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2019 | OriginalPaper | Chapter

6. Candidate Features and Technology Options

Authors : Didier Sornette, Wolfgang Kröger, Spencer Wheatley

Published in: New Ways and Needs for Exploiting Nuclear Energy

Publisher: Springer International Publishing

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Abstract

Nuclear power stations have become more efficient and safer inter alia due to learning from valuable operational experience, largely in reaction to major and near accidents. However, dread of rare but possible severe accidents, reliance upon unfailing human performance at various levels, and dependence on social stability, emphasize the importance of further safety improvements, for which challenging criteria were conveyed in Sect. 2.2. To achieve them, key design features (“building blocks”) are viewed and revisited and should be combined in a radically new way, to come up with “revolutionary” or even “exotic” system designs. To check whether such designs are feasible, we track most recent developments of reactor concepts focusing on differing (1) coolants, including liquid metals and molten salt, (2) neutron spectrum from thermal to fast, (3) power level, (4) fundamental design features (architecture) and purpose, and (5) ability to extend fuel reserves and “burn” waste. The designs selected are scored against the set of very stringent, highly ambitious criteria. The results show a high potential for far-reaching improvements compared to most advanced LWRs in use today. Small modular reactors emerge as being the most attractive. However, thus far, none of the candidate concepts fulfill all the criteria convincingly; avoiding criticality induced accidents and maximizing proliferation resistance appears most challenging. There is also a potential for new concept-specific risks to be introduced but this appears manageable. Although caution is warranted, a purely deterministic safety approach is tempting, in that we would like to absolutely exclude the possibility of severe accidents.

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A fission probability is the probability that, upon the impact of a neutron, a given nucleus will undergo a fission reaction, i.e., will split into several smaller clusters of protons and neutrons (i.e. other nuclei), including ejected neutrons. The fission probability is conveniently represented by the concept of a “cross section”, which is an effective measure of the surface of capture of the incident neutron to trigger the fission reaction. The larger the cross section, the larger the probability of fission.

Actinides encompass 15 metallic chemical elements with atomic numbers from 89 to 103; elements with atomic numbers from 93 onwards like Neptunium 93, Americium 95 and Curium 96 are called minor actinides.

Significant extension of burn up and more efficient use of fuel.

In nuclear engineering, coefficients of reactivity are used to estimate how much the reactivity of a reactor changes as physical parameters change. The void coefficient, for example, indicates the effect as voids (typically bubbles) form in the reactor moderator or coolant. If the coefficient of reactivity is positive, the core power tends to increase; if it is negative the core power tends to decrease.

A basic principle of thermodynamics is that the efficiency of thermal machines is an increasing function of the difference of temperatures between the “cold” and “hot” heat sources.

The neutron economy is defined as the ratio of the weighted average of the excess neutron production divided by the weighted average of the fission production. In other words, the neutron economy of a reactor results from the balance between neutrons created and the neutrons lost through absorption by non-fuel elements, resonance absorption by fuel, and leakage.

The Na risk could be mitigated with a system where the sealed reactor hall is flooded with N or CO₂.

2 m/s compared to 8 m/s for sodium before turbulence occurs.

Half-life T_1/2 = 138 days, α-emitter causing operational difficulties.

Chlorides are selected as being the best; fluorides feature higher melting point (450 °C) but lower boiling point (1430 °C) and smaller operational margin (Dupont, J., Consorti, C. S., & Spencer, J. (2000). Room temperature molten salts: Neoteric “green” solvents for chemical reactions and processes. Journal of the Brazilian Chemical Society, 11(4), 337–344.).

About 1.74 million times higher than petrol, 2.78 million times higher than coal, 4.98 million times higher than wood, 16.12 million times higher than alkaline batteries (Wikipedia/energy density).

E.g., Zircaloy 4 with melting point of 1760 °C instead of 1450 °C for stainless steel (see also Fig. 2.2).

with Ti₂AlC or functionally graded TiAlN/TiN to protect cladding from oxidation with H₂-formation under heat/steam conditions in case of unprotected loss of coolant accident.

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It is important to distinguish the energy generated in the form of thermal energy from the smaller energy ultimately obtained in the form of usable electric energy. The MWt unit refers to the former while the MWe unit refers to the later.

High temperature, helium cooled, graphite moderated reactor of small size (200–300 MWt), low power density (8 MWt/m³), fully ceramic core with high inertia and inherent capability to avoid fission product release under accident conditions, see also Sect. 6.2.4.

IAEA, “Managing Siting Activities for Nuclear Power Plants”, IAEA Nuclear Energy Series No. NG-T-3.7, Nuclear Energy Series Technical Reports (2012).

IAEA, “Site Evaluation for Nuclear Installations”, IAEA Safety requirements no. NS-R-3, Safety Standards Series (2003).

Willful actions by third parties are outside the scope of these requirements.

X. Wang, “Study on Plume Emergency Planning Zone Determination for CAP 200 SMR”, IAEA Int. Conference on Topical Issues in Nuclear Installation Safety, 6–9 June, Vienna, 2017.

W. Kröger, “Verbrauchernahe Kernkraftwerke aus sicherheitstechnischer Sicht” (Nuclear power plants near to consumers from a safety-engineering point of view), Jül-2103, 1986.

₁₁Na²³, as the only stable isotope, needs to be prepared from its compounds.

Factor 60 compared to current LWR with UO₂ fuel.

K. Aoto, P. Dufour, Y. Hongyi et al., A summary of sodium-cooled fast reactor development, Progress in Nuclear Energy 77, 247–265 (2014).

I. Pioro, ed. Handbook of generation IV nuclear reactors. Woodhead Publishing, 2016.

The most serious leak occurred in the secondary circuit of the Monju plant, possibly at a weld point damaged by intense vibration, on December 1995; the leaked out sodium amounted to 640 kg and caused high temperature fumes.

The capacity factor of a power plant is defined as the ratio of its actual output over a period of time, to its potential output obtained by operating it at full capacity continuously over the same period of time.

J.E. Kelly, Generation IV International Forum: A decade of progress through international cooperation, Progress in Nuclear Energy 77, 240–246 (2014).

Phénix end-of-life tests, restart of Monju, lifetime extension of BN-600 and start-up of China Experimental Fast Reactor (CEFR).

P. Hejzlar, Todreas, N.E., Shwageraus, E., Nikiforova, A., Petroski, R., Driscoll, M.J., Cross Comparison of fast reactor concepts with various coolants, Nuclear Engineering and Design 239, 2672–2691 (2009).

As foreseen in the ANL design based in the former S-PRISM 1000 MWt design; the core design was extrapolated to 2400 MWt and studied by MIT (P. Hejzlar, Todreas, N.E., Shwageraus, E., Nikiforova, A., Petroski, R., Driscoll, M.J., Cross comparison of fast reactor concepts with various coolants, Nuclear Engineering and Design 239, 2672–2691 (2009)).

Small thermal expansion coefficient, low absorption cross-section, low slowing down power and high scattering cross section.

A. Alemberti, Smirnov V et al., Overview of lead-cooled fast reactor activities, Progress in Nuclear Energy 77, 300–307 (2014).

A total of 12 reactors and 15 reactor cores, 155 MWt each, were built and deployed including two reactors/three of the cores were operated onshore.

European Facility for Industrial Transmutation.

Multi-purpose hybrid research reactor for high technology application, 50–100 MWt, 55% lead and 45% bismuth eutectic as coolant, full power operation around 2025, total investment costs Euro 960 million (as of 2009), visit www.myrrha.scken.be

Kelly J.E., Generation IV International Forum: A decade of progress through international cooperation, Progress in Nuclear Energy 77, 240–246 (2014).

K. Tuček, J. Carlsson, H. Wider, Comparison of sodium and lead-cooled fast reactors regarding reactor physics aspects, severe safety and economical issues, Nuclear Engineering and Design 236, 1589–1598 (2006).

Following specific numbers are given for the Seaborg waste-burner (SWaB) pilot plant early design.

The salt plug is actively cooled to melting temperature and opens in case of loss of power or overheated fuel.

Oak Ridge National Laboratory molten salt reactor experiment (MSRE) with a 7,4 MWt test reactor with LiF-BeF₂-ZrF₄-4F₄ fuel salt, graphite core moderated, 650 °C outlet temperature, running for 4 years; the molten salt breeder (MSBR) design project with LiF-BeF₂-ThF₄-UF₄ fuel salt, graphite moderated, 705 °C peak temperature, closed down in the early 1970s.

J. Serp, M. Allibert, O. Beneš, S. Delpech, O. Feynberg, V. Ghetta, D. Heuer, D. Holcomb, V. Ignatiev, J.L. Kloosterman, L. Luzzi, E. Merle-Lucotte, J. Uhlíř, R. Yoshioka, D. Zhimin, The molten salt reactor (MSR) in generation IV: overview and perspectives, Progress in Nuclear Energy 77, 308–319 (2014).

The MSFR is a 3000 MWt reactor with a total fuel salt volume of 18 m³ (reactor power density 300 MW/m³) composed of lithium fluoride and thorium fluoride, operated at maximum fuel salt temperature of 750 °C.

For example, Transatomic Power Corporation (TAP), USA; Seaborg Technologies, Denmark.

E. Mearns, Molten Salt Fast Reactor Technology – An Overview, (Online) http://euanmearns.com/molten-salt-fast-reactor-technology-an-overview/

Notably, fuel molten during normal operation and absence of cladding, strong negative feedback coefficients, no separation of reactor and processing/recycling plant, etc.

The Very High Temperature Reactor is one of the six concepts within the Generation IV development framework, see also p. 55 of Pioro (2016)²⁶.

M.A. Fütterer, L. Fu, C. Sink, S. de Groot, M. Pouchon, Y. Wan Kim, F. Carré and Y.Tachibana, Status of the very high temperature reactor system, Progress in Nuclear Energy 77, 266–281 (2014).

100 GWd/tHM and beyond, double compared to modern LWR; approaching 200 GWd/tHM as a visionary goal.

About 8 MW/m³ compared to 100 MW/m³ for LWR.

Physically, helium cannot get lost in case of leaks but heat transfer capability will be reduced significantly.

Beck et al., 2010. High Temperature Gas-Cooled Reactors Lessons Learned Applicable to the Next Generation Nuclear Plant (INL/EXT-10-19,329). Idaho National Laboratory, Idaho Falls, ID.

Developed and pushed by Prof. R Schulten.

In particular, the AVR demonstrated passive safety performance and survived a water ingress accident provoked by a steam generator leak.

Private communication, Sept. 2017.

Filling the containment building with inert gas; safe steam generator arrangement/placement or replacing the steam-turbine cycle by a gas-turbine cycle.

IAEA, Advanced nuclear plant design options to cope with external events, Vienna, 2006.

Kelly J.E., Generation IV International Forum: A decade of progress through international cooperation, Progress in Nuclear Energy 77, 240–246 (2014).

Spallation is the process where nucleons are ejected from a heavy nucleus being hit by a high-energy particle. In this case, a high-energy proton beam directed at a heavy target, e.g. depleted uranium, thorium, lead/lead-bismuth, expels a number of spallation particles, including neutrons.

World Nuclear Association (WNA), Accelerator-driven Nuclear Energy (Online), 3.10.16, http://www.world-nuclear.org/information-library/current-and-future-generation/accelerator-driven-nuclear-energy.aspx

Megawatt Pilot Experiment, www.psi.ch/info

Wikipedia, Subcritical Reactor (Online), 3.10.16, https://en.wikipedia.org/wiki/Subcritical_reactor

C. Rubbia et al., Conceptual Design of a Fast Neutron Operated High Power Energy Amplifier, CERN report 289,551, Geneva, 1995.

1500 MWt lead-cooled, fast hybrid reactor with thorium based closed fuel cycle (see PSI Nr. 96–17, 1996 for detailed assessment).

See also contributions on developments in accelerators in: Thorium Energy for the World, Revol, J. P., Bourquin, M., Kadi, Y., Lillestol, E., de Mestral, J. C., & Samec, K. (2016). Thorium Energy for the World. Thorium Energy for the World, by J.-P. Revol. ISBN 978–3–319-26,540-7. Springer International Publishing Switzerland, 2016.

The IAEA defines “small” as under 300 MWe, and “medium” as under 600MWe. “SMR” is often used as an acronym for “small modular reactor”; a subcategory of very small SMR is proposed for units under 15 MWe.

OECD-NEA, “Nuclear Energy Market Potential for Near-term Deployment”, NEA Nuclear Development Publication (2016).

World Nuclear Association (WNA), Small Nuclear Power Reactors (Online), 3.10.16, http://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/small-nuclear-power-reactors.aspx

For example, Russian designers offer a new class of water cooled floating SMR for electricity and heat production to remotely located areas or nuclear newcomer states.

WNA, “Facilitating International Licensing of Small Modular Reactors”, Report No. 2015/004 (2015).

S. Magruder, “SMR Regulators’ Forum”, IAEA (2016).

W. Kröger, Small-sized reactors of different types: Regulatory framework to be re-thought, Modern Science and Engineering (ISSN 2333–2581), Academic Star Publishing Company, 2017.

For overview and further details, see also the IAEA booklet on Advances in SMR /www.iaea.org/…/, IAEA ‘Status of small and medium sized reactor designs’, 9/2012 (http://aris.iaea.org) and IAEA “Advances in Small Reactors Technology Development”, 2014.

See also S. Buchholz, A. Krüssenberg and A. Schaffrath, Safety and International Development of Small Modular Reactors (SMR) – A Study of GRS, atw 60 (11), (2015), with a summary of SMR under development and characteristics of safety systems.

World Nuclear News (WNN), Funding for mPower reduced (Online). 3.10.16, http://www.world-nuclear-news.org/C-Funding-for-mPower-reduced-1404141.html

M. V. Ramana, S. Saini, “A Radioactive Money Pit - The hidden risks of small-scale nuclear reactors”, Harpers Magazine, 2/2016.

International Risk Governance Council (IRGC), “Preserving the nuclear option - Overcoming the institutional challenges facing small modular reactors”, Opinion Piece (2015).

Small Modular Reactors: Nuclear Energy Market Potential for Near-term Deployment, NEA No.7213, OECD, 2016.

S.Buchholz et al., “Studie zur Sicherheit und zu internationalen Entwicklungen von Small Modular Reactors”, GRS 376, 2015.

D.T. Ingersoll, Deliberately small reactors and the second nuclear era, Progress in Nuclear Energy 51, 589–603 (2009).

The name refers to the fact that fission remains to a boundary zone in the reactor core (rather than involving the whole core), which slowly advances over time. TWR were first proposed in the 1950s and have been studied intermittently.

Wikipedia, Traveling Wave Reactor (Online), 20.10.16, https://en.wikipedia.org/wiki/Traveling_wave_reactor

Wald M., TR10: Traveling-Wave Reactor, MIT Technology Review (Online), 20.10.16, http://www2.technologyreview.com/news/412188/tr10-traveling-wave-reactor, 2009.

The breed burn wave does not move from one end of the reactor, travel through the reactor, but gradually from the center out; the fuel rods themselves are moved through a largely stationary burn wave.

Ahlfeld C. et al., “Conceptual Design of a 500MWe Traveling Wave Demonstration Reactor Plant”, ICAPP 2011, Nice, France, May 2–5, 2011.

Like in molten salt reactors with dispersed fuel.

Ahlfeld, Charles, T. Burke, T. Ellis, P. Hejzlar, K. Weaver, C. Whitmer, J. Gilleland et al. “Conceptual design of a 500 MWe traveling wave demonstrator reactor plant.”, Proceedings of ICAPP 2011, Societe Francaise d’Energie Nucleaire – SFEN (2011).

Reactor Vessel Air Cooling System (PVACS) without moving parts and required operator actions.

In nuclear fusion, two or more atomic nuclei merge to form one or more different small atomic nuclei and subatomic particles. The primary source of solar energy and of similar size stars is the fusion of hydrogen to form helium (the proton-proton chain reaction), which occurs at a solar-core temperature of 14 million kelvins. The International Thermonuclear Experimental Reactor (ITER) is under construction, next to the Cadarache facility in Saint-Paul-lès-Durance, in southern France, to become the world’s largest magnetic confinement plasma physics experiment (a tokamak nuclear fusion reactor). It aims to demonstrate the controlled principle of producing more thermal power from the fusion process than is used to heat the plasma.

U.S. Department of Energy, Research Needs for Fusion-Fission Hybrid System, Report of the Research Needs Workshop, Gaithersburg, Maryland, Sept. 30–Oct. 2, 2009.

L. M. Lidsky, Fission-fusion systems – Hybrid, symbiotic and Augean, Nuclear Fusion 15, 151–173 (1975); H. Bethe, The fusion hybrid, Physics Today 32, 44–51 (May 1979).

R. Piovan et al. The RFP as neutron source for fusion-fission hybrid systems, second Int. Conf. on Fusion-Fission Sub-critical Systems for Waste Management and Safety.

i.e. having the shape of a torus

U.S. Department of Energy, Research Needs for Fusion-Fission Hybrid Systems, Report of the Research Needs Workshop, Gaithersburg, Sept 30–Oct. 2, Maryland, 2009, p. 41.

D. Escande, private communication (October 2017).

Wald M., TR10: Traveling-Wave Reactor, MIT Technology Review (Online), 20.10.16, http://www2.technologyreview.com/news/412188/tr10-traveling-wave-reactor, 2009.

P. Hejzlar, Todreas, N.E., Shwageraus, E., Nikiforova, A., Petroski, R., Driscoll, M.J., Cross. “Comparison of fast reactor concepts with various coolants”, Nuclear Engineering and Design 239, 2672–2691 (2009).

K. Tuček et al., “Comparison of sodium and lead-cooled fast reactors regarding reactor physics aspects, severe safety and economic issues”, Nuclear Engineering and Design 236, 1589–98 (2006).

K.Tuček et al., “Comparative study of minor actinide transmutation in sodium and lead-cooled fast reactor cores”, Progress in Nuclear Energy 50, 382–388 (2008).

100

Heterogeneous and/or homogeneous incineration of minor actinides (MA).

101

Loss-Of-Flow (LOF), Loss-Of-Heat-Sink (LOHS), total Loss-Of-Power/Station Blackout (LOP).

102

Metallic (e.g., U-TRU-Zr) or oxide (U/Th-TRU)O₂.

103

Liquid sodium cooled (SFR), lead cooled (lead or lead/bismuth cooled (LFR)), molten salt cooled (MSFR), all fast.

104

Stewardship burden (“husbandry times”) could be determined by long-lived fission products (J-129, Tc-99), no longer by minor actinides – depending on separation and incineration effectiveness.

105

SFR cores require special, albeit passive devices, large SFR face more difficulties than small; LFR and SFR call for slight moderation (softer spectrum), albeit with potential negative impact on “burn-up swings” (see Table 6.5).

106

IAEA. Low Level Event and Near Miss Process for Nuclear Power Plants: Best Practices. IAEA, Safety Reports Series No. 73 (2012).

Title: Candidate Features and Technology Options
Authors: Didier Sornette
Wolfgang Kröger
Spencer Wheatley
Publisher: Springer International Publishing
Book: New Ways and Needs for Exploiting Nuclear Energy
Print ISBN: 978-3-319-97651-8

Electronic ISBN: 978-3-319-97652-5

Copyright Year: 2019
DOI: https://doi.org/10.1007/978-3-319-97652-5_6