Re: deep dose equivalent and hot particles

[Judd Sills <sillsj@GAT.COM>]

At 09:48 AM 10/29/97 -0600, you wrote:
>
>I am looking for practices currently being used to calculate the DDE from
>point sources.  As I understand it, there is nothing in the regs that
>gives guidence to calculating this quantity.  Any information regarding
>deep dose equivalent, hot particles and point source calulations would be
>of great interest to me.  
>
>Thank you in advance,
>
>Sara Casey
>University of Missouri-Columbia
>NE grad student
>
>
I assume that this question is in reference to the situation of a discrete
radioactive particle (i.e., "hot particle") on the skin or clothing....
The NRC Computer Code VARSKIN Mod2 will calculate the DDE if one exists and
if you select this option during the interactive execution of the code.

The subject of DDE from hot particles was also discussed by the staff in
the questions and answers on the "new" 10CFR 20 with respect to 10CFR20.1201.
See Q/A 435, copied below.

"Question 435:  The rule requires that "the assigned
deep-dose equivalent... must be for the part of the body
receiving the highest exposure.  [The dose] may be assessed
from surveys or other radiation measurements for the
purpose of demonstrating compliance with the occupational
dose limits, if the individual monitoring device was not in
the region of highest potential exposure."  In the event of
a hot particle exposure to a portion of the whole body, it
is unlikely that the associated deep dose equivalent (DDE)
resulting from the hot particle gamma radiation would be
appropriately measured by an individual monitoring device
due to the localized nature of the exposure.  Is it
required that the DDE associated with a hot particle
exposure be assessed and added to the monitored DDE for the
purpose of demonstrating compliance with the occupational
dose limits?

"Answer:   Yes.  Although, for a hot particle on the skin,
the deep dose equivalent is generally a small fraction of
the shallow dose equivalent, it does need to be assessed.
(Reference:  10 CFR 20.1201)."

Best regards

Judd M. Sills, CHP           |   Office: (619)455-2049
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