Pu-239; Type M, f(sub1)= 5(-4) E(sub
ing)(50) =2.5(-7)
Pu-239; Type S, f(sub1)= 1(-5) E(sub
ing)(50) =9.0(-9)
Type
S, f(sub1)= 1(-4) E(sub ing)(50) =5.3(-8)
That is, the commited dose per Bq from ingested Po-210 equal to, or smaller
than that from Pu-239
FYI, f(sub1) is the fraction of the radioactivity
that enters the GI tract that goes blood and is one of the largest uncertainties
in internal dosimetry. ICRP would be justified in changed their recommendation
by an order of magnitude.
John
_______________________
John R Johnson,
PhD
----- Original Message -----
Sent: Tuesday, June 18, 2002 10:12
AM
Subject: RE: HP question - alpha sources
- THANKS + redux
Thanks again to all who responded and helped me
understand.
For others who wanted to know, the answer (see question below)
is of course that Po-210 has a much shorter physical and biological T½ -- only
138d & 50d respectively, versus the 50-year bio-T½ of both Pu-239 &
Am-241. This was the main point in the replies. The ALI for Po-210 is 100x
higher than those of Pu-239 & Am-241, implying that Po-210 is considered
100x less harmful than Pu-239 & Am-241.
Some also suggested its the progeny ingrowth over 50 years --
the fact that Po-210 turns to stable lead-206, whereas the two transuranics
have radioactive progeny. My guess is that this is not such a big factor,
since the ingrowth would be minute over 50y -- Pu-239 & Am-241 decay to
U-235 & Np-237 (respectively, I think) both of which have
multi-million-year T½.
Some replies also suggested that I should have been able to
figure this out by myself -- which is true.
My
confusion started when I read a publication which stated that "The
International Commission on Radiological Protection calculates that
polonium-210 is five to ten times more harmful than plutonium 239." This is
evidently false. The problem is that it was written by a respected scientist -
which made it hard for me to believe that it could possibly be wrong !
Oh well, live & learn.....
....its
so easy to get mixed up in these things !
Cheers,
Jaro
-----Original Message-----
From:
Franta, Jaroslav [mailto:frantaj@AECL.CA]
Sent: 18 June 2002 15:26
To: Radsafe
(E-mail)
Subject: HP question - alpha
sources[Scanned]
Dear Radsafers,
Would anyone be able
to tell me why it is that the ALI (IC-W) for Po-210 is 100 times HIGHER (0.6
µCi) than for Pu-239 & Am-241 (both 0.006 µCi), even though the T½ for
Po-210 is 1140-times shorter than that of Am-241, and 63570-times shorter than
that of Pu-239 ? Can someone please enlighten me about the reasons for this
?
Thanks in advance.
Jaro