Re: Frequency of SRD Calibration

[James G. Barnes <mail15077@pop.net>]

Dear Jerry,

I'll try to keep my response brief:

1)  Check your licensing and regulations.  The State of California stipulates 
that TLD/Film is the primary dosimeter.

2)  If your pocket dosimeter is not NVLAP/DOELAP certified, I don't think it 
can truly be the "primary" dosimeter.  (This is off the top of my head; I would 
need to check into it further).

3)  If a TLD is lost or damaged, an investigation should be conducted.  The 
pocket dosimeter data is certainly valuable, but I would not consider it 
"unequivocaly" equivalent to assigned dose, especially where the energy 
spectrum of the radiation is of significance.  In fact, I don't consider TLD 
dose to necessarily "unequivocally" a correct indication of total dose 
(particularly where the dose is "beamed" or where non-homogeneous exposure 
occurs).  One assumes that under "normal" conditions that it is, but normal 
conditions don't always exist.

4)  An economic issue; we have a dosimeter exposure table to calibrate 
dosimeters.  We have found that for convenience and economy, it is fairly easy 
to calibrate every quarter and swap out all the dosimeters with the TLDs.  We 
specify, however, a six month dosimeter calibration period.

Jim Barnes, CHP
Rocketdyne Division; Boeing North American
Radiation Safety Officer

=======================================
    >      Happy Holidays Radsafe,
    >      
    >      Two HPs at my site disagree on whether or not our Self Reading 
    >      Dosimeters (SRDs) should be treated as primary dosimeters based on 
    > the 
    >      guidance given in Reg Guide 8.4.  Reg Guide 8.4 states that when 
    > used 
    >      as primary dosimeters these devices need to be calibrated every 3 
    >      months, while when used as secondary dosimeters, a 6 month 
    > calibration 
    >      frequency is sufficient.
    >      
    >      The point of disagreement stems from consideration of what happens 
    >      when our normal primary dosimeter (TLD) is lost or damaged.  One HP 
    >      contends that if the SRD is calibrated every three months, then the 
    >      SRD dose can be used "unequivocally" in providing a dose estimate 
    > (the 
    >      monitored individual is hence wearing two primary dosimeters, if the 
    >      TLD is lost, just use the dose from the SRD).
    >      
    >      The other HP thinks that their is only one primary dosimeter, and 
    > that 
    >      if this dosimeter is lost, the SRD should be used as part (hopefully 
    >      as a big part) of the ensuing dose estimate which must be performed 
    >      (see Sandy Pearle's recent post).
    >      
    >      Truth often lies somewhere in the middle.  What do Radsafers who 
    > work 
    >      in external dosimetry think (anybody left that uses SRDs!!!)??  FYI, 
    >      at our site individuals always wear their SRD and TLD if they are in 
    >      areas where they may receive exposure.
    >      
    >      Hopefully posts on this thread will be of interest to the list.  If 
    > in 
    >      doubt, please contact me directly.
    >      
    >      Thanks
    >      
    >      Jerry Barber
    >      M4 Environmental
    >      1000 Clearview Ct.
    >      Oak Ridge, TN 37830
    >      barberj@m4lp.com
    >