ULTRASONICS AND DECONTAMINATION

["Scarboro, Michael G." <mgscarboro@tva.gov>]

> 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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