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5.0 DISCUSSION OF CONTINGENCIES
There are two criticality scenarios associated with the use of Capture Coating &
InstaCote material to remove surface contamination from a glovebox and ancillary
equipment, which can be shown to meet the requirements of the double contingency
principle.
Scenario #1: Either 520 grams of Pu in a compact or spherical homogeneous aqueous
mixture which is optimally moderated and fully reflected by water (indirectly via
Reference 2), or 270 grams of Pu in a compact or spherical homogeneous mixture of Capture
Coating & InstaCote (i.e., InstaCote) material which is optimally moderated and fully
reflected by water.
|
Upset Condition |
| 1 |
270 grams of fissile material accumulate in the
Capture Coating & InstaCote material |
|
Barrier |
| 1.1. |
Assay scans will be performed prior to the use
of stripcoat within the glovebox. Assay scans must show that at the upper 95% confidence
level for the measurement, there is less than 200 grams of fissile material in the
glovebox if the entire box is to have the stripcoat applied and removed. |
| 1.2. |
If Assay scans indicate greater than 200 grams
of fissile material are present inside a glovebox, then only a section of
stripcoat, which
would contain a maximum of 200 grams fissile material, may be removed at a time. The
allowable area of stripcoat can be determined from areal density assay data. |
| 2 |
Material forming an optimally moderated, compact
shape |
| 2.1. |
Controls restrict geometric volume to 4 liters
or less. Restriction to 4 liters or less in volume precludes the formation of the
necessary volume for criticality. A Pu mass of 520 grams will be critical if it is
homogeneously mixed with water in an approximately 17-liter spherical shape (12.5 inch
diameter) and fully reflected with water. A Pu-239 mass of 270 grams will be critical if
it is homogeneously mixed with InstaCote material in an approximately 6-liter spherical
shape (8.9-inch diameter) and fully reflected with water, but realistic isotopic mixtures
of RFETS plutonium would still be subcritical by greater than 2 percent. |
Scenario #2: Two 4-liter containers of 1.629-g/cc Capture Coating &
InstaCote containing 200 gram of fissile material (specifically plutonium).
|
Upset Condition |
| 1 |
Two 200-gram, 4-liter containers of 1.629-g/cc
Capture Coating & InstaCote are collected without the first of the two containers
being removed from the area before the second is filled. |
|
Barrier |
| 1.1. |
Administrative procedures and posted controls
require removal of 200 grams of accumulated stripcoat prior to generating/accumulating a
second batch. |
| 1.2. |
Controls restrict individual
geometric volumes to 4 liters or less. Restriction to 4 liters or less in volume precludes
the formation of the necessary volume for criticality in one container. A Pu mass of 520
grams homogeneously mixed with water in an approximately 17-liter spherical shape (12.5
inch diameter) and fully reflected with water will be critical. A Pu-239 mass of 270 grams
homogeneously mixed with InstaCote material in an approximately 6-liter spherical shape
(8.9-inch diameter) and fully reflected with water will be critical, also, but realistic
isotopic mixtures of RFETS plutonium would still be subcritical by greater than 2 percent.
Two 4-liter cylindrical volumes (adjacent to each other and without the presence of a
container) each having their height equal to their diameter and each containing a Pu-239
mass of 200 grams homogeneously mixed with InstaCote material will be slightly
supercritical (see Table 1, Case E); however, this scenario is unrealistic--the same two
volumes having 200 grams of the most reactive RFETS plutonium isotopic mixture, i.e., the
RFRAG mixture, would be subcritical by approximately 4 percent. |
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