Talk:Three Mile Island accident/Archive 3

Pilot Operated Relief Valve (PORV)
The valve did not fail to due a problem with the valve design but due to lack of proper maintenance by the plant operator. (But note last paragraph in this section.)

The TMI-2 PORV was temporarily installed in TMI-1 while the TMI-1 PORV was being refurbished. After the refurbishment was complete the TMI-2 PORV was removed from TMI-1 and re-installed in TMI-2 without any maintenance being performed.

In the early 1980's the TMI-1 PORV was removed for inspection. Upon disassembly it was noted that the valve internals were all corroded and both the main disc and the pilot disc could not be moved. An analysis of the corrosion indicated that it was caused by sulfur. A review of the TMI-1 primary coolant system indicated that a sodium thiosulfate tank was piped to the system and was probably the source of the sulfur. The conclusion was that in the steam bubble inside the pressurizer the sulfur came out of solution and migrated to the PORV. The plant operator did remove the sodium thiosulfate tank from the primary system and chemically cleaned the primary system.

Because the TMI-2 PORV was installed in TMI-1 it was exposed to the sulfur environment. Also because it was re-installed in TMI-2 with any maintenance being performed the sulfur was allowed to stay in the valve.

Photographs of the valve indicate the following: 1. The solenoid plunger is in the retracted position indicating that the solenoid functioned properly when electrical power was removed. Background: The solenoid plunger contacts the pilot valve operating lever (causing the pilot valve to open which then allows the main disc to open) when the solenoid is activated (electrical power applied to the solenoid). When electrical power is removed from the solenoid the solenoid plunger retracts from the pilot valve operating lever allowing the pilot valve to close (moving the operating lever to the closed position) causing the main disc to close. 2. The pilot valve operating lever is in the open position which means the pilot valve did not close. No conclusion can be reached about the main disc as it is internal to the valve with no external position indication.

Thus the electrical part of the valve performed as required but the mechanical part did not. The most likely explanation is sulfur corrosion allowed initial movement upon activation but prevented subsequent movement due to interference with the tight clearances in the valve.GPU Engineer (talk) 18:10, 28 March 2017 (UTC)


 * Good discussion, but in the wrong place. The Talk area is for discussions about how to make the article better.  This sort of information belongs there, but only if it can b backed up by reliable sources.  Wikipedia has a no-original-research requirement of its editors; we're not allowed to theorize on the content, but rather to site research done by the competent engineers and such.  It sounds like this was a conclusion reached by the engineers who did the reactor decommissioning, or the accident investigation people.  Get a citation (or several) and write it into the main article. SkoreKeep (talk) 22:38, 28 March 2017 (UTC)

No-original-research requirement or not, GPU Engineer raises the important issue of repeat PORV failure. This valve repeatedly fails in normal operation. Routine turbine trips open this valve in B&W reactors, which have small pressurizers to save money. Prior to the PORV opening, pressurizer spray turns on which results in large amounts of water droplets at supersonic velocities passing thru the repeatedly reversing valve path in the PORV. This is the primary cause of the PORV failures, this is what causes the sound of "a freight train". The supersonic water droplets act like bullets and beat the crap out of the valve. A rugged steam dryer before the PORV or in the upper pressurizer would help greatly. Thus the PORV valve fails in routine operation, a situation still not addressed. This also happens in Westinghouse reactors, but happens far less because Westinghouse reactors have larger pressurizers. Full PORV valve testing could be best accomplished by locating a PORV and condensate tank in a secure location just outside the containment building.207.237.87.163 (talk) 13:18, 28 November 2018 (UTC)BG

Statistics and neutrality
The current wording in the introduction is

"... studies ... determined there was a small statistically non-significant increase in the rate and thus no causal connection ..."

I expect a significant number of people who read this will come away with the thought "there was an increase in the cancer rate". This is bad, since the whole point of the sentence is to emphasize the insignificance of the change, and that there is no causal connection between the accident and cancer cases.

I had made a small edit to improve this sentence (to say there was a "statistically insignificant change"), but to my surprise the change was reverted back to the language telling the reader there is an increase.

Since this is apparently a controversial change, but one I still believe will improve the introduction, I'm bringing the issue to the talk page to get more opinions on whether this should go through. Hurkyl (talk) 20:32, 18 September 2017 (UTC)

Science deniers are everywhere. It seems is the numbers are statistically insignificant, then the text should reflect those facts, and not the emotional verbiage that users may prefer.

As John Adams said, “Facts are stubborn things.” (https://www.brainyquote.com/quotes/john_adams_134175) DrBobDrBob (talk) 02:10, 3 August 2018 (UTC)


 * It seems if the numbers are statistically insignificant... DrBobDrBob (talk) 02:11, 3 August 2018 (UTC)

Change in cost figure
Comes 207.197.114.179 changing Sovacool's damage estimate from $2.4 billion to $2.8 billion. The reference to the journal Energy Policy in 2007 is unchanged, so I assume that if the estimate changed then the article reference is no longer current, and a new reference is needed to support the new cost. SkoreKeep (talk) 21:01, 23 October 2017 (UTC)