Effects of Zircaloy oxidation and steam dissociation on PWR core heat-up under conditions simulating uncovered fuel rods

Technical Report · Tue Apr 01 04:00:00 EST 1986

OSTI ID:5855933

Viskanta, R; Mohanty, A K

The studies described in this report identify the regimes of slow transients in a partially uncovered core of a PWR. The threshold height and onset time for oxidation of the cladding of a fuel rod have been evaluated. The effects of oxidation in increasing the decay heat load, component temperature, reduction of cladding thickness and generation of hydrogen have been estimated. The condition for steam starvation has been determined. At high uncovered core heights, typically say 2.8 m for a geometry simulating the TMI-2 type of reactor, the solid and coolant temperatures can reach the limits of steam dissociation. The effects of radiation heat exchange between cladding and coolant, Zircaloy oxidation, steam dissociation, gap conductance between fuel and cladding and system pressure on the heatup of fuel rods have been investigated. The time for uncovering a certain core height is taken as the independent parameter. It is seen that if the uncovering process is allowed to continue beyond 9 minutes corresponding to an uncovered height of 1.9 m, onset of cladding oxidation can be a reality. These values provide a guideline for the response time of the emergency core cooling systems. 10 refs., 22 figs.

• Research Organization: Purdue Univ., Lafayette, IN (USA). School of Mechanical Engineering
• OSTI ID: 5855933
• Report Number(s): EPRI-NP-4529; ON: TI86920259
• Country of Publication: United States
• Language: English

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