periods each last 6 months. The experiment in the
TABLE II
chamber containing MHFT-27 was terminated (see
Section J1.D.2). Two additional chamber experiments were started underarid winter conditions
(3 to 28°C, 21 to 87% RH). Three other experiments
were started under humid winter conditions. All
seven
current chamber
TERRESTRIAL ENVIRONMENTAL CHAMBER EXPERIMENTS
Experiment
Number
experiments are now
operating under summer conditons, two in arid
summer weather (26 to 53°C, 7 to 33% RH), the
other five under humid conditions.
The fuel material sample was placed in the center
of the tray on the soil surface. Each sample under
humid conditions received a 3-cm rain once a week.
Therainsfor arid conditions occurred approximately
once a month during the winter. There have been no
1
MHFT-12 chunks on loam:
6-21-73
2A
MHFT-23 in GIS on sand;
humid climate
6-10-75
3
MHFT-12 fines on loam;
humid climate
9-27-73
6
MHFT-50 fines on loam:
circular soil partitioner;
humid climate
4-9-75
7
MHFT-27 fines on sand;
arid climate
2-25-75
8
MHFT-50 chunks on loam:
circular soil partitioner;
humid climate
4-9-75
MHFT-27 chunks on sand;
arid climate
2-26-75
humid climate
rains during the first three months of arid summer.
The rainwater that percolates through the soil is
analyzed for plutonium. The condensate from the
refrigeration-type dehumidifier in the chamberconditioning system is also analyzed to get a relative indication of the airborne plutonium in the chamber.
Core samples of the soil are collected at approximately 6-monthintervals. Each core is divided
into 5 to 14 sections that are analyzed separately to
determine the plutonium variation with depth in the
soil.
Smail air samplers, fitted with approximately 40-
mm-diam filter papers, were operated several times
in two chambers to measure the airborne plutonium.
The filter papers were changed frequently during
operation, and the plutonium was measured by
counting the papers and in somecasesbydissolving
them and scintillation-counting the resultant
solutions.
Time-lapse movies were taken in four chambers
during rains. Emissions from some fuel samples were
studied by time exposure photographs, withoutex-
Date
Started
Description
10
Photographsof the emissions from the large pieces ©
in the near-ir, visible, and near-uv spectral regions
showed that the external temperature of the pieces
was 250 to 300°C, and that an air glow around them
was emitted mainly in the visible region, although
some of it may have been uv. This air glow was
probably caused byionization of air by the alpha or
gamma activity of the pieces.
Plutonium airborne concentrations increase during periods of rain on the large pieces. This effect
results in a greater plutonium pickup from theair by
the dehumidifier, which can be measured by
plutonium analyses in the dehumidifier condensates
Analyses for a period of 2 months are shownin Fig. 1.
The explanation seems to be that material spalls
from the hot pieces of PPO because of thermal shock
when the cold rain first hits them. Spallation has
ternal lighting, in the near-ir, visible, and near-uv
marized in Table I.
1. MHFT-12. This was a PPOtest sphere for the
Multi-Hundred Watt (MHW) program which
shattered during a simulated reentry and impact.
The sphere fragments were removed from the container andsorted by size. The pieces with diameters
greater than 6 mm, weighing 224 g, were placed in
one environmental test chamber on June 21, 1973,
and 28 g of 0.01- to 6-mm-diam material was placed
in another on September 28, 1973. These experiments are now in their third summerin a humid
environment.
&
rT
—_-
7 ©
i
Pu in Condensate (ng/day)
periments are currently under way. They are sum-
NEDO OH A a1
D. Test Samples and Results
Seven terrestrial environmental chamber ex-
PE
J
y
1
}
i
J
“T
q
Diagonallines indicate periods cf
i
ceilection in which relas cccurrad
sk USS
regions of the spectrum.
20
«25
30.35
Fig. 1.
Effect of rain on plutonium content of
dehumidifier condensates.
1
5