Method of improving the spent nuclear fuel burnup credit

A method of determining the acceptability of the placement of a new spent nuclear fuel assembly within a spent fuel storage container wherein there are X number of spent fuel assemblies surrounding the placement of the new spent fuel assembly and X+1 is a number of the new spent fuel assembly plus the X number of spent fuel assemblies surrounding the placement of the new spent fuel assembly, comprising the steps of:

• generating a series of curves made up of a number of curves of enrichment vs. current burnup, each curve representing a different number of the X+1 spent fuel assemblies that have a commonly used adverse axial burnup distribution;
• determining the actual axial burnup distribution of each of the X+1 fuel assemblies;
• noting how many of the X+1 spent fuel assemblies have the adverse axial burnup distribution;
• identifying which of the number of curves applies to the new fuel assembly from the number of spent fuel assemblies noted as having the adverse axial burnup distribution;
• finding the point on the graph on which the applicable curve is plotted that corresponds to a current burnup and initial enrichment for the new spent fuel assembly;
• and
• determining whether the point on the graph is above the applicable curve, wherein if the point on the graph is above the applicable curve the placement of the new spent fuel assembly is acceptable.