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.