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Final report on TREAT tests R4 and R5; seven-pin, loss-of-flow tests with full-length, unirradiated FFTF-type fuel pins

Technical Report ·
DOI:https://doi.org/10.2172/711091· OSTI ID:711091

Two seven-pin loss-of-flow (LOF) simulation tests have been performed in-pile in support of LMFBR safety analyses. These integral-type tests were carried out in the R-series test apparatus at TREAT, designed to provide a prototype thermal-hydraulic flowing sodium system. The test fuel pins were full-length FFTF-type, containing unirradiated UO{sub 2} fuel. In LOF Test R4, the sequence was run at constant fuel power well beyond the inception of molten-fuel motion; in R5, the sequence was terminated before fuel melting to preserve evidence of early molten-cladding motion. The tests were consistent with one another, showing the anticipated sequence of sodium boiling, channel voiding, cladding dryout, cladding failures, molten-cladding motion, and, for R4, fuel melting and motion. Thin planar upper cladding blockages were formed as were thick lower steel blockages, effectively plugging the bundle at the extremities of the active fuel region. There was no sodium reentry, and there were no significant pressurization events. Comparison of test results with SAS-code calculations revealed differences associated with early voiding behavior, release of noncondensible fuel-pin plenum gas, and the thickness and location of the upper blockage. In general, however, the overall sequence of significant events observed in R4 and R5 is in quite good agreement with SAS-code analysis of the test conditions. Features of SAS related to overall voiding, cladding motion, and, to some extent, fuel motion have been substantiated in these results.

Research Organization:
Argonne National Lab., IL (United States)
Sponsoring Organization:
USDOE
DOE Contract Number:
W-31109-ENG-38
OSTI ID:
711091
Report Number(s):
ANL--79-106
Country of Publication:
United States
Language:
English