MODÜLER HELYUM REAKTÖRÜNÜN KAZA DURUMUNUN ZAMANA BAĞLI ISIL AKIŞ ANALİZİ

Öz

Modüler Helyum Reaktörü (MHR)’nün en önemli özelliği kaza durumunda aktif soğutma sistemi çalışmadığı zaman kendiliğinden soğuyabilmesidir. Bu çalışmanın ilk amacı; kaza durumunda MHR’nin atık ısı uzaklaştırma yeteneğini incelemek için sayısal bir model geliştirmek ve oluşan tepe sıcaklığı hesaplamaktır. İkinci amacı; grafit iletimi, atık ısı gibi parametrelerdeki değişiminin maksimum aktif kor sıcaklığına etkisini belirlemek için duyarlılık analizleri yapmaktır. Bu çalışmada, aktif soğutmanın çalışmadığı kaza durumunda, atık ısının pasif olarak reaktörden atılmasını simule etmek için bir sayısal model oluşturulmuştur. Zamana bağlı ısıl-akış simülasyonları sayısal akışkanlar dinamiği yazılımı Ansys Fluent kullanılarak yapılmıştır. Simule edilen geometri Eşdeğer Silindir Modeli olarak seçilmiştir. Korun içindeki kompleks yapıyı modellemek için gözenekli ortam yaklaşımı kullanılmıştır. Hesaplamalar basınçsız kaza durumu için yapılmıştır. Basınçsız kaza durumunda pasif soğuma 100 saat için nümerik olarak çözülmüştür. Nümerik metodun güvenirliği diğer çalışmalar ile karşılaştırılarak doğrulanmıştır. Kaza durumunda meydana gelen maksimum sıcaklığın 1492°C olduğu bulunmuştur. Duyarlılık analizlerinin sonuçları kaza durumunda oluşan maksimum sıcaklığa en çok grafit ısı iletim katsayısı ve atık ısı değişiminin etkisi olduğunu göstermektedir.

Anahtar Kelimeler

• Modüler helyum reaktörü
• kaza
• SAD
• zamana bağlı
• Isıl-akış

TRANSIENT THERMAL HYDRAULIC ANALYSIS OF MODULAR HELIUM REACTOR UNDER ACCIDENT CONDITION

Öz

The main characteristic of MHR is that it can automatically cool down when the active cooling system does not work under accident condition. The first purpose of the study is to develop a numerical model to analyze the decay heat removal capabilities and evaluate peak temperature in the MHR under accident condition. The second purpose of the study is to perform some sensitivity analyses to evaluate the effect of varying the parameters, i.e. graphite conductivity, decay heat, etc., on the maximum active core temperature. In this study, a numerical model has been constructed to simulate the passive decay heat removal under a loss of active cooling accident. Thermal-hydraulic transient simulations were carried out by using Computational Fluid Dynamics software Ansys Fluent. The simulated geometry was chosen as an Equivalent Cylinder Model. The porous media approach has been applied to model the complex structure in the core. Calculations were performed for loss of forced cooling without pressurization condition. Passive cooldown under depressurized accident is solved numerically for 100 hours. The reliability of the numerical method was validated by comparing with the published data. It was found that the maximum temperature was 1492°C under accident condition. The results of sensitivity analyses show that the graphite thermal conductivity and decay power has a strong effect on the maximum temperature under accident condition.

Anahtar Kelimeler

• Modular helium reactor
• Accident
• CFD
• Transient
• Thermal–hydraulic

Kaynakça

1. ANSYS Inc., 2019, Ansys Fluent Theory Guide, ANSYS Inc., Canonsburg.
2. ANSYS Inc., 2019, Ansys Fluent User’s Guide, ANSYS Inc., Canonsburg.
3. Ball, S., 2006, Sensitivity Studies of Modular High-Temperature Gas-Cooled Reactor Postulated Accidents, Nucl. Eng. Des., 236, 454–462.
4. Ball, S., 2004, Sensitivity Studies of Modular High-Temperature Gas-Cooled Reactor (MHTGR) Postulated Accidents, 2nd International Topical Meeting on High Temperature Reactor Technology, Beijing-China, 1–13.
5. Fukuda, K., Kendall, J., Kupitz, J., Matzner, D., Mulder, E., Pretorius, P., Shenoy, A., Shiozawa, S., Simon, W., Sun, Y., Uselton, P. ve Xu, Y., 2001, Current Status and Future Development of Modular High Temperature Gas Cooled Reactor Technology, IAEA-TECDOC-1198, IAEA, Vienna.
6. Haque, H., Feltes, W. ve Brinkmann, G., 2006, Thermal Response of a Modular High Temperature Reactor during Passive Cooldown under Pressurized and Depressurized Conditions, Nucl. Eng. Des., 236, 475–484. https://doi.org/10.1016/J.NUCENGDES.2005.10.027
7. Haque, H., Feltes, W. ve Brinkmann, G., 2004, Thermal Response of a High Temperature Reactor during Passive Cooldown under Pressurized and Depressurized Conditions, 2nd International Topical Meeting on High Temperature Reactor Technology, Beijing-China, 1–17.
8. Hossain, A.S.M.K., 2011, Development of a Fast Running Multidimensional Thermal-Hydraulic Code to be Readily Coupled with Multidimensional Neutronic Tools, Applicable to Modular High Temperature Reactors, PhD Thesis, University of Stuttgart, Stuttgart.

9. Hossain, K., Buck, M., Bernnat, W. ve Lohnert, G., 2008, TH3D, A Three-Dimensional Thermal Hydraulic Tool, for Design and Safety Analysis of HTRS, HTR’2008, Washington-USA.
10. Huning, A.J., Chandrasekaran, S. ve Garimella, S., 2021, A Review of Recent Advances in HTGR CFD and Thermal Fluid Analysis, Nucl. Eng. Des., 373, 111013. https://doi.org/10.1016/j.nucengdes.2020.111013
11. IAEA, 2001, Heat Transport and Afterheat Removal for Gas Cooled Reactors under Accident Conditions, IAEA TECDOC-1163, IAEA, Vienna.
12. Internet, 2021, National Institute of Standards and Technology, Thermophysical Properties of Fluid Systems, https://webbook.nist.gov/chemistry/fluid.
13. IV, J.H.L., V, J.H.L., 2019, A Heat Transfer Textbook, Phlogiston Press, Cambridge.
14. Kiryushin, A.I., Kodochigov, N.G., Kouzavkov, N.G., Ponomarev-Stepnoi, N.N., Gloushkov, E.S. ve Grebennik, V.N., 1997, Project of the GT-MHR High-Temperature Helium Reactor with Gas Turbine, Nucl. Eng. Des. 173, 119–129. https://doi.org/10.1016/S0029-5493(97)00099-X
15. Li, S., 2005, Parametric Thermal-Hydraulic Studies of HTGR Reactor Vessel System - Consequences on the Structure Lifetime, SMIRT 18, Beijing-China, 4311–4325.
16. MacDonald, P.E., Sterbentz, J.W., Sant, R.L., Bayless, P.D., Schultz, R.R., Gougar, H.D., Moore, R.L., Ougouag, A.M. ve Terry, W.K., 2003. NGNP Point Design-Results of the Initial Neutronics and Thermal-Hydraulic Assessments During FY-03, INEEL/EXT-03-00870. INEEL, Idaho.
17. Mays, B.E., Woaye-Hune, A., Simoneau, J.-P., Gabeloteau, T., Lefort, F., Haque, H. ve Lommers, L., 2004, The Effect of Operating Temperature on Depressurized Conduction Cooldown for a High Temperature Reactor, ICAPP’04, Pittsburgh-USA, 1–9.
18. Moses, D.L., 2010, Very High-Temperature Reactor (VHTR) Proliferation Resistance and Physical Protection (PR&PP), ORNL/TM-2010/163, Oak Ridge National Laboratory, Oak Ridge.
19. Nouri-Borujerdi, A. ve Tabatabai Ghomsheh, S.I., 2015a, Porous Media Approach in Thermohydraulic Analysis of High Temperature Reactors in Pressurized/Depressurized Cooldown: An Improvement, Prog. Nucl. Energy, 80, 119–127. https://doi.org/10.1016/J.PNUCENE.2014.11.017
20. Nouri-Borujerdi, A. ve Tabatabai Ghomsheh, S.I., 2015b, An Improved Porous Media Approach to Thermal–Hydraulics Analysis of High-Temperature Gas-Cooled Reactors, Ann. Nucl. Energy, 76, 485–492. https://doi.org/10.1016/J.ANUCENE.2014.10.006
21. Nuclear Energy Agency, 2018, NEA Benchmark of the Modular High-Temperature Gas-Cooled Reactor-350 MW Core Design Volumes I and II, NEA/NSC/R(2017)4, OECD.
22. Pietrak, K. ve Wisniewski, T.S., 2015, A Review of Models for Effective Thermal Conductivity of Composite Materials, J. Power Technol, 95, 14–24.
23. Pioro, I.L., 2016, Handbook of Generation IV Nuclear Reactors, Handbook of Generation IV Nuclear Reactors, Elsevier Inc, https://doi.org/10.1016/C2014-0-01699-1
24. Potter, R.C., 1995, GT-MHR Conceptual Design Description Report, GA Project No. 6302, General Atomics, San Diego.
25. Reza, S.M., Harvego, E.A., Richards, M., Shenoy, A. ve Peddicord, K.L., 2006, Design of an Alternative Coolant Inlet Flow Configuration for the Modular Helium Reactor, ICAPP’06, Reno-USA.
26. Roache, P.J., 1994, Perspective: A Method for Uniform Reporting of Grid Refinement Studies, J. Fluids Eng, 116, 405–413.
27. Şahin, H.M., Erol, Ö. ve Acır, A., 2012, Utilization of Thorium in a Gas Turbine – Modular Helium Reactor, Energy Convers. Manag, 63, 25–30. https://doi.org/10.1016/j.enconman.2012.01.027
28. Şahin, S., Erol, Ö. ve Mehmet Şahin, H., 2016, Investigation of a Gas Turbine-Modular Helium Reactor Using Reactor Grade Plutonium With 232Th And 238U, Prog. Nucl. Energy, 89, 110–119. https://doi.org/10.1016/j.pnucene.2016.02.006
29. Shi, D., 2015, Extension of the Reactor Dynamics Code MGT-3D for Pebblebed and Blocktype High-Temperature-Reactors, PhD Thesis. RWTH Aachen University, Aachen.
30. Siccama, N.B. ve Koning, H., 1998, Afterheat Removal from a Helium Reactor under Accident Conditions: CFD Calculations for the Code-to-Code Benchmark Analyses on the Thermal Behavior for the Gas Turbine Modular Helium Reactor, ECN-RX-97-066, ECN Nucleaire Research/Faciliteiten (NRG), Netherlands.
31. Stainsby, R., Worsley, M., Dawson, F. ve Grief, A., 2009, Investigation of Local Heat Transfer Phenomena in a Prismatic Modular Reactor Core, NR001/RP/001 R02, AMEC NSS Limited, Toronto.
32. Vilim, R.B., Feldman, E.E., Pointer, W.D. ve Wei, T.Y.C., 2005, Generation IV Nuclear Energy System Initiative Initial VHTR Accident Scenario Classification: Models and Data, ANL-GenIV-057, Argonne National Laboratory, Lemont.
33. Woaye-Hune, A. ve Ehster, S., 2002, Calculation of Decay Heat Removal Transient by Passive Means for a Direct Cycle Modular HTR, HTR2002, Petten-NL, 1–7.