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TMI 2 Question

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nspunx4:
Thank you for your very enlightening replies. I have tried to read any material that is available on this subject and on commercial nuclear power in general. I think it is a safe, clean, efficient way to generate electricity. I think that history has shown that even when things go really really wring that the defense in depth safe guards will protect the public health and safety. I also think that the fact that there have been so few serious incidents is a testament to the training and professionalism of you folks, I am very fortunate to be able to read this site and learn from professionals like yourselves.

On another note I have found the B&W Cross Training Manual (available on the NRC sit)e section on TMI 2 and the Davis Besse loss of feed water event from the 80's to be the most educational and intriguing information out there. If anyone can point to any other good resources it would be appreciated.

mjd:
This topic is fairly old, however I just read it for the first time and would like to offer some comments relative to less than 100% totally accurate responses. First, the original question has been answered correctly, the "EFW 12s" being initially closed at TMI2 had no effect on the initial primary pressure response, for the reasons stated. There is this comment response "I am not sure if this is correct.  I am betting that the trip and initial SG blow down did not lift the PORV.  The PZR Spray should have been enough to stay away from the PORV lift setpoint.  This is all just an educated guess from me and should in no way be construed as a fact."
The PRZR spray valve, in auto, on a B&W plant can not in fact overcome the RCS pressure increase if the initiating event is a loss of MFW, even from low initial power. This is a fact; during the Sept 24, 77 event (TMI2 precursor) at DBNPP the spray valve did open, the PORV still opened, both before an RPS HP trip occurred. These two actions prevented an RPS HP trip, RCS pressure was decreasing when the RO manually tripped the reactor in response to the PRZR level approaching off-scale high. The observation that a manual 100% open spray valve may prevent PORV lift on the transient may be true, but with the current ARTS system it is about impossible to simulate. The spray valve at TMI2 was in manual at the time of event initiation, for B equilization. When the TMI2 reactor tripped an RO put the spray valve back in auto and hit the start switch for the 2nd MUP, which did not start; it was successfully started slightly later by a different RO. This may have added to control room confusion also.
There is a comment response "Actually in the 70s a turbine/reactor trip on a BW tended to operate the PORVS 100% of the time." This just is not true, I saw plenty of 100% power trips without a PORV lift. It totally depends on the initiating event. The terminology "turbine/reactor" trip is misleading for the '70s/early '80s as a turbine trip did not automatically trip the reactor then, so the terms should not be combined for discussions of that era.
There is a comment response relative to root cause of TMI2 (discussing RCP trip vs HPI shutdown). Much has been written, and officially not written, about the "Root Cause" of the TMI2 accident. The real root cause of the TMI2 accident is identified here: http://www.nukeknews.com/index.html

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