
UN World Water Development Report 2003.
Seneviratne, G 2007, Research projects show nuclear desalination economical, Nuclear News April 2007.

Khamis, I, 2010, Nuclear Desalination