Because the fission representation goes to infinity at zero time,
the ratio of fission activity to uranium capture activity mst be
found at some other time.
In general, the time chosen wag 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
coystructed
for times shortly after the shote ves, 289, Np*29, peeand Np*40
were found to be significant contributors to the decay curve.
the parent—daughter relationship
(ete M2")
ug
From
(3.6)
Apy= activity of 0239 at initdal tine
where
Ag = activity of daughter Np239
wh = decay constant of y239
ug = decay constant of Np239
t+
= tim after shot
In the case of the U239 and Np23? decay scheme, u, is much greater
than tu, ande@1* 1s mch less than eW%2" at any time after initial
timee
hence
Ag + Ag®
(367)
thus, setting t = 0
(3-8)
of
Np239
can be found from Eqe 308, ass
a
rotatingectivityef 1 te 1239, Similarly, in the case of Np240, it
can
°
he shown that its activity equals up/(ug — wu.) times the activity
e
ibrium is reac
therelativeactivities of ye? to U239 and U240 to 0239 are
determined by the ratio of their decay constants multiplied by bhgir
ida s The relative activity and decay constants of U®~';
cankure
U<77, aes
U 40 and Np240 are gummarized in Table 3.l.
38