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49
Fig. 4.
Radiation contours from a TLD grid abovesoil
in chamber containing fine material from
MHFT-12.
2
7
Fig. 3.
238Py in soil cores from chamber containing
large pieces from MHFT-12 (ng).
Weanalyzed eight soil cores from each ofthese
two chambers for plutonium. The results and core
locations are shown in Figs. 2 and 3. Bach core was
taken 25 cm from the central pile of fuel material.
Cores 1 and 2 were collected at the end ofthefirst
summer, cores 3 and 4 duringthefirst winter, cores 5
and 6 during the second summer, and cores 7 and 8
during the second winter. The top two or three sec-
tions of cores 3 and 4 in both of these chambers were
divided into two nearly equa! parts by a vertical cut.
Six of these half sections, as indicated in Figs. 2 and
3, were examined for particle size distribution and
agglomeration by LFE Environmental. The rest of
the half-sections were analyzed for plutonium. Zcros
indicated that less than 0.02 ng of plutonium was
found.
The datain Figs. 2 and 3 indicate that, in addition
to downward movement of plutonium through the
soil, there was surface movementto the right and
back of each chamber,the effect being greater in the
chamber containing the fine particles of fuel. This
movement was confirmed by a radiation contour
map (Fig. 4) of the y- and x-ray intensities in the
chambercontainingthe fine particles. An array of 17
thermoluminescent detectors (TLD’s) was placed 10
cm above the center of the tray containing the fine
material, one at each horizontal and vertical in-
tersection of the grid in Fig. 4, except for the 10-cm
tick marks. The intensities ranged from 0.3 R/h at
the front (lower) left corner to 8.8 R/h at the center.
If all the plutonium werestill concentrated at the
center of the tray, the contours would be circular.
Their deviation indicates that some of the
plutonium on the.surface has been moved toward
the back and to the right. This movement seems to
have been caused by water released from a gate
valve directly above core position 1 whenever
summer humid conditions prevailed and the valve
was opened to the building exhaust to provide air
flow when the chamber door was opened. (This artifact was eliminated in June 1975, by deflecting
the water away from the tray of soil.) The radiation
map measurements were confirmed by an
autoradiograph of the activity of the soil surface.
A seasonal effect was seen in three cores from the
chambercontainingthefine particles (Fig. 2). Cores
2, 4, and 6 all had higher plutonium concentrations
than cores 1, 3, and 5 becauseof the gate valve ar-
tifact mentioned above. Cores 2 and 6, however.
which werecollected in the summer,had higher concentrations than core 4, collected in the winter, and