blast. This bubble may break the surface depending on how much energy is dispersed and the depth of the nuclear device. The bubble displaces large amounts of water that then collapses in on the bubble after all the energy is expended. The water collapsing in on the cavity is called the "radioactive pool" and has the highest concentration of radioactive material. Many different projects were put in place to test the two underwater blasts. Wave generation, hydrodynamic variables, and energy released were all studied using multiple sensors. These sensors were placed in multiple areas such as target ships and floating balloons. Oceanographic, seismographic and hydrographic surveys were completed after each nuclear blast. A project that used a nuclear blast to clear minefields was studied using the Umbrella blast. One hundred and twenty inert mines were placed at different distances ranging from . These mines were then picked out of the water to study the effects of the blast at each interval. Radiation preparations Another reason for underwater tests was to detect radiation contamination of ships after an underwater nuclear explosion. This meant that the contaminated ships required unique "radsafe" preparations so that the data could be quickly accounted for. After the data on the damage and radiation was recorded, the ships needed decontamination work completed before repairs could be completed. The Radiological and Decontamination Unit consisting of 200 enlisted and one officer was created for the task of decontamination. After decontamination, the target ships were repaired for use in a second underwater nuclear weapons test. The amount of radiation exposure was debated for the safety of the crews. Roentgens ( = ca 0,01 Gy in soft tissue) were used to gauge the gamma radiation that affected the units working on the nuclear tests. For the underwater test crew, a limit of per blast along with per operation was referenced as the limit for exposure. These initial limits were rejected and maximum permissible exposure standards (MPE) were solidified by commanders for the crews working on the decontamination unit. Due to the fast recovery of ships, high contamination values were expected by commanders and set the standard to four roentgens per hour (R/hr). An excess of was designated off limits of recovery units. Personnel were given special breathing equipment to work in the interior of ships with an R/hr higher than one. High numbers of personnel working the tests were used to