Page:Operation Crossroads 1946.pdf/33

 the device and the time that elapsed between detonation and instrument recovery; the nearer in space or time to the detonation, the greater the potential for exposure.

Systems Response Experiments

To document the response of systems to the hostile environment, military hardware (aircraft parts, ammunition, radar, petroleum, tanks, field stoves, clothing, and medical equipment) was exposed to nuclear detonation effects. Techniques used for these experiments were conceptually simple: exposure of the system of interest and observation of its response. Actual conduct of the experiments was far more complex. The level of threat to which the system was exposed almost always required measurement to properly understand the response, necessitating an environmental experiment along with each systems response experiment. It was often not enough to know whether the system survived, but rather what the effects were on the component parts and their interactions. This required the placement of extensive instrumentation and recording devices throughout the test area.

While the potential radiological exposure of personnel during these systems response experiments was governed primarily by the proximity of personnel in space or time to the detonation, an additional problem arose. Often, when the exposed object was recovered for closer examination, it could be contaminated by device debris or even be radioactive itself due to neutron activation. Personnel recovering or handling such objects could be exposed to radiation. For this reason, reboarding parties who inspected vessels, aircraft, and equipment after such detonation were given published guidelines and radsafe instructions (see Appendix B).

MARSHALL ISLANDS SETTING

The Marshall Islands are in the easternmost part of the area known as Micronesia ("tiny islands"). The Marshalls are spread over 770 thousand mi² (2 million km²) of the Earth's surface, but of this area only about 70 km² (180 km²) is land. Two parallel chains form the islands: Ratak (or Sunrise) to the east, and Ralik (or Sunset) to the west; Bikini is in the Ralik chain at its northern extreme. Figure 1 shows these islands in the Central Pacific; Figure 2 is a map of Bikini Atoll.

A typical atoll, Bikini is a coral cap set on truncated, submerged volcanic peaks that rise to considerable heights from the ocean floor. It consists of 27 small islands that encircle a broad lagoon 25 miles (40.2 km) long and 15 miles (24.1 km) wide, with a maximum depth of about 200 feet (61 meters). The dry land area, 2.72 mi² (7 km²), is covered with low, scrubby brush and coconut and pandanus trees. The land area is concentrated in the eastern islands, from Bikini to Eneu Islands, which form about 53 percent of the land total, with 24 percent taken up by the southern section of Enidrik to Berokoj.

Climate is tropical marine, generally warm and humid. Temperature changes are slight, ranging from 70° to 90°F (21° to 32°C). Rainfall is moderate, and prolonged drought may occur. North of the atoll is open ocean for a thousand miles, the only inhabited island being Wake. East of Bikini are

28