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Feasibility study of high temperature reactor utilization in Czech Republic after 2025
Nuclear Engineering and Design 271 (2014) 46–50
Contents lists available at ScienceDirect
Nuclear Engineering and Design journal homepage: www.elsevier.com/locate/nucengdes
Feasibility study of high temperature reactor utilization in Czech Republic after 2025 Evˇzen Losa a,∗ , Bedˇrich Heˇrmansky´ a , Duˇsan Kobylka a , Jan Rataj a , L’ubomír Sklenka a , Václav Souˇcek b , Petr Kohout b a b
Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Nuclear Reactors, Czech Republic AZIN CZ, s.r.o., Hanusova 3, 140 00 Praha 4, Czech Republic
a r t i c l e
i n f o
Article history: Received 28 May 2013 Accepted 29 October 2013
a b s t r a c t High temperature reactors (HTRs) were examined as an option to intended future broadening of the nuclear energy production in Czech Republic. The known qualities as the inherent safety, high thermal utilization and non-electrical applications have been assessed in years 2009–2011 during the survey funded by Czech Ministry of Industry and Trade. The survey of high temperature reactors with spherical fuel was initiated by reason of mature state of the art of this technology type in South Africa and in China, where in both countries pilot plants were planned. Unfortunately, the global financial crisis caused the decision of stopping the governmental support in South African programme was made. In China, however, the development still continues. Czech Republic has almost 60 years nuclear research history and the knowledge of operation of gas cooled and heavy water moderated reactor has been gained in the past. Nevertheless, the design of light water reactors was more developed in former Soviet Union, which provided Czech scientists by initial knowledge base; hence the research has been reoriented to this technology. But, the demands on future nuclear reactors application are still growing and the same or even higher living standard of next generations have to be taken into consideration. Therefore the systems, which can produce more energy and less waste, are getting into foreground of interest of Czech decision makers. The high temperature reactor technology seems to be the successful representative of the GEN IV reactor types, which will be operated commercially in the near future. The broad spectrum of utilization enables this system to be an option after 2030, when the electricity demand is planned to be covered from about 50% by nuclear in our country. © 2013 Elsevier B.V. All rights reserved.
1. Introduction High temperature gas cooled reactor technology, designed almost 60 years ago and verified by number of experiments and also by pilot plants in U.S.A. and Germany, seems to be an eligible candidate for heavy- and energy industry development in 21st century. Potential of this technology has been recently rediscovered particularly in South Africa and China, where the decision of governmental financing of the pilot plant construction based on spherical fuel technology (pebble bed) was made. As a consequence of global financial crisis, the support for this project has been temporarily stopped in South Africa but, in China the research continues and the HTR-PM pilot plant is expected to be commissioned in 2013 and will serve to prove mainly the inherent safety features as the impossibility of core melting and economic viability (Zhang et al., 2009).
∗ Corresponding author. E-mail address: evzen.losa@fjfi.cvut.cz (E. Losa). 0029-5493/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nucengdes.2013.11.007
Current status of High Temperature Gas Cooled Reactor (HTGR) technology development shows that prior to the direct Brayton cycle coupled with gas turbine employment to reach highly efficient energy conversion, the first stage of nuclear market penetration will have to be done with reactor systems supplying the steam of high parameters for energetic and industrial applications. The capability of high parameter steam production was proven by commercial plant operation in the past and the safety issues are well documented (Copinger and Moses, 2004). On account of industrial heat application focus, the proposed power output of single modules is much smaller, than of classical Light Water Reactors (LWRs) offered. The conception of smaller modular reactor should also bring some investment savings thank to higher number of construction repetition. The possibilities of the HTGR’s utilization in environment of Czech Republic were surveyed during the three year’s project supported by Czech Ministry of Industry and Trade (MoIT). In three stages of the project, the compatibility of this technology with local legislation and energy conception was proved and also the capability of Czech subcontractors to take part on the potential
E. Losa et al. / Nuclear Engineering and Design 271 (2014) 46–50
construction was verified. Although there is reactor operation experience with both prismatic and spherical fuel type in the world, the survey was focused on the reactor type with spherical fuel elements (Pebble Bed Modular Reactor (PBMR) or HTR-PM type) because of the recent development states of those technologies in afore mentioned countries. Only the future massive operation of the HTGRs will show the practical advantages and disadvantages, concerning technology and economics, of these two proposed designs. 2. Description of Czech environment There are already two nuclear power plant sites in Czech Republic, with the Russian VVER 440 (V 213 type, power output 500 MW) and VVER 1000 (V 320 type) reactors operated. The nuclear energy supply is more than 32% of overall energy produced. This production is planned to rise up to 50% in the future due to coal fired power plants replacement. The aim of the study was the survey of the possibility of the HTGR technology utilization as one of the ways of energetic independence increase of the country in long term perspective. The conventional energy sources orientation is not feasible neither from economic, nor strategic point of view. The advantages of high temperature reactor, which employs spherical fuel is the advanced degree of development and the projection of near term operation, which will show the economic and technical benefits. The main factor influencing the plant performance is also continuous fuel replacement during the operation. The progress in past decades definitely proved the necessity of at least 50% growth in electricity production in the horizon of next 20–30 years. The increase will be covered particularly by traditional fossil and nuclear sources which are of extraordinary meaning for Czech Republic, fully dependent on crude oil and gas import. The nuclear sources are mainly used for electricity production. The crucial problem from the point of view of energy balance is the provision of high potential source of heat for industrial and population’s needs. These needs are recently covered by combustion of fossil fuels partially from steadily declining domestic resources and partially from imported resources. However, the stable supply of imported materials cannot be guaranteed as seen during the gas crisis in Central Europe in 2009 (Doran, 2009). Equally, the environmental protection accompanied by carbon dioxide emissions reduction plays important role. 3. The research outputs There have been huge amounts of work done in the world during the years of development of the HTGRs. A part of the survey was focused on the summarization of historical as well as recent knowledge of the technology. The second part should provide the information about the convenience of this technology for the Czech Republic. 3.1. Power plant siting In the Czech Republic it is possible to choose two of four feasible sites of the new nuclear power plant. The first site in Dukovany locality is now occupied by four VVER 440 reactors, but this place provides enough space for the fifth reactor of similar output. The problem, however, is the chronic shortage in cooling water during the summer period. The power plant based on cycle with lower heat rejection would be a solution. The second proposed site, Blahutovice, lies in the part of the country with strong concentration of heavy industry. The public in this region is very favourable to new nuclear cogeneration projects just because of smog situation and long term exceeding of the limits for dust particles in air. There is also demand for source of electricity
47
Table 1 The costs of the front and back end fuel cycle parts (Shropshire et al., 2008). Parameter
Unit
Front end U3 O8 Conversion Enrichment Fabrication [PWR] Fabrication [BWR] Fabrication [HTGR]
$/lb U3 O8 $/kgU $/SWU $/kgU $/kgU $/kgU
Back end SNF storage SNF pack Reposition
$/kgHM $/kgHM $/kgiHM
Cost (2012 US$) 51.00 6.50 135.00 260.37 314.61 10,848.70 130.18 100.89 594.51
with power output of 500–750 MW. The operation of nuclear plant in Blahutovice would enable to shut down the majority of local conventional plants. The heat produced could be distributed into highly efficient district heating network for more than a half million residents. 3.2. Economic indicators of the new HTGRs The economic factors of electricity production of new built reactor are recently hard to assess. But it is possible to do so, on the basis of statements that unit construction and operation costs are similar to these costs of large light water reactors (LWRs) (Yuliang, 2011). Fuel costs can then be calculated and added to fixed costs giving the total electricity production costs. The fuel costs are consisting of cost of natural uranium, conversion, enrichment, fuel fabrication, spent nuclear fuel storage and packaging and the permanent reposition. The cost of natural uranium, conversion and enrichment can be obtained from the exchange spot prices. Other parameters are uncertain. But, the assumption about the similarity with light water reactor (LWR) fuel cycle can be done. Thus the unknown costs will be the same as in case of the LWRs. The reason for this assumption is that if the HTGRs should be competitive with the LWRs, the maximum variable costs should be the same as in case of the LWRs for the same capital costs of the HTGR and the same capacity factor. All parameters taken into account for the study are listed in Table 1. The cost of parts of fuel cycle compared to the LWRs can be found in (Shropshire et al., 2008). Let’s assume, the costs of the back end of the cycle be the same for different fuel types. The differences in costs are arising in the front end of fuel cycle due to the need of the uranium product with different enrichment. The substantial difference lies also of course in the fabrication cost of the HTGR fuel against LWR fuels. For the comparison the recent concept designs of HTGRs were chosen and compared with operated power plants with pressurized water reactors (PWRs) and boiling water reactors (BWRs). The parameters of chosen power plants and the HTGR concepts are in Table 2. Most of the LWRs (PWRs and BWRs) were randomly chosen from the portfolio in West and Central Europe to correspond with the conditions of the region, where Czech Republic lies. However, one Japanese reactor was added by the reason of being one of the operated reactors of the current most advanced (3rd) generation representative. Also reactors EPR, AP – 1000 and MIR – 1200 were chosen for the comparison because of their possible future importance for Czech Republic energy industry. The fuel enrichment of Russian concept MIR – 1200 was estimated (no exact value was found to date) to be the same as the enrichment of AP – 1000 concept, based on the same fuel burn-up quoted by both vendors. The quantities of uranium ore, conversion and separative work for different fuel types are directly given by fuel enrichment. Table 3
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E. Losa et al. / Nuclear Engineering and Design 271 (2014) 46–50
Table 2 Parameters of operated LWRs and proposed HTGRs. Reactor data
Fuel enr. (%)
Fuel burn-up (MWd /kg)
HTGR GT-MHR PBMR HTR-PM
15.5 9.6 8.9
121 92 90
Net el. power output (MWe )
Thermal power output (MWt )
286 180 210
600 400 500
Plant net eff. (%) 48 45 42
PWR VVER-1000 Konvoi (Isar-2) EPR AP-1000 MIR-1200
4.25 4.4 5 4.8 4.8
43.4 55 60 60 60
1000 1400 1600 1115 1114
3000 3900 4500 3415 3200
33.3 35.9 35.6 32.7 34.8
BWR BWR-72 (Gun-C) ABWR (Kashiwazaki 7)
4.6 3.7
50 45
1284 1315
3840 3811
33.4 34.5
Table 3 Front end fuel cycle component amounts and costs without fuel fabrication. Parameter
U3 O8
Conversion
Reactor type
Unit count/cost 2012 US$
GT-MHR PBMR HTR-PM VVER-1000 (Temelin) Konvoi Isar-2 EPR AP-1000 MIR-1200 BWR-72 (Gun-C) ABWR (Kashiwazaki 7)
86.4/4406.4 53.0/2703.0 49.0/2409.9 22.7/1157.7 23.5/1198.5 26.9/1371.9 25.8/1315.8 25.8/1315.8 24.7/1259.7 19.6/999.6
33.1/21,515 20.3/131.95 18.8/122.2 7.0/45.5 9.0/58.5 10.3/67.0 9.9/64.35 9.9/64.35 9.4/61.1 7.5/48.8
Enrichment
31.3/4225.5 18.0/2430.0 16.4/2214.0 4.8/648.0 6.7/904.5 7.9/1066.5 7.5/1012.5 7.5/1012.5 7.1/958.5 5.2/702.0
illustrates these quantities. The trend of rising fuel costs concerned with rising fuel enrichment is clearly visible. The increase is caused not only by higher separative work usage, but also by higher natural uranium consumption. There can be found an optimum in the enriched uranium cost, based on the costs of different components. The costs of the fuel cycle back end are considered to be the same for all types of fuels. To assume the total fuel cycle cost, the costs of front end and back end should be simply added (Table 4). The column heat produced means the cost of heat, which is then changed with defined cycle efficiency into electricity in turbine. It can be seen that the more than 40 times higher fabrication costs for the HTGR fuel are doubling the cost of unit of electricity production against electricity produced in LWRs. To be potentially competitive, the fuel fabrication for HTGRs should range from 1600 to 1900 US$. For comparison, the costs of fuel cycle without fuel fabrication are tabulated in Table 5. The HTGRs seem to be highly competitive then with the LWRs in this regard.
Table 4 Total fuel cycle costs for selected nuclear power plants and the costs of unit energy produced. Parameter
Fuel
Heat produced
Reactor type
US$/kg
US$/MWh
GT-MHR PBMR HTR-PM VVER-1000 (Temelin) Konvoi (Isar-2) EPR AP-1000 MIR-1200 BWR-72 (Gun-C) ABWR (Kashiwazaki 7)
20,521.33 16,939.23 16,509.48 2717.85 3247.45 3591.3 3478.6 3478.6 3419.49 2890.54
7.07 7.67 7.64 2.61 2.46 2.49 2.42 2.42 2.85 2.68
Electricity produced
14.72 17.05 18.20 7.84 6.85 7.01 7.39 6.94 8.53 7.76
Table 5 Fuel cycle costs (without fabrication) for selected nuclear power plants. Parameter
Fuel
Heat produced
Reactor type
US$/kg
US$/MWh
GT-MHR PBMR HTR-PM VVER-1000 (Temelin) Konvoi (Isar-2) EPR AP-1000 MIR-1200 BWR-72 (Gun-C) ABWR (Kashiwazaki 7)
9672.63 6090.53 5660.78 2457.48 2987.08 3330.93 3218.23 3218.23 3104.88 2575.93
3.33 2.76 2.62 2.36 2.26 2.31 2.23 2.23 2.59 2.39
Electricity produced 6.94 6.13 6.24 7.09 6.30 6.50 6.83 6.42 7.75 6.91
Table 6 Electricity cost breakdown (without fuel costs) for Generation III thermal reactor (1300 MWe ) in 2012 US$ and discount rate 5%. Cost
US$/MWhe
Capital Operations Fuel cycle Decommissioning Total
20.33 10.16 see Table 4 0.31 30.80 + Fuel
The other costs (including capital and decommissioning), forming the total electricity costs can be estimated for the HTGRs. The cost breakdowns of electricity production from advanced reactors can be found in Shropshire et al. (2008) or in EMWG (2004). On the basis of the accessible sources and fuel calculation, the cost breakdown should look like in Table 6. The fuel cycle cost varies from 18.20% to 37.14% of total levelized unit electricity cost (LUEC) according the reactor type considered. After the fuel cost addition, the LUEC of different reactors can be calculated in Table 6. The difference between the LUEC of the HTGRs and the LWR average varies from 18.94% (GT-MHR) to 28.02% (HTRPM) (Fig. 1). 3.3. Modelling of nuclear physics parameters The calculations were performed by the MCNP5 code and the influence of fuel particle distribution on temperature reactivity effect was studied. The randomness in the HTGR fuel matrix geometry can be modelled by built in function (URAN card). It was shown, that the modelling of random fuel distribution influences the temperature reactivity coefficient of the fuel matrix. The infinite fuel matrix and the infinite array of fuel pebbles was modelled with fuel kernels positioned in stochastic and cubic lattice. The results are contained in Table 7.
E. Losa et al. / Nuclear Engineering and Design 271 (2014) 46–50
49
To reach an adequate nuclear safety, the nuclear power plant is designed to meet national as well as international safety standards and general safety criteria. The general safety criteria must be met during all in design anticipated states. In other words, the power plant is safe, unless the general safety criteria for all systems are met. There are there basic general criteria:
Fig. 1. Total LUEC for chosen nuclear power plants.
Table 7 Temperature reactivity effects of infinite fuel matrix and infinite array of fuel spheres. Geometry type
∂/∂T [pcm/K]
Infinite matrix Infinite matrix (URAN) Infinite array Infinite array (URAN)
−4.200 −4.300 −3.510 −3.550
± ± ± ±
0.005 0.005 0.004 0.001
Other computations done were concerned the fuel burnup. The simplified model of reactor core with pebbles in hexagonal lattice has been created and the pebble path through the core has been followed. The fuel pebbles contained 8.48 g of fuel in form of UO2 with enrichment 9.6%. The maximum theoretical burn up was then on the level of 120 MWd /kgHM . The effective coefficient of multiplication and burn up change with the time operation is shown on Fig. 2. 3.4. Legal compatibility and safety requirements specification For the HTGR licensing in the Czech Republic, the nuclear reactor must comply with requirements claimed by Czech law. Czech legislation concerning nuclear devices comes out of the IAEA standards (NS-R-1). Recent experience in safety assessment of light water reactors (LWRs) will not satisfy the needs of new sources commission because of being excessively prescriptive and not taking higher degree of innovations into account.
Fig. 2. The multiplication coefficient and burn up evolution with time of reactor operation.
1. The ability to shut down the reactor safely and keep it subcritical in all designed operational regimes and accidents (reactivity control). 2. The ability of residual heat removal in all designed operational regimes and accidents (emergency core cooling). 3. The ability to reduce the radioactive material releases so that the limits for the releases are not exceeded in all designed operational regimes, during accidents and after them (the radioactivity control). These criteria are met by defence in depth principles and by keeping the safety functions. Based on recent development, it can be said that the HTGRs have the potential of meeting the general safety requirements formulated in 2002 by Generation IV International Forum (GIF): • new reactors operation must be inherently safe and reliable, • the probability and degree of core melting in new reactors must be extremely low, • the outside emergency planning need is eliminated. In spite of huge differences in safety systems of the LWRs and the HTGRs, it can be seen that the differences between requirements on these systems are not fundamental. Also on the LWRs proven methodology of safety analyses is applicable to the HTGRs. It is to be expected that the results of research projects on this topic in frame of 5th, 6th and 7th Framework Programmes will help to establish unified approach to carrying out of safety analyses. Some integration effort was made by International Atomic Energy Agency (IAEA), however, the collaboration among states was not established. 3.5. National Energy Conception The National Energy Conception contains a vision and strategic priorities of energy industry in the Czech Republic. The long term view till 2030 is characterized by detailed strategy and the period between 2030 and 2050 by strategic vision. The Czech Republic has geographically advantageous position, which can be used for strengthening of its role in energy market integration, where energy transit will guarantee the energy independence and security. Our country is also presented as the electricity and regulation services supplier for the region of Central Europe. Principal change in European energy politics came with Treaty of Lisbon, where this policy was for the first time defined. The energy supply security shall be reached by respecting the principle of solidarity. Nevertheless, the treaty guarantees the sanctity of the energy mix choice of the individual member states. The conception states to support the nuclear power industry as one of the significant pillar for electricity and heat production and also for air pollution mitigation. The support shall accelerate the process of new nuclear blocks commissioning. Competitiveness of Czech economy shall be secured by research and development of perspective nuclear technologies of III.+ and IV. generation, which are contributing to high added value export potential. The electricity consumption prognosis of Czech Republic is showed in Fig. 3. The coverage of predicted electricity consumption shows Fig. 4. This scenario is based on the meeting the international
50
E. Losa et al. / Nuclear Engineering and Design 271 (2014) 46–50
Fig. 3. Electricity consumption history and prognosis (purple) in Czech Republic till 2050 (MIT, 2012).
in Dukovany location would help to cover the annual demand for heat for technological processes and district heating of 4.6 PJ in total. The demand for heat in the second proposed site in heavily industrialized region Blahutovice would help to cover the similar demand. The cost of electricity and heat production was estimated. Due to high fuel fabrication costs, the total LUEC of the HTGRs is about 19–28% higher than the same value of new LWRs. Yet the planed commercial operation will show the real cost. It is also to expect that the fuel fabrication cost will dramatically drop with the industrial application. The modelling showed that the multiplication coefficient and also the temperature reactivity coefficient are influenced by the stochastic geometry of the fuel particles. The differences in the temperature reactivity coefficient were calculated to be on the level of about 2%. In spite of huge differences between conception of safety systems of the LWR and the HTGR, the differences between requirements on the safety systems are not fundamental for these two reactor types. The methodology of the safety analyses of LWRs is directly applicable on the HTGRs. Although, there are some specific issues linked to the pebble bed cores, which need further attention (Wahlen etal., 2002). Concrete implementation of safety analyses is in jurisdiction of national policy, but it is to be expected that European Union will use the results of research projects and unify the approach safety of the HTGRs. Acknowledgement This research was done with financial support of Ministry of Industry and Trade, contract no.: FR-TI1/104 (Survey of High Temperature Nuclear Device Technology for Long Term Perspective of Energetic Self-sufficiency of Czech Republic).
Fig. 4. The electricity production structure outlook in Czech Republic till 2050 (MIT, 2012).
liabilities of our country concerning renewable sources development. From 2020 also the growing share of nuclear electricity is visible. The scenario calculates with convenient measure of energetic dependency and with minimal impacts of factors influencing the unemployment level and the security of energetic independence and source diversification of the country is emphasized. Following assumptions are done (MIT, 2012): • the number of residents will stagnate till 2030, then the slow decrease will start, • the number of households will be at the same level, • the gross domestic product growth will be on the level of 2–3% per year till 2030, then on the value below 2% per year. 4. Conclusions Two convenient sites were proposed for realization of nuclear power plant with high temperature gas cooled reactor. The site
References Copinger, D.A., Moses, D.L., 20555-0001, NUREG/CR-6839, ORNL/TM-2003/223 2004. Fort Saint Vrain Gas Cooled Reactor Operational Experience. U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, Washington, DC. Doran, B., 2009. After the Gas Crisis – Europe Remains Vulnerable. CEPA (Center for European Policy Analysis), web pages, http://www.cepa.org/publications/ view.aspx?record id=86 (accessed 02.03.12.). Economic Modeling Working Group (EMWG), 2004. Commissioned by the Generation IV International Forum, A Generic EXCEL-based Model for Computation of the Projected Levelized Unit Electricity Cost (LUEC) from Generation IV Reactor Systems, Technical report. Ministry of Industry and Trade, State Energetic Conception Actualisation, Prague, February 2012. Shropshire, D.E., Williams, K.A., et al., 2008. Advanced Fuel Cycle Cost Basis. Idaho National Laboratory, USA. Wahlen, E., Wahl, J., Pohl, P., 2000. Status of the AVR Decommissioning Project with Special Regard to the Inspection of the Core Cavity for Residual Fuel, WM’00 Conference , February 27–March 2, Tucson, AZ. Yuliang, S., 2011. HTR-PM Project Status and Test Program, IAEA TWG-GCR-22. Zhang, Z., Wu, Z., Wang, D., et al., 2009. Current status and technical description of Chinese 2 × 250 MWth HTR-PM demonstration plant. Nuclear Engineering and Design 239 (2009), 1212–1219.
Contents lists available at ScienceDirect
Nuclear Engineering and Design journal homepage: www.elsevier.com/locate/nucengdes
Feasibility study of high temperature reactor utilization in Czech Republic after 2025 Evˇzen Losa a,∗ , Bedˇrich Heˇrmansky´ a , Duˇsan Kobylka a , Jan Rataj a , L’ubomír Sklenka a , Václav Souˇcek b , Petr Kohout b a b
Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Nuclear Reactors, Czech Republic AZIN CZ, s.r.o., Hanusova 3, 140 00 Praha 4, Czech Republic
a r t i c l e
i n f o
Article history: Received 28 May 2013 Accepted 29 October 2013
a b s t r a c t High temperature reactors (HTRs) were examined as an option to intended future broadening of the nuclear energy production in Czech Republic. The known qualities as the inherent safety, high thermal utilization and non-electrical applications have been assessed in years 2009–2011 during the survey funded by Czech Ministry of Industry and Trade. The survey of high temperature reactors with spherical fuel was initiated by reason of mature state of the art of this technology type in South Africa and in China, where in both countries pilot plants were planned. Unfortunately, the global financial crisis caused the decision of stopping the governmental support in South African programme was made. In China, however, the development still continues. Czech Republic has almost 60 years nuclear research history and the knowledge of operation of gas cooled and heavy water moderated reactor has been gained in the past. Nevertheless, the design of light water reactors was more developed in former Soviet Union, which provided Czech scientists by initial knowledge base; hence the research has been reoriented to this technology. But, the demands on future nuclear reactors application are still growing and the same or even higher living standard of next generations have to be taken into consideration. Therefore the systems, which can produce more energy and less waste, are getting into foreground of interest of Czech decision makers. The high temperature reactor technology seems to be the successful representative of the GEN IV reactor types, which will be operated commercially in the near future. The broad spectrum of utilization enables this system to be an option after 2030, when the electricity demand is planned to be covered from about 50% by nuclear in our country. © 2013 Elsevier B.V. All rights reserved.
1. Introduction High temperature gas cooled reactor technology, designed almost 60 years ago and verified by number of experiments and also by pilot plants in U.S.A. and Germany, seems to be an eligible candidate for heavy- and energy industry development in 21st century. Potential of this technology has been recently rediscovered particularly in South Africa and China, where the decision of governmental financing of the pilot plant construction based on spherical fuel technology (pebble bed) was made. As a consequence of global financial crisis, the support for this project has been temporarily stopped in South Africa but, in China the research continues and the HTR-PM pilot plant is expected to be commissioned in 2013 and will serve to prove mainly the inherent safety features as the impossibility of core melting and economic viability (Zhang et al., 2009).
∗ Corresponding author. E-mail address: evzen.losa@fjfi.cvut.cz (E. Losa). 0029-5493/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nucengdes.2013.11.007
Current status of High Temperature Gas Cooled Reactor (HTGR) technology development shows that prior to the direct Brayton cycle coupled with gas turbine employment to reach highly efficient energy conversion, the first stage of nuclear market penetration will have to be done with reactor systems supplying the steam of high parameters for energetic and industrial applications. The capability of high parameter steam production was proven by commercial plant operation in the past and the safety issues are well documented (Copinger and Moses, 2004). On account of industrial heat application focus, the proposed power output of single modules is much smaller, than of classical Light Water Reactors (LWRs) offered. The conception of smaller modular reactor should also bring some investment savings thank to higher number of construction repetition. The possibilities of the HTGR’s utilization in environment of Czech Republic were surveyed during the three year’s project supported by Czech Ministry of Industry and Trade (MoIT). In three stages of the project, the compatibility of this technology with local legislation and energy conception was proved and also the capability of Czech subcontractors to take part on the potential
E. Losa et al. / Nuclear Engineering and Design 271 (2014) 46–50
construction was verified. Although there is reactor operation experience with both prismatic and spherical fuel type in the world, the survey was focused on the reactor type with spherical fuel elements (Pebble Bed Modular Reactor (PBMR) or HTR-PM type) because of the recent development states of those technologies in afore mentioned countries. Only the future massive operation of the HTGRs will show the practical advantages and disadvantages, concerning technology and economics, of these two proposed designs. 2. Description of Czech environment There are already two nuclear power plant sites in Czech Republic, with the Russian VVER 440 (V 213 type, power output 500 MW) and VVER 1000 (V 320 type) reactors operated. The nuclear energy supply is more than 32% of overall energy produced. This production is planned to rise up to 50% in the future due to coal fired power plants replacement. The aim of the study was the survey of the possibility of the HTGR technology utilization as one of the ways of energetic independence increase of the country in long term perspective. The conventional energy sources orientation is not feasible neither from economic, nor strategic point of view. The advantages of high temperature reactor, which employs spherical fuel is the advanced degree of development and the projection of near term operation, which will show the economic and technical benefits. The main factor influencing the plant performance is also continuous fuel replacement during the operation. The progress in past decades definitely proved the necessity of at least 50% growth in electricity production in the horizon of next 20–30 years. The increase will be covered particularly by traditional fossil and nuclear sources which are of extraordinary meaning for Czech Republic, fully dependent on crude oil and gas import. The nuclear sources are mainly used for electricity production. The crucial problem from the point of view of energy balance is the provision of high potential source of heat for industrial and population’s needs. These needs are recently covered by combustion of fossil fuels partially from steadily declining domestic resources and partially from imported resources. However, the stable supply of imported materials cannot be guaranteed as seen during the gas crisis in Central Europe in 2009 (Doran, 2009). Equally, the environmental protection accompanied by carbon dioxide emissions reduction plays important role. 3. The research outputs There have been huge amounts of work done in the world during the years of development of the HTGRs. A part of the survey was focused on the summarization of historical as well as recent knowledge of the technology. The second part should provide the information about the convenience of this technology for the Czech Republic. 3.1. Power plant siting In the Czech Republic it is possible to choose two of four feasible sites of the new nuclear power plant. The first site in Dukovany locality is now occupied by four VVER 440 reactors, but this place provides enough space for the fifth reactor of similar output. The problem, however, is the chronic shortage in cooling water during the summer period. The power plant based on cycle with lower heat rejection would be a solution. The second proposed site, Blahutovice, lies in the part of the country with strong concentration of heavy industry. The public in this region is very favourable to new nuclear cogeneration projects just because of smog situation and long term exceeding of the limits for dust particles in air. There is also demand for source of electricity
47
Table 1 The costs of the front and back end fuel cycle parts (Shropshire et al., 2008). Parameter
Unit
Front end U3 O8 Conversion Enrichment Fabrication [PWR] Fabrication [BWR] Fabrication [HTGR]
$/lb U3 O8 $/kgU $/SWU $/kgU $/kgU $/kgU
Back end SNF storage SNF pack Reposition
$/kgHM $/kgHM $/kgiHM
Cost (2012 US$) 51.00 6.50 135.00 260.37 314.61 10,848.70 130.18 100.89 594.51
with power output of 500–750 MW. The operation of nuclear plant in Blahutovice would enable to shut down the majority of local conventional plants. The heat produced could be distributed into highly efficient district heating network for more than a half million residents. 3.2. Economic indicators of the new HTGRs The economic factors of electricity production of new built reactor are recently hard to assess. But it is possible to do so, on the basis of statements that unit construction and operation costs are similar to these costs of large light water reactors (LWRs) (Yuliang, 2011). Fuel costs can then be calculated and added to fixed costs giving the total electricity production costs. The fuel costs are consisting of cost of natural uranium, conversion, enrichment, fuel fabrication, spent nuclear fuel storage and packaging and the permanent reposition. The cost of natural uranium, conversion and enrichment can be obtained from the exchange spot prices. Other parameters are uncertain. But, the assumption about the similarity with light water reactor (LWR) fuel cycle can be done. Thus the unknown costs will be the same as in case of the LWRs. The reason for this assumption is that if the HTGRs should be competitive with the LWRs, the maximum variable costs should be the same as in case of the LWRs for the same capital costs of the HTGR and the same capacity factor. All parameters taken into account for the study are listed in Table 1. The cost of parts of fuel cycle compared to the LWRs can be found in (Shropshire et al., 2008). Let’s assume, the costs of the back end of the cycle be the same for different fuel types. The differences in costs are arising in the front end of fuel cycle due to the need of the uranium product with different enrichment. The substantial difference lies also of course in the fabrication cost of the HTGR fuel against LWR fuels. For the comparison the recent concept designs of HTGRs were chosen and compared with operated power plants with pressurized water reactors (PWRs) and boiling water reactors (BWRs). The parameters of chosen power plants and the HTGR concepts are in Table 2. Most of the LWRs (PWRs and BWRs) were randomly chosen from the portfolio in West and Central Europe to correspond with the conditions of the region, where Czech Republic lies. However, one Japanese reactor was added by the reason of being one of the operated reactors of the current most advanced (3rd) generation representative. Also reactors EPR, AP – 1000 and MIR – 1200 were chosen for the comparison because of their possible future importance for Czech Republic energy industry. The fuel enrichment of Russian concept MIR – 1200 was estimated (no exact value was found to date) to be the same as the enrichment of AP – 1000 concept, based on the same fuel burn-up quoted by both vendors. The quantities of uranium ore, conversion and separative work for different fuel types are directly given by fuel enrichment. Table 3
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Table 2 Parameters of operated LWRs and proposed HTGRs. Reactor data
Fuel enr. (%)
Fuel burn-up (MWd /kg)
HTGR GT-MHR PBMR HTR-PM
15.5 9.6 8.9
121 92 90
Net el. power output (MWe )
Thermal power output (MWt )
286 180 210
600 400 500
Plant net eff. (%) 48 45 42
PWR VVER-1000 Konvoi (Isar-2) EPR AP-1000 MIR-1200
4.25 4.4 5 4.8 4.8
43.4 55 60 60 60
1000 1400 1600 1115 1114
3000 3900 4500 3415 3200
33.3 35.9 35.6 32.7 34.8
BWR BWR-72 (Gun-C) ABWR (Kashiwazaki 7)
4.6 3.7
50 45
1284 1315
3840 3811
33.4 34.5
Table 3 Front end fuel cycle component amounts and costs without fuel fabrication. Parameter
U3 O8
Conversion
Reactor type
Unit count/cost 2012 US$
GT-MHR PBMR HTR-PM VVER-1000 (Temelin) Konvoi Isar-2 EPR AP-1000 MIR-1200 BWR-72 (Gun-C) ABWR (Kashiwazaki 7)
86.4/4406.4 53.0/2703.0 49.0/2409.9 22.7/1157.7 23.5/1198.5 26.9/1371.9 25.8/1315.8 25.8/1315.8 24.7/1259.7 19.6/999.6
33.1/21,515 20.3/131.95 18.8/122.2 7.0/45.5 9.0/58.5 10.3/67.0 9.9/64.35 9.9/64.35 9.4/61.1 7.5/48.8
Enrichment
31.3/4225.5 18.0/2430.0 16.4/2214.0 4.8/648.0 6.7/904.5 7.9/1066.5 7.5/1012.5 7.5/1012.5 7.1/958.5 5.2/702.0
illustrates these quantities. The trend of rising fuel costs concerned with rising fuel enrichment is clearly visible. The increase is caused not only by higher separative work usage, but also by higher natural uranium consumption. There can be found an optimum in the enriched uranium cost, based on the costs of different components. The costs of the fuel cycle back end are considered to be the same for all types of fuels. To assume the total fuel cycle cost, the costs of front end and back end should be simply added (Table 4). The column heat produced means the cost of heat, which is then changed with defined cycle efficiency into electricity in turbine. It can be seen that the more than 40 times higher fabrication costs for the HTGR fuel are doubling the cost of unit of electricity production against electricity produced in LWRs. To be potentially competitive, the fuel fabrication for HTGRs should range from 1600 to 1900 US$. For comparison, the costs of fuel cycle without fuel fabrication are tabulated in Table 5. The HTGRs seem to be highly competitive then with the LWRs in this regard.
Table 4 Total fuel cycle costs for selected nuclear power plants and the costs of unit energy produced. Parameter
Fuel
Heat produced
Reactor type
US$/kg
US$/MWh
GT-MHR PBMR HTR-PM VVER-1000 (Temelin) Konvoi (Isar-2) EPR AP-1000 MIR-1200 BWR-72 (Gun-C) ABWR (Kashiwazaki 7)
20,521.33 16,939.23 16,509.48 2717.85 3247.45 3591.3 3478.6 3478.6 3419.49 2890.54
7.07 7.67 7.64 2.61 2.46 2.49 2.42 2.42 2.85 2.68
Electricity produced
14.72 17.05 18.20 7.84 6.85 7.01 7.39 6.94 8.53 7.76
Table 5 Fuel cycle costs (without fabrication) for selected nuclear power plants. Parameter
Fuel
Heat produced
Reactor type
US$/kg
US$/MWh
GT-MHR PBMR HTR-PM VVER-1000 (Temelin) Konvoi (Isar-2) EPR AP-1000 MIR-1200 BWR-72 (Gun-C) ABWR (Kashiwazaki 7)
9672.63 6090.53 5660.78 2457.48 2987.08 3330.93 3218.23 3218.23 3104.88 2575.93
3.33 2.76 2.62 2.36 2.26 2.31 2.23 2.23 2.59 2.39
Electricity produced 6.94 6.13 6.24 7.09 6.30 6.50 6.83 6.42 7.75 6.91
Table 6 Electricity cost breakdown (without fuel costs) for Generation III thermal reactor (1300 MWe ) in 2012 US$ and discount rate 5%. Cost
US$/MWhe
Capital Operations Fuel cycle Decommissioning Total
20.33 10.16 see Table 4 0.31 30.80 + Fuel
The other costs (including capital and decommissioning), forming the total electricity costs can be estimated for the HTGRs. The cost breakdowns of electricity production from advanced reactors can be found in Shropshire et al. (2008) or in EMWG (2004). On the basis of the accessible sources and fuel calculation, the cost breakdown should look like in Table 6. The fuel cycle cost varies from 18.20% to 37.14% of total levelized unit electricity cost (LUEC) according the reactor type considered. After the fuel cost addition, the LUEC of different reactors can be calculated in Table 6. The difference between the LUEC of the HTGRs and the LWR average varies from 18.94% (GT-MHR) to 28.02% (HTRPM) (Fig. 1). 3.3. Modelling of nuclear physics parameters The calculations were performed by the MCNP5 code and the influence of fuel particle distribution on temperature reactivity effect was studied. The randomness in the HTGR fuel matrix geometry can be modelled by built in function (URAN card). It was shown, that the modelling of random fuel distribution influences the temperature reactivity coefficient of the fuel matrix. The infinite fuel matrix and the infinite array of fuel pebbles was modelled with fuel kernels positioned in stochastic and cubic lattice. The results are contained in Table 7.
E. Losa et al. / Nuclear Engineering and Design 271 (2014) 46–50
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To reach an adequate nuclear safety, the nuclear power plant is designed to meet national as well as international safety standards and general safety criteria. The general safety criteria must be met during all in design anticipated states. In other words, the power plant is safe, unless the general safety criteria for all systems are met. There are there basic general criteria:
Fig. 1. Total LUEC for chosen nuclear power plants.
Table 7 Temperature reactivity effects of infinite fuel matrix and infinite array of fuel spheres. Geometry type
∂/∂T [pcm/K]
Infinite matrix Infinite matrix (URAN) Infinite array Infinite array (URAN)
−4.200 −4.300 −3.510 −3.550
± ± ± ±
0.005 0.005 0.004 0.001
Other computations done were concerned the fuel burnup. The simplified model of reactor core with pebbles in hexagonal lattice has been created and the pebble path through the core has been followed. The fuel pebbles contained 8.48 g of fuel in form of UO2 with enrichment 9.6%. The maximum theoretical burn up was then on the level of 120 MWd /kgHM . The effective coefficient of multiplication and burn up change with the time operation is shown on Fig. 2. 3.4. Legal compatibility and safety requirements specification For the HTGR licensing in the Czech Republic, the nuclear reactor must comply with requirements claimed by Czech law. Czech legislation concerning nuclear devices comes out of the IAEA standards (NS-R-1). Recent experience in safety assessment of light water reactors (LWRs) will not satisfy the needs of new sources commission because of being excessively prescriptive and not taking higher degree of innovations into account.
Fig. 2. The multiplication coefficient and burn up evolution with time of reactor operation.
1. The ability to shut down the reactor safely and keep it subcritical in all designed operational regimes and accidents (reactivity control). 2. The ability of residual heat removal in all designed operational regimes and accidents (emergency core cooling). 3. The ability to reduce the radioactive material releases so that the limits for the releases are not exceeded in all designed operational regimes, during accidents and after them (the radioactivity control). These criteria are met by defence in depth principles and by keeping the safety functions. Based on recent development, it can be said that the HTGRs have the potential of meeting the general safety requirements formulated in 2002 by Generation IV International Forum (GIF): • new reactors operation must be inherently safe and reliable, • the probability and degree of core melting in new reactors must be extremely low, • the outside emergency planning need is eliminated. In spite of huge differences in safety systems of the LWRs and the HTGRs, it can be seen that the differences between requirements on these systems are not fundamental. Also on the LWRs proven methodology of safety analyses is applicable to the HTGRs. It is to be expected that the results of research projects on this topic in frame of 5th, 6th and 7th Framework Programmes will help to establish unified approach to carrying out of safety analyses. Some integration effort was made by International Atomic Energy Agency (IAEA), however, the collaboration among states was not established. 3.5. National Energy Conception The National Energy Conception contains a vision and strategic priorities of energy industry in the Czech Republic. The long term view till 2030 is characterized by detailed strategy and the period between 2030 and 2050 by strategic vision. The Czech Republic has geographically advantageous position, which can be used for strengthening of its role in energy market integration, where energy transit will guarantee the energy independence and security. Our country is also presented as the electricity and regulation services supplier for the region of Central Europe. Principal change in European energy politics came with Treaty of Lisbon, where this policy was for the first time defined. The energy supply security shall be reached by respecting the principle of solidarity. Nevertheless, the treaty guarantees the sanctity of the energy mix choice of the individual member states. The conception states to support the nuclear power industry as one of the significant pillar for electricity and heat production and also for air pollution mitigation. The support shall accelerate the process of new nuclear blocks commissioning. Competitiveness of Czech economy shall be secured by research and development of perspective nuclear technologies of III.+ and IV. generation, which are contributing to high added value export potential. The electricity consumption prognosis of Czech Republic is showed in Fig. 3. The coverage of predicted electricity consumption shows Fig. 4. This scenario is based on the meeting the international
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E. Losa et al. / Nuclear Engineering and Design 271 (2014) 46–50
Fig. 3. Electricity consumption history and prognosis (purple) in Czech Republic till 2050 (MIT, 2012).
in Dukovany location would help to cover the annual demand for heat for technological processes and district heating of 4.6 PJ in total. The demand for heat in the second proposed site in heavily industrialized region Blahutovice would help to cover the similar demand. The cost of electricity and heat production was estimated. Due to high fuel fabrication costs, the total LUEC of the HTGRs is about 19–28% higher than the same value of new LWRs. Yet the planed commercial operation will show the real cost. It is also to expect that the fuel fabrication cost will dramatically drop with the industrial application. The modelling showed that the multiplication coefficient and also the temperature reactivity coefficient are influenced by the stochastic geometry of the fuel particles. The differences in the temperature reactivity coefficient were calculated to be on the level of about 2%. In spite of huge differences between conception of safety systems of the LWR and the HTGR, the differences between requirements on the safety systems are not fundamental for these two reactor types. The methodology of the safety analyses of LWRs is directly applicable on the HTGRs. Although, there are some specific issues linked to the pebble bed cores, which need further attention (Wahlen etal., 2002). Concrete implementation of safety analyses is in jurisdiction of national policy, but it is to be expected that European Union will use the results of research projects and unify the approach safety of the HTGRs. Acknowledgement This research was done with financial support of Ministry of Industry and Trade, contract no.: FR-TI1/104 (Survey of High Temperature Nuclear Device Technology for Long Term Perspective of Energetic Self-sufficiency of Czech Republic).
Fig. 4. The electricity production structure outlook in Czech Republic till 2050 (MIT, 2012).
liabilities of our country concerning renewable sources development. From 2020 also the growing share of nuclear electricity is visible. The scenario calculates with convenient measure of energetic dependency and with minimal impacts of factors influencing the unemployment level and the security of energetic independence and source diversification of the country is emphasized. Following assumptions are done (MIT, 2012): • the number of residents will stagnate till 2030, then the slow decrease will start, • the number of households will be at the same level, • the gross domestic product growth will be on the level of 2–3% per year till 2030, then on the value below 2% per year. 4. Conclusions Two convenient sites were proposed for realization of nuclear power plant with high temperature gas cooled reactor. The site
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