Resonance absorption treatment in the calculation of the moderator void coefficient for tight lattice LWRs

Resonance absorption treatment in the calculations of the moderator void coefficient were analyzed by comparing results based on the application of equivalence relations to tabulated resonance intergrals with results of detailed transport methods with very fine group structure. Good agreement between the two methods was found for relatively dry lattices with void fraction up to 0.5. Significant discrepancies found for a void fractions above 0.5 are ascribed to different resonance treatment methods. The possibility to obtain a less negative (or more positive) value of void coefficient was demonstrated and discussed.