AW: [ RadSafe ] surface emission rate,surface DPM from 27 pCi Tc-99

Fri Dec 14 13:37:58 CST 2007

"27 pCi, not nCi."

Thanks to all who pointed out my goof-up! Rainer

________________________________

Von: NIXON, Grant [mailto:Grant.NIXON at mdsinc.com]
Gesendet: Fr 14.12.2007 19:39
An: Facius, Rainer
Betreff: RE: [ RadSafe ] surface emission rate,surface DPM from 27 pCi Tc-99

27 pCi, not nCi.

Cheers,

Grant

Grant I. Nixon, Ph.D., P.Phys.
Science Specialist (Physics)
Radiation Applications Development Team
Engineering, Development & Compliance
MDS Nordion
447 March Road
Ottawa, ON  K2K 1X8
Canada

Tel: +1 613 592 3400 ext. 2869
Fax: +1 613 591 7423

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Rainer.Facius at dlr.de
Sent: Friday, December 14, 2007 12:55 PM
To: GEOelectronics at netscape.com; radsafe at radlab.nl
Subject: AW: [ RadSafe ] surface emission rate,surface DPM from 27 pCi
Tc-99

Assuming that DPM stands for decay per minute, my answer would be:

27*10^-9 Ci * 3.7*10^10 decays/s/Ci = 999 decays/s

Since Tc 99 is a pure beta emitter, each decay emits one beta particle.

Hence 999 beta-particles/s leave the "plane" onto which the Tc 99 has
been dispersed (with 294 keV/particle).

999 beta-particles/s * 60 s/min = 59940 beta-particles/min (DPM?)

Ignoring all the stated corrections, including reflection from the
stainless-steel support, half of this number, i.e. 30000
beta-particles/min, leaves the test disk into one half-space.

So what is/was the problem; what did I/we miss or misunderstand? :-)

Rainer

________________________________

Von: radsafe-bounces at radlab.nl im Auftrag von Geo>K0FF
Gesendet: Fr 14.12.2007 16:39
An: Geo>K0FF; radsafe at radlab.nl
Betreff: [ RadSafe ] surface emission rate,surface DPM from 27 pCi Tc-99

In case there is some confusion or a problem in translation, the
information
being
requested is the 2 pi beta emission rate from the source delineated
below.

Another way of stating it is: the total number of beta particles coming
from
the front working surface of the disc.

Forget about self absorption, counting error, confidence level, and
systematic error.

This is not a trick question. To determine the beta efficiency of a
probe,
one needs to know how many particles are leaving the test disc.

Reply if you care to, to

George Dowell at

GEOelectronics at netscape.com

The calculations will be posted here after a short time.

George Dowell
NLNL
New London Nucleonics Lab

----- Original Message -----
From: "Geo>K0FF" <GEOelectronics at netscape.com>
To: <radsafe at radlab.nl>
Sent: Tuesday, December 11, 2007 7:45 PM
Subject: [ RadSafe ] DPM from 27 pCi Tc-99

> What is the surface DPM of a 27 pCi Tc-99 electroplated disc source?
The
> substrate is stainless steel. (by calculation only please)
>
> George Dowell
> NLNL
> New London Nucleonics Lab

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