Fuel Fragmentation, Relocation, and Dispersal During the Loss-of-Coolant Accident (NUREG-2121)

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Publication Information

Manuscript Completed: February 2012
Date Published: March 2012

Prepared by:
Patrick A.C. Raynaud

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

In light of recent results from the U.S. Nuclear Regulatory Commission loss-of-coolant accident (LOCA) research program, the staff of the Division of Systems Analysis in the Office of Nuclear Regulatory Research conducted a comprehensive review of past research programs for observations related to the phenomena of fuel fragmentation, relocation, and dispersal. The goal of this investigation was to determine whether these phenomena occur during a LOCA, and whether they were or should be incorporated into the criteria used to evaluate the acceptability of emergency core cooling systems. The review of over 90 LOCA test results performed in eight different programs over the last 35 years prompted the staff to conclude that fragmentation, relocation, and dispersal of fuel could not be precluded as possible phenomena during a LOCA. In addition, a number of conditions for the occurrence of these phenomena, as well as trends aggravating these phenomena, were derived from the analysis of the data compiled. The report also presents a preliminary assessment of the consequences of fuel fragmentation, relocation, and dispersal. The topics discussed are core damage distribution, fuel-coolant interaction, hydraulic and mechanical effects with relation to downstream effects, and radiological consequences. The preliminary assessment concludes that the consequences of fuel fragmentation and dispersal are not likely to result in an imminent safety hazard. This conclusion was made in consideration of the anticipated low number of fuel rods expected to burst and the conservative manner in which radiological consequences for a postulated LOCA are calculated.