Post-test examination observations for the W-2 SLSF experiment. [Sodium Loop Safety Facility]

Conference · Thu Sep 01 04:00:00 EDT 1983

OSTI ID:5348860

Pitner, A L; Smith, D E; Culley, G E

Gamma scanning measurements revealed that the axial power profile in these test trains was more peaked than expected based on pretest calculations and critical facility measurements. These results implied that the thermal flux incident on the test assembly was greater than expected, which was manifested in highly skewed and extensive fuel melting zones in the outer pin fuel pellets. Observations indicated that the extent of fuel melting near the midplane exceeded 90% of the pellet radius in some of the outer fuel pins toward the end of the overpower transient, with penetration of molten fuel to the cladding inner surface. It is postulated that this extensive fuel melting and penetration combined with bowing-induced high temperature oscillations to produce the initial disruptive failure in an outer pin at the midplane. Subsequent failure events were induced by the inrush of argon fill gas following rupture of the fluted duct tube. Up to one-third of the total fuel inventory was expelled from the test pin bundle into the coolant channels, with substantial upward sweepout of the ejected fuel noted in the post-test examination. The overall nature of the failure event was judged to be relatively nonviolent, based largely on the survival of unclad, free standing fuel pellet columns in the upper levels of the test section. The observed midplane failure in the W-2 experiment has been attributed to conditions unique to the test. These conditions would not exist in full-size LMFBR fuel assemblies, for which fuel pin failure under slow, unprotected TOP conditions would be expected by a different mode at a higher elevation.

• Research Organization: Hanford Engineering Development Lab., Richland, WA (USA)
• DOE Contract Number: AC06-76FF02170
• OSTI ID: 5348860
• Report Number(s): HEDL-SA-2962-FP; CONF-831047-132; ON: DE84006345
• Country of Publication: United States
• Language: English

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