# MDA and LLD

1. Jan 26, 2006

### daveb

I can't seem to find a definitive equation for calculation of LLD (lower limit of detection). Cember has one equation, and other sources I research have completely different equations. I'm more apt to go with Cember's equation ,especially seeing as many of the govermental guides have conflicting equations. I know sometimes the equation can be application specific, so mostly wipes for contamination (whether routine wipes or decommission wipes) is the equation I'm looking for.

2. Jan 26, 2006

### Staff: Mentor

Is this for homework problem or laboratory measurement problem?

LLD would depend on the type of detector and radiation. Are you using a 2$\pi$ detector?

3. Jan 26, 2006

### daveb

Neither. It's for the job. Apparently, some idiot used the wrong formular for the MDA way back when, and no one in the office can seem to find the correct formula. If we could find another that agrees with Cember, we'd most likely go with that one.

4. Jan 26, 2006

### Staff: Mentor

:rofl: Yep, I've seen that many times before. Something that someone did 20, 30, 40+ years ago, and that person has long since gone (terminated, retired or died), and no one knows why it was done that way. The stories I could tell.

I'll look around. I have an old Cember. You might try Glenn Knolls book, and IIRC there is a Radiation Protection Handbook or Radiological Health Handbook.

Last edited: Jan 26, 2006
5. Jan 26, 2006

### Staff: Mentor

Try these resources

http://hps.org/publicinformation/ate/q807.html

http://www.eml.doe.gov/publications/procman/

http://www.eml.doe.gov/publications/procman/Sect4/4_5-3.pdf

6. Jan 27, 2006

### daveb

Thanks. I meant to look at the HP website but it completely slipped my mind. DOH!

7. Jan 27, 2006

### Morbius

Astronuc,

Yes, the Health Physics Society is a great place for people to get answers to their
questions with regard to health effects and safety of nuclear technology.

I referred several anti-nukes who were trying to stir up support for "The Tooth Fairy Project".
I pointed them to:

http://www.hps.org/publicinformation/ate/q616.html

The Tooth Fairy Project is an attempt to assign blame to nuclear power plants for
trace amounts of Strontium-90 found in the deciduous teeth [ "baby teeth" ] of
children from a given area.

The "study" is terribly flawed as discussed by numerous scientists at:

http://mailman.mcmaster.ca/mailman/private/cdn-nucl-l/9911.gz/msg00011.html

For example, Bob Flood of the Stanford Linear Accelerator Center at Stanford
University concludes the following:

"...Ignoring such things as transport mechanisms and food chain
characteristics and jumping straight to assigning blame to nuclear
power plants seems a fair demonstration to the preconceived notions
they are now simply deriving the question..."

Dr. Gregory Greenman
Physicist

8. Feb 24, 2009

### JRtheHP

Hello Astronuc, Your verbal explanation of LLD clarified so much for me. I was searching for a similar definition for MDA. If it helps, I use a Protean gas-flow proportional counter to quantify gross beta-gamma.

Last edited: Feb 24, 2009