explosive energy from the fusion, or joining, of hydrogen atoms. These explosive devices were developed by the AEC, the civilian agency authorized to perform this activity by the Atomic Energy Act of 1946. The devices were tested at the PPG by a joint military and civilian organization designated as Joint Task Force 7 (JTF 7). This was a military organization in form, but was populated by military, civil service and contractor personnel of the Department of Defense (DOD) and AEC. The commander of this force was the appointed representative of the AEC and reported also to the Joint Chiefs of Staff (JCS) and the Commander in Chief, Pacific (CINCPAC). The peak DOD numerical strength of CASTLE was approximately as follows: Uniformed military DOD civil service DOD contractors Total personnel 9,800 250 60 10, 110 Numerous technical experiments were carried out in conjunction with each of the six detonations. These experiments measured the power and efficiency of the devices and attempted to gauge the military effects of the explosions. DOD personnel participated in this test operation as individuals whose duty stations were at the AEC design laboratories, as units performing separate experiments, and as units performing various support roles. The CASTLE operations placed almost all of the Navy support group at Bikini, where its ships provided living space for personnel who were evacuated from the islands for the first test and then could not return to live there because of the potential radiation exposure. An extensive radiological safety program was instituted wnose objectives were: 1. Maintenance of personnel radiation exposure at the lowest possible level consistent with medical knowledge of radiation effects and the importance of the test series. 2. Avoidance shipping. of inadvertant contamination of populated islands or transient The program established an organization to provide radiological safety (radsafe) expertise and services to the separate components of the task force who were responsible for personnel safety within their commands. Personnel were trained in radiological safety and standards governing maximum permissible exposures (MPE) were established. Film badges were provided to a large portion of the participating personnel. Persons likely to be exposed to radiation were badged as well as a representative group of the remainder. An extensive weather forecasting group was established fallout. in order to predict wind directions and areas of potential Personnel were evacuated from danger areas before each detonation, and reentry to contaminated areas was restricted to the personnel required to retrieve important data. amount of radiation exposure for these personnel was monitored. The TEST ‘OPERATIONS AND EXPOSURES The first event of this series, designated BRAVO, had a yield of 15 MT and was the largest device ever detonated in atmospheric nuclear testing by the U.S. Government. Significantly exceeding its expected yield, BRAVO, detonated at Bikini Atoll, released large quantities of radioactive materials into the atmosphere, which were caught up in winds that spread the particles over a much larger area than anticipated. This resulted in the contamination and exposure of some individuals either stationed or residing on distant atolls or aboard various vessels. Acute radiation effects were observed among some of these people. A limited number of JTF 7 personnel] received radiation exposures considerably in excess of the initially established CASTLE MPE. This operational limit was established at 3.9 roentgens (R) gamma within.any 13-week period of the operation. In particular, three members of the U.S. Navy Bikini Boat Pool had heavily exposed badges with readings from 85 to $6 R, and 28 Army and Air Force personne] had film badge exposures that read as high as 78 R. All these men were medically evaluated at Kwajalein. Subsequently, follow-up on 29 of them was done at