NPU / Ventilation Help

[White, Perry, J.]

New subscriber to radsafe (started about the time of the Radon / Smoking

debate whew!).

I was looking for any information from someone with experience or some

expertise in dealing with the use of NPU's, and or any references that

may be out there on this subject.

We had an airborne problem resulting from some problems with our NPU's

and are performing a self assessment on the event and what we need to do

to correct it.

Short synopsis:

One of the 2 NPU's we used was found off.  The exhausts of the 2 units

were "Y'ed" together and ran to the suction of the building ventilation.

The "y" created a back flow through the "off" unit back into the area,

which caused at least part of the airborne problem.

Some of the things we are looking at:

The flow physics in placing a "Y" in the exhaust ventilation, what kind

of back pressure does this create, is it based solely on the areas of

the hoses?

How much is flow reduced based on the length of run (assuming a minimum

of tight bends)?

Does anybody use, or know of a check valve for NPU hose?

How helpful are the use of booster pumps added to the exhaust, what

about adding inline charcoal filters?

What is the best way to verify flow?  Magnahelic, (can you calculate

flow changes if you establish the initial flow with an anemometer), or

use some type of inline flow gauge (mass flow or other).

Any other information or comments welcome as well.



Thanks,



Perry White

Farley Nuclear Plant

pejwhite@southernco.com







 



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