Because the fission representation goes to infinity at zero time, the ratio of fission activity to uranium capture activity must be found at some other time. In general, the time chosen was that at which the uranium capture activity was measured. A variation in this value could be used as a method of indication of fractionation of uranium capture products with respect to fission products. 3.3 el Shot 1 Since little experimental decay data were obtained prior to 250 hours, a composite neutron capt decay curve was ructed for times shortly after the shoto e387, 239» Np 39 ’ eBis Np240 were found to be significant contributors to the decay curve. From the parent-daughter relationship wy Ao = Ao. 1-01 (e*1bgM2*) (3.6) Ag)= activity of 0239 at initial time where Ao = activity of daughter Np239 239 wy, = decay constant of U ug = decay constant of Np239 t+ = time after shot In the case of the U239 and Np23? decay scheme, u, is much greater than U, and e1® 4s mch less than e"Y2* at any time after initial timee hence Ags = Age (367) Aon s we (3-8) thus, setting t = 0 Aon “A a The initial activity of Np239_can be found from Eq. 38, ass it Np240, of case the in rly, Simila 1235, for 1 ty or ve activi relati can @shown that its activity equals up/(up - uw.) times the activity of after equilibrium is reac The relative activities of ve to 0239 and 0240 to 0239 are r determined by the ratio of their decay constants miltiplied by U*"'; of The relative activity and decay constants lds, ure oo55, wee88, 240, and Np240 are summarized in Table 3.1. 38