Evaluation and Modification of the Probability Table Method for Bubble Reactivity Worth Calculations

The probability table representation of neutron transport in bubbly media, developed by Hoffman and Petrie for neutron flights initiated by collision, is extended to neutron flights initiated at interfaces. Both forms are compared with appropriate Monte Carlo estimates of one-flight transmission through bubbly slabs, with encouraging results for slabs thicker than the bubble diameter. These forms are then combined into a modified probability table method. Application of the modified method to transport calculations requires high spatial and angular resolution but shows that the interface modification can have a substantial effect on calculated bubble worths. Fortunately, the results agree well with the simple Benoist method, which does not require high resolution.