NUCLEONICS DATA SHEET No. 15 
induced Radioactivity 
Nomogram for Radioactivity 
Induced in Irradiation 
By EDWARD C. FREILING 
(7. S. Naval Radiological Defense Laboratory 
San. Francisco, California 
FREQUENT CALCULATIONS in radioac- 
tivity laboratories answer such ques- 
tions as this: If a sample is irradiated 
in a flux for a specified time, how many 
atoms are transmuted? How much 
radioactivity is induced? 
The known quantities of one prob- 
lem may be the unknowns of another: 
If a certain irradiation produces a 
measured activity, how much of a par- 
ticular nuclide was originally present? 
In terms of an observed activity and 
half-life, what is the capture cross 
section? 
This nomogram can be used for 
determinations of this type. It sum- 
marizes the relationships among: 
1. Total exposure (¢ X ¢) 
2. Product of amount of material in 
sample (n) and activation cross section 
per atom (c) 
3. Amount of material transmuted 
(N) 
4. Amount of resulting activity 
5. Decay constant (A) or 
life (7). 
Example: Activation analysis of a 
sample of U288 exposed to 10'7 thermal 
neutrons/em? produced 1,500 dpm of 
2.34-day Np?8*, The nomogram shows 
that there are 7 X 10° atoms of Np?*° 
in the sample. A second line from 
gt to N shows that the target material 
had a total cross section of 10~' mole- 
barns. Since the thermal-neutron cap- 
ture cross section of U2%8 is 2.8 barns, 
there were 3.6 X 107!! moles of U?5, or 
8.5 X 10-* gm. 
half- 
232 
N 
(atoms) (moles) 
pt no be 
(4. omp-hr (atom- 
(particles per cma) barns) 3 +1072! 
per cm2) (e5ptd+) (cm2) oes 10 
1028 10-24 
109 
. 1026 loner 10-8 
burn |! 
fori-mb 1 
moterial " 
loam 1016 x 
9 oa 
10 10'2 Pe 
1% burn 
for Ib 1022 1o“!2 \ 
moterial 107 \ 
\ 
1920 10-87 10-!2 : 
1% burn 5 A 
for -kb ie oo 
moterial 
10!8 7 107 
02) | jee 10-9 
10 !6 1.0 
Complete 
es particle 10!'7. 
1o!4 1.0 absorption 10-8 
fi 
10 !2 
3 
10 102! 10-3 
19'0 
10-5 
1075 
108 | 
10-7 1028 
ios 110? 1927--10% 
\ 
oN 
Decay constant 
(min-!) 
10°? 
10-24 
loses 
10°20. 
lore 
Ac tivity, 
(dpm) (curies) 
10-5 lone 
\ 10-'5 
lo-! 10-/4 
\ 190!2 
109+ 19-9 107! 
‘ 
-6 
107 +! 10 12 
\ 
1073 
10! \10R?. 
\ 
\ 
io'Sti53 10. “& 
\ 
\ 
6 
io'9{'0 10 -43 
102 
102 10 @ 
io!2 
1027 1.0 
iT 
Half- 
life 
1020, 
10!2y 
Io!?y 
10!Sy 
1o!3y 
lolly 
109y 
