- 38 high temperatures needed for fusion, but in turn, the high neutron flux from fusion was used to fission more material. This is the fission-fusion-fission process and is used in the largest of current nuclear devices. The radioisotopes released to the environment by this process include those that are created by both fission and fusion. Because the hazard per unit of energy released is less for the fusion process than for the fission process the term "clean device" or “clean bomb" has become associated with devices or bombs using the fusion process. Actually a "clean device” is one in which the ratio of fission to fusion is at a minimun, i.e., as little fission as possible in order to keep to a minimum the hazard from radioisotopes released to the environment. A third source of radioisotopes in the sea is the waste disposed from the operation of nuclear reactors or from research and clinical laboratories. Little use 1s now being made of the oceans for disposal of radioactive wastes and, although the United States always may dispose of most of its waste by underground burial, necessity, future. other countries, by are expected to make use of the sea in the near Once the radioisotopes are deposited in the sea