Structural integrity issues with Gen IV proposals: fast reactors and PBMR

Abstract

Structural integrity issues are discussed for two generation IV reactor concepts: the fast reactor and the high temperature reactor, more specifically, the pebble bed modular reactor. The pebble bed modular reactor and other designs of high temperature reactor are claimed to possess built-in safety features leading to safe shutdown: they do, however, involve >8% enrichment of ²³⁵U. Many high temperature creep, creep–fatigue and stress relaxation issues remain to be addressed. With lead/lead–bismuth cooled fast reactors running at ∼500°C, there appear to have been none of the issues in the steam generator experienced with sodium cooling. The aspiration of both reactor types is to operate at high temperatures and to produce hydrogen from water thermochemically. A view has been expressed that temperatures up to 900°C could be achieved using metallic alloys (with ceramics for higher temperatures), but it is concluded that something of the order of 750°C represents a more realistic upper limit for economic service lives.

Keywords:

• Fast breeder reactors
• Pebble bed modular reactors
• High temperature reactors
• Nuclear fission power
• Gen IV
• Structural integrity
• Creep
• Creep–fatigue