Nuclear Power Applications: Supplying Heat for Homes and Industries

FEATURES

Nuclear power applications: Supplying heat for homes and industries

More countries are interested in applying smaller sized nuclear reactors to help meet industrial and urban heating needs

When the first nuclear power reactor at Calder hot water or steam for industrial or space heat- by Bela J. Csik Hall in the United Kingdom came into commer- ing purposes. There are, however, substantial and cial operation in October 1956, it provided elec- differences between the properties and applica- Juergen Kupitz tricity to the grid and heat to a neighboring fuel tions of electricity and of heat, as well as reprocessing plant. After more than 40 years, between the markets for these different forms of the four 50 megawatt-electric (MWe) Calder energy. These differences as well as the intrinsic Hall units are still in operation. In Sweden, the characteristics of nuclear reactors are the rea- Agesta reactor provided hot water for district sons why nuclear power has predominantly pen- heating to a suburb of Stockholm for a decade, etrated the electricity market and had relatively starting in 1963. minor applications as a direct heat source. These examples show a side of nuclear energy that is unfamiliar to many people — its capacity to deliver heat for industrial processes The energy market and urban needs. Such applications started at a very early date, practically at the same time About 33% of the world's total energy con- when nuclear power reactors were first applied sumption is currently used for electricity gener- to electricity generation. ation. This share is steadily increasing and is Since these early days of nuclear power expected to reach 40% by the year 2015. Of the development, the direct use of heat generated in rest, heat consumed for residential and industri- reactors has been expanding. Countries such as al purposes, and the transport sector constitute Bulgaria, Canada, China, the Czech Republic, the major components, with the residential and Germany, Hungary, India, Japan, Kazakstan, industrial sectors having a somewhat larger Russia, Slovakia, Sweden, Switzerland, and share. Practically the entire heat market is sup- Ukraine have found it convenient to apply plied by burning coal, oil, gas, or wood. nuclear heat for district heating or for industrial Overall energy consumption is steadily processes, or for both, in addition to electricity increasing and this trend is expected to continue generation. Though less than 1% of the heat gen- well into the next century. Conservation and erated in nuclear reactors worldwide is at present efficiency improvement measures have in gen- used for district and process heating, there are eral reduced the rate of increase of energy con- signs of increasing interest in these applications. sumption, but their effect is not large enough to The direct use of nuclear heat is nothing stabilize consumption at current values. new. After all, the result of the nuclear fission A modest increase in the generation of process is the generation of heat within the reac- nuclear electricity is expected during the next tor. The heat is removed by the coolant circulat- couple of decades. In the transport sector, prac- ing through the core, that can then be applied to tically no application of nuclear energy is fore- the generation of electricity or used in providing seen, except indirectly through the increased use of electricity. The heat market is an open challenge. Though Mr. Csik is a senior staff member in the IAEA's Section on Nuclear Power Technology Development, of which Mr. nuclear energy has been used to supply a portion Kupitz is the Section Head. of the heat demand, it has not yet achieved sig-

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nificant penetration. How far and how fast it ty must be provided. This implies the need for could capture part of this market will depend redundancy and generating unit sizes corre- mainly on how the characteristics of nuclear sponding to only a fraction of the overall peak reactors can be matched with the characteristics load. The temperature range required by district of the heat market, in order to successfully com- heating systems is around 100 to 150° C. pete with alternative energy sources. In general, the district heating market is expected to expand substantially. Not only because it can compete economically in dense- Characteristics of the heat market ly populated areas with individual heating arrangements, but also because it offers the pos- Transport of heat is difficult and expensive. sibility of reducing air pollution in urban areas. The need for a pipeline, thermal isolation, pump- While emissions resulting from the burning of ing, and the corresponding investments, heat fuel can be controlled and reduced up to a point losses, maintenance, and pumping energy in relatively large centralized plants, this is not requirements make it impractical to transport practical in small individual heating installa- heat beyond distances of a few kilometers or, at tions fueled by gas, oil, coal, or wood. most, some tens of kilometers. There is also a Industrial processes. Within the industrial strong size effect. The specific costs of transport- sector, process heat is used for a very large vari- ing heat increase sharply as the amount of heat to ety of applications with different heat require- be transported diminishes. Compared to heat, the ments and with temperature ranges covering a transport of electricity from where it is generated wide spectrum. While in energy intensive indus- to the end-user is easy and cheap, even to large tries the energy input represents a considerable distances measured in hundreds of kilometers. fraction of the final product cost, in most other The residential and the industrial sectors processes it contributes only a few percent. constitute the two major components of the Nevertheless, the supply of energy has an essen- overall heat market. Within the residential sec- tial character. Without energy, production tor, while heat for cooking has to be produced would stop. This means that a common feature directly where it is used, the demand for space of practically all industrial users is the need for heating can be and is often supplied from a rea- assurance of energy supply with a very high sonable distance by a centralized heating sys- degree of reliability and availability, approach- tem through a district heating transmission and ing 100% in particular for large industrial distribution network serving a relatively large installations and energy intensive processes. number of customers. Regarding the power ranges of the heat District heating. District heating networks sources required, similar patterns are found in generally have installed capacities in the range most industrialized countries. In general, about of 600 to 1200 megawatt-thermal (MWth) in half of the users require less then 10 MWth and large cities, decreasing to approximately 10 to another 40% between 10 and 50 MWth. There 50 MWth in towns and small communities. is a steady decrease in the number of users as Exceptionally, capacities of 3000 to 4000 the power requirements become higher. About MWth can be found. Obviously, a potential 99% of the users are included in the 1 to 300 market for district heating only appears in cli- MWth range, which accounts for about 80% of matic zones with relatively long and cold win- the total energy consumed. Individual large ters. In western Europe, for example, Finland, users with energy intensive industrial processes Sweden, and Denmark are countries where dis- cover the remaining portion of the industrial trict heating is widely used, and this approach is heat market with requirements up to 1000 also applied in Austria, Belgium, Germany, MWth, and exceptionally even more. This France, Italy, Switzerland, Norway, and the shows the highly fragmented nature of the Netherlands, though to a much lesser degree. industrial heat market. The annual load factors of district heating sys- The possibility of large-scale introduction of tems depend on the length of the cold season heat distribution systems supplied from a cen- when space heating is required, and can reach tralized heat source — which would serve sev- up to about 50%, which is still way below what eral users concentrated in so-called industrial is needed for base load operation of plants. parks — seems rather remote at present, but Also, to assure a reliable supply of heat to the could be the trend on a long term. Contrary to residences served by the district heating net- district heating, the load factors of industrial work, adequate back-up heat generating capaci- users do not depend on climatic conditions. The

22 IAEA BULLETIN, 39/2/1997 FEATURES demands of large industrial users usually have Regarding the temperature ranges, up to base load characteristics. about 300° C are obtained in light- and heavy- The temperature requirements depend on water reactors, up to 540°C in liquid metal- the type of industry, covering a wide range up to cooled fast reactors, up to 650°C in advanced around 1500° C. The upper range above 1000° gas-cooled reactors, and up to about 1000° C in C is dominated by the iron/steel industry. The high temperature gas-cooled reactors. lower range up to about 200 to 300° C includes For applications to district or process heat- industries such as seawater desalination, pulp ing, there are basically two options. Co-genera- and paper, or textiles. Chemical industry, oil tion of electricity and heat, and heat-only reac- refining, oil shale and sand processing, and coal tors. Co-generation has been widely applied, gasification are examples of industries with while there is not much experience in heat-only temperature requirements of up to the 500 to reactors. In principle, any amount of heat can be 600° C level. Non-ferrous metals, refinement of extracted from co-generation reactors, subject coal and lignite, and hydrogen production by to design limitations. Whatever heat is not need- water splitting are among applications that ed to supply the heat demand can be used for require temperatures between 600 and 1000° C. electricity generation, which means a high All industrial users who require heat also degree of flexibility. Heat-only reactors, on the consume electricity. The proportions vary other hand, have only one objective, as they are according to the type of process, where either not intended for generating electricity. heat or electricity might have a predominant The availability of nuclear reactors is, in role. The demand for electricity can either be general, similar to fossil-fuelled power plants. supplied from an electrical grid, or by a dedi- As shown by experience, availability factors of cated electricity generating plant. Co-generat- 70% to 80% or even 90% can be achieved. The ing electricity and heat is an attractive option. It frequency and duration of unplanned outages increases overall energy efficiency and provides can be kept very low with good preventive and corresponding economic benefits. Co-genera- predictive maintenance. Availability and relia- tion plants, when forming part of large industri- bility of a reactor, however, can never reach the al complexes, can be readily integrated into an nearly 100% levels required by most large heat electrical grid system to which they supply any users. Consequently, as for fossil-fueled heat surplus electricity generated. In turn, they sources, redundancy is needed. Multiple unit would serve as a back-up for assurance of elec- co-generation power plants, modular designs, or tricity supply. Such arrangements are often back-up heat sources are suitable solutions. found to be desirable. Nuclear reactors are capital intensive. The influence of the fixed cost component is predominant in the final cost of energy. Therefore, Characteristics of nuclear heat sources base-load operation with load factors as high as achievable is needed for competition with alter- From the technical point of view, nuclear native sources. This is only possible when the reactors are basically heat generating devices. demand of the heat market to be supplied has There is plenty of experience of using nuclear base-load characteristics, or when the combined heat in both district heating and in industrial electricity and heat market enables overall processes, so the technical aspects can be con- base-load operation of a co-generation plant. sidered well proven. There are no technical Nuclear reactors can be technically proven, impediments to the application of nuclear reac- safe, reliable and environmentally clean energy tors as heat sources for district or process heat- sources, but for commercial deployment they ing. In principle, any type and size of nuclear also have to be economically competitive with reactor can be used for these purposes. alternative energy sources. Compared to fos- Potential radioactive contamination of the sil-fuelled sources, nuclear reactors are charac- district heating networks or of the products terized by higher investment costs compensated obtained by the industrial processes is avoided by lower fuel costs. The penetration of nuclear by appropriate measures, such as intermediate power into the electricity market would not heat exchanger circuits with pressure gradients have been possible without having fulfilled the which act as effective barriers. No incident condition of economic competitiveness. Even involving radioactive contamination has ever with prevalent low fossil fuel price levels, been reported for any of the reactors used for nuclear power has retained its competitive posi- these purposes. tion in most parts of the world. Should fossil

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fuel prices increase, as is expected to occur, the Prospects for nuclear heat applications economically competitive position of nuclear power, both for electricity generation and for The technical viability of employing nuclear heat supply, will improve. heat sources for district heating or for industrial Due to the size effect, nuclear economics are, processes has existed since the very start of in general, improved for larger units. This has nuclear development. A substantial penetration led to the development and predominant deploy- into the commercial heat market, however, has ment of large-size reactors in industrialized not yet taken place. Prospects will mainly countries with very large interconnected electri- depend on where and how the demand charac- cal grid systems. Nevertheless, there has been teristics of the heat market can be matched by and there continues to be a market for small- and what nuclear reactors are able to offer. medium-sized power reactors (SMRs). Current District heating market. For the district design SMRs are not scaled down versions of heating market, co-generation nuclear power large commercial reactors, and they are intended plants are one of the supply options. In the case to be economically competitive. of medium to large nuclear reactors, due to the Siting of nuclear plants has become a major limited power requirements of the heat market issue, even in those countries which are pro- and the relatively low load factors, electricity- ceeding with their nuclear programmes by ini- would be the main product, with district heating tiating new projects. Building additional units accounting for only a small fraction of the over- at existing nuclear sites has been standard prac- all energy produced. These reactors, including tice lately, and opening up new sites for nuclear their siting, would be optimized for the condi- plants are a rare occurrence. Economic factors tions pertaining to the electricity market, district promote siting as close as possible to load cen- heating being, in practice, a byproduct. Should ters even for electricity generating power such power plants be located close enough to plants. For co-generation or heat-only reactors, population centers in cold climatic regions, they this is practically a necessary condition to be could also serve district heating needs. This has fulfilled. The NIMBY (not in my back yard) been done in Russia, Ukraine, the Czech syndrome, however, is an important factor Republic, Slovakia, Hungary, Bulgaria, and affecting site selection. It promotes a trend to Switzerland, using up to about 100 MWth per choose remote but accessible locations, in power station. Similar applications can be order to avoid potential conflicts and opposi- expected for the future wherever similar bound- tion. Remote siting far from densely populated ary conditions exist. areas makes it also easier to comply with regur For small co-generation reactors corre- latory requirements, which are getting more sponding to power ranges of up to 300 MWe and more demanding. Advanced reactor and 150 MWe, respectively, the share of heat designs, in particular in the SMR range with energy for district heating would be larger. But improved safety features, could be perceived as electricity would still be expected to constitute acceptable for close siting by the public. They the main product, assuming base-load opera- also could more easily meet regulatory require- tion, for economic reasons. The field of appli- ments and could maintain heat transmission cation of these reactors would be similar to the costs at reasonable levels. case of medium or large co-generation reactors. In nuclear power, unlike in many industrial Additionally, however, they could also address undertakings, the long-term viewpoint is pre- specific objectives, such as the energy supply of dominant. The planning, design, project concentrated loads in remote and cold regions preparatory activities, and licensing takes of the world. years to be completed for any nuclear reactor. Heat-only reactors for district heating are Reactors are designed and built to last for another option. Such applications have been about 40 years or more, and to achieve the eco- implemented on a very small scale (a few nomic benefits expected, they have to be oper- MWth) as experimental or demonstration pro- ated with high load factors during their eco- jects. Construction of two units of 500 MWth nomic lifetime. There are also infrastructure was initiated in Russia in 1983-85, but later requirements, which require time and consid- interrupted. There are several designs being erable development efforts, if not already pursued, and it is planned to start construction available. These efforts are only justifiable of a 200 MWth unit soon in China. Clearly the under a long-term perspective directed to a potential applications of heat-only reactors for nuclear programme. district heating are limited to reactors in the

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very small size range. These reactors are could be converted to co-generation. Should designed for siting within or very close to pop- there be a large process heat user close to the ulation centers so that heat transmission costs plant interested in receiving this product, the cor- can be minimal. Even so, economic competi- responding conversion to co-generation would be tiveness is difficult to achieve due to the rela- technically feasible. It would, however, involve tively low load factors required, except in cer- additional costs, which would have to be justified tain remote locations where fossil fuel costs are by a cost/benefit analysis. Some such conversion very high and the winter is very cold and long. projects could be implemented but, in general, In summary, the prospects for nuclear dis- prospects for this option seem rather low. trict heating are real, but limited to applications Installing a new nuclear co-generation plant where specific conditions pertaining to both the close to an existing and interested industrial district heating market and to the nuclear reac- user has better prospects. Even better would be tors can effectively be met. The prospects for a joint project whereby both the nuclear co-gen- co-generation reactors, especially in the SMR eration plant and the industrial installation range, seem better than for heat-only reactors, requiring process heat are planned, designed, mainly because of economic reasons. built, and finally operated together as an inte- Industrial process heat. The characteristics grated complex. of the market for process heat are quite different Current and advanced light- or heavy-water from district heating, though there are some reactors offer heat in the low temperature range, common features, particularly regarding the which corresponds to the requirements of sever- need for minimal heat transport distance. al industrial processes. Among these, seawater Industrial process heat users, however, do not desalination is presently seen as the most attrac- have to be located within highly populated tive application. Other types of reactors, such as areas, which by definition constitute the district liquid metal-cooled fast reactors and high tem- heating market. Many of the process heat users, perature gas-cooled reactors can also offer low in particular the large ones, can be and usually temperature process heat, but in addition, they are located outside urban areas, often at consid- can cover higher temperature ranges. This erable distances. This makes joint siting of extends their potential field of application. nuclear reactors and industrial users of process These reactors still require substantial develop- heat not only viable, but also desirable in order ment in order to achieve commercial maturity. to drastically reduce or even eliminate the heat Should they achieve economic competitiveness transport costs. as expected, their prospects seem to be promis- For large size reactors, the usual approach is ing in the medium to long term, especially for to build multiple unit stations. When used in the high temperature industrial applications. co-generation mode, electricity would always Heat-only reactors have not yet been applied constitute the main product. Such plants, there- on an industrial/commercial scale for the supply fore, have to be integrated into the electrical of process heat. Several designs have been grid system and optimized for electricity pro- developed and some demonstration reactors duction. For reactors in the SMR size range, and have been built. Economic competitiveness in particular for small and very small reactors, seems to be an achievable goal according to the share of process heat generation would be many studies which have been performed, but larger, and heat could even be the predominant this is something yet to be proven in practice. product. This would affect the plant optimiza- The potential market for such heat-only reactors tion criteria, and could present much more would be limited to the very small size range, attractive conditions to the potential process i.e. below about 500 MWth. heat user. Consequently, the prospects of SMRs The prospects for applying nuclear energy to as co-generation plants supplying electricity district and process heating are closely tied to and process heat are considerably better than the prospects of deploying SMRs. A recent mar- those of large reactors. ket assessment for SMRs found that 70 to 80 Several co-generation nuclear power plants in new units are planned in about 30 countries up operation already supply process heat to industri- to the year 2015. It was also found that about a al users. The largest projects implemented are in third of these units are expected to be applied Canada (Bruce, heavy-water production and specifically to nuclear desalination. Of the rest, other industrial/agricultural users) and in a substantial share could very well supply heat Kazakstan (Aktau, desalination). Other power in addition to electric energy, while a few are reactors which currently produce only electricity, expected to be heat-only reactors. •

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