vary with core and fuel design, presence of burnable poisons, and so on (see Chapter 2).
The calculations used to determine spent fuel characteristics subject to these variations are fairly complicated and are performed with large, standardized computer codes and neutronics databases. We have not performed such calculations ourselves for this study, but have relied instead on the calculations performed for similar purposes over the past few years by reactor manufacturers and national laboratories. The quantitative comparisons in this chapter are based largely on the set of such calculations summarized in Table 6-1, which includes a range of reactor types-and, within types, ranges of fuel characteristics and operating modes-sufficient to illustrate the key dependencies and variations.1
The bulk of the comparison of options in this chapter focuses on options for disposition of U.S. WPu. This was inevitable, given the amount of relevant information available in the United States. Given the importance of disposition of plutonium in Russia as well, however, several paragraphs at the end of each section in this chapter are devoted to a preliminary discussion of how the options in Russia compare by the same criteria. The panel believes that additional study rigorously comparing plutonium disposition options in Russia against the criteria outlined in this chapter is urgently needed.
As noted in Chapter 3, the primary motivation of the U.S. government in preparing to carry out disposition of excess WPu is to minimize the risks to national and international security posed by the existence of this material. Thus, options must meet this objective to be worthy of further consideration.
The panel was not charged with examining many of the issues related to security that are described in the report of our parent committee (NAS 1994), such as the interaction of WPu disposition with the future efforts to reduce nuclear arms and stem their spread. The panel takes note, however, of a number of important considerations outlined in the committee's 1994 report:
The presentation of numbers in this table to three- or four-digit precision should not be taken either as indicative of the actual accuracy of the calculations, which is generally less, or as suggesting that small differences in these values are important, which generally they are not: the largely illusory precision in Table 6-1 is maintained simply to facilitate consistency checks and to permit associating the values in the table with particular calculations in the literature. Nor should it be assumed that the presence in the table of reactors designed by particular manufacturers constitutes a preference by the panel for these manufacturers' designs in comparison to other manufacturers' designs of the same general type; unless otherwise noted, the purpose of this specificity is simply to associate the tabulated parameters with the particular design, fuel type, and operating mode for which they were calculated.