DNA 1240H-2 17.4 17.4.1. FIREBALL-PLUME-CLOUD RADIATION Introduction As noted in 17,33, for surface or very shallow underwater bursts, four components contribute sipnificantly to the total F.P.C. radiation” incident on a target. The relative contribution of each component depends primarily on the weapon type |! (The prompt, or fission-process, gomma rays are emitted within a fraction of a second after burst, and are irmored in this discussior since they are almost complictely absorbed by the bomb materials.) js brief review of the 4& components follows. Many of the prompt neutrons emitted in the fission or fusion process are slowed down and captured by the bomb materials. However, a sufficient number escape co that the resulting prompt neutron flux forms a significant direct contribution to F.P.C. radiation. In add- ition, gamma rays, resulting from inelastic scattering of neutrons and nitrogen-capture gamma rays also contribute sirpnificantly. These three components of F.P.C. radiation are all due to neutrons, and will re- sult only from surface or very shallow underwater bursts, since the prompt neutrons are completely absorbed by oa thin (about 3 ft) layer of water. The early-time tission-product gamma rays emitted during the first minute after detonation (once the bomb materials have vaporized) by the rapidly decaying radioactive fission fragments are the fourth significant component of F.P.c. 17,12, radiation. As noted in the fission products will be carried into the air and mixed with the water thrown up by a water-surface or underwater burst. Thus, F.P.C. radiation is also emitted by the fission products carried in the column, plumes, and cloud. Those characteristics of the above four F.P.C. radiations that affect their interaction with ships are discussed in this section, along with shipboard shielding iweinst F.P.C. radiation and available field-test dose and dose-rate data. Curves that may be used to estimate F.P.C. neutron dose vs distance ure presented, as well as curves for free-field F.P.C. ganuna dose. When both doses are expressed in rads they are additive. In the discussion of the interaction of the target ship with F.P.C. radiation, the effects of neutrons and gama rays are considered separately, since the two kinds of radiation differ in many respects. No method of calculating F.P.C. dose at shielded locations is presented, since no such method exists explicitly in current literature. Current information as to the effects of F.P.C. radiation on shipboard equipment will also be summarized. “Fireball-plume-cloud radiation is defined in 17. 3. 3. EGT AVAILABLE COPY eS 17-20 -- . rn a ee rn ts en et ee ee ereee ee