A study on reactivity insertion controlled LMR cores with metallic fuel

✍ Scribed by Tsugio Yokoyama; Takashi Fujiki; Hiroshi Endo; Hisashi Ninokata

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 448 KB
• Volume: 47
• Category: Article
• ISSN: 0149-1970
• DOI: 10.1016/j.pnucene.2005.05.025

✦ Synopsis

An inherently safe core concept with metallic fuel for sodium cooled fast reactor is proposed that has a negative void reactivity at the loss of coolant events without scram as well as a small excess reactivity during the operation cycle. The relationship of sodium void reactivities and burn-up reactivities to different core configurations has been studied quantitatively to clarify the core concept for large metallic fuel reactors. It has shown that the sodium void reactivity is greatly dependent on the core shapes while the excess reactivity is on the fuel compositions. It has also indicated that the core configuration that enables to enhance the neutron streaming through the region above the active core at coolant voiding is most effective to decrease sodium void reactivity.

A 3000 MWt core composed of the flat inner core and annular outer core where the fuel volume fraction is relatively high and the sodium plenum is placed just above the active core region has been selected as a candidate core.

The maximum excess reactivity of the candidate core at UTOP is about 0.4 $ and it can be reduced to approximately zero by power or inlet temperature adjustment during the operation cycle, meanwhile the sodium void reactivity is as low as -1.3 $ in negative that is enough to prevent ULOF sequences.