JEM Spotlight: Nuclear desalination—environmental impacts and implications for planning and monitoring activities

Abstract

Nuclear desalination has been identified as an option since the 1960s, but only recently, as climate change intensifies, has it gained interest again. Although environmental impacts of nuclear desalination have not been paid a lot of attention in the few implemented projects, now more than ever, it is essential to provide an overview of their nature and magnitude. The gathered information and basic analysis allow for a general comparison of a 200,000 m³/d nuclear desalination facility using a once-through cooling system as a reference case, with alternative co-location options. Results of the review indicate that the potential for marine impacts requires careful planning and monitoring. They also reveal that adverse coastal, atmospheric and socio-economic impacts are minor in comparison with other co-location alternatives. The issues regarding public health are discussed and experiences presented. Nuclear desalination facilities are expected to show a better environmental performance than other co-located power/desalination options. Environmental planning and monitoring activities are thus much simpler and their scope smaller, with the most important monitoring parameters listed. In conclusion, the application of nuclear desalination is recommended as a less environmentally harmful option.

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Vladimir Anastasov

Vladimir Anastasov is an Environmental Consultant at the IAEA, working with the Nuclear Power Technology Development Section. He obtained his M.Sc. degree in Environmental Sciences and Policy at the CE University in Budapest, Hungary. His specific work field is on power and water interaction and assessment of their environmental implications. Apart from nuclear desalination, he works on projects referring to water requirements for nuclear power, as well as siting criteria for nuclear power plants.

Ibrahim Khamis

I. Khamis earned his MSc in 1986 and his PhD in 1988 in Nuclear Engineering from the University of Arizona, Tucson, Arizona, USA. Since 2006, he has been the Project Manager for nonelectric applications of nuclear energy at the Nuclear Power Technology Development Section, Division of Nuclear Power, IAEA. His duties involve nuclear desalination, hydrogen production, district heating and other industrial applications of nuclear energy. He is the author or co-author of more than 70 research publications and conference presentations. His main interests are reactor physics, design and simulation, and nonelectric applications of nuclear energy.

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Environmental Impact

Assessing the feasibility of nuclear desalination, studies have been conducted on the economical and technical issues. But there is a need for a more comprehensive assessment. Therefore, this paper looks at nuclear desalination from the main aspects of a detailed environmental impact assessment, including the socio-economic and public health aspects. This is done by encompassing the typical impacts of stand-alone desalination and nuclear power plants, extrapolating the cumulative impact of a nuclear desalination plant. Where possible, the article includes data from the few nuclear desalination plants in operation, especially for the safety of public health as a crucial point in nuclear desalination. In this manner, the paper provides an insight into nuclear desalination’s environmental advantages and disadvantages.

1. Introduction

In today's world, burdened with climate change and water scarcity issues, desalination is given significantly higher importance than before. Often seen as the ultimate water supply option, seawater desalination supported the development of the Middle Eastern countries as well as arid regions in Europe, Australia and the United States beyond their environmental limits. With a capacity of 39 million cubic meters in 2008, the global seawater desalination capacity continues to expand at an exponential rate.¹

A great interest in the environmental performance of desalination followed the capacity growth. Subsequently, it revealed major adverse impacts due to energy intensity and seawater pollution with concentrated brine. Although desalination processes have improved significantly, major reduction in desalination's adverse impacts (on the atmosphere, marine environment, land use, etc.) is only possible through co-located operation with power plants. In this way, the environmental performance optimization of a desalination facility brings out the issue of power plant selection for co-located operation, since its footprint will reflect in the environmental issues of the desalination facility. Recognized as a low-carbon energy, nuclear is a strong candidate for such co-located facilities.

The coined term “nuclear desalination” defines production of potable water from seawater in a facility in which a nuclear reactor is used as the source of energy for the desalination process. Electrical and/or thermal energy may be used in the desalination process.

The facility may be dedicated solely to the production of potable water, or may be used for the generation of electricity and production of potable water, in which case only a portion of the total energy output of the reactor is used for water production.² So far, nuclear desalination has accumulated more than 200 reactor-years of experience worldwide, summarized in Table 1 (derived from IAEA, 2007). Its environmental impacts though, were not assessed through a comprehensive monitoring program. As the need for low-carbon options renewed and even enhanced the interest for nuclear desalination in many countries,³ a preliminary assessment of impacts based on gathered and applicable experiences seems appropriate.

Table 1 Installed nuclear desalination capacities in the world. Source: IAEA.^a,^b

Plant name	Location	Gross power [MW(e)]	Water capacity [m^3/d]	Power/Desalination plant type
a LMFBR - Liquid Metal Fast Breeder Reactor, PWR - Pressurised Water Reactor, PHWR - Pressurized Heavy Water Reactor. b MSF - Multistage Flash, MED - Multiple Effect Distillation, RO - Reverse Osmosis. c MAEC was shut down in 1999, after 26 years of operation.
MAEC^c	Aktau, Kazakhstan	150	80,000–145,000	LMFBR/MSF&MED
Ikata-1,2	Ehime, Japan	566	2000	PWR/MSF
Ikata-3	Ehime, Japan	890	2000	PWR/RO
Ohi-1,2	Fukui, Japan	2 × 1175	3900	PWR/MSF
Ohi-3,4	Fukui, Japan	1 × 1180	2600	PWR/RO
Genkai-4	Fukuoka, Japan	1180	1000	PWR/RO
Genkai-3,4	Fukuoka, Japan	2 × 1180	1000	PWR/MED
Takahama-3,4	Fukui, Japan	2 × 870	1000	PWR/RO
NDDP	Kalpakkam, India	170	1800	PHWR/RO
Diablo Canyon	San Luis Obispo, USA	2 × 1100	2180	PWR/RO

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This article aims to provide a basis for feasibility studies and environmental planning, as well as a provisional outline for monitoring priorities. Although there is a wide choice of process and design combinations, nuclear desalination will be presented here through a reference case of a plant with 1 GW generating capacity, coupled to a 200,000 m³ MED, and a shared once-through cooling (OTC) system.

2. Environmental impacts of the reference facility

The fact that the nuclear desalination plant is a co-located facility does not preclude its potential to cause serious adverse impacts. The factors that will influence the character and magnitude of these impacts are biological, technical, political and of course, economic. The following sections will offer an overview of the impact potential through the perspective of the reference plant.

2.1. Marine impacts

Apart from being a resource and waste sink for nuclear desalination purposes, the oceans also represent a habitat rich in biodiversity. Coastal waters, host sensitive marine ecosystems and, not surprisingly, significant portion of the scientific literature on seawater desalination is dedicated to the specific environmental impacts it has on the marine environment, especially through concentrate discharge.

However, new studies have shifted the focus by suggesting greater marine environmental impacts from direct intakes rather than brine discharges, even for stand-alone desalination operations,⁴ through entrainment and impingement of organisms. Most of the adverse effects of co-located facilities are due to entrainment of massive numbers of fish eggs, larvae and plankton. For nuclear desalination the impingement of larger (adult) organisms, which is also known to add to these adverse effects, may even cause reactor shut-downs by blocking intakes.⁵

It is important to note that many factors contribute to the marine species' demographics, and their interactions are difficult to assess with the current knowledge on the subject. Yet, some of the fish species that have experienced population decline in Southern California were also noticed to be the ones with most entrained larvae,⁶ adding to arguments that intake systems may have a substantial environmental impact.

To put the marine impacts into perspective, we can take the case of Diablo Canyon NPP which was built in the times when the adverse impacts of any power plant on the environment were largely unknown and overlooked. The 2.2 GWe plant is situated in a coastal cove with an OTC system withdrawing 9.5 million m³/d of seawater. After almost two decades, researchers have estimated its attributed entrainment/impingement rate for five selected near-shore fish larvae to be from 10 to 30 percent with “potential dramatic effects on the local coastal environment”.⁷ The California Energy Commission analysis of the Diablo Canyon intake impact suggests that the larvae loss due to entrainment equals 1.2–2.4 km² of rock reef habitat.⁸

One of the reasons for such large impact, apart from the intake location being chosen in an area of high biological activity, is the higher specific requirement for cooling water in nuclear power plants (see Table 2). These requirements are predominantly a result of higher waste heat available due to the thermal efficiency of nuclear plants, which is lower than that of fossil fuel plants (5–10 percent).

Table 2 Cooling water withdrawal for different cooling systems and power plant fuels (m³/MWh). Source: EPRI, 2002

Fuel	Cycle	Once-through cooling (OTC)	Pond cooling	Cooling towers
Nuclear	steam	95–230	2–4	3–4
Fossil	steam	76–190	1–2	2
Fossil	steam-gas (CC)	29–76	not available	1

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Knowing that volume and velocity of water withdrawal are two major marine impact factors for direct intakes used in once-through cooling, higher specific entrainment and impingement rates can be expected. In order to avoid large adverse impacts on the marine environment, nuclear OTC intakes must involve advanced screening technologies and intake locations in the deeper, biologically less active marine zones.

For the reference plant, estimating conservative 200 m³ per MWh, we can calculate a 4,800,000 m³/d of seawater intake capacity. Based on the actual average process recovery ratio of 40 percent for thermal desalination (instead of the average “apparent” recovery ratio of 20 percent which accounts for cooling water as well⁹), the additional intake of 500,000 m³/d seawater should be taken into account for the needs of the desalination plant. Since the reactor takes over the role of the boiler, desalination cooling water is not necessary. With a 5,300,000 m³/d of total withdrawal rate, the intake impacts of the OTC system will depend on its location, intake speed of seawater, screening technology applied etc. However, they still have the potential to be proportionally larger when compared to other (fossil fuelled) co-locating options.

As for marine impacts originating from the discharge, it can be said that the reference nuclear desalination plant has a lower impact than stand alone facilities. Compared with other co-location options, the advantage, based on the average intake figures, is not as clear, although the higher cooling water intake flows mitigate the adverse impacts from the brine. Assuming average seawater value for Total Dissolved Solids (TDS) of 35,000 ppm, our reference desalination brine of 300,000 m³/d would have approximately 58,000 ppm TDS. Dilution with the remaining 4,800,000 m³/d of cooling water would result in water with ∼36,000 ppm TDS prior to discharge. That is less than 4 percent salinity increase, which is below the 10 percent natural variations,¹⁰ and almost the conservative estimate by Del Bene that 3 percent of salinity increase will not affect the benthic communities.¹¹ Such discharge characteristics would be suitable even for surface discharge.

Of course, dilution also mitigates the impacts of low oxygen levels as well as all chemicals in the brine, for instance chlorine or acids. In the reference case, chemicals concentration will be reduced around 15 times prior to discharge, but will probably require additional techniques for further concentration reduction to No Effect Concentration (NEC). For corrosion products from the MED plant, dilution may not be the solution, since the load, and not the concentration is of greater importance. Bioaccumulation of corrosion products such as copper and iron can cause significant adverse impacts in higher trophic levels.¹² Of course, in this case other measures can be taken, but they are not specific for nuclear desalination.

Further said, the high temperature of the OTC discharge is usually quite an issue for the power plants in general. However, in the specific case of co-located facilities, the desalination plant is used as a heat sink, significantly reducing the impact of its OTC discharge. For the reference case, there is one specific feature: the standard intermediate loop separating the nuclear and the desalination loop. This is a safety requirement, but also an undesired heat barrier. The calculations show that, for smaller rated capacity reactors, about 23 percent of the waste heat can be used for desalination,² instead of being dissipated into the environment. If we can presume that at least that much waste heat would be available in the reference case, its MED plant would have more than enough energy available for the process.

For the reference plant, presuming an energy intensity of 200 MJ/m³ for the MED process, which according to the US National Academy of Science is a value on the low-side,⁹ the production of 200,000 m³/d will result in 40 TJ/d removed from the heat dispersed in the marine environment. The temperature range necessary for that process can be provided by the steam's temperature in the nuclear loop. On the other hand, a NPP of 1 GW_e installed capacity, will disperse 2 GW_t per hour which corresponds to ∼175 TJ per day. Not all of that heat will end up in the seawater, but we may presume so in this case, allowing for a conservative estimate of 10 °C of temperature increase in the OTC discharge. In comparison, the same presumption that 100 percent of the waste heat is removed by the OTC, for the reference nuclear desalination plant, the discharge will have 8 °C temperature increase prior to release and thus a smaller area of impact. Based on a simple mixing fluid equation we can estimate a decrease of around 20 percent in affected areas with temperatures higher then 1 °C, which are estimated to be of no ecological importance.¹³

Other co-locating desalination options may offer the same generic results. For a stand alone nuclear power plant though, there is a significant advantage in coupling with a desalination facility: the subsequent measures to lower the temperature of the OTC discharge from 8 °C will be cheaper and simpler in the case of nuclear desalination facility compared to a stand-alone nuclear plant. The increase of temperature gap between the actual discharge and the discharge temperature limit must not be disregarded: intake of warmer seawater may result in warmer discharge which, due to discharge thermal limits, can cause reduction in power and water output.

Additionally, these 40 TJ of heat used for desalination increase the efficiency of the NPP from the usual 33 percent to almost 50 percent which has its further implications when assessing the nuclear waste per energy used, when leveling costs per production output or, assessing cooling needs.

2.2 Coastal impacts

As any other coastal industrial project, nuclear desalination plants have impacts on the environment through construction, land use, noise and visual disturbances. However, all of these impacts are smaller, or even minor, compared to other comparable power and desalination co-located plants.

Construction of a nuclear desalination plant, or adding a desalination facility to an existing nuclear power plant, requires a construction effort typical for any industrial development at the coast. This will entail use of heavy machinery for grading, removal of vegetation, excavation, de-watering, transport of materials, sand and gravel covering, pipe laying, power supply, building road infrastructure etc.

Comparing the resulting impacts with other desalination co-location options, the smaller size of the construction site and the lower specific use of materials for the power plant, gives nuclear desalination an advantage. As an illustration, wind infrastructure takes five to ten times the steel and concrete per MW_e generating capacity as that of nuclear.¹⁴ On the other hand, due to its prolonged construction time, nuclear desalination has the potential for a large impact, so special attention will have to be paid to this issue through a construction management plan. This plan consists of site-specific measures for use of existing infrastructure, seasonal restriction of certain activities, strict refueling procedures, vegetation restoration, sediment retention structures, use of biodegradable materials etc.¹⁵

Land use for nuclear desalination is in fact one of its advantages, especially if the needs for water and power should be addressed simultaneously or in case of spatial limitations requiring the plant to be fitted in an already developed zone. In general, co-location of nuclear power with desalination has a negligible land use aspect because of infrastructure sharing. In addition, the land necessary for the piping and pumping stations must be considered. This is strongly influenced by the siting of the desalination facility in relation to the consumers.

Typically, the estimated area required for a seawater desalination plant of 200.000 m³/d is about 0,4 km².³ In our reference case, the estimated 40 TJ heat for the process will need additional 10 percent for the auxiliary desalination systems,¹⁶ amounting to 44 TJ. According to the figures given by WEC,¹⁷ the average area of 3 km² for the reference nuclear desalination plant is smaller compared to fossil plants and significantly smaller area than the one necessary for a renewable energy sources coupled with desalination plants.

Noise from the reference facility is expected to be minimal, since distillation plants have lower noise levels than RO,¹² and OTC systems are superior to cooling towers in this respect. Still, thermal power plants, including nuclear, can be a source of noise from the steam ejectors and turbines.

As said, OTC systems have an advantage over cooling towers in lower noise levels. California Energy Commission has even described noise as a “major disadvantage” of the Air Cooled Condenser systems compared to once-through cooling.⁸ Compared with renewable energy sources, it should be said that windmills also have a disturbing noise effect.¹⁴ Nevertheless, if the nuclear desalination plant's operation results in noise which is disturbing to the surrounding habitats and residential areas, appropriate acoustical measures can lower noise levels sufficiently enough.

Visual impact should not be expected in case of retrofitting a nuclear power plant with a desalination facility. However, newly constructed nuclear desalination plants would be situated in coastal areas which are often considered to be of great scenic value. As for any other coastal development, mitigation measures mainly involve use of site topography. Of course, although the visual impact is appropriately small due to the low land use requirements for nuclear desalination, lower visual impact are assured with construction in an already developed area. Once-through cooling systems are also the better option in this case.

As a comparison, for a power/desalination plant with renewable energy, which does not result in waste heat as a by-product, the most suitable choice would be the energy-efficient RO desalination. Although the siting would have a large role in the efficiency and output of renewable plants and therefore its size, according to the generic figures provided by WEC¹⁷ for land use by power sources, just for the water production, without extra power available for other purposes, this alternative would imply covering equally large area with 80 meters tall wind turbines or 1.2 km² with solar panels. If the power capacities are equal for both: the nuclear and the renewable power/desalination plants, the later would have a far greater visual impact.

2.3 Atmospheric impacts

Nuclear desalination has the lowest impact on the atmosphere when compared to any other co-location option, having in mind that the main adverse impacts of desalination on the atmosphere are indirect, originating from the power source driving the process. Air emissions as a direct result from the desalination processes consist only of oxygen and nitrogen discharges due to de-aeration processes, with a negligible environmental significance.¹²

Although the desalination's energy intensity has been significantly lowered in the past decades, it is approaching the thermodynamic minimum energy value,⁹ which does not offer a lot of opportunities for further reduction of the impact on the atmosphere. Indeed, other energy solutions are required.

The atmospheric impacts of nuclear power are well studied and are considered minor in comparison with impacts from other energy sources (Fig. 1), offering a mitigating solution for one of desalination's greatest impediments – its atmospheric impact.

Fig. 1 Carbon footprint of different energy sources. Life-cycle calculation. Source: WEC, Jancovici 2008.

In case that we consider waste heat from electricity production as an energy source with no additional environmental impact, then the emissions of 200,000 m³/d of co-located MED desalinated water, per m³ will be only due to the auxiliary systems using 4 TJ per day. Thus, using the values from Fig. 1, we can calculate that:

- for natural gas, every m³/d will contribute ∼2.5 kg of CO₂, or in total − 480 tons of CO_2eq per day to the atmosphere.

- for coal as an energy source in co-located MED desalination, one m³/d of desalinated water contributes approximately 5 kg of CO₂ to the atmosphere, amounting in 1000 tons CO_2eq per day. To put this in perspective, this CO₂ emission per day, equals 225,000 modern passenger cars (150 g/km) commuting 30 km/d on average.

- the respective case for windmills, which is without available waste heat and RO would be the natural choice, due to the 4 TJ/d needed for RO desalination, may result in CO_2eq emissions per m³/d of ∼0.08 kg with a total of 16 tons CO_2eq per day. It is necessary to note in this specific case that the wind power varies considerably during plant operation, requiring back-up power for uninterrupted water supply. As usually this back-up power is from a fossil fuel source, the carbon footprint of desalinated water with renewable energy can be an order of magnitude higher than calculated with the generic figures given here. Having in mind the 0.7 power availability factor for wind power,¹⁷ a simple calculation reveals that 1 m³ of desalinated water would have a carbon footprint of ∼0.8 to ∼1.6 kg CO_2eq, depending whether the back-up power comes from, a coal or gas plant, respectively.

Such is the case with the Perth RO desalination plant, where wind power is used to offset the emissions resulting from other energy sources used by the plant.

For comparison, the CO_2eq emissions for the reference nuclear desalination plant per m³/d can be approximated around 0.035 kg, or 7 tons CO_2eq per day which can be attributed to its capacity for desalination. This is less than 5 percent of the second best alternative: the wind-powered RO desalination backed-up by gas power. On top of that, radioactive emissions to the atmosphere for a NPP are 100 times lower compared to a coal power plant of comparable size (1000 MW).¹⁸

Therefore, such a nuclear desalination facility may be considered as environmentally benign from the aspect of air pollution and a suitable energy source for desalination capacities, allowing for mitigation of atmospheric pollution. The US National Academy of Sciences also suggests the use of nuclear and different types of renewable energies for desalination.⁹

2.4 Socio-economic impacts

Socio-economic impacts have a direct influence on the other environmental impacts and must be included in the assessment as well as the monitoring activities. Several factors influence the importance of nuclear desalination as a socio-economic stimulus. The most significant would be the development potential due to availability of energy and water. It may change not only patterns of consumption behavior, but also cause major redistribution of people, capital and resources.

Availability of water and energy may have profound effects on local development, either limiting or enhancing it. The potential of nuclear desalination to provide the basis for development has its best example in the emerging and growth of Aktau (Kazakhstan), where nuclear desalination was used to support the growing city and industry in the area rich with minerals. (Fig. 2)

Fig. 2 Aktau in 1961 and in 1975. Source: http://www.aqtau.kz.

Compared to power though, water distribution is geographically limited and thus the attributed impacts may not be as dispersed over large areas as the energy-related ones. Water induced growth impacts may therefore be more intense, with the development surpassing the local or regional plans.

Indeed, the California Coastal Commission has suggested that growth-inducement related desalination impacts are likely to be “the most significant potential indirect adverse impacts”.⁷ Growth due to availability of water can stimulate new residential and commercial development,¹⁵ putting additional (unsustainably high) strain on the local environment and resources. Energy availability of course, may enhance this effect.

In reviewing the socio-economic impact of the reference facility, we may start with agriculture as a highly water intensive activity. FAO assumes 1000 m³/y necessary for the average daily ingest of 2800 kcal/d/capita, out of which 15 percent are usually provided from irrigation.¹⁹ This means that the reference capacity can be used, depending on the climate, to provide sufficient irrigation for food for up to half a million people. Furthermore, such a nuclear desalination plant is enough for sustaining a city with 400,000 to 500,000 citizens on a Sidney lifestyle and average water needs.²⁰

The consequences of such a development are huge and need to be addressed before the desalinated water is made available; not only a water management plan, but also all the necessary infrastructure for an increased population should be planned. Uncontrolled development may impact the social balance, affecting the local organization and structure. Population rise beyond local or regional development plans can result in environmental degradation by outgrowing the available capacities of public services and necessary supporting infrastructure (e.g. utility), adding to the social and economic disturbances. Regardless of the desalination option, it should not conform to tendencies to exceed the natural limitations with water-dependant development, causing damage to coastal ecosystems.

Nevertheless, desalination offers positive effects, such as diversity of supply which mitigates the impacts of prolonged water stress. It may increase the quality of drinking water, alleviate water scarcity and may be, as mentioned in the desalination report by the US National Academy of Sciences,⁹ even environmentally less damaging. Water availability can reduce conflicts over scarce water resources, reducing the strain on them, and it can create wealth through tourism, industry and agricultural growth, offering employment.¹² The case of Malta, for instance, shows how desalination combined with measures that prevent water misuse may help the profitable tourist industry.¹⁶

Furthermore, Bezdek and Wendling's research on the nuclear power plant effects on local property values, economic growth, tax revenues, public services, community development, jobs and employment, and schools, concludes that the effects have largely been positive.²¹ As pointed earlier, water availability also has a significant influence on development, property values, jobs etc. This indicates that nuclear desalination facility of the reference capacity, if properly framed within a national, regional or local development plan will most probably have a large, mainly beneficial social impact.

The economic competitiveness of nuclear energy is well known compared to other energy prices. As for the costs for desalinated water, they depend on a number of variables. The simulations using IAEA's DEEP software have indicated price ranges between 0.5 and 0.96 US$/m³, which is a competitive cost value for desalinated water.³ Additional factor for economic competitiveness is the high power availability of the NPP with 83 percent on average in 2006,¹⁷ allowing for uninterrupted energy supply to the reference MED plant. Half of the reactors in the world have availability of 86 percent and above, quarter of the world's reactors have availability of 91 percent or above.¹⁷ The data for fossil fuel power plants is currently being updated to provide a more accurate picture of the actual availability.

3. Public health implications for nuclear desalination

First of all, it should be noted that incidents with radioactivity cross-contamination to the product water were never reported, in Aktau, as well as Kalpakkam. This is important, since public health and associated risks are probably the most important factors impacting the public opinion for a nuclear desalination plant project. The concern is mainly due to tritium, radioactive isotope of hydrogen, as it is able to diffuse through various physical barriers into the product water.²² The possibility for radioactive contamination of the product water, as well as the mechanisms that ensure its prevention, must be well presented to the public. This is of great importance for the project implementation.

Nuclear desalination involves several safety features and operating practices. The most specific is the previously mentioned isolation loop, which has a higher pressure than the nuclear loop, and ideally, lower pressure than the desalination loop. Not only that this pressure of the isolation loop prevents possible leaks of contaminated coolant from the nuclear to the desalination loop, but it also lowers the chance of tritium diffusion through the isolation heat exchanger. Furthermore, removal of tritium from the nuclear coolant is continuously done, keeping even the coolant tritium levels per liter, below the WHO standards. Finally, the product water is kept in hold-up tanks where its tritium activity levels can be measured prior to release in the water distribution system, thus making sure that the product water is safe for use.

The experience so far does not show any contamination issues or health problems caused by tritium in the desalinated water. Muralev reports maximum tritium concentration in MAEC's desalination stream of 6 Bq/l.²³ The reverse osmosis facility in Kalpakkam has delivered desalinated water outside the facility with tritium content bellow the detectable limit.²⁴ Similarly, use of desalinated water for on-site potable purposes has not been reported to be a health hazard in the US or Japan. From the perspective of the regulatory limits for tritium in drinking water (Table 3), nuclear desalination experiences with tritium show that the product water is safe for use by the public.

Table 3 Allowed tritium levels in drinking water Source: IAEA, 2008

Country	Tritium limit (Bq/l)
Australia	76103
Canada	7000
EU	100
Kazakhstan	7700
Switzerland	10000
United States	740
WHO	10000

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As an applicable example of waste heat being used from the nuclear loop in non-electrical applications, we can take the local district heating loop in the Bohunice NPP, Slovakia. This loop has a tritium concentration which is below 1 Bq/l; even the isolation loop has tritium levels well within the WHO standards.²⁵

Furthermore, the radiological survey of the facility in Aktau, based on nearby soil and cooling pond bottom sediments, has concluded that the facility has a negligible contribution to the radiological situation within the investigated territories.²⁶ Thus, the brine is also excluded from posing as a possible radioactivity threat to public health.

With such safety and operating practices, the experience so far indicates that the public can accept nuclear desalination as a water supply option. For instance, located in a water-scarce region, the facility in Kalpakkam is experiencing growth of demand for desalinated water.²⁴ The other applicable experience of nuclear desalination is even more convincing: founded in a desert, Aktau owns its existence, and population growth, to the water supplied from the nuclear desalination plant. Nevertheless, it cannot be predicted with sufficient certainty that nuclear desalination will be accepted by the public in every case. Therefore, proper communication based on facts must be established with the public as the project is developed.

4. Environmental planning and monitoring

Based on the expected environmental impacts of nuclear desalination, we can list the priorities in the environmental planning. Mitigation measures must be a part of the environmental plan, for impacts which cannot be avoided. Subsequently, the monitoring activities should be designed to confirm that the operation of a nuclear desalination facility is within the limits of the expected impacts and the planned mitigation measures.

The environmental planning should begin with the choice of a suitable site for the facility. Of course, a region that lacks water and energy would be preferable. Following that, the site should present the possibility of seawater intake with constant quality (regarding the solids content and temperature), low pollution levels and solids in the seawater and low biofouling prospects. For nuclear desalination it seems that it would be necessary to position the intake in deeper waters, further away from the coast, where the biological activity is lower than in the coastal areas. In addition, different types of filters and screens would need to be applied, thus preventing large entrainment and impingement rates, as seen with some of the nuclear power plants. A monitoring program will have to be in place, providing a feedback on the intake's impact and possible necessary improvements.

The discharge impact due to the nuclear desalination operation is not expected to be different from other co-located facilities. The environmental planning should concentrate mainly on the thermal impact on the marine environment, and the increased toxicity of the discharge effluents due to the desalination operation. The mitigation solution may likely be based on heat recovery systems (i.e. heat pipes and heat exchangers), cooling structures (towers or ponds), submerged discharge with diffusers further away from the coastline, or a combination of these. Positioning the discharge in areas with strong, mixing currents may greatly reduce the impact of the discharge. A monitoring program for the discharge effluents is required by the IAEA Safety Guide No. NS-G-3.2,²⁷ and it is recommended for implementation. In the specific case of the reference nuclear desalination facility, attention should be primarily given to the temperature as well as the copper levels of the discharge.

The coastal impacts mentioned above, are expected to be lower than for the alternative co-located power/desalination options. The visual impact and the land use aspect in particular, offer a possibility for mitigation measures that are considerably simpler in the case of nuclear desalination. Still, the planning approach for such a facility will not differ greatly from the approach used in planning the other co-located options. As noise levels are easily controllable with suitable acoustical planning, the monitoring program should be based more on the issue of pipe leakage, eliminating the possibility of aquifer contamination with seawater. The construction phase of the facility would also require a monitoring plan, ensuring that no activity will take place to cause increased sedimentation from the settling material, thus affecting the turbidity and thereby the photosynthetic process in the coastal ecosystem, or if significant runoff increases the toxicity in that ecosystem. Atmospheric impacts are expected to be insignificant from a nuclear desalination facility and therefore this type of monitoring is likely to be based only on complying with the local regulations.

As for the socio-economic impacts, the environmental planning should address several factors, such as population increase, productivity change or increase as well as infrastructure development necessary to withstand those changes and the environmental strain they might impose. The monitoring program will therefore be based on parameters such as population increase, energy and water intensity, waste and pollution generation, environmental justice etc. It is important that the potentially large effects of a nuclear desalination plant, such as the reference facility, are used to enhance the regional socio-economic situation without adverse impacts on its balance. This will also prevent the associated environmental impacts.

Probably the most important aspect of nuclear desalination though, in order to achieve public acceptance, is the public health issue. Planning of the product water safety will concentrate on materials, tritium removal operations and procedures, as well as product water tanks which ensure that contaminated water will not be released into the water distribution system. The monitoring program should therefore be structured around several points, three of which are the most important: the isolation loop, the desalination loop and the water tanks. The water tanks would have to be continuously monitored for tritium activity for several hours before release into the water distribution system, depending on the monitoring equipment and legal safety requirements.

5. Conclusion

A nuclear desalination facility such as the reference one, will offer large quantities of energy and water, a relatively small environmental impact, it will be economically feasible and have a high reliability of supply—all of which formulates it as a viable option for addressing the water and energy requirements of today's societies, especially when compared to other co-located power/desalination options.

The environmental impacts assessment of a nuclear desalination facility with once-through cooling will have to compare the actual benefits and adversities for the marine environment originating from the intake and the discharge practice under site-specific conditions. In such a situation, without many possibilities for an “off-the-shelf” solution, identification of the best options will have to be done carefully and with the help of advanced modeling techniques. Since the environmental circumstances are site-specific, different repercussions on the layout of the facility can be expected, as well as the consequent nature and magnitude of its environmental impacts.

As for the coastal and atmospheric impacts, we can say with great certainty that they are lower than the alternative co-location options, which presents a great environmental advantage for nuclear desalination. Furthermore, the socio-economic impacts of a nuclear desalination facility are substantially larger than for the alternative power/desalination facilities, and beneficial when properly managed. These impacts can be felt on a local or regional level, depending on the quantity of produced water and amplified by the plant's excess electricity and subsequent revenue.

The adverse effects of nuclear desalination compared with other co-located options require less mitigation efforts while the benefits can be significantly higher. Based on everything presented, we consider that the application of nuclear desalination is more compatible with the Millennium Development Goals that require mitigation of water scarcity issues, and it should be supported by decision-makers. As a final recommendation, a tool for preliminary environmental impact assessment must be provided for that purpose, providing a basis for environmental planning and monitoring of nuclear desalination facilities.

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Footnote

† Part of a themed issue dealing with water and water related issues.

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