Re: Whole Body Deep Dose & Non-uniform fields (5)

["Sandy Perle" <sandyfl@earthlink.net>]

>>1.  How many medical facilities you know are applying NCRP     
         122 or HPS 13.11?

The appropriate place for dose weighting, in the medical field, is 
very useful in interventional procedures, such as catheritization, 
etc. Some states do allow a dose weighting for the deep dose, if an 
individual wears 2 dosimeters, one on the collar, and the second 
under a lead apron at about the waist level. There is also an 
equation for individuals who only wear a single dosimeter on the 
collar. Not all states allow this, and not for all individuals performing 
the procedure. Report 122, abstract below, defines several 
methods for performing a dose weighting for individuals. The NRC 
does not currently permit dose weighting. Report 122 may 
eventually lead to workers under NRC regulations, to employ one of 
the methods defined in the report, to more accurately assess the 
dose assigned to the worker.

HPS 13.11 (ANSI N13.11-1993) is a performance standard. It is the 
standard under the auspices of NVLAP, which meets the 
requirements accepted by the NRC and states, where a processor 
of dosimetry must be NVLAP accredited. ANSI N13.11-1993, or its 
predecessor, ANSI N13.11-1983, do not have anything to do with 
dose weighting.


NCRP Report No. 122

Use of Personal Monitors to Estimate Effective Dose Equivalent 
and Effective Dose to Workers for External Exposure to Low-LET 
Radiation  

NCRP Report No. 122 takes cognizance of the fact that in many 
external exposure circumstances, dose equivalent estimates 
obtained from personal monitors significantly overestimate effective 
dose equivalent (HE) or effective dose (E), particularly when the 
body is not uniformly irradiated due to the irradiation conditions or 
due to protective shielding of portions of the body. Specifically, in 
these cases, the numerical relationships between monitoring data 
and HE or E need to be better understood so that appropriate 
monitoring practices are selected and monitoring data are properly 
evaluated. This Report explores these numerical relationships for 
external exposure from low-LET radiation and gives 
recommendations for estimating HE or E in practice,  using 
personal monitors.

>>2.  Do you think there is any difference or benefit on monitoring   
         rad workers (and applying the 5R limit) in any 12 month         
         besides using the standard calendar year?

The question is one of monitoring frequency, and has nothing to do 
with whether or not the individual was assigned a proper dose, or 
the degree of dose. In the USA, and I expect most countries, the 
time period for annual dose monitoring is a calendar year. There 
can be some slippage in this, i.e., for individuals who start 
monitoring on the 15th of the month. In that case, the annual dose 
is based on 1/15 thru 1/14 of the following year. To answer your 
question, in my opinion, there is nothing to be gained from a varied 
12 month calendar. For recordkeeping, it is much simpler to have a 
standard year, and, from a computer system, it is easier to 
maintain. If not, the system must be developed to handle rotating 
frequencies. In the end, what is to be gained, must be answered. 
But the regulators most likely would not accept. The regulations 
are based on specific dose for a specific period. If under federal or 
agreement states, the limits are for a calendar year. If under many 
states, the limits are quarterly, and they are well defined.

------------------------
Sandy Perle
E-Mail: sandyfl@earthlink.net
Personal Website: http://www.geocities.com/capecanaveral/1205

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