Table 5 Summary of Criticality Safety Envelope for dissolution

DOE-STD-3007-93

The envelope of criticality safety for dissolution of the EBR-II bundle and the TRR bundles is

summarized in Table 5, based on consideration of the nine criticality control parameters (fissile

mass, moderation, geometry, spacing, concentration / fissile density, neutron absorption,

enrichment, reflection, and temperature). Table 5 lists the bounding assumptions (BA) and

criticality safety limits (CSL) for the nine criticality control parameters. Since the average

equivalent enrichments of the EBR-II and TRR materials are both so low (0.77 % and 0.79 %;

respectively), the restrictions that had to be assumed in the criticality safety evaluation (Section 6)

are minimal: no limits were assumed on the moderation, spacing, neutron absorbers, reflection, or

temperature. The fissile mass and the enrichment are controlled only in the sense that the items

allowed to be loaded into the dissolver are restricted to the specified EBR-II bundle and TRR

bundles. The concentration / fissile density is controlled two ways: (1) The beginning of the first

batch will contain 5 0.1 gram fissile per liter in the jet heel after the last rinse just prior to the first

batch. This limit only applies if the enrichment of the materials in the previous dissolution

campaign > 0.9635 %.

Table 5

Summary of Criticality Safety Envelope for dissolution

Of EBR-II bundle and TRR Bundles

Criticality Control

Bounding Assumption (BA)

Criticality Safety Limit

Parameter

(CSL)

Fissile Mass

Unrestricted, except that only the

TRR bundles and EBR-II bundle

may be loaded into the dissolver.

Moderation

Unrestricted

Geometry

Fuel rods are unrestricted.

Annular dissolver geometry is

assumed.

Spacing

Unrestricted

Concentration, Fissile Density

Fuel rods are unrestricted.

Nitric acid concentration is high

enough in the dissolver to prevent

Pu polymerization. Must be

< 0.1 g fissile/liter in jet heel after

last rinse prior to first batch.

Absorbers

Unrestricted

Enrichment

Uranium is depleted (EBR-II

bundle) or is natural (TRR

bundles), since only the TRR

bundles and EBR-II bundle may

be loaded into the dissolver.

Reflection

Unrestricted

Temperature

Unrestricted

6-11