( in the PATAPSCO deck log for 10 March 1954. In order to estimate the cumulative gamma dose (D) over various time intervals (t,, to) as expressed by equation (1), t (1) f D a: 1 R, ‘ dt it is first necessary to evaluate the dose rate (R,) as a function of time. This is usually accomplished by defining a set of “unit reference dose rate" fallout deposition contours so that subsequent decay corrected dose rates can be expressed relative to these unit hour (t = H + 1) reference rates, (R,) according to the equation (2) R, == Ry t -1.2 . ‘Actually since the fallout is seldom if ever all down at H+1 hour at any location, and since the R, values must be based on the total cumulative deposition, Ry is a ficticious quantity defined and used to simplify computations. In practice R is calculated from dose rate measurements made at various locations and times from the relationship. (3) This R, = R is approximately valid, assuming 100% retention of bomb debris deposited on an infinite plane surface. All these gamma dose rates are defined for a point three feet above the surface and are proportionally reduced if some fraction of the radioactivity is removed by wind, rain or other decontamination, (2)