Chapter 3—Containing Underground Nuclear Explosior Figure 3-6—Vessel| point room, a muffler, a modified auxiliary (MAC), a gas Seal auxiliary closure (GSAC) Vessel 1 tunnel and pipe seal (TAPS). All these closu End of stemming ag pe Mechanical closurg Working point Mechanica! closure (MAC) M “re echanica closure “#— Bypass drift eg LOS rift Test chamber End of stemming (GSAC) Key: GSAC =gas seal auxiliary closure; MAC = moditied auxiliary closure; TAPS =Tunnel and pipe seal The HLOS Vessel | is designed to protect the experimental equipment after allowing radiation to travel down the pipe. SOURCE: Modified trom Defense Nuclear Agency. the test chamber.*4 The entire pipe is vacuum pumpedto simulate the conditions of space and to minimize the attenuation of radiation. The bypass drift (an access tunnel). located next to the line of sight pipe, is created to provide access to the closures and to different parts of the tunnel system. These drifts allow for the nuclear device to be placed in the zero room and for late-time emplacement of test equipment. After the device has been emplaced at the working point, the bypass drift is completely filled with grout. After the experiment, parts of the bypass drift will be reexcavated to permit access to the tunnel system to recoverthe pipe and experimental equipment. The area around the HLOSpipe is also filled with grout, leaving only the HLOS pipe as a clear pathway between the explosion and the test chamber. Near the explosion, grout with properties similar to the surrounding rock is used so as notto interfere with the formation of the stress containmentcage. Near the end of the pipe strong grout or concrete is used to support the pipe and closures. In between, the stemming is filled with super-lean grout designed to flow under moderate stress. The super-lean grout is designed to fill in and effectively plug any fractures that may form as the ground shock collapses the pipe and creates a stemming plug. Asillustrated in figure 3-6, the principal components of an HLOS pipe system include a working 24On occasion, the diameter of the pipe has increased 10 20 feet installed primarily to protect the experimenta. ment. The closures are designed to shut off t after the radiation created by the explosi traveled down to the test chamber, but material from the blast can fly down the pi destroy the equipment. The working point room is a box desig house the nuclear device. The muffler is pandedregion of the HLOSpipe thatis desi; reduce flow down the pipe by allowing ex] and creating turbulence and stagnation. The (figure 3-7(a)) is a heavy steel housing thatc two 12-inch-thick forged-aluminum doors d to close openings up to 84 inches in diamet doors are installed opposite each other, perp lar to the pipe. The doors are shut by high p gas that is triggered at the time of detc Although the doors close completely with seconds (overlapping so that each door f tunnel), in half that time they have metin the and obscure the pipe. The GSACis similai MACexceptthatit is designed to providea g: closure. The TAPS closure weighs 40 tons | design (figure 3-7(b)) resembles a largetoil The door, which weighs up to 9 tons, is hinge: top edge and held in the horizontal (open) p Whenthe dooris released, it swings down by and slams shut in about 0.75 seconds. Any f remaining in the pipe pusheson the door mal seal tighter. The MAC and GSAC will wi pressures up to 10,000 pounds per square in TAPSis designed to withstand pressures up | pounds per square inch, and temperature: 1,000 °F. Whenthe explosion is detonated radiatior down the HLOS pipe at the speed of lig containmentprocess(figure 3-8(a-e). trigger time of detonation, occurs in the following s: to protect experimental equipment and radioactive material produced by the explos e After 0.03 seconds (b), the cavity create explosion expands and the shock wav: away from the working point and apf the MAC. The shock wave collapses 1 squeezing it shut, and forms a st **plug.’* Both the MAC and the GSAC