a sample are known, then all emitted particle or photon properties of the mixture can be computed. If, in addition, calibrated radiation detectors are available, then the effects of the sample emissions in those instruments may also be computed and compared with experiment. Fi- nally, air-ionization or dose rates may be derived for this mixture under specified geometrical conditions and concentrations. In the calculations to follow, quantity of sample is expressed in time-invariant fissions, i.e., the number of device fissions responsible for the gross activity observed; diagnostically, the quantity is based on radiochemically assayed Mo” and a fission yield of 6.1 percent. This nuclide, therefore, becomes the fission indicator for any device and any fallout or cloud sample. The computation for slow-neutron fission of U**, as given in Reference 41, is taken as the reference fission model; hence, any R®%(x) values in the samples differing from unity, aside from experi- mental uncertainty, represent the combined effects of fission kind and fractionation, and necessitate modification of the reference modelif it is to be used as a basis for computing radiation properties of other fission-product compositions. (An R-value may be defined as the ratio of the amount of nuclide x observed to the amount expected for a given number of reference fissions. The notation R°*(x) means the R-value of mass number x referred to mass number99. ) Two laboratory instruments are considered: the doghouse counter employing a 1-inchdiameter-by-1-inch-thick Nal(T1) crystal detector, and the continuous-flow proportional beta counter (Section 2.2). The first was selected because the decay rates of many intact OCC collections and all cloud samples were measuredin this instrument; the second, because of the desirability of checking calculated decay rates independent of gamma-ray decay schemes. Although decay data were obtained on the 4-7 gamma ionization chamber, response curves (Reference 42) were not included in the calculations. However, the calculations madein this section are generally consistent with the data presented in Reference 42. The data obtained are listed in Table B.26. 3.4.2 Activities and Decay Schemes. The activities or disintegration rates of fission products for 10‘ fissions were taken from Reference 41; the disintegration rates are used where a ‘Fadioactive disintegration is any spontaneous change in a nuclide. Other kinds of activities are qualified, e.g., beta activity. (See Section 3.4.4.) Those of induced products of interest were computed for 104 fissions and a product/fission ratio of 1, that is, for 10‘ initial atoms (Refer- ence 43), ~ Pyrepublication results of a study of the most-important remaining nuclear constants—the decay schemes of these nuclides—are contained in References 42 and 44. The proposed Schemes, which provide gammaand X-ray photon energies and frequencies per disintegration, include all fission products known up to as early as ~45 minutes, as well as most of the induced Products required. All of the following calculations are, therefore, limited to the starting time ‘Mentioned and are arbitrarily terminated at 301 days. 3.4.3 Instrument Response and Air-Ionization Factors. A theoretical response curve for the doghouse counter, based on a few calibrating nuclides, led to the expected counts/disintegration iat each fission and induced product as a function of time, for a point-source geometry and 10‘ , 58ions or initial atoms (Reference 43). The condensed decay schemes of the remaining induced - Miclides were also included. To save time, the photons emitted from each nuclide were sorted “tato Standardized energy increments, 21 of equal logarithmic width comprising the scale from .& kev to 3.25 Mev. The response was actually computed for the average energy of each increent, which in general led to errors no greater than ~ 10 percent. > ae Counting rates expected in the beta counter were obtained from application of the physical1,&ometry factor to the theoretical total-beta and positron activity of the sample. With a rey_mnse curve essentially flat to beta Emax over a reasonably wide range of energies, it was not peessary to derive the response to each nuclide and sum forthe total. Because the samples _ ete essentially weightless point sources, supported and covered by 0.80 mg/cm?ofpliofilm, Ting and absorption corrections were not made to the observed count rates; nor were . “mma-ray contributions subtracted out. Because manyof the detailed corrections are self57