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The High Temperature Gas-Cooled Reactor The High Temperature Gas-cooled Reactor Safety considerations of the (V)HTR-Modul Kugeler, K., Nabielek, H., Buckthorpe, D. Editors: Scheuermann, W., Haneklaus, N., Fütterer, M. 2017 EUR 28712 EN KJ - NA - 28712 - EN - C This publication is a Book with editorship by the Joint Research Centre (JRC), the European Commission’s science and knowledge service. It aims to provide evidence-based scientific support to the European policymaking process. The scientific output expressed does not imply a policy position of the European Commission. Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use that might be made of this publication. Contact information Name: Fütterer, M. Address: European Commission, DG Joint Research Centre – JRC, Directorate G, Unit G.I.4 – Nuclear Reactor Safety & Emergency Preparedness; P.O. Box 2, NL-1755 ZG Petten, Netherlands Email: [email protected] Tel.: +31 22456-5158 JRC Science Hub https://ec.europa.eu/jrc JRC107642 EUR 28712 EN PDF ISBN 978-92-79-71311-8 ISSN 1831-9424 doi:10.2760/270321 Print ISBN 978-92-79-71312-5 ISSN 1018-5593 doi:10.2760/970340 Luxembourg: Publications Office of the European Union, 2017 © European Atomic Energy Community, 2017 Reuse is authorised provided the source is acknowledged. The reuse policy of European Commission documents is regulated by Decision 2011/833/EU (OJ L 330, 14.12.2011, p. 39). For any use or reproduction of photos or other material that is not under the EU copyright, permission must be sought directly from the copyright holders. How to cite this report: Scheuermann, W., Haneklaus, N. and Fütterer, M., editor(s), Kugeler, K., Nabielek, H. and Buckthorpe, D., The High Temperature Gas-cooled Reactor: Safety considerations of the (V)HTR- Modul, EUR 28712 EN, Publications Office of the European Union, Luxembourg, 2017, ISBN 978-92-79-71311-8, doi:10.2760/270321, JRC107642. Acknowledgement European researchers and engineers gained considerable experience with the High Temperature Gas- cooled Reactor (HTR or HTGR). After the successful operation of experimental and commercial HTRs, the Three Mile Island accident in 1978 led to a reorientation of HTR designs towards reduced power (200-600 MWth) and inherent decay-heat removal features based on the demonstrated fission- product retention capability of coated-particle fuel up to about 1 600 °C. The concept of such a reactor was developed by Siemens/Interatom in the 1980s: the so-called HTR Module. Based on a reduced thermal power of 200 MW and construction details, the release of radioactivity in accident conditions can be avoided. However, the Chernobyl accident in 1986 marked the end of the HTR Module development in Germany. In particular, the licensing process was stopped due to political decisions. However, after a decade of interruption, the European and international effort on the development of an inherently safe nuclear reactor picked up speed again with the creation of the European High Temperature Reactor Technology Network (HTR-TN). HTR-TN has proposed and executed several European R & D projects and launched international collaboration initiatives. One of these, the Generation IV International Forum (GIF), founded in May 2001, selected this concept for the very high temperature reactor (VHTR). At that time, the VHTR was primarily seen as a candidate for a Generation IV reactor with the particular mission of electricity and large-scale bulk hydrogen production via thermochemical processes. Today, and due to the large market sector in industrial heat demand, more emphasis is given to the cogeneration of heat (mostly steam) and power with HTRs. In Europe, along with several smaller projects, two large projects specifically related to HTR technology were put in place. Raphael (reactor for process heat, hydrogen and electricity generation), a 4-year project with 37 partners, started in 2005. Archer (advanced high-temperature reactors for cogeneration of heat and electricity R & D), again a 4-year project, with 33 partners, started in 2010. Both projects successfully performed the R & D required with a view to confirming the high technology readiness level for the design, demonstration and deployment of such a reactor, in particular for their use as highly efficient plants for cogeneration of heat and power. The Raphael project focused on (V)HTR technology developments needed for industrial reference designs in the areas of reactor physics, safety, fuel and fuel-cycle back end, materials and components. Moreover system integration with the reference designs was carefully checked and documented. The Archer project then extended the current state of knowledge of the European (V)HTR technology basis with R & D to support the demonstration of nuclear cogeneration with HTR. One of the deliverables of Archer was to document the current state of knowledge in the form of an HTR handbook with a specific focus on safety. It was meant to provide the basis for future research and development. The present book is composed of chapters recalling the concept of the HTR Module, fuel and fuel performance, components, materials and safety. The appendix summarises the most important experiments concerning safety. As editors we thank the authors of the book, Professor emeritus Dr Kurt Kugeler, from the RWTH Aachen, Germany, who contributed to chapters of the HTR concepts, components and safety, Dr Heinz Nabielek, from Forschungszentrum Jülich, Germany, who provided the chapter on fuel and fuel 3 performance, and Mr Derek Buckthorpe from AMEC Foster Wheeler, who wrote the chapter on materials. We are grateful to the colleagues who did the hard job of digitising drawings and plots from printed paper of older reports to be included in this book, namely Janis Lapins, Dustin Sanchristobal and Nicolai Kaufmann from the Institute of Nuclear Technology and Energy systems (IKE), University of Stuttgart, Germany. Last but not least our acknowledgements are addressed to the European Commission, especially to Dr Georges van Goethem for his encouragements to produce and publish this book. The editors Walter Scheuermann (University of Stuttgart, Germany) Nils Haneklaus (University of Berkeley, United States) Michael Fütterer (European Commission — Joint Research Centre, Petten, the Netherlands) 4 Contents List of figures .............................................................................................................. 1 List of tables ............................................................................................................... 8 1. Introduction ........................................................................................................ 11 2. The concept of the HTR Module ........................................................................ 15 2.1. Concept of the plant .................................................................................... 16 3. Core layout parameter for the HTR Module ....................................................... 20 3.1. Overview ..................................................................................................... 20 3.2. Core power density ...................................................................................... 21 3.3. H/D ratio of the core .................................................................................... 23 3.4. Layout of the core of the HTR Module ......................................................... 25 3.5. Helium pressure .......................................................................................... 26 3.6. Helium temperatures in the primary circuit .................................................. 26 3.7. Heavy metal and burnup ............................................................................. 27 3.8. Feeding principles ....................................................................................... 28 3.9. Questions concerning the plant layout ......................................................... 28 4. Fuel and fuel performance ................................................................................. 30 4.1. Fuel manufacturing ...................................................................................... 32 4.1.1. UO2 fuel kernels .................................................................................... 32 4.1.2. TRISO coating ...................................................................................... 32 4.1.3. Spherical fuel element .......................................................................... 34 4.1.4. As-manufactured fuel quality ................................................................. 38 4.2. HTGR fuel performance under accident conditions ..................................... 40 4.2.1. Simulation testing of core heat-up depressurisation under dry conditions 40 4.2.2. Fission-product release from UO2 kernels at 1 600 °C ......................... 41 4.2.3. Comparison of fuel quality at 1 600 °C .................................................. 42 4.2.4. KÜFA tests in Jülich 1985-1995 and in Karlsruhe 2005-2010 ............... 43 4.3. Accident simulation testing under oxidising conditions ................................ 47 4.3.1. Simulation of water ingress accident ..................................................... 47 4.3.2. Simulation of air ingress accident ......................................................... 48 4.4. Fuel performance limits ............................................................................... 49
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