RE: HP question - alpha sources[Scanned]

To: "Franta, Jaroslav" <frantaj@AECL.CA>

Subject: RE: HP question - alpha sources[Scanned]

From: "Christoph Hofmeyr" <chofmeyr@nnr.co.za>

Date: Tue, 18 Jun 2002 18:01:40 +0200

Cc: <radsafe@list.vanderbilt.edu>

Reply-To: "Christoph Hofmeyr" <chofmeyr@nnr.co.za>

Sender: owner-radsafe@list.vanderbilt.edu

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Thread-Topic: HP question - alpha sources[Scanned]

Title: HP question - alpha sources

Jaro,

From the dose tables for worker intake (Sv/Bq) in the IBSS (IAEA) the difference should be more like a factor of 10 for medium solubility. I guess that the biological halflife (excretion) is shorter, i.e. the body gets rid of the Po quicker. The physical halflife of Am-241 or Pu-239 is effectively infinite compared to the 50 years the commitment is calculated for. The dose is due to the activity integrated over time (i.e. the number of decays that took place before the source was excreted OR 50 years had elapsed) and not the number of atoms (mass) of uptake. If the Po-210 were not excreted, but decayed inside the body, the physical halflife of 138 days would come into play (the uptake would have decayed away in a couple of years), allowing a higher ALI (lower specific dose per intake) compared with the other nuclides.

Regards

Chris Hofmeyr

-----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