Three Mile Island - Stuck open PORV 2

[matkenmd]

I'm doing some reading on the TMI incident.

There were human factors at play, but a critical pilot operated relief valve was also faulted. I've seen this noted in many reports (Rogovin report) as well as all over the net and unfortunately also Wikipedia which everyone references.

What I don't find is what exactly was the mechanical fault of this particular valve. As it turns out there were other failures in plants of similar design in the same valve (from different manufacturers).

I've done what scouring I can do to find out. What do you know about it? As valve designers, it seems like this is the kind of 'learning from history' is a good thing.

 

[PetroSynergy]

About a year ago I spoke with someone at Ferris engineering on the matter of failing PORV's. He himself said that the PORV sales have descresed rapidly over the past decade. They are useful in some applications, but I would much rather have a mechanically controlled relief valve than one that uses system pressure. IMHO

 

[JLSeagull]

I think that the TMI relief valve problem was some type remotely activated electrical device instead of a traditional section VIII process or section I safety valve. The failure issue would be good information.

 

[vpl]

You might want to read some of the Nuclear Regulatory Commission documents published at the time. (

http://www.nrc.gov

then follow links to > Electronic Reading Room > Document Collections> Generic Communications or > Electronic Reading Room > Document Collections > NUREG Publications). Ones that you might be interested in are Bulletins 79-05, 79-06 and their supplements, Information Notice 79-016, and NUREG 0578, "TMI-2 Lessons Learned." These are all available electronically.
You may also want to look at NUREG 0462 "Technical Report on Operating Experience with BWR Pressure Relief Systems",
dated July 1978. It's mentioned in Generic Letter 79-027. I couldn't find the NUREG itself in an electronic format.

However, there is a link on the NRC public website to contact the public document room staff (

http://www.nrc.gov

then follow links to > Electronic Reading Room > Public Document Room > Contact the PDR Staff.) They may be able to provide you a copy or be able to locate it for you.

Just a final word though -- be careful what conclusions you draw from these 31 year old documents about today's components.

Patricia Lougheed

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[MJCronin]

Patricia..

Just curious..... The need for pressure release is still there in the new PWR and BWR plant designs.

Do you know what the design details are for these new valves in the new generation of nuclear plants ?

-MJC

 

[vpl]

MJCronin

Not off the top of my head; I'm not involved in new construction at all.

Would you want me to find out (can't promise results as I'm not sure how much is publicly available)? I think my profile mentions how to get hold of me.



Patricia Lougheed

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