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JassenB

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Contamination wipe tests
« on: Feb 12, 2004, 07:27 »
Is there a standard method in the commercial world of taking a swipe?

The Navy taught me to use a certain size "S" curve pattern to get the minimum 100 cm^2. A professor today told my lab class to make something up, and that area doesn't matter, which didn't make sense to me, since contamination is expressed in terms of concentration per unit area.

The issue came up because we had to survey our radiochemistry lab today, and I was the only person that had ever counted swipes or lugged around a survey meter, and I'm by no means experienced.

Thanks!
-Jassen

Offline Roll Tide

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Re: Contamination wipe tests
« Reply #1 on: Feb 12, 2004, 07:46 »
Jassen,
You are exactly right. Cover 100 cm2 (15.5 in2) with your "S"-motion wipe. I am happy to see you are in a classroom with a professor learning these things. Learn the theory well from these theory experts, but don't let their answers get in the way of common sense.

More brilliant Professors without an understanding of real world made the following statements:

     "I'll give you a "C", the business model won't work in the "Real world" to the founder of Fedex."

     "CRT's and keyboards are a passing fad, punch-cards are here to stay" by my professor in computer class in 1984.

     "No one would ever want to read anything like that in a newspaper. You should choose another major." to Dave Barry, winner of Pulitzer prize.


In my humble opinion, Professors can get too full of themselves to admit they don't know an answer, and in an arena of classroom theory, practical applications aren't that good. Much of the industry training is better, because trainers are encouraged to give only right answers (even if they have to wait until the next day to find the right answers.)

+Karma for your questioning attitude. It will continue to serve you well.
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Offline Roll Tide

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Re: Contamination wipe tests
« Reply #2 on: Feb 12, 2004, 07:47 »
If the surface area is <100 cm2, record it as 1000 dpm / smear vice 1000 dpm / 100cm2.
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.
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JassenB

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Re: Contamination wipe tests
« Reply #3 on: Feb 12, 2004, 08:06 »
Roll Tide:

Thank you for the clarification. That makes a lot more sense than taking a random section of a surface, especially in terms of being able to make quick comparisons between samples.

Thanks!
-Jassen

alphadude

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Re: Contamination wipe tests
« Reply #4 on: Feb 13, 2004, 07:13 »
18" S is the standard method. PCB uses a template. if u are not sure of your technique, report the results in dpm/swipe.  the 18" S is tried and true and can be repeated with pretty good statistics.  tell that professor to get some experience.  there is an old reg guide document that describes the methods of swipe samples-but i forget the number. 

moke

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Re: Contamination wipe tests
« Reply #5 on: Feb 13, 2004, 09:50 »
JassenB,

You may consider surface areas greater  than 100 cm2 and stay on the conservative end of the spectrum that you should consider with all radiological surveys because of Variables within each persons technique not to mentioned detection equipment.

Your main objective is to locate contamination and detect trends and abnormalities. That is what we get paid to do. When you identify contamination you always want to determine the EXTENT. Tell a complete story.

Of importance, in most cases, is the fact that you should always consider large area Masslinn smears so that you have a better chance detecting even the slightest trend.

Have a Great Weekend!

Moke

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Re: Contamination wipe tests
« Reply #6 on: Feb 13, 2004, 05:53 »
JassenB,

You may consider surface areas greater  than 100 cm2 and stay on the conservative end of the spectrum that you should consider with all radiological surveys because of Variables within each persons technique not to mentioned detection equipment.

Your main objective is to locate contamination and detect trends and abnormalities. That is what we get paid to do. When you identify contamination you always want to determine the EXTENT. Tell a complete story.

Of importance, in most cases, is the fact that you should always consider large area Masslinn smears so that you have a better chance detecting even the slightest trend.

Have a Great Weekend!

Moke

I agree that our job is to find contamination, then quantify it. I once was chewed out by a duke power house supervisor  >:(  for using a all over masslinn smear on welding equipment prior to free releasing it. Needless to say, I still did all over wipes looking for stuff prior to putting my sig on the release paperwork. (doing your job can really torque some people off)  8)
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Re: Contamination wipe tests
« Reply #7 on: Feb 16, 2004, 09:01 »

A professor today told my lab class to make something up, and that area doesn't matter, which didn't make sense to me, since contamination is expressed in terms of concentration per unit area.

The issue came up because we had to survey our radiochemistry lab today
this is an oft repeated professorial attitude, which is one of the primary reasons the labs are contamination prevelent areas.  lots of labs have got into trouble with various requlators due to laxity on controls, which are based on survey sloppiness.
ya wanna be technically proficient, use the area expressed as the area to be surveyed.  express contamination in the area that was surveyed.
period.
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