1.76 x 108 Ja(t) Radiation from the deposited material Ip is determined by subdividing it into two components, viz, that due to deposits on the coracle decks Igq, and that due to deposits on the de- tector case Iy- ; thus, Ip = laa + lee Neglecting decay for the moment, the radiation intensity due to both deposited sources increases at a rate primarily determined by the terminal falling velocity V,, of the fallout material. Under the worst conditions, the radiation intensity due to material deposited on the detector case (which is a domed cylinder, see Figure 1.4) may be approximated by assuming a uniform deposition on a spherical shell surrounding the sensitive volume; thus, lac = Iplt) = Ialt) Vp (t- t) where Jp(t) is the radiation intensity deposited per unit area and (t—t,) is the time elapsed since the arrival of fallout. This approximation probably overestimates Ig. by a factor ranging between 1 and 2, since only the upper hemisphere is equivalent to the actual detector case, and the shorter radial distance and normal photon incidence over the lower hemisphere prob- ably overcompensates for the increased surface area of the cylinder. The radiation intensity due to the deck deposit was calculated from an expression developed in Reference 39 for a point above a smooth, uniformly contaminated plane: In(t) - laa = Zo f(z: (- Ham] +Ke an where x, is the slant range between the sensitive volume and the edge of a nonradiating disk whose center is a distance h below the sensitive volume. With a deck radius of 3.7 feet, this expression was evaluated at Idd = 0.55 Ip(t) = 0.55 Ja(t) Vp (t— te) As might be expected from its proximity to the sensitive volume, the deposition on the instrument case itself causes a greater instrument response than deposition on the coracle deck. Therefore, it appears more important to reduce deposition on the detector case than to shield the detector from the deck deposits. The total radiation due to deposited activity is: Ip = 1.55 Spit) = 1,55 Salt) Vp (t — ty) The radiation ly resulting from fallout material deposited in the surrounding water is estimated on the basis of Redwing data (Reference 40). For water surface bursts, the general behavior of that portion of fallout remaining near the ocean surface may be approximated by certain simple parameters. Assuming that these parameters also apply to subsurface detonations and assuming further that all fallout material remains in the surface laver, the maximum concentration of suspended fallout Jy(t) is approximated as follows: Jy (t) = Ta(t) Vp (t = ty) M where M is the depth of surface mixing. Redwing data (Reference 33) indicates that fallout reached a depth of 7 to 20 meters shortly after deposition in surface waters and, after cessation of fallout, settled to the thermocline at a rate of 2.6 m, hr. A value of 7 meters is there- 32