Large Ukraine Nuke Pwr Plant Being Shelled

Does this mean they couldn’t shut down the reactors in a week before the diesel runs out? That seems odd.

That isn’t how a nuclear reactor works.
Even after you shut it down there is what is called decay heat that has to be removed…for a long time.
Right after shutdown from full power the reactor still produces 6%-7% of full heat that has to be removed. This amount decays down to about 1% after 24 hours. But that is still a lot of BTUs.
Cooling water needs to be circulated to remove this heat.
This is one of the key safety improvements in some newer reactor designs, having the ability to circulate cooling water without the need for pumps.

The note from Tim about the Canadian reactors being able to shutdown with control rods OR chemically (Boron) makes no difference. Shutting down just means no nuclear chain reaction…decay heat still has to be removed (not sure how the Canadian reactors handle this)

Mike

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That isn’t how a nuclear reactor works.
Even after you shut it down there is what is called decay heat that has to be removed…for a long time.
Right after shutdown from full power the reactor still produces 6%-7% of full heat that has to be removed. This amount decays down to about 1% after 24 hours. But that is still a lot of BTUs.
Cooling water needs to be circulated to remove this heat.
This is one of the key safety improvements in some newer reactor designs, having the ability to circulate cooling water without the need for pumps.

^ This issue was the core reason for the Chernobyl disaster. The plant had backup generators, but they took about a minute or so to reach full power. The Russians wanted to test using the residual heat to generate power for the cooling pumps in the interim.

Turns out, that’s not a good idea.

It was also the core reason for the Fukushima disaster. The backup generators got knocked out by the tsunami.

In numerous conversations we’ve had about nuclear power over the years, someone invariably says “if we just got rid of all the regulations it would be cost effective.” That’s true, but not accounting for every contingency leads to disaster. And disasters are really not cost effective.

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Shutting down just means no nuclear chain reaction…decay heat still has to be removed (not sure how the Canadian reactors handle this)

Mike

I don’t claim to be a nuclear engineer but my understanding is that the rods are held in place magnetically, when the power quits they fall into the cooling pond below.

Both China, India and others are using the CANDU Heavy water reactors. India has in the past experimented with using thorium as fuel because they don’t have domestic uranium reserves … oh still going on?

https://www.google.com/search?q=india+thorium+reactor+progre…

https://www.google.com/search?q=how+many+candu+reactors+in+t…

Another nice feature is the ability to refuel while the reactor is operating. I think this is because they use natural uranium rather than enriched?

https://www.neimagazine.com/news/newscanadas-darlington-1-br….

Anymouse

^ This issue was the core reason for the Chernobyl disaster.

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The biggest problem at Chernobyl was the design of the reactor, which resulted in a positive void coefficient. The positive void coefficient produced a runaway positive feedback loop during the strange experiment they were running. In short, boiling in the reactor produced more power, which resulted in more boiling, and even more power. Things got out of control very quickly and the reactor tore itself apart with a large steam explosion from the quick power spike.

US plants do not have this kind of design problem, and would never be licensed to operate in the US. BTW, the plant in question in Ukraine is a VVER, which is more closely similar to the western pressurized water reactor (PWR). The Chernobyl-style RBMKs are no longer operated in Ukraine, but Russia does still have them in operation.

All of the discussion in other posts about emergency power ignores things like steam-driven emergency feedwater pumps. Those safety systems are very common in the US, and something like them exist in PWRs as well as BWRs. Steam is produced in either the steam generators or reactor. The steam goes to drive a small turbine connected to a pump. The pump then delivers cooling water back to the steam generators or reactor. No outside power is needed drive the pump. There might be a small amount of electricity needed to run the control systems for the pump and regulation valves, but that is a small draw.

  • Pete
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All of the discussion in other posts about emergency power ignores things like steam-driven emergency feedwater pumps. Those safety systems are very common in the US, and something like them exist in PWRs as well as BWRs. Steam is produced in either the steam generators or reactor. The steam goes to drive a small turbine connected to a pump. The pump then delivers cooling water back to the steam generators or reactor. No outside power is needed drive the pump. There might be a small amount of electricity needed to run the control systems for the pump and regulation valves, but that is a small draw.

  • Pete

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This is a complex Mickey Mouse way to recover from a Station Blackout. It did not work at Fukushima. Most operators do not know how to do all this reconfiguration during a Station Blackout. It was does not provide any electricity to monitor the status of the reactor, the containment, and many other safety systems. It is not part of any design basis accident procedure authorized by NRC.

Jaak

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This is a complex Mickey Mouse way to recover from a Station Blackout. It did not work at Fukushima. Most operators do not know how to do all this reconfiguration during a Station Blackout. It was does not provide any electricity to monitor the status of the reactor, the containment, and many other safety systems. It is not part of any design basis accident procedure authorized by NRC.
Jaak

The plant operators I know would disagree. The Auxiliary Feedwater Pumps I am familiar with are Safety Class 2 systems. That means they are SAFETY RELATED, and are needed for safe shutdown during accident scenarios.

I only did a short Google search, but below is what Westinghouse says about steam-driven emergency pumps in nuclear power plants.

https://www.westinghousenuclear.com/Portals/0/operating%20pl…

The most safety-significant systems in the case of an SBO [Station Blackout] in a nuclear power plant are the reactor core isolation cooling (RCIC) system for boiling water reactors (BWRs) and the auxiliary feedwater (AFW) system for pressurized water reactors (PWRs). The steam-driven water pump in these systems is typically the frontline component that addresses SBO and provides core heat removal.

If I wanted to spend more time on, I could provide more documentation on the safety significance of these systems. They are not “Mickey Mouse”.

  • Pete
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I don’t claim to be a nuclear engineer but my understanding is that the rods are held in place magnetically, when the power quits they fall into the cooling pond below.

You are still confusing the process of shutting down (inserting control rods or chemicals) and the process of removing heat. Even in normal operation where the operators slowly insert the control rods to perform a shutdown, the decay heat has to be removed in the days after. Note that a slow shutdown generates less decay heat than a sudden shutdown.
I think most designs hold the rods electromagnetically … and then some type of ratchet keeps them from bounding back up.
But in the following second gobs of decay heat is generated that must be removed to prevent damage.
And this heat gradually declines. Probably hundreds of good web sites that can explain all this with nice graphs.
Most disaster plans assume some numbers of days that external power must be supplied to keep the cooling pumps running AFTER the control rods have shutdown due to loss of power (or other reason). The also assume that things like diesel fuel can get resupplied.
I doubt they have planned for a military invasion.

Mike

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The plant operators I know would disagree. The Auxiliary Feedwater Pumps I am familiar with are Safety Class 2 systems. That means they are SAFETY RELATED, and are needed for safe shutdown during accident scenarios.

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Yes it can be used for short term Station Blackout. But after 4 hours it is questionable that these AFW pumps can continue operation because of lack of electricity from batteries. Even Westinghouse says so in the link you provided. Here is Westinghouse statement:

“Proper operation of the AFW system in a PWR traditionally requires DC power from a station
battery, steam from the steam generators and an adequate supply of secondary plant water. The total amount of current draw on the station battery can be a limiting factor in determining the duration of SBO coping.”

https://www.westinghousenuclear.com/Portals/0/operating%20pl…

Again I say that the AFW for long term (>4 hours) Station Blackout is Mickey Mouse. I am also an expert on nuclear power plant systems having worked for Westinghouse and Bechtel Power Corporation for over 30 years on nuclear power plant engineering.

Fukushima became a disaster in their long term Station Blackout.

Jaak

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If anyone hasn’t seen the amazing HBO series “Chernobyl” I highly recommend it. In it, there is a court scene which has an incredibly lucid explanation of exactly what went wrong. Videos are below, each is about three minutes. If anyone has an interest in this topic it is well worth a watch.

https://www.youtube.com/watch?v=TmIEI4ky-Zc

https://www.youtube.com/watch?v=3azNLCo0wyU

https://www.youtube.com/watch?v=IzbOgvWQhHA

The whole series is well worth a watch too. On one hand are the fumbling, bumbling Soviet bureaucrats, and on the other are the incredibly heroic Russian people. Ripping good yarn. Great acting and all star cast.

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syke6’s three links of the Chernobyl movie are representative of the excellence of the movie, and show not only the fatal flaw in much nuclear reactor design but also the fatal flaw in modern human culture. The “men who worked in the control room” of a nuclear power plant “did not understand it either.” Ummm, that was the death sentence. A universal death sentence for modernity if we do not change course.

LOOK, there is something utterly, almost incomprehensibly important, but that important thing is something that “we”*** do not want to accept or even take cognizance of; the possibiity that the catastrophes we are now in and others that we are bringing on ourselves is because of our clinging to one of the fundamental superstitions of mankind: that the sandbox playground of earth will always somehow renew itself erasing our idiocies so we can “play again”. NO.

HUMANS have become the “controllers” of something far more complex and almost infinitely more powerful than a nuclear reactor, to wit, a planetary atmospheric and ecological system now [for the first time in planetary history] profoundly linked to our amoral human political economic systems.

Disaster disaster disaster.

Yes, my point is that GCC and Chernobyl and the idiocy of Putin and others I will not name are all symptoms of the failure of human wisdom to grow anywhere near as rapidly as human knowledge. The growth of human knowledge is now driven more by avarice and power hunger than by an awed loving curiosity about the universe.

So we are damned.

david fb

the ***we above is the crux of the post. I mean by that “we” not only an aggregation of billions of individual “I’s”, but more profoundly by far the now dying and looted common wealth of our mutually inherited wisdom and loving connection across generations through all time.

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HUMANS have become the “controllers” of something far more complex and almost infinitely more powerful than a nuclear reactor, to wit, a planetary atmospheric and ecological system now [for the first time in planetary history] profoundly linked to our amoral human political economic systems.

Disaster disaster disaster.

On a more positive note…

An Explosion of Green
www.theatlantic.com/magazine/archive/1995/04/an-explosion-of…
In the early nineteenth century the cleric Timothy Dwight reported that the 240-mile journey from Boston to New York City passed through no more than twenty miles of forest. Surveying the changes wrought by farmers and loggers in New Hampshire, he wrote, “The forests are not only cut down, but there appears little reason to hope that they will ever grow again.”

Less than two centuries later, despite great increases in the state’s population, 90 percent of New Hampshire is covered by forest. Vermont was 35 percent woods in 1850 and is 80 percent today, and even Massachusetts, Connecticut, and Rhode Island have seen woodlands rebound to the point where they cover nearly three fifths of southern New England…

This unintentional and mostly unnoticed renewal of the rural and mountainous East — not the spotted owl, not the salvation of Alaska’s pristine ranges — represents the great environmental story of the United States, and in some ways of the whole world. Here, where “suburb” and “megalopolis” were added to the world’s vocabulary, an explosion of green is under way, one that could offer hope to much of the rest of the planet. The forests, as a recent federal study pointed out, will still take centuries of care before they recover their original grandeur. And backsliding is always a danger; the regreening of the East faces many threats. But it is undeniably real. In his journal Thoreau listed the species gone from Concord by the middle of the nineteenth century: bear, moose, deer, porcupine, “‘rav’nous howling Wolf,’” and beaver. In 1989 environmental police had to kill a moose that had decided to make its home on the median strip of Route 128, famous as “America’s Technology Highway.” “We’ve never been faced with a moose ten miles from Boston,” said one game warden, who donated the animal’s carcass to a Salvation Army soup kitchen.

DB2

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Disaster disaster disaster.

On a more positive note…

First Comes Global Warming, Then an Evolutionary Explosion
https://e360.yale.edu/features/first_comes_global_warming_th…
In 1997, Arthur Weis found himself with an extra bucket of seeds. Weis, who was teaching at the University of California at Irvine at the time, had dispatched a student, Sheina Sim, to gather some field mustard seeds for a study. When Sim was done with her research, Weis was left with a lot of leftover seeds. For no particular reason, he decided not to throw the bucket out. “We just tossed it in a cold, dry incubator,” said Weis.

Weis is glad they did. When a severe drought struck southern California, Weis realized that he could use the extra bucket of seeds for an experiment. In 2004 he and his colleagues collected more field mustard seeds from the same sites that Sim had visited seven years earlier. They thawed out some of the 1997 seeds and then reared both sets of plants under identical conditions. The newer plants grew to smaller sizes, produced fewer flowers, and, most dramatically, produced those flowers eight days earlier in the spring. The changing climate had, in other words, driven the field mustard plants to evolve over just a few years. “It was serendipity that we had the seeds lying around,” says Weis.

Weis is convinced that his experiment is just a harbinger of things to come. Global warming is projected to drastically raise the average global temperature, as well as producing many other changes to the world’s climate, such as more droughts in California. And in response, Weis and other researchers contend, life will undergo an evolutionary explosion.

DB2

On a more positive note…

An Explosion of Green

DB2

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DB2 is dreaming of the past with this is an article from 28 years ago. It ain’t that way any longer. Soon we will be seeing the remaining forests burning bright.

Jaak

“The growth of human knowledge is now driven more by avarice and power hunger than by an awed loving curiosity about the universe.”

Yes

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