Analysis of a hypothetical array criticality accident involving units of aqueous uranyl fluoride

In this study a model is developed to predict the results of a hypothetical nuclear excursion involving an array of six polyethylene bottles containing an aqueous solution of low-enriched UO₂F₂. The computer model calculates the power history, the total energy release, and various thermal-hydraulic parameters. The model employs point neutronics coupled with simple lumped parameter feedback.

The model has been used to predict the results of various nuclear excursion experiments. Good agreement with the experiments for the initial peak fission rate, the total number of fissions, and for some of the subsequent fission pulses is demonstrated. For the six bottle array, ramp insertion rates of 0.5 $/sec to 35.0 $/sec and a step of 35.0 $ are postulated. The peak fission rates range from 3.1 x 10¹⁶ fissions/sec to 1.9 x 10²² fissions/sec. The total number of fissions range from 3.3x10¹⁶ fissions to 7.7x10¹⁸ fissions. Most of the array results appear to be quite reasonable