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Evaluation Results cont'd - s3007cn10115
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Guidelines For Preparing Criticality Safety Evaluations at Department of Energy Non-Reactor Nuclear Facilities
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Evaluation Results cont'd - s3007cn10117


DOE-STD-3007-93
GB-18, thus flooding above a two-inch depth is precluded. The following conditions are thus
evaluated.
6.4.1 Normal Condition: There is clearly no criticality safety issue, due to favorable geometry,
for the columns or equipment containing supernate liquid from the R6 filter. Due to the large
spacings between these components, each column can be evaluated individually. Accordingly,
each 6" column is subcritical for concentrations up to about 2500 grams Pu/l, with one inch water
reflection, as referenced in figure 3.7 of TID-7016. Even with an additional 3 centimeters to
account for tolerances in diameter, each column is still subcritical for concentrations up to 1000
grams Pu/l. Since the maximum upset mass from section 6.5 is 6000 grams, concentrations
greater than 1000 grams Pu/l in each column are still subcritical, since the minimum subcritical
mass for concentrations greater than 1000 grams Pu/l is about 10.1 kg in a one inch water
reflected sphere, reference figure 3.5 of TID-7016. The R6 filter assembly is over two feet away
from the clarifier columns, thus it is also evaluated individually with a one-layer planar array of
three 2" pans loaded with precipitate from the R6. The 2" height of the R6 filter assembly, pans,
and used R6 filters is bound by an infinite 2" slab, which is, per figure 3.8 of TID-7016, subcritical
for all concentrations up to at least 5 kg Pu/l, even with one inch of water reflection. The 2" slab
also bounds any precipitate or materials which could be spilled onto the glovebox floor. The used
R6 filter media is very thin, i.e., <1/4" thick, and six of them would, together, be less than two
inches thick, even if folded up. Six used R6 filter media were evaluated, in the unlikely event that
two additional filters were present. Note that precipitate in pans is restricted to the approximate
height of each pan, though it is reasonable for small amounts to be slightly above the pan height as
a result of pan loading or handling. Fulflo filter FL-2434 with two used filter cartridges in contact
would have a cross sectional area equal to a 5.16 inch D cylinder, which is critically safe, as
referenced in TID-7016, for the small amount of fissionable material in the filters. Finally, the 1 -
liter pump is critically safe as referenced in LA- 10860, assuming a spherical volume.
It should be noted that a significant margin exists between the critical concentration for a 6"
diameter cylinder (reference TID-7016) and the maximum credible concentration available to
columns in the CWTS, i.e., > 1000 g Pu/l versus 150 g Pu/l. Note that concentrations in excess
of 150 Pu/l, though evaluated as an upset condition in paragraph 6.1.2.5 and 6.1.2.6, would notbe
credible in the columns, since liquids are verified as less than 25 g/l from the D-2401 A/B/C/D
tanks, thus any upset concentration would be detected. These significant margins are supportive
of the approach taken with interaction in the preceding paragraph.
Further review of criticality safety evaluation HD-20, "Precipitation and Calcination", also
substantiates the subcriticality of glovebox 18 components. In HD-20, KENO calculations for six
6" diameter by 72" precipitators, each directly above a stacked 3" filter boat and 1-3/8" catch
pan, arrayed circularly on 32" centers resulted in a k-effective of 0.8346 +/0.0062. In this case
200 g Pu/l solution was in each precipitator, 2.101 kg Pu/l was in each filter boat, and 4.708 kg
Pu/l was in each pan. This arrangement is clearly more reactive than that in glovebox 18, as there
was no spacing between precipitators and filter boat/pan combinations as there is between the
columns and R6 filter/pans in glovebox 18. Also, spacing between precipitators in HD-20 is,
overall, closer than that between columns in glovebox 18.
5-13


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