Re: Radioactive Material Thresholds

[Richard Smart <R.Smart@unsw.edu.au>]

At 03:41 A 5/8/97 -0500, you wrote:
>     My question is this:
>     Is there a definitive legal threshold activity per mass value defining 
>     the limit below which material can be considered non-active (either 
>     generically or individually)? i.e. have I missed something?
>     
In NSW, Australia, the use of radioactivity is regulated by the Radiation
Control Act, 1990.

The Regulations to this Act define a "radioactive substance" as follows:

5. (1) For the purposes of the definition of radioactive substance in
section 4 (1) of the Act, the prescribed amount is 100 becquerels per gram. 
	
5. (2) For the purposes of the definition of radioactive substance in
section 4 (1) of the Act, a substance has the prescribed activity if the
expression: 

	 A1 + A2 +  A3 +  A4  
	 ----    ----     ----     -----
	 40    400   4000 40000 
is greater than or equal to one. 
	
5. (3) In the expression referred to in subclause (2): 

(a)	A1 represents the total activity, in kilobecquerels, of the Group 1
radionuclides contained in the substance; 
(b)	A2 represents the total activity, in kilobecquerels, of the Group 2
radionuclides contained in the substance; 
(c)	A3 represents the total activity, in kilobecquerels, of the Group 3
radionuclides contained in the substance; 
(d)	A4 represents the total activity, in kilobecquerels, of the Group 4
radionuclides contained in the substance. 

Examples of Group 1 radionuclides are Am241, Ra 226
of Group 2 radionuclides are Co60, I125, Sr90
of Group 3 radionuclides are C14, Cr51, Tl201
of Group 4 radionuclides are H3, Tc99m, Xe133

Therefore, effectively we have lower activity limits of 40kBq, 400kBq, 4MBq
and 40 MBq for Groups 1-4 respectively for single radionuclides.

Regards

Richard Smart PhD
Department of Nuclear Medicine
St. George Hospital
Kogarah, NSW 2217
Australia
Tel:61 2 9350 3112
Fax:61 2 9350 3991
Email:R.Smart@unsw.edu.au