PROSPECTS OF AN INTEGRATED NUCLEAR DESALINATION SYSTEM

Transcription

1 PROSPECTS OF AN INTEGRATED NUCLEAR DESALINATION SYSTEM Si-Hwan Kim and Young-Dong Hwang. Korea Atomic Energy Research Institute, Yuseong, Daejon, Republic of Korea 1. Introduction Currently over one billion persons suffer from water shortages, unreliable water supplies, and unsanitary conditions related to inadequate water supplies. Hence the global need and demand for clean fresh water is ever increasing. Seawater desalination has become a proven and reliable process to produce clean fresh water. Since 1950, a large number of seawater desalination plants have been installed and it is projected to continue to increase. Seawater desalination requires energy in the form of heat, electricity or both. Fossil fuels have been the energy source for a desalination, and they are expected to remain as the major energy source for seawater desalination in the future. However, many concerns from using fossil fuels as an energy source have been raised such as an air pollution, the greenhouse effect, depletion of valuable natural energy resources, etc. In this regard, several alternative energy sources can be considered to partly replace the fossil fuels used for a seawater desalination. One of the potentially rewarding alternative energy sources is nuclear energy. Nuclear power plants are well suited to supply the energy required for a seawater desalination.[1,2] Also, nuclear desalination has economic advantages over the alternative energy options. In view of the growing worldwide demand for fresh water, it is expected the use of nuclear desalination technologies will be considerably enhanced in the future. For a dual purpose application, seawater desalination and electricity generation, various types of advanced reactors are currently under development worldwide. In particular for a desalination of seawater and an electricity generation, s Small and Medium sized reactor (SMR) has the beneficial advantages of a reactor safety by an easy implementation of advanced design concepts and technology.[2,3] 2. Nuclear desalination as an alternative option Desalination technologies have been well established since the mid-20th century and widely deployed in many parts of the world facing a water scarcity. The contracted capacity of desalination plants has increased steadily since 1965 and is now about 36 million cubic meters per day.[6] The energy for these plants is generally supplied in the form of either steam or electricity. Conventional fossil fuel-powered plants have normally been utilized as the primary energy sources, but their intensive use raises increasing environmental concerns especially in relation to greenhouse gas emissions. Burning these fuels causes serious environmental problems from emissions of sulfur oxides, nitrogen oxides and carbon dioxide into the atmosphere. The depleting sources and the future price uncertainty of the fossil fuels and their better use for other vital industrial applications are also factors to be considered. One approach to solve these problems is to use nuclear energy for the desalination process. Electrical and/or thermal energy produced from a nuclear plant may be used in the desalination process to produce potable water. Nuclear reactors are used mainly for the production of either heat or electricity. The steam may be used for supplying the required energy to produce potable water. The electricity generated from a nuclear plant can be used to drive the high-pressure pumps of the RO desalination plants. Since a nuclear power is a proven technology, all the nuclear reactor types can be used to provide the energy required by the various desalination processes. And the most crucial factor that will determine the feasibility of a nuclear desalination is to develop the most appropriate plant configuration of the integrated nuclear desalination system. A coupling with a nuclear system is not difficult but it needs some special consideration. Various concepts of the coupling of nuclear and desalination systems were proposed for an integrated nuclear desalination system. Technical feasibility of the integrated nuclear desalination plants has been proven through the

2 worldwide operating experiences on nuclear desalination for over 150 reactor-years. Economic competitiveness of a nuclear desalination has been demonstrated through IAEA s desalination economic evaluation program. The study results showed that an integrated plant can produce electricity and water at a reasonable cost.[4-5] Several demonstration programs of a nuclear desalination are also in progress to confirm its technical and economical viability under country-specific conditions, with technical co-operation or support of the IAEA.[6] 3. Development status of a nuclear desalination Nuclear power plants produce about 17% of the world's power. There are about 440 nuclear reactors operating in various countries. All the nuclear reactor types can provide the energy required by the various desalination processes. All the desalination technologies are applicable for a nuclear desalination. The energy required for a seawater desalination can be readily supplied by the steam and/or electricity produced by the nuclear power plant. In this regard, it has been shown that Small and Medium Reactors (SMRs) offer a big potential as the coupling options to nuclear desalination systems.[2,3] Innovations in the reactors and desalination technologies and cost reduction have been made. Design aspects of nuclear desalination plants, including the reactors, their coupling with the desalination plants, the safety and security aspects are well established. [5,6] Nuclear desalination plants have been operated in Kazakhstan and Japan for many years. A cogeneration power plant with a liquid metal cooled fast reactor (LMFR) BN-350 has been operated in Aktau, Kazakhstan as an energy source for a multi-purpose energy complex since 1973 supplying 135 MWe of electricity, about 80,000 m 3 /day potable water and heat to the local population and industries. While in Japan, the first Japanese nuclear power and seawater desalination plant started operation in 1978 at the Ohi Nuclear Power Station. The plant used a 1175 MWe pressurized water reactor (PWR) coupled to a MSF distillation process with a capacity of 1300 m 3 /day. Nine additional nuclear seawater desalination plants were installed by India has successfully operated a desalination experimental facility in Trombay since Kalpakkam pressurized heavy water reactor (PHWR) in Tamil Nadu was coupled with a hybrid RO MSF plant. The Kalpakkam nuclear desalination complex with a capacity of a 6,300 m 3 /day has been in operation since This MSF-RO Hybrid Nuclear Desalination Plant consists of a 4,500 m 3 /day MSF plant and a 1,800 m 3 /day SWRO plant. The Pakistan project for a desalination with the Karachi nuclear power plant is now on the way to establishing a MED thermal desalination demonstration plant with a capacity of up to 4,800 m 3 /day at KANUPP.[6] Technical and economical feasibility studies of a nuclear desalination have also been completed in Korea. The feasibility of SMART with a MED based integrated desalination plant for the Madura island in Indonesia was completed in The primary objective of the study is to investigate the economical feasibility of a nuclear desalination by providing the Madurese with a sufficient power and potable water to support an industrialization as well as tourism in the Madura Region. The French-Tunisian collaboration, known as the TUNDESAL project was also finished in These two studies concluded that a nuclear desalination is a viable option for the future. 4. SMART nuclear desalination plant An integrated nuclear desalination plant coupled with the advanced integral reactor SMART), has been developed at KAERI to produce forty thousand (40,000)m 3 /day of water and to generate ninety (90) MW of electricity to an area with approximately a ten thousand (100,000) population or an industrialized complex. SMART design combines firmly established commercial reactor design technologies with the new advanced technologies focusing on an enhancement of the safety and an improvement of the economics.[7] The enhancement of safety is realized by incorporating inherent safety improving features and reliable passive

3 safety systems. The improvement in the economics is achieved through a system simplification, component modularization, construction time reduction, and increased plant availability. The new advanced design technologies implemented into the SMART were proven by experience, testing or analysis. The equipments were designed and qualified according to the applicable industrial standards. For the verification of the new technologies adopted in SMART design, comprehensive fundamental thermalhydraulic experiments were carried out during the design concept development stage. Upon the completion of the basic design, various thermal-hydraulic and mechanical tests were conducted. The MED process and the steam extraction method were both chosen for the SMART desalination plant. In the coupling of a desalination system with SMART, the economical and safety aspects were taken into account as the most important factors.[8,9] The SMART desalination plant consists of 4 units, capacity of 10,000m 3 /day per each unit. The unit capacity was determined from an operational flexibility aspect of the desalination plant. An intermediate isolating loop with a spray flash steam chamber is considered to be the best option to meet the requirements of both an economic effectiveness of the desalination process and a radioactive contaminant protection. The intermediate heat transfer loop completely separates the process steam used for the desalination from the steam flow extracted from the turbine. The radioactivity monitoring systems were also installed in the water production system and the intermediate loop where the concentration of radioactivity is higher than in the desalination system. The safety of the SMART design was assessed for more than 1500 design based events of 21 different types. A safety analysis methodology was developed, including a set of DBEs based on the ANSI/ANS (R1988), and a full set of safety analyses with basic design data was performed by using a computer code developed by the Korea Atomic Energy Research Institute.[6] Based on the analyses results, it is concluded that a significant impact on the safety of the SMART plant is not expected due the transients initiated from the desalination system. The results also show that the safety systems of the SMART design adequately mitigate the consequences of all the design based accidents and thus secure the plant to a safe condition. In addition, a study was carried out to establish the proper range of the water production cost. Although the study involves some uncertainties in the estimation, the results show that the SMART plant can produce the potable water comparable to or more economically than the other options. Since the SMART technology is technically sound and has sufficient economics, the SMART desalination plant has good prospects for deploying it as a nuclear desalination plant. 5. Future developments The activities on a nuclear desalination are now shifting towards techno-economic feasibility studies for a possible deployment of nuclear power desalination plants at specific sites experiencing a water scarcity problem. In addition to the techno-economic aspects, socio-economic aspects, and environmental aspects of a nuclear desalination should be addressed in the future. For the introduction of nuclear desalination plants, the issues related to a nuclear desalination should be resolved and also a nuclear desalination should provide economic benefits. The following lists the issues to be resolved for a nuclear desalination. 5.1 Safety consideration Safety aspect of a nuclear desalination includes the overall safety of an integrated nuclear desalination plant complex, safety of a nuclear reactor, design impact of a nuclear reactor to a desalination plant, and the transient interactions between the nuclear reactor, coupling system and desalination plant. The safety of a nuclear desalination plant depends mainly on the safety of the nuclear reactor and the interface between the nuclear plant and the desalination system. Safety considerations have a direct impact on the socio-environmental aspects of a nuclear desalination. 5.2 Environmental issues

4 Environmental issues related to nuclear desalination should be adequately addressed. Some of the important issues are a brine disposal, environmental impact of the chemicals used for a pretreatment, impact of the chemicals used for a corrosion control, marine environment protection, radioactivity content in the feed and product water of a desalination plant, and corrosion products. Comprehensive studies are required to be carried out on the environmental impact of the emissions from nuclear desalination plants. In general, a nuclear desalination plant has a positive impact on the environment in so far as it provides good quality water which all human beings need for their survival. The environmental impact assessment should at least contain an assessment during the period of pre-construction, a construction, an operation and during the period after operation. 5.3 Socio-economic aspects Public perception and public support is very important while introducing nuclear desalination system. A dual purpose nuclear desalination plant has advantages such as public support, awareness about the potential benefits to the public and the local community, awareness about the safety concepts and the environmental impact, availability of water and power leading to the development, direct/indirect employment, better standard of living, energy security, and water security. Socio-economic aspects play an important role in setting up a nuclear desalination plant. They include siting considerations, civil emergency preparedness planning, role of the water supply authorities and the nuclear regulatory authorities, product quality, product cost, economy of scale, economic optimization, cogeneration plant, and cost reduction strategies. 5.4 Quality of water The quality of potable water produced in a nuclear desalination plant should meet the current international (WHO) drinking water standard. Water quality standard can be classified as a physical quality, chemical quality (organics and in-organics), microbiological quality and radiological quality. However, the WHO guideline only considers a radionuclide concentration arising from natural sources. For the assurance of product water especially free of radioactive contaminants, the water stream requires to be monitored continuously. However, continuous radiation monitoring of product water stream is difficult because of the sensitivity limitations of the current detectors. Thus, a practical engineering solution for the issues on a continuous radiation monitoring of a product water is needed. 6. Conclusions Seawater desalination has become a proven and reliable process to meet the global demand for clean fresh water. Fossil fuels have been the major energy source for a seawater desalination, but the use of fossil fuels has raised many concerns. Since a desalination is an energy incentive process, the use of nuclear energy becomes a very attractive option to replace the fossil fuels used for a seawater desalination. Nuclear power plants are well suited to supply the energy required for a dual purpose: seawater desalination and electricity generation. All the nuclear reactor types can provide the energy required by the various desalination processes. The energy required for a seawater desalination can be readily supplied by the steam and/or electricity produced by the nuclear power plants. Innovations in the reactors and desalination technologies and a cost reduction have been made. Design aspects of the nuclear desalination plants, including the reactors, their coupling with the desalination plants, and the safety and security aspects are well established. The activities on a nuclear desalination are now shifting towards the techno-economic feasibility studies for a possible deployment of nuclear desalination plants at specific sites with a water scarcity problem. For an introduction of nuclear desalination plants throughout the world, the issues related to a nuclear desalination should be resolved and also a nuclear desalination should provide economic benefits. In view of the growing worldwide demand for fresh water, the use of nuclear technologies will be considerably enhanced in the future. For a deployment of nuclear desalination plants at any given site, the techno-economic aspects, and the socio-economic and environmental aspects of a nuclear desalination should be addressed in the future.

5 7. Acknowledgement This study has been carried out under the nuclear research and development program supported by the Ministry of Science and Technology of the Republic of Korea. The authors are sincerely grateful for the financial support. 8. References [1] "Options identification program for demonstration of nuclear demonstration", IAEA, IAEA- TECDOC-898, Vienna, 1996 [2] IAEA, Design and Development Status of Small and Medium Reactor Systems, IAEA TECDOC- 881, International Atomic Energy Agency, Vienna, 1996 [3] IAEA, Introduction of Small and Medium Reactors in Developing Countries, IAEA-TECDOC- 999, Vienna, September 1996 [4] IAEA, Thermodynamic and economic evaluation of co-production plants for electricity and potable water, IAEA-TECDOC-942, Vienna, May 1997 [5] IAEA, Design Concepts of nuclear desalination plants, IAEA-TECDOC-1326, Vienna, November 2002 [6] B. Misra, Status and Prospects of Nuclear Desalination, IDA World Congress on Desalination and Water Reuse, Singapore, September 11-16, 2005 [7] M.H. Chang, et al., SMART An Advanced Small Integral PWR for Nuclear Desalination and Power Generation, Proc. of Global 99, International Conference on Future Nuclear Systems, Jackson Hole, USA, Aug Sept. 3, 1999 [8] C.S. Kang, et. al., A Planning Study Project of Developing an Integral Reactor (SMART), KAERI/CM-469/2001, KAERI, Taejon, Korea, 2001 [9] H.Y. Yoon, et. al., Thermal Hydraulic Model Description of TASS/SMR, KAERI/TR-1835/01, KAERI, Taejon, Korea, 2001 [10] S.K. Sim, et al, "Development of Safety Analysis Technology for Integral Reactor", KAERI, KAERI/RR, 1999