Re: To Bioassay or not to Bioassay!!

[a.zapantis@qut.edu.au (Alex Zapantis)]

Robert, thanks for the response. I have answered your questions below and
provided a bit more information. In particular I am interested in anyones
views on my assumption of 1% uptake of the total activity of all
radioisotopes handled by workers.

>>To receive an effective dose of 30% of the limit 0.3ALIs must be
>>ingested/inhaled. Since 1% is ingested/inhaled, the number of ALIs required
>>to be handled is 30 (ie 0.3/0.01).
>>
>
>What are the Regs down-under for when individual monitoring is required?
>I assume from your basis that they are no less stringent than 30% of an ALI.

Unfortunately our regs were written in 1961 and are deficient in many
respects. In particular, all provisions relating to monitoring apply solely
to external irradiation (ie TLD/film). Rather than defining a "dose which is
likely to be received" above which external monitoring is required, the regs
literally say 'at the direction of the Director General of Health'. 

>This seems a bit relaxed (IMHO).  For comparison purposes, the USNRC
>requires monitoring when an individual is likely to exceed 10% of an ALI and
>the USDOE requires monitoring at 2%. 

> Assuming that your Regs limit total effective dose equivalent (EDE + CEDE)
to >0.05 Sv, and doesn't specify when to establish bioassay monitoring, I
would >suggest a monitoring level of 10% as being adequate.  I personnally
would not be >comfortable in establishing a bioassay program where the
"missed dose" was as >high as 0.015 Sv (1.5 Rem).

The regs do limit total effective dose to 50mSv however I have adopted
ICRP60 recommendations for the Radiation Procedures Manual. Thus I am using
a limit of 20mSv and ICRP61 ALIs. Thus the missed dose could be as high as
6mSv (0.6 rem). 

>Would you not require TLDs (or film) when external exposures were of the
>order of 0.01 Sv (1 Rem)?

Yes but that is another issue!!




                        Alex Zapantis
                        Radiation Safety Officer                               
                        Queensland University of Technology          
                        Health & Safety Section                             
                        Locked Bag No.2
                        Red Hill Qld 4059
                        AUSTRALIA

                        Ph     : 61 7 864 3566
                        fax     : 61 7 864 3993
                        email  : a.zapantis@qut.edu.au