HTGR Knowledge Base

Topical Article 4: Reactor Physics

A strong negative temperature coefficient over the entire range of plant operation is an essential inherent feature of a modular HTGR. It limits the power level that can be attained under accident conditions and provides a natural passive mechanism for decreasing power under conditions of increasing temperature. Providing assurance of a negative temperature coefficient as well as the ability to accurately predict other nuclear characteristics of the core are essential requirements for modular HTGR development.

The development of data for validation of reactor physics analysis methods through an experimental program at the PROTEUS facility of the Paul Scherrer Institute in Switzerland was the primary objective of a six year IAEA Co-ordinated Research Project (CRP) beginning in 1990. IAEA Member States participating in the CRP included China, France, Germany, Japan, the Netherlands, the Russian Federation, Switzerland, and the United States. Finalization of the documentation has been delayed to allow incorporation of the results of work that continued beyond completion of the CRP. The results of this effort will be reported in an IAEA TECDOC addressing the following topical areas:

• Available validation data and additional needs at the beginning of the CRP
• Analytical benchmark problems
• Experimental results
• Analysis of experimental results

Release of the TECDOC is expected in mid 2001.

Additional reactor physics 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".