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Table 5 Summary of Criticality Safety Envelope for dissolution
Guidelines For Preparing Criticality Safety Evaluations at Department of Energy Non-Reactor Nuclear Facilities
Second Defense

And, (2) the nitric acid concentration in the dissolver will be maintained high enough to prevent
plutonium in solution from polymerizing. The geometry is assumed to be that of the annular
dissolver. Since the EBR-II bundle will not be placed into an insert, there is no geometry control
to prevent it from falling over in the dissolver. This is an allowed condition, and is shown to be
critically safe in Sections 6.2 and 6.3. Process changes (initiating events) which can challenge the
criticality safety of the EBR/TRR dissolution can only come from exceeding or violating the
assumptions / limits in Table 5. Based on these assumptions and limits, only three process
changes can challenge criticality safety. These possible initiating events are:
IE #1. Other than the intended EBR-II and TRR material could, by mistake, be loaded into the
IE #2. The dissolver solution may not be maintained sufficiently acidic. This could cause a local
concentration of plutonium to build up due to polymerization of the plutonium in the
dissolver solution.
Initiating events IE #1 and IE #2 are common to the previous campaign which dissolved
only TRR rods, i.e. the presence of one EBR-II bundle does not make these initiating
events more severe than they were in the TRR campaign. This means that the double
contingency analysis (DCA) for these initiating events for the EBR/TRR dissolution is
already covered by the DCA for dissolution of only TRR rods, which is given in Ref. 2.
By adopting the administrative controls from the TRR dissolution for the EBR/TRR
dissolution, the results of a DCA for the above two initiating events will automatically be
incorporated into the administrative controls for the EBR/TRR dissolution. Therefore,
there is no need to repeat that documentation here.
IE #3. The dissolver solution at the start of the first EBR/TRR batch could already contain
significant (defined below) fissile material, at a significant fissile enrichment (> 0.9635 %),
from the previous dissolver campaign. This initiating event only applies if the enrichment
of the materials in the previous dissolution campaign > 0.9635 %, i.e. was plutonium
without uranium.
As shown in Section 6.3, initial dissolver solutions containing fissile enrichments
< 0.9635 % can only decrease the dissolver K-eff, so that there are no additional criticality
safety requirements for these low enriched (E < 0.9635 %) solutions. But it is also
possible for the fissile enrichment of the initial dissolver solution to be > 0.9635 %. For
example, this may be due to the previous dissolution of the sand, slag, and crucible
(SS&C) material that contains plutonium but no uranium. If the fissile enrichment is
above 0.9635 % in the dissolver solution just prior to the first batch, then sampling must
be done to prove that the amount of fissile material in solution is insignificant. Since an
average equivalent U-235 loading for the first batch will be approximately 8.03 kg (Table
4), a value of 0.01 kg = 10 grams fissile in solution will have a very insignificant effect on
the dissolver K-eff. 10 grams of fissile material in solution thus qualifies as an
"insignificant amount". Therefore, if E > 0.9635 %, then during the last rinse after the
previous dissolution campaign, and before loading the first batch for the EBR/TRR

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