TABLE XI
PLUTONIUM RELEASE. RATES FROM PMC IN WATER
Power
Sample
PMC-142
PMT-113
PM-148-T
Wt
(W)
(g)
50
50
29
138
135
74
Dimensions (mm)
Height
Diam
5.5
5.5
3.7
Immersed
54.4
54.4
54.4
100 days after immersion. This is the earliest dis-
integration observed for any disk, and it should be
compared with 190 days for disk PMT-113 tested in
seawater at 10°C for 417 days. As did PMC disks
tested in seawater, this disk showed a preferential
release of molybdenum compared to plutonium,
which indicates that corrosion of the molybdenum
coating of individual pressed plutonium particles led
to its disintegration. It is surprising that an
accelerated plutonium release was not observed.
Despite the final decrease, the averagereleaserate is
the highest observed for a PMC disk. These data in-
Average
Days
548
417
326
Release Rate
Water
sea
sea
fresh
(uCi/m?-s)
10°C
10°C
10°C
2.3
7.0
15.6
1. In Seawater. The plutonium release rate from
the 2.5-W pellet HPZ-3 (Table XII) has remained at
20 nCi/m?-s for the last three months, followingits
earlier drop from a maximum of 69 nCi/m?-s rate
observed nine months ago. Duringthefirst 400 days
of immersion, its average release rate was fairly
linear at 54 to 75 nCi/m?-s, different from the
continually accelerating rates from PMC disks.
Since then, the rate has decreased slowly and
appears now to haveleveled off. Despite the lengthy
immersion, the pellet has not deteriorated visibly
pointing to the superior stability of PPO compared
to PMC.
dicate that freshwater corrosion of PMC disks
proceeds more rapidly than saltwater corrosion and
produces an average release rate slightly greater
than 12 uCi/m2-s.
The plutonium release rate from the 2.5-W pellet
HPZ-60-3, immersed in 37°C water typical of
tropical near-shore shallows, has averaged 2.9
E. PPO Dissolution or Release Rates.
second lowest rate from any 2“®8Pu fuel tested thus
nCi/m2-s for 544 days, practically unchanged from
last quarter’s average of 3.2 nCi/m2-s. This is the
These tests are to compare release rates from 2.5-
and 25-W PPO pellets in both fresh water and
seawater. Because of the remote chance that a heat
source may drop into a warm tidal pool, seawater
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Days of Immersion
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Fig. 6.
Plutonium release from PMC disks in
simulated seawater.
Fig. 7.
Plutonium release from a PMCdisk in fresh
water.
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13