Power Flattening Study of Ultra-Long Cycle Fast Reactor Core

  • Taewoo Tak
  • Jiwon Choe
  • Yongjin Jeong
  • Jinsu Park
  • Deokjung LeeEmail author
  • T. K. Kim
Conference paper


A design study of ultra-long cycle fast reactor with a rated power of 1000 MWe (UCFR-1000) was performed to flatten its radial power distribution throughout the cycle depletion of the core. It is expected that the flattening of the radial power distribution lowers the power peak factor at the center and consequently the maximum peak temperature of the fuel and clad. Thorium fuel has lower reproduction factor than uranium; thus, thorium-loaded fuel zone has relatively lower power. A lot of test cases were introduced that have thorium-loaded fuel in the inner fuel region to lower the center power peak. Each test case had a different zoning strategy; different fuel forms were loaded for both the upper blanket region and the lower low enrichment uranium (LEU) region. The final evaluation models were designed by loading the thorium-loaded fuel only in the inner blanket for the 1-zone case, in both blanket and LEU regions for the 2-zone case, and in an additional zone for the other cases. It was demonstrated that the fuel zoning has a significant impact on the power flattening, and a gradual fuel zoning can achieve a flattened radial power distribution, and can consequently reduce the maximum power peak.


SFR UCFR Power peaking factor Power flattening Thorium fuel 



Beginning of cycle


End of cycle


Low enriched uranium


Middle of cycle


Narrow center


Natural uranium


Ultra-long cycle fast reactor


Wide center



This work was supported by the National Research Foundation of Korea (NRF), grant funded by the Korean government (MSIP).


  1. 1.
    T. Tak, D. Lee, T.K. Kim, Design of ultra-long cycle fast reactor employing breed-and-burn strategy. Nucl. Technol. 183, 427–435 (2013)CrossRefGoogle Scholar
  2. 2.
    T. Tak, D. Lee, T.K. Kim, Ser Gi Hong, Optimization study of ultra-long cycle fast reactor core concept. Ann. Nucl. Energy 73, 145–161 (2014)CrossRefGoogle Scholar
  3. 3.
    H. Seo, J. Kim, I. Bang, Subchannel analysis of a small ultra-long cycle fast reactor core. Nucl. Eng. Des. 270, 389–395 (2014)CrossRefGoogle Scholar
  4. 4.
    T. Tak, H. Lee, S. Choi, D. Lee, Power flattening study for ultra-long cycle fast reactor UCFR-1000, in Transactions of America Nuclear Society Summer Meeting, 16–20 June 2013Google Scholar
  5. 5.
    H. Shim et al., McCARD: Monte Carlo code for advanced reactor design and analysis. Nucl. Eng. Technol. 44, 161–176 (2012)CrossRefGoogle Scholar

Copyright information

© Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  • Taewoo Tak
    • 1
  • Jiwon Choe
    • 1
  • Yongjin Jeong
    • 1
  • Jinsu Park
    • 1
  • Deokjung Lee
    • 1
    Email author
  • T. K. Kim
    • 2
  1. 1.Ulsan National Institute of Science and TechnologyUlsanSouth Korea
  2. 2.Argonne National LaboratoryIllinoisUSA

Personalised recommendations