16 © The Containment of Underground Nuclear Explosions Figure 2-2—Nevada Test Site r! idaho Rainier Tonopah SOURCE: Modified from Department of Energy. DOEcontractors and other agencies involved in Nevada Operations. Mercury contains a limited amountof housing for test site personnel and other ground support facilities. Near the center of the test site, overlooking Frenchman Flat to the South and Yucca Flatto the North, is the Control Point (CP). The CP is the command headquarters for testing activities and is the location from which ali tests are detonated and monitored. Frenchman Flat is the location of the first nuclear test at the test site. A total of 14 atmospheric tests occurred on Frenchman Flat between 1951 and 1962. Mostof these tests were designed to determine the effects of nuclear explosions on structures and military objects. The area was chosen for its flat terrain which permitted good photography of detonations and fireballs. Also, 10 tests were conducted underground at Frenchman Flat between 1965 and 1971. Frenchman Flat is no longer used as a location for testing. The presence of carbonate material makesthe area less suitable for undergroundtesting than other locations on thetestsite. !? Yucca Flat is where most undergroundtests occur today. These tests are conducted in vertical drill holes up to 10 feet in diameter and from 600 ft to more than 1 mile deep.It is a valley 10 by 20 miles extending north from the CP. Tests up to about 300 kilotons in yield have been detonated beneath Yucca '9During an explosion, carbonate material can form carbon dioxide which, under pressure, can cause venting.