RE: Nuclear Enterprises, Ltd. - IPM7/8D Humidity Problems

["Lavera, Ron" <Ron.Lavera@nypa.gov>]

Ben

Yes, we've seen these types of problems with the IPM-7 & 8.  There are
several potential problem areas :

1	The high voltage components may be dirty.  
*	Dust build up around the HV connectors can cause arcing and
subsequent spurious counts.
*	Clean the cables and check the cables for cracks.  Just like your
car, aging can cause insulation cracks that  result in arcing and noise.
*	Dust build up underneath the pre-amplifier shields can cause arcing.
Clean !
*	Pointy connections under the pre-amplifier covers can cause arcing.
*	Clean everything well.  If your site allows, coat the circuit board
with a sealant rated for the HV.
*	Use Electrical tape to coat the inside of the pre-amplifier cover.
2	Moisture may be permeating through the detector mylar.  
*	NE makes a heavier gauge Mylar that you can use on the detectors.
It reduces the humidity problem.  This change has the added benefit of
reduced mylar maintenance work because the mylar is more puncture resistant.
This change also has a couple of negative aspects, such as a very large
decrease in alpha detection efficiency in addition to a not so modest
reduction in beta efficiency.
3	Change the gas.  We started using P-5 ( 95% Argon 5% Methane ) as
opposed to P-7.5 or P-10.  This allowed us to reduce the voltage applied to
the detectors, which resulted in less sensitivity to humidity.


Best of luck to you.

...   mine and mine alone  ...

Ron LaVera
Lavera.r@nypa.gov


		-----Original Message-----
		From:	Morgan, Ben [mailto:ben.morgan@cplc.com]
		Sent:	Monday, June 14, 1999 12:51 PM
		To:	Multiple recipients of list
		Subject:	Nuclear Enterprises, Ltd. - IPM7/8D Humidity
Problems

		Greetings:

		Harris Nuclear Plant has experienced shut downs of the
subject whole body
		contamination monitors due to high relative humidity (>80%).
We would
		appreciate answers to the following from other IPM users:

		1. Have you experienced similar problems?

		2. If so, how did you correct them?

		Thanks,

		Ben

		ben.morgan@cplc.com 
	
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