RE: Colorado Pocket Dosimeter Requirements

[L_K_II_Les_Aldrich@RL.GOV]

We (a DOE contractor, responding to a requirement in the "old" DOE RadCon

Manual) have had a similar procedure in place for several years.  It

requires that an investigation be done if results from pocket and/or

electronic dosimeters vary from the primary dosimeter results by more than

50% and the primary dosimeter result is greater than 100 mrem.  There is a

"TLD Investigation" button on our access control entry system reports page

that does the comparison  for us.  It then prints out all the monthly and

quarterly results that meet the criteria.



Most of the investigations are done on workers who have a whole bunch of

entries during the primary dosimeter wear period.  Most of the

investigations conclude that, as you pointed out, a whole bunch of pencil

readings with small doses on them usually far exceed the TLD result.

Philosophically, anyone who records a 1 or 2 mrem difference on a pencil

dosimeter either has an exceptional eye or is kidding themselves and should

be recording either 0 or 5 mrem, minimum.



Assuming you're comparing deep dose (1000 mg/sq.cm) with a pencil (~300-400

mg/sq.cm.), the pencil results should be higher than the TLD results

(especially if you throw in some low energy gamma or high energy beta).  Our

investigations usually include comparing the pencil dose to the eye dose

(~330 mg/sq.cm.) and get reasonably close results.



I don't think we've had an investigation that discovered a "real" dose

difference in the last three years.



I don't know how "valid" your comparison is going to be.  It depends on how

you "investigate".  If you do reasonable evaluations, the comparison will at

least lead to some confidence that your workers' recorded doses are

accurate.



I wish you "lotsa luck" with that 20% criteria, especially if you don't have

a minimum dose specified below which you don't have to do the investigation.



Les Aldrich, CHP

l_k_ii_les_aldrich@rl.gov







-----Original Message-----

From: Bruce Bristow [mailto:radcons@YAHOO.COM]

Sent: Tuesday, March 05, 2002 1:52 PM

To: radsafe@list.vanderbilt.edu

Subject: Colorado Pocket Dosimeter Requirements





Colorado has recently required that we compare our

monthly TLD results with our daily pocket dosimeter

readings, at the end of each month and conduct an

investigation if the variation between the two exceeds

20%. 

I was wondering if anyone has heard of any other

regulatory authority with this requirement and also if

this is a valid comparison (dose -vs- exposure).

Thanks



Bruce Bristow

Radiation Consultants

e-mail: radcons@yahoo.com



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