[ RadSafe ] Infinite Thickness of KCl

Rahim Ghanooni rahim.ghanooni at gmail.com
Tue Sep 6 21:12:31 CDT 2011


I used Microshield to calculate the dose rate.  Since I do not have enough
information I made the following assumptions.

I created a disk with 1 cm radius; consist of K-40, at density of 1.98 g/cc,
activity of 0.416 uCi/cc, and thickness of 1 cm, the dose rate was
calculated at distance of 5 cm from front center of the disk.

The calculation started at thickness of one cm, with buildup, and continues
adding to the thickness while the activity distribution kept constant (0.416

Rahim Ghanooni, CHMM

Shielding Engineer/ Health Physicist

Thickness of 1 cm exposure rate 3.27E-2 mr/hr

Thickness of 10 cm exposure rate 1.1E-1 mr/hr

Thickness of 15 cm exposure rate 1.18E-1 mr/hr

Thickness of 25 cm exposure rate 1.208E-1 mr/hr

Thickness of 30 cm exposure rate 1.22E-1 mr/hr

Thickness of 35 cm exposure rate 1.23E-1 mr/hr

On Tue, Aug 30, 2011 at 10:49 AM, <Nielsen.Erik at epamail.epa.gov> wrote:

> I am trying to determine the infinite thickness of the 1460 keV gamma
> emission (10.5% abundance) of a planar source of KCl (416 pCi/g) and a
> density of 1.98 g/cc.
> In other words, what is the thickness of a KCl planar source where any
> additional thickness does not increase the surface dose rate?
> I have scoured my references but have not located the appropriate formula
> for calculating this value.
> I would appreciate any references or suggestions for an appropriate
> calculation.
> Erik C. Nielsen
> USEPA, National Air and Radiation Environmental Laboratory
> 540 South Morris Ave.
> Montgomery, AL 36115
> Phone 334-270-3475
> Fax 334-270-3454
> "Those who do not read are no better off than those who cannot"
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