RE: ULTRASONICS AND DECONTAMINATION

[Jim Kost <jkost@mgpi.com>]

I know this might sound stupid but have you consider freezing the area
with Liquid Nitrogen (during your outage)....when it thaws out it would
loosen the crud in that area.  I have seen 12 inches diameter pipes
froze solid, 500 degrees, during temperature and pressure.   Note: Not
freeze the whole pipe just the area in question.  Just a wild thought!

Whatever,

Jim Kost
jkost@mgpi.com

> -----Original Message-----
> From:	Scarboro, Michael G. [SMTP:mgscarboro@tva.gov]
> Sent:	Friday, October 16, 1998 12:09 PM
> To:	Multiple recipients of list
> Subject:	ULTRASONICS AND DECONTAMINATION
> 
> 
> > At the Browns Ferry Nuclear Plant (GE BWR) we have a decontamination
> > dilemma. A TORUS ring header has accumulated crud that is causing
> elevated
> > dose rates (100 mR/hr contact).  Unfortunately, there is no
> practical way
> > to access the internals of the header.  So, we would like to
> decontaminate
> > the header without being intrusive to the header internals.  The
> header is
> > a ~30 inch diameter pipe with a ~3/4" pipe wall thickness that
> encircles
> > the TORUS.  The header transmits water from the TORUS to various
> systems
> > used for reactor cooling (both shutdown and emergency).  The header
> is
> > completely filled with water at all times.  We can initiate flow
> through
> > the header, but it is not of sufficient velocity to flush away the
> crud.
> > An idea I am pursuing is the use of an ultrasonic wave applied on
> the
> > header pipe exterior surface to try and agitate the crud adhering to
> the
> > bottom of the pipe.  This when combined with flow might be able to
> flush
> > the crud from the ring header and back into the TORUS.  The TORUS is
> > normally desludged during each outage.  Incidentally, internal ring
> header
> > access can be physically achieved during an outage, but due to
> operability
> > requirements for cooling water supplies it is not practical nor
> safe.
> > 
> > Has anyone out there ever employed such a technique?  Can anyone
> point me
> > to a reference or source of such ultrasonic devices?
> > 
> > Thanks,
> > 
> > 
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