Chapter 3—Contatning Underground Nuclear Explosi
Figure 3-4—‘‘Typical’’ Stemming Plan
Cable tanouts
so that the grout and fines can seal betwe
Frequently, radiation detectorsare installed
plugs to monitor the post-shot flow of
through the stemming column.
CONTAINING HORIZONT
TUNNEL TESTS
Emplacement pipe
(if used)
Sanded
Plug
gypsum
concrete
.
Fines
Coarse
The containment of a horizontal tunne
different from the containmentofa vertical
test because the experimental apparatusis
to be recovered. In most tests, the object
allow direct radiation from a nuclear exp!
reach the experiment, but prevent the e
debris and fission products from destre
Therefore, the containment is designed
tasks: 1) to prevent the uncontrolled re
radioactive material into the atmosphere fi
safety, and 2) to prevent explosive deb
reaching the experimental test chamber.
Cabie gas blocks
Both types of horizontal tunneltests (eff
and cavity tests) use the same containment
of three redundant containment*‘vessels”’
(Plug to
true scale)
inside each other and are separated by plug
(Diagram not to scaie)
Typical stemming sequence of coarse material, fina material, and
sanded gypsum piug used by Lawrence Livermore National
Laboratory for vertical drill hole tests.
SOURCE: Modified from Lawrence Livermore National Laboratory.
Livermore test with six sanded gypsum concrete
3-5).23 Each vessel is designed to indep
contain the nuclear explosion, even if t
vessels fail. If, for example, gas leaks fron
into vessel [I, vessel IT has a volume large e
that the resulting gas temperatures and |
would be well within the limits that the |
designed to withstand. The vessels are org:
follows:
plugs.?? The plugs have two purposes: 1) to impede
Vessel I is designed to protect the expenn
preventing damage to the equipmentandallc
to be recovered.
gas flow, and 2) to serve as structural platformsthat
prevent the stemming from falling out if only a
partial collapse occurs. Under each plugis a layer of
Vessel II is designed to protect the tunnel
sand-size fine material. The sand provides a base for
so that it can be reused evenif vessel | fails
experimental equipmentis lost.
the plug. Alternating between the plugs and the
fines, coarse gravel is used to fill in the rest of the
stemming. The typical repeating pattern used for
stemming by Los ALamos, for example,is 50 feet of
gravel, 10 feet of sand, and a plug.
All the diagnostic cables from the nuclear device
are blocked to prevent gas from finding a pathway
through the cables and traveling to the surface. Cable
fan-out zones physically separate the cables at plugs
Vessel III is designed purely for conta
such that even if the experimental equipmer
and the tunnel system contaminated, rad
material will not escape to the atmosphere.
In addition to the three containmentves:
is a gas Seal doorat the entrance of the tunn
that serves as an additional safety measure
seal door is closed prior to detonation ant
22Although Livermore and Los Alamos use the samegeneral stemmung philosophy, there are some differences: For example. Livermor
gypsum concrete plugs while Los Alamos uses plugs made of epoxy. Also, Livermore uses an emplacementpipe for lowering the device doy
Los Alamos lowers the device and diagnostic canmuster on a wire rope harmess.
23S¢e ch. 2 for a discussion oftypes of nuclear tests.