Re: Exempt Quantities

["J. J. Rozental" <joseroze@netvision.net.il>]

----- Original Message -----
From: William V Lipton <liptonw@dteenergy.com>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Sent: Wednesday, April 19, 2000 7:01 PM
Subject: Re: Exempt Quantities


> I suggest that you read the Dangerous Goods Regulations of the
International
> Air Transport Association.  These have the force of law when required by
an
> airline.  Virtually all airlines require compliance. These regulations
state:
>
> 3.7.1:  "For the purposes of these Regulations,a radioactive material is
any
> article or substance with a specific activity greater than 70 kBq/kg
(0.002
> uCi/g)."
>
The transport regulations have always contained an exemption criterion which
defined materials subject to their requirements. The current regulations
define radioactive material as any material having a specific activity
greater than 70 Bq/g. The IAEA Basic Safety Standards - Safety Series 115,
however,
use a radionuclide-specific approach which leads to derived exemption values
spanning
seven orders of magnitude,and straddling 70 Bq/g in the case of activity
concentration.
The BSS also present exemption values for total activity quantities (Bq).

It was recognized that the single exemption level of 70 Bq/g has no dose
basis and that it was unlikely that this level satisfied the primary dose
criteron of 10 microsievert in a year for exemption for all radionuclides. A
set of transport-specific scenarios were developed which reflected various
exposure situations (exposure times, distances, source geometries, etc.).
Based on these scenarios, both activity concentration and total activity
values were calculated which would result in meeting the 10 microsievert per
year value. These transport derived values were comparable to the exemption
values in the BSS and resulted in recommended activity concentrations
ranging from 1 to 106 Bq/g.

Given the difficulty in technically justifying the 70 Bq/g value and the
similarity in results from the transport scenarios and the BSS scenarios, it
was determined to be preferable to simply adopt the BSS derived exemption
values. Consequently, the regulations contain both activity concentration
and "total activity per consignment" exemption values. For mixtures of
radionuclides, the "ratio rule" must be applied so that the sum of the
activities (or activity concentrations) present for each radionuclide
divided by the applicable exemption value is less than or equal to one.

Jose Julio Rozental
joseroze@netvision.net.il
Israel


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