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Burial depth required will vary with somewhere between the
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of 55 feet,
After four months the peak activity measured
along a line at the level of the zero point was 800 mr/hour, while
along a line aimed at a point 50 feet below zero from a point 210
feet away horizontally the peak was 40 r/hour, Outside of the shell
the activity as measured by a counter was indistinguishable from
background. Peak temperature along the horizontal line was 45°C,
along the other line it was 65°, Diffusion appears to have carried
elevated temperature into the zero point, and sorne rise above ambient
is also noted out to about 70 feet,
Thus a 55-foot radius hole appears to have been established
momentarily but then to have collapsed, and the falling in appears
to have continued up to a point 400feet above zero, where a hole 25
feet iniradius and 25 feet high was discovered in drilling. This hole
contained gaseous fission products at the same concentration as they
appear inSide the 55-foot radius region around zero, so the entire
volume in between appears to be simply connected.
This accounts
for only a few percent of the gaseous fission products, and it is
thought that the remainder were trapped in the resolidification of the
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solid fission products are contained in a shell a few feet thick at a
radius
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Exploration of the region around the zero point by drilling
in from the tunnel at a distance of 210 feet has revealed that the
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region accessible without drilling. The horizontal access tunnel,
1700 feet long from the portal, showed some slabbing and cavein
for several hundred feet beyond the point where it was blocked.
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activity is not merely absence of a radioactive cloud at several
hundred miles, but of any radioactivity above ground or in any other
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No activity above background was discernable either above the
ground or in the tunnel leading to the explosion chamber, which was
blocked off only 200 feet from the shot site. Thus the absence of
ams
(W in KT).
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1/3 and 1/4 power of the yield; a reasonable formula is 400 W ©-3 feet
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One could expect to contain the shot completely without
venting by using as little as 500 feet distance to the surface if
more disturbance of the surface were allowed; such disturbance
would still not be characteristic of an explosion rather than an earth-
:
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needed before any such difference could be established.)
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and that this might be ascertained by examination of the ground around
the event and by questioning of the local population, if any, but extensive experience in the local effects of underground shots would be