Methods for Calculating Vapor and Fuel Transport to the Secondary Containment in an LMFBR Accident

Abstract

Calculational models were developed for estimating the transport of sodium vapor and the relatively large (≥10-µm) fuel particles resulting from a fuel-coolant interaction to the secondary containment in an LMFBR core disruptive accident. Following the formation of a large sodium vapor bubble resulting from a fuel-coolant interaction, a potential sequence of events was analyzed. This analysis covers bubble condensation, bubble rise time, aerosol fallout during the bubble rise, gas flow rate through the cover, cover-gas escape during the bubble rise, bubble and cover-gas mixing, and aerosol escape to the secondary containment.Two parametric calculations were made for specified accident conditions for a 1000-MW(e) LMFBR conceptual design. The bubble did not condense in this analysis. Results of the analysis indicated that 2 and 10% of the fuel that took part in the fuel-coolant interaction eventually reached the secondary containment for the two assumed flow areas through the cover, i.e., 0.1 and 1.0 ft2, respectively.