Chapter 14 FE EXAM FORMATTED PROBLEMS
14-1. The radioactive intensity measured 12 m from a spill is 18,000 times the safe level. At
what distance must a safe perimeter be established to prevent access during the cleanup?
Using Eq. 14-22
r 
I 2  I  1 
 r2 
2
 12 m 

I 2  18000 I 2 
 r2 
144
0.000056  2
r2
2
144
0.000056
r2  1.61  10 3 m
r2 
2
14-2. Determine the radioactive decay constant for radon. The half-life is 3.825d.
Using Eq. 14-7

ln 2
0.693

0.181d 1
T1/ 2 3.825 d
14-3. If the sewer discharge standard for phosphorus-32 is 9x10-6 μCi/mL, how long must a
solution containing 0.60 μCi/mL be held to meet the discharge standard? The half-life of
phosphorus-32 is 14.3d.
Using Eq. 14-6

0.693
 0.048 d 1
14.3d
9  10 6 Ci / mL  (0.6Ci / L)(10 3 L / mL )e ( 0.048d
1
)t
1
0.015  e ( 0.048d )t
4.20  0.048t
t  87.49 d or 88 days
14-4. What particle is emitted in the decay shown below?
238
92U 
234
92Th
From Eq. 14-2
An Alpha particle is emitted since:
A
A4
4
Z X  Z 2 X  2 He