A Finnish district heating reactor: Thermal-Hydraulic Design and Transient Analyses

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

5 Citations (Scopus)


Development of a small district heating reactor was started at VTT Technical Research Centre of Finland. The concept features a 50 MW reactor that operates at low temperature and pressure. Traditional LWR technology, passive safety functions and natural circulation are combined in the integrated design. This paper presents the thermal-hydraulic design and transient analyses done with Apros simulation software. The studied cases include station blackout with reactor trip and as an ATWS scenario, and small break LOCA in the lower downcomer. During the station blackout transients, both temperature and pressure remained at safe levels. The innovative containment design functioned as planned and was capable of efficient decay heat removal. The small break LOCA ceased the natural circulation, but the core was not uncovered at any point and the core temperatures remained low. The results from the thermal-hydraulic analyses are promising and show that the reactor design is capable of producing low temperature heat to the district heating network. The analyzed transients posed no risk to reactor safety, and the passive containment function was capable of removing decay heat efficiently. These preliminary analyses give valuable insight to the design work in the future.
Original languageEnglish
Title of host publicationProceedings of the 2021 28th International Conference on Nuclear Engineering
Subtitle of host publicationOperating Plant Challenges, Successes, and Lessons Learned; Nuclear Plant Engineering; Advanced Reactors and Fusion; Small Modular and Micro-Reactors Technologies and Applications
PublisherAmerican Society of Mechanical Engineers (ASME)
Number of pages7
ISBN (Electronic)978-0-7918-8524-6
Publication statusPublished - 2021
MoE publication typeA4 Article in a conference publication
Event28th International Conference on Nuclear Engineering: Online - Virtual
Duration: 4 Aug 20216 Aug 2021

Publication series

SeriesInternational Conference on Nuclear Engineering (ICONE)


Conference28th International Conference on Nuclear Engineering


  • SMR
  • Apros
  • district heating
  • transient
  • SBO
  • decay
  • heat removal


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