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Re: Tritiate organic compounds via irradiation?
In general this is not a very practical approach.
Aside from the difficulty in achieving desired specific activities high
radiation doses to the chemical and heat tend to have undesireable
deleterious effects. A calculation for the typical elements (H,N,C,O,P)
given below assuming natural abundance and 1 gram of material gives the
indicated results (at end of a 10 hr, 1E14 irradiation, after 24 hrs,
after 1 week). The fast neutron based reactions assume a flux of 2E12.
Once you start correcting for real masses you are not dealing with much
tritium and you have several interferences.
Health Physics Neutron Activation Database
Notation on nuclide name
m,m1,m2 indicate metastable states. Decay may be the ground state or
another nuclide.
+ indicates radioactive daughter production already included in
daughter listing
several parent t1/2's required to acheive calculated daughter
activity. All act. assign
In most cases the added activity to the daughter is small.
* indicates radioactive daughter production NOT calculated, approx
secular equilibrium
s indicates radioactive daughter of this nuclide in secular
equilibrium after several daug
t indicates transient equil via beta decay. Accumulation of that
nuclide during irradiatio
Reaction = b indicates production via decay from an activation
produced parent
|
Effective
+--------
Xsectn | 10 <<< Length
of irra
+--------
initial 2n prod Activity Activity
Activity
+-----------------
effect. and n,g end of | 24
168
+-----------------
Target Nuclide Half- X-sect. react f burnup irradtn + hours +
hours
Nuc. Produced life (b) -ion ? (b) (uCi) (uCi)
(uCi)
H-2 H-3 12.346y 0.00053 act n 0 0.004158 4.2E-03
4.2E-03
C-12 C-11 20.30 m 4.2E-10 n,2n y 0 0.001127 5.0E-25
4.0E-153
IAEA156
C-13 C-14 5736 y 0.0014 act n 0 0.000269 2.7E-04
2.7E-04
N-14 C-14 5736 y 0.00183 n,p n 0 0.02924 2.9E-02
2.9E-02
N-15 N-16 7.14 s 2.6E-05 act n 0 10.23561 0.0E+00
0.0E+00
P-31 P-32 14.3 d 0.1737 act n 0 182325.6 1.7E+05
1.3E+05
P-31 Si-31 2.62 h 0.036 n,p y 0.18 35122.57 6.1E+01
1.8E-15
IAEA156, fission averaged
P-31 Si-32 100 y 0.036 2n n 0.18 2.38E-06 2.4E-06
2.4E-06
produced from Si-31
O-16 N-16 7.14 s 1.9E-05 n,p y 0 38.5636 0.0E+00
0.0E+00
IAEA156
O-16 O-15 122 s 5.3E-10 n,2n y 0 0.001076 7.7E-217
0.0E+00
IAEA156
O-17 C-14 5736 y 0.235 n,a n 0 0.00121 1.2E-03
1.2E-03
O-17 N-17 4.2 s 8.6E-06 n,p y 0 0.006423 0.0E+00
0.0E+00
IAEA156
O-18 O-19 27.1 s 0.00018 act n 0 32.88789 0.0E+00
0.0E+00
In <01BCCA5B.E3EDABD0@RENE>, on 09/26/97
at 10:28 AM, Tom Paquette <Tom.Paquette@usa.net> said:
>Radsafers:
> Is it possible and reasonable to label organic compounds by neutron =
>bombardment? I need to label mg. to g. quantities of a compound with =
>tritium and could do this in 10-30% yield with available reagents to =
>produce a molecule with alkyl T's that are not exchangeable in aqueous =
>solution. I suppose that is the way to do this but the question has =
>arisen whether or not alternatives are possible. The reliability of the
>=
>synthesis on small scale is uncertain, particularly if we elect to use =
>an outside labeling group. Any comments? Thanks.
>Tom Paquette
>Univera Pharmaceuticals
>Broomfield, CO 80021
--
the above are the personal musing of the author,
and do not represent any past, current, or future
position of NIST, the U.S. Government, or anyone else
who might think that they are in a position of authority.
NBSR Health Physics
NIST
Gaithersburg, MD 20899
301 975-5810
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Lester.Slaback@nist.gov
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