Evaluation of the calculated results of an unprotected transient undercooling accident in a large, heterogeneous-core, liquid-metal-cooled fast breeder reactor
Disrupted-core (transition-phase) behavior has been evaluated for a hypothetical, unprotected transient undercooling accident in an early version of the heterogeneous-core liquid-metal-cooled fast breeder reactor (LMFBR) developed for the Conceptual Design Study. SAS3D was used to predict initiating-phase phenomena and SIMMER-II was used to predict transition-phase phenomena. Two complete calculations were performed, one at the beginning-of-life cycle and one at the end-of-equilibrium cycle. As a result of low sodium-void reactivity and high incoherence, the initiating phase was nonenergetic. Extensive blockage formation in the axial blankets restricted fuel escape in the transition phase. However, because several critical masses of fuel were available, only after the removal of large quantities of fissile fuel from the core would permanent subcriticality be assured. Although dispersive phenomena were predicted, the effects were temporary and several recriticalities occurred. Permanent subcriticality was predicted only after large-scale disruption of core structure and intermixing of blanket materials. Separate-effects calculations were performed to determine the adequacy of SIMMER-II modeling of important predicted phenomena.
- Research Organization:
- Los Alamos National Lab., NM (USA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6775785
- Report Number(s):
- NUREG/CR-3031; LA-9553-MS; ON: DE83007056
- Resource Relation:
- Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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