I see this was a complete waste of time for you. Hopefully other FR readers will benefit. You used the term downcomer incorrectly and imprecisely in your post -- you even admit as much. I have worked on severe accident studies for all reactor types during the years since 1991. In addition, I worked at one of the American BWRs with a Mark I containment during construction so I was able to walk the entire reactor building and inside the RPV itself unimpeded for months. Skimming one NUREG makes you some sort of armchair nuclear quarterback rather than a nuclear engineer with a specialty in risk assessment.
The point of the original post I shared from NEI is that the corium is contained within the concrete structure of the reactor building. Corium cannot "
go wherever it wants" -- you are absolutely wrong. And like Chernobyl, the world is offered more empirical evidence via Fukushima that there is no credible means to create the hypothetical "China Syndrome".
You noted that "
If a LOCA occurs, steam flows from the drywell through a set of vent lines and downcomers into the suppression pool, where the steam is condensed." That LOCA description is appropriate when there is a break in the pipe connected to the RPV. It is wrong to equate the Fukushima sequence to the design-basis-LOCA you cited. In the Fukushima sequence the long-term loss of AC-power led to a lack of water for injection and the water in the core barrel boiled away. The RPV and connected lines were intact. The steam lines are connected high on the RPV. Between the top-of-active-fuel there are large steel structures (steam separators, steam dryers). Corium forms because there is no water (LOCA) and the fuel rod cladding melts (like a candle burning down) letting the ceramic UO2 pellets (with a much higher melting temperature point) fall to the core support plate. In the Fukushima sequence, first water is driven out of the core barrel by boiling it away without replacement (LOCA). ADVs and SRVs dump the steam to the suppression pool -- a fairly routine occurrence. Then the corium forms. Corium will not flow up to the steam lines. Furthermore, the torus (steam suppression chamber) is considered part of containment in a Mark I (sometimes referred to as the wet-well). Thus your understanding of core melt progression, RPV design, and containment design (liner et al) are all seriously flawed.
Only pathetic anti-nukes who cannot tell reality from a Jane Fonda propaganda movie would believe "
... containment is lost and that corium will go wherever it wants, including the wet wells via vent lines and downcomers."
Even if 2 meters (about 6.5 feet) of that structure has been eroded, another 8.2 meters (almost 27 feet) of reinforced steel and concrete lies between the melted fuel and the external environment. It is sad to see that even FR has a virulent group of anti-nukes.
If I used the term wrong, then so did the NRC. See above post. The mistake you made was referring to the downcomer in the RPV. The RPV is immaterial to the corium melt on the drywell floor. At least you could have admitted your mistake, instead of mumbling on about the RPV in your previous post. All I did was the same thing the NRC did.
And once the corium breaks out of containment, it will go where ever it wants. Why else call it containment ?
I never once typed China Syndrome in this thread. Only you did.
Will check the rest of rant tomorrow. Will let you know your additional mistakes then. And note, only you went political. There is nothing political about making thousands of acres of land off limits to humans.
Hopefully other FR readers will benefit. Well that should raise a bunch of red flags around here. If you are just worried about what other freepers think, it means your function here is to sway opinion. You are not worried about discovering what is really going on in Fukushima, where the Japanese themselves admit they cannot precisely verify the location of the corium.
You used the term downcomer incorrectly and imprecisely in your post -- you even admit as much.
Not really. Just used it the same way the NRC did. So your problem is with them. I do however admit that it was like throwing a bone to a dog. You did not have to bite.
Skimming one NUREG makes you some sort of armchair nuclear quarterback rather than a nuclear engineer with a specialty in risk assessment.
First of all, I applaud your work. It is obviously needed and lets all hope we never have another TMI in America. Now kindly point out where the heck I ever claimed to be a nuclear quarterback ? All I did was post one sentence to you. And that set you off. Your initial reply made no sense. I was thinking, why the heck is he even mentioning the RPV ? So I assumed you knew very little. That is why I asked you to go to the manual.
The point of the original post I shared from NEI is that the corium is contained within the concrete structure of the reactor building. Corium cannot "go wherever it wants" -- you are absolutely wrong.
That corium is not just traveling vertically. It is also traveling horizontally. And at drywell floor level it is right up against the steel containment wall with very little between the back side of the wall and the wet wells down below. You do realize how many vent lines and downcomers there are, right ?
You noted that "If a LOCA occurs, steam flows from the drywell through a set of vent lines and downcomers into the suppression pool, where the steam is condensed." That LOCA description is appropriate when there is a break in the pipe connected to the RPV.
That was a reference that you pointed out. I just pulled a sentence from the paragraph in the NRC manual that you pointed too. Those are not my words. There are the NRC's.
..Corium will not flow up to the steam lines. Furthermore, the torus (steam suppression chamber) is considered part of containment in a Mark I (sometimes referred to as the wet-well).
It is the splash affect when the corium comes pouring out of the concrete pedestal base and through the open single doorway in the pedestal base. That corium crashes into the wall opposite the doorway and rides up high with the splash. When you are talking tons of corium coming through a doorway, 2 foot splash is not out of the question when it crashes into the containment wall.
Thus your understanding of core melt progression, RPV design, and containment design (liner et al) are all seriously flawed.
It is all from the NRC manual.
Even if 2 meters (about 6.5 feet) of that structure has been eroded, another 8.2 meters (almost 27 feet) of reinforced steel and concrete lies between the melted fuel and the external environment.
The vertical profile of that concrete core catcher like assembly is not the only way it can leave. It can also travel horizontally and along cracks. And the depth on the concrete in the wet well, especially the horizontal depth, is much smaller.
I am done with this thread. Have fun. You can have the last word. At this point could care less. Your reaction to the bone I tossed, tells me a lot. Will continue trying to learn the truth, because I know you never get 100 % truth from government. And just in case you think the concrete has not been cracked.
