RE: TMI

["George J. Vargo" <vargo@physicist.net>]

Ok, this discussion sent me back to the thermo books, steam tables and a

Mollier diagram that still lives in my desk drawer from power plant days

gone by.  



The stuck open PORV (or safety relief valve in a BWR) is a throttling

process and is isenthalpic (i.e., enthalpy remains constant)



In a nominal 2200 psia system (h(g) ~1120 BTU/lbm -- sorry about the British

engineering units), throttling to standard atmosphere results in a tailpiece

temperature of only ~150F



In a BWR, which operates at a nominal 1020 psia, h(g) ~1192 BTU/lbm,

throttling through a stuck open relief valve to standard atmosphere gives a

tailpiece temperature of  ~305F



Knowing that in both cases, the reactor coolant system is at ~550F, a lack

of understanding of the thermodynamic process obviously lulled the operators

into a false sense of security with respect to the integrity of the RCS.



In operator interviews subsequent to the TMI accident, the ability to

recognize and properly diagnose this phenomena was identified as a glaring

omission in operator training. It resulted in NRC-mandated specific training

in thermal hydraulics for reactor operator candidates.  When I took my SRO

exam in 1983 there was a "Heat Transfer and Fluid Flow" section that

specifically tested the ability to diagnose and identify this kind of an

event in addition to a whole bunch of other neat stuff.



Belated thanks to whoever gave me my now well-worn copy of the 1967 ASME

Steam Tables printed and distributed by CE Power Systems.



George J. Vargo, Ph.D., CHP

Senior Scientist

MJW Corporation

http://www.mjwcorp.com

610-925-3377

610-925-5545 (fax)

vargo@physicist.net





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

From: owner-radsafe@list.vanderbilt.edu

[mailto:owner-radsafe@list.vanderbilt.edu] On Behalf Of Thomas E. Potter

Sent: Tuesday, March 09, 2004 9:44 PM

To: RADSAFE

Cc: 'Bill Prestwich'

Subject: re: TMI





Don't know about stuff deliberately hidden from NRC.  But I have doubts

about the connection of primary coolant leakage to problems detecting flow

from the pressurizer during the accident.  It seems to me that if the

elevated temperatures from the open pressurizer relief valve could not be

distinguished from elevated temperatures from primary coolant leakage, that

must have been one helluva leak.



Thomas E. Potter 



------------------------------



Date: Mon, 08 Mar 2004 15:24:11 -0500

From: Bill Prestwich <prestwic@mcmaster.ca>

Subject: TMI



So far I have not seen anyone refute the statement that a problem at TMI

sometime before the accident was deliberately hidden from the NRC. Is this

true? If so, is it not an indictment of someone? Cheers, Bill Prestwich





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