Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!dali.cs.montana.edu!uakari.primate.wisc.edu!sdd.hp.com!mips!apple!veritas!amdcad!amdcad!military
From: jfs@beno.CSS.GOV (Jim Scheimer)
Newsgroups: sci.military
Subject: Re: How is a nuke tested underground?
Summary: U.S. Testing Experience
Message-ID: <1991May9.064418.13758@amd.com>
Date: 8 May 91 21:33:10 GMT
References: <1991May8.034438.11095@amd.com>
Sender: military@amd.com
Organization: Advanced Micro Devices, Inc.
Lines: 42
Approved: military@amd.com


From: jfs@beno.CSS.GOV (Jim Scheimer)


Underground Nuclear Testing - Geologic Effects
	
	The question asked is unclear. If the question is whether there
is some widespread effect on seismic risk due to underground tests or
if such tests can trigger earthquakes at large distances (say, more
than a few tens of km.) , the short form answer is simply NO.

	However, (isn't there always an however?) when a test is
conducted in a region where there are pre-existing faults, the shock
from the test can trigger what is known as local tectonic strain
release. This is not a problem from an environmental sense, but it does
add some more energy to the seismic wave radiating from the vicinity of
the test and can add uncertainties to estimates of the yield of the
test based on seismic measurements.  Tectonic strain release has been
observed for both U.S. and Soviet underground tests. French tests are
conducted on an atoll which is not, apparently, heavily faulted. Also,
the nominal equivalent of the largest test allowed (150 kiloton yield)
is an earthquake of magnitude between 5.5 and 6.5. this means you don't
want it to be set off under you town, but it's no big shakes if it goes
off 30 or so km from you. (Sorry, I couldn't help the awful pun.)

Testing Procedures

	If the question is about procedures, we basically drill a large
diameter hole (about 2.5m to 3.5m in diameter) to a depth of several
hundred meters. The larger the expected yield, the deeper you bury it.
The depth also depends on material properties (e.g. rock types,
strengths, etc.).  The test canister is lowered in the hole with a
plethora of cables coming to the surface for diagnostics. The hole is
then filled with some of the original material removed during drilling
and a special epoxy grout is used for the last several 10's of meters.
The actual design of the emplacement and amount and type of grout is
the responsibility of the containment program at each weapons lab. The
bottom line is that we don't want to allow any "venting" of radioactive
material into the air.

Jim Scheimer, S-Cubed, Reston, Virginia.
My opinions only, don't hold anyone else responsible.