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Re: sodium iodide scintillation detectors



Oops.  Senility is setting in...or maybe the effects of radiation exposure.

Rexon was started by ex Bicron or Harshaw guys, iirc.



Syd H. Levine

AnaLog Services, Inc.

Phone:  270-276-5671

Telefax:  270-276-5588

E-mail:  analog@logwell.com

URL:  www.logwell.com



----- Original Message ----- 

From: "Frank Bloe" <bloe@en.com>

To: "Syd H. Levine" <syd.levine@MINDSPRING.COM>; <John_Sukosky@DOM.COM>;

"Dave Oshlo" <doshlo@mgpi.com>

Cc: <radsafe@list.Vanderbilt.Edu>

Sent: Monday, August 09, 2004 11:40 AM

Subject: Re: sodium iodide scintillation detectors





> FYI

>

> Rexell is Rexon at (216) 292-7373

>

> http://www.rexon.com/

>

> FB

>

>

>

> ----- Original Message ----- 

> From: "Syd H. Levine" <syd.levine@MINDSPRING.COM>

> To: <John_Sukosky@DOM.COM>; "Dave Oshlo" <doshlo@mgpi.com>

> Cc: <radsafe@list.Vanderbilt.Edu>

> Sent: Friday, August 06, 2004 3:28 PM

> Subject: Re: sodium iodide scintillation detectors

>

>

> > There is no excuse for a crystal failure due to the glue.  Though more

> > expensive, we use special ruggedized hermetically sealed crystals,

usually

> > in stainless steel, in well logging sondes.  I have some of these built

in

> > the 1970's still working perfectly.  If I were you, I would talk to

other

> > manufacturers than just St. Gobain (they own what was Harshaw / Bicron /

> > Solon).  There is an outfit in that same area called Rexell that is more

> > responsive, and usually a bit cheaper.  Also try Gintek in South

Carolina,

> > and a new outfit down near Huntsville (the name slips my mind).

> >

> > Syd H. Levine

> > AnaLog Services, Inc.

> > Phone:  270-276-5671

> > Telefax:  270-276-5588

> > E-mail:  analog@logwell.com

> > URL:  www.logwell.com

> >

> > ----- Original Message ----- 

> > From: <John_Sukosky@DOM.COM>

> > To: "Dave Oshlo" <doshlo@mgpi.com>

> > Cc: <radsafe@list.vanderbilt.edu>

> > Sent: Friday, August 06, 2004 6:58 AM

> > Subject: Re: sodium iodide scintillation detectors

> >

> >

> > >

> > >

> > >

> > >

> > > Dave,

> > >

> > > Based on our experience with two 4 x 4 x 16 inch NaI detectors used in

> our

> > > standup whole body counter, the life expectancy is about 12 years.

The

> > > limiting factor is not the crystals themselves but the glue used to

seal

> > > the detector housing the NaI crystal.  The glue starts to degrade

after

> > > about ten years allowing humidity to invade the crystal.  When the

glue

> is

> > > degrading and conditions are humid (e.g., summertime in Virginia), the

> NaI

> > > crystal absorbs water and you'll see a significant decrease in

detector

> > > efficiency.  When conditions are dry (e.g. wintertime), the NaI

crystal

> > > will start to dry out and you'll see a corresponding increase in

> detector

> > > efficiency.  The good news is that you can send your NaI detectors

back

> to

> > > the manufacturer (e.g., St. Grobain) and they dry out the crystal and

> > > reseal it into another detector housing.  By doing this you can

> > > indefinitely extend the life of your NaI detector.  The drying out and

> > > resealing process takes about a month for the large 4 x 4 x 16 NaI

> > > detectors.

> > >

> > > I'm not sure what the shelf life of NaI detectors are in a warehouse.

> > > However, it's likely to also be dependent on the glue that's used as a

> > > sealant.  Check with a crystal manufacturer such as St. Grobain to get

a

> > > definitive answer to this.  Hopefully, the glue they're using today is

> > > better than what they used 20 years ago.

> > >

> > > John M. Sukosky, CHP

> > > Dominion

> > > Surry Power Station

> > > (757)-365-2594 (Tieline: 8-798-2594)

> > >

> > >

> > >

> > >

> > >                       "Dave Oshlo"

> > >                       <doshlo@mgpi.com>             To:

> > <radsafe@list.Vanderbilt.Edu>

> > >                       Sent by:                      cc:

> > >                       owner-radsafe@list.Van        Subject:  sodium

> > iodide scintillation detectors

> > >                       derbilt.Edu

> > >

> > >

> > >                       08/05/2004 02:46 PM

> > >                       Please respond to

> > >                       "Dave Oshlo"

> > >

> > >

> > >

> > >

> > >

> > >

> > > Dear radsafers,

> > >

> > >

> > > I’m looking for two pieces of data on a typical sodium iodide

> > scintillation

> > > detector but can find inadequate documentation.

> > >

> > >

> > > 1.      What is the life expectancy of a sodium iodide scintillation

> > > detector in an operational nuclear power plant environment?

> > >

> > >

> > > 2.      What is the shelf life of a sodium iodide scintillation

detector

> > > (in the warehouse as a spare part)?

> > >

> > >

> > > An exhaustive web search has not provided any solutions.  If someone

> could

> > > point me in the right direction, I would be much obliged.

> > >

> > >

> > > Thanks,

> > >

> > >

> > > Dave Oshlo

> > >

> > >

> > > MGP Instruments

> > >

> > >

> > >

> > >

> > >

> > >

> > >

> > >

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> > >

> > >

> >

> >

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> >

>

>

>





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