Development of a thermal-hydraulic analysis code for thermal sizing of once-through steam generators for SMR

Youngjae Park, Iljin Kim, Hyungdae Kim, Kyungjoon Kang

Research output: Contribution to journalArticlepeer-review


A one-dimensional thermal-hydraulic analysis code was developed for the conceptual design and sizing of once-through steam generators (OTSGs) with application to small modular nuclear reactors. The OTSG in the model is represented by one characteristic double-tube heat exchanger with countercurrent flow. The secondary side of the OTSG is divided into subcooled liquid region, saturated two-phase mixture region, and superheated vapor region. Heat transfer and pressure drop correlations for each flow region were selected and implemented. To benchmark predictability of the developed computer code, the B&W OTSG whose design data is available in open literature was simulated. The results were compared both to the design data of the OTSG and to the analysis results obtained using a best-estimate thermal-hydraulic analysis code. The overall characteristics of the heat transfer area, pressure, and temperature distributions calculated with the developed code were in good agreement with the design data as well as the results from the best-estimate code. Lastly, a new concept of OTSG that incorporates feedwater circulation to reduce its volume for SMR application was simulated using the developed code. This demonstrates that the code can be used for design innovation and performance analysis of OTSGs.

Original languageEnglish
Article number103883
JournalProgress in Nuclear Energy
Publication statusPublished - Sep 2021


  • Computer code
  • Once-through steam generator
  • SMR
  • Thermal sizing
  • Thermal-hydraulics


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