Analysis for No Uranium in Solution cont'd

DOE-STD-3007-93

There are three events related to the EBR/TRR dissolution which require special consideration for

criticality safety. These events are: 1) the EBR-II bundle falling over in the dissolver, 2) a

missing insert, and 3) double batching. It is shown below that none of these events can lead to a

criticality.

Since the EBR-II bundle will not be placed into an insert in the inner annulus of the dissolver,

there is no control to prevent it from falling over in the dissolver toward one of the Mark-42/TRR

inserts containing TRR fuel, especially during dissolution of the bundle aluminum during the

NaOH strike. Though the flat bottom of the EBR-II bundle could make it unlikely that the bundle

would fall over, the annular geometry of the dissolver and the diameter of the EBR-II bundle

would make it possible for the top of the EBR-II bundle to fall against one of the Mark 12/TRR

inserts. To bracket this possibility, let us assume that the EBR-II bundle DU006 were, in some

unspecified way, to come into a close parallel orientation to the Mark-42/TRR insert containing

six TRR rods, each containing the maximum amount of Pu-239. According to Table 3, the

equivalent U-235 content of the combined EBR-II bundle and six TRR rods would be 2.21 kg +

3.26 kg = 5.47 kg. The equivalent U-235 enrichment would be 5.47 / (320.9 + 285) = 0.90 %.

The 5.47 kg equivalent U-235 is much below the appropriate 13.1 kg limit for < 1.0 %

enrichment, so that criticality can not occur under any condition with this low fissile content and

low enrichment.

An insert may not be present in one of the dissolver ports when it is required. It should be noted

that if the insert is not present in the dissolver port, then it would be very difficult for the crane

operator to lower six TRR bundles into the port without the inserts to guide them. But if six TRR

bundles could be inserted into the port even though the Mark-42/TRR insert is not present, they

could fall over toward one of the other inserts containing TRR rods. If the EBR-II bundle also

falls (there are no controls against this) toward the same insert, then according to Table 3, the

total equivalent U-235 content (for the maximum plutonium case) could be up to 3.26 + 3.26 +

2.29 = 8.81 kg, which is less than the 10 kg limit for < 1.01 % enriched material. This condition

will therefore be critically safe.

Double batching of materials into the same port may take place. The worst hypothetical double

batching event is to place 12 TRR rods into a Mark-42/TRR insert, instead of 6 TRR rods.

Though this may not be possible due to spacing constraints, it is simply assumed to occur for this

argument. According to Table 3, the equivalent U-235 loading of this insert (for the maximum

plutonium case) would be 3.26 + 3.26 = 6.52 kg. If the EBR-II bundle were to also fall over

toward this double-batched Mark-42/TRR insert, the total loading of the combination would be

6.52 + 2.29 = 8.81 kg, the same value as for the above case. Therefore, this condition will also be

critically safe for the same reason.

Even if there is a missing insert and a double batching at the same time, there will still not be a

criticality. For example, if 12 TRR bundles (doubling batching) were loaded into a port with the

insert missing, then they could fall toward an insert containing 6 TRR rods. If the EBR-II bundle

also fell toward the same insert, then the EBR-II bundle could be assumed to be next to 18 TRR

rods. If these 18 TRR rods are assumed to contain an average amount of plutonium, then the

total equivalent U-235 loading in this configuration, based on the values in Table 3, would be (3 x

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