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A New Fuel Management Plan for The Pennsylvania State University TRIGA Reactor Including Supporting Experiments and Calculations

Patrick G. Boyle, Daniel E. Hughes, Samuel H. Levine

Nuclear Technology

Volume 123 / Number 2 / August 1998 / Pages 222-230


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The Pennsylvania State University Breazeale (TRIGA) Reactor (PSBR) has operated for 25 yr (440 MWd) using a mixed 12 wt% ZrHx-U and 8.5 wt% ZrHx-U fuel configuration (both enriched to 20 wt% 235U, and x, the ratio of H to Zr, is nominally 1.65). In this configuration, the most reactive 12 wt% ZrHx-U fuel is always in the B-ring. The B-ring is the innermost hexagonal ring, incorporating 6 fuel elements, and the C-ring is the next outward ring, having 12 fuel elements. PSBR experience during pulsing and steady-state operation indicates that with these configurations the maximum fuel temperatures should be reduced in order to extend the useful life of the 12 wt% ZrHx-U fuel. This is because during the past 10 yr, the fuel temperatures of the new fuel have been significantly higher than the original fuel. The instrumented fuel element (I-15) loaded into the core ~10 yr ago and the most recent batch of fresh 12 wt% ZrHx-U fuel elements (six total, including I-16 and I-17) measured temperatures more than 100°C higher than any previous instrumented fuel element. Subsequent pulsing of I-15 increased its measured fuel temperature to where it began to approach the limiting safety system setting. Recent pulsing of I-16 and I-17 caused their steady-state fuel temperatures to decrease slightly, but they remain high. The new fuel management plan reduces these fuel temperatures by replacing the used 12 wt% ZrHx-U fuel in the C-ring with fresh 12 wt% ZrHx-U fuel. The 12 wt% ZrHx-U fuel in the B-ring is replaced with 8.5 wt% ZrHx-U fuel. Experiments have been performed to verify the predicted core parameters for the new plan. The lifetime of the new 12 wt% ZrHx-U fuel should now be limited by its maximum allowed burnup, which has not occurred so far.

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