[ RadSafe ] Request information for shielding purpose

[John Jacobus]

Yuri,
I assume you talking about leakage radiation for the
x-ray tube assembly.  Our regulatory agency states

"(k) Leakage radiation from the diagnostic source
assembly. The leakage radiation from the diagnostic
source assembly measured at a distance of 1 meter in
any direction from the source shall not exceed
2.58×10¥5 coulombs per kilogram (C/kg) (100
milliroentgens
(mR)) in 1 hour when the x-ray tube is operated at the
leakage technique factors. If the maximum rated peak
tube potential of the tube housing assembly is greater
than the maximum rated peak tube potential for the
diagnostic source assembly, positive means shall be
provided to limit the maximum xray tube potential to
that of the diagnostic source assembly. Compliance
shall be determined by measurements averaged over an
area of 100 square centimeters with no linear
dimension
greater than 20 centimeters."

See page 9 at 
http://a257.g.akamaitech.net/7/257/2422/01apr20051500/edocket.access.gpo.gov/cfr_2005/aprqtr/pdf/21cfr1020.30.pdf

We have gone to reporting exposures in air kerma last
year, so the regulations are a year behind.  Note from
another regulation:

900.2(d) Air kerma means kerma in a given mass of air.
The unit used to measure the quantity of air kerma is
the Gray (Gy). For X-rays with energies less than 300
kiloelectronvolts (keV), 1 Gy = 100 rad. In air, 1 Gy
of absorbed dose is delivered by 114 roentgens (R) of
exposure.

I have never seen air kerma listed in uSv.

--- Yuri Ravello <yravello at ipen.gob.pe> wrote:

> Dear Sirs,
> 
> We are testing a shielding design for a x-ray
> medical use equipment. We
> measured the expose (kerma) rate: it is about 500
> uSv/h. Because we cannot
> measure integrated exposure, we are looking for the
> limit for expose rate.
> So please, if anyone has experience about it, write
> me. Thanks in advance.
> 
>  
> 
> Sincerely,
> 
>  
> 
> Lic. Yuri Ravello
> 
> Evaluador-Inspector
> 
> Oficina Técnico de la Autoridad Nacional
> 
> Instituto Peruano de Energía Nuclear
> 
> Calle Justo Vigil 456 - Magdalena del Mar
> 
> Teléfono: +51.1.4631170 o +51.1.4631171
> 
> Fax: +51.1.4631166


+++++++++++++++++++
"Those who corrupt the public mind are just as evil as those who steal from the public purse."
Adlai Stevenson

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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