HTGR Knowledge Base

Topical Article 3: Passive Heat Removal

Modular HTGRs are designed to limit fuel temperatures and retain fission products in the fuel for all foreseeable events and conditions by passive radiation and convection heat losses from the uninsulated steel reactor vessel. This capability is made possible by the following features:

• Low power density
• High core and reflector heat capacity
• Negative temperature coefficient of reactivity
• High temperature fission product retention capability of the fuel

Heat transfer phenomena associated with passive removal of decay heat from modular HTGRs was the subject of a five year IAEA Co-ordinated Research Project beginning in 1992, with participating countries including China, France, Germany, Japan, the Netherlands, the Russian Federation, and the United States.

The results of this effort are reported in IAEA-TECDOC-1163 addressing the following topical areas:

• Code to Code Benchmark Exercises
  • VGM RCCS Mockup
  • HTTR Analysis of Heatup Conditions
  • HTR-10 Analysis of Heat Up Accident
  • GT-MHR Plutonium Burner
• Code to Experiment Benchmark Exercises
  • HTTR RCCS Mockup
  • The SANA-1 Experiments for Self-Acting Removal of the Afterheat from a Pebble Bed
• Detailed Information
  • Experimental Data Sets
  • Code Descriptions

Additional thermal hydraulics benchmark activities are under way in the IAEA CRP on Evaluation of HTGR Performance. The scope and status of this CRP is provided in "Overview of IAEA Co-ordinated Research Project on Evaluation of HTGR Performance".