Ukraine nuke shutdown...

[Jeroen Belleman]

On 2022-09-12 17:16, Glen Walpert wrote:

On Mon, 12 Sep 2022 15:24:24 +0100, Martin Brown wrote:

On 12/09/2022 14:12, upsidedown@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the
coolant pumps full bore and the amount of power needed is within what
emergency backup generators can supply. ISTR most have two independent
grid connections so that cooling can be maintained even if one link
fails. That\'s how its done in the UK anyway. I don\'t think anyone
considered the possibility of having a full scale war raging round a
nuclear plant.

At least in some countries they run dedicated direct high voltage lines
from a nearby hydroelectric plant. The hydros are considered foolproof.

That assumes you have one nearby. Most UK nuclear sites do not. The only
one that might have was the experimental reactor at Dounreay home of the
worlds only radioactive caustic soda plant. Using liquid sodium as
coolant made life too interesting. Cleaning it all up is still ongoing:

https://www.neimagazine.com/features/featuresodium-success-story-at-
dounreays-pfr-9408761/

Sodium cooled FBR\'s now in the planning stage:
https://www.terrapower.com/our-work/natriumpower/

I did a lot of testing of shaft seals for sodium pumps for the
subsequently canceled Clinch River FBR in \'74-75 while I was a full time
lab tech at the Stein Seal Co. & part time engineering student. Safely
pumping hot pressurized radioactive sodium is now a long solved problem,
although those who solved the problem last time are either retired or dead
now.

Yes, but their methods are no longer accepted practice, so even if
they\'d still be around, they would have been useless. Nuclear safety
has changed a lot since the 1970\'s.

Jeroen Belleman

 

[Mike Monett VE3BTI]

Glen Walpert <nospam@null.void> wrote:

Sodium cooled FBR\'s now in the planning stage:
https://www.terrapower.com/our-work/natriumpower/

The thermal storage only supplies power for 5.5 hrs. What happens when the
demand lasts longer than that?

The turbines and generators need to be rated for the full 500 MWe of
combined power. It would be cheaper to skip the sodium storage and simply
upgrade the reactor from 345 MWe to the full 500 MWe.

This will result in a cheaper system with fewer failure points, that will
last longer than 5.5 Hrs.

This is simply a familiar money-grubbing scheme that will enrich the
owners, who will disappear before the system is scheduled to be put in
operation.

They will claim they ran into an unexpected roadblock that will take more
time and investment to solve. When they don\'t get the money, they will
simply shut down and enjoy the money.

There are thousands of excuses they could use. They could say they failed
to get a license from the Nuclear Regulatory Commission (NRC) due to some
obstacle they could not overcome, like sodium thermal storage. This will be
well-planned in advance and will run like clockwork.




--
MRM

 

[Glen Walpert]

On Mon, 12 Sep 2022 11:20:19 -0700 (PDT), Lasse Langwadt Christensen
wrote:

mandag den 12. september 2022 kl. 17.16.07 UTC+2 skrev Glen Walpert:
On Mon, 12 Sep 2022 15:24:24 +0100, Martin Brown wrote:

On 12/09/2022 14:12, upsid...@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the
coolant pumps full bore and the amount of power needed is within
what emergency backup generators can supply. ISTR most have two
independent grid connections so that cooling can be maintained even
if one link fails. That\'s how its done in the UK anyway. I don\'t
think anyone considered the possibility of having a full scale war
raging round a nuclear plant.

At least in some countries they run dedicated direct high voltage
lines from a nearby hydroelectric plant. The hydros are considered
foolproof.

That assumes you have one nearby. Most UK nuclear sites do not. The
only one that might have was the experimental reactor at Dounreay
home of the worlds only radioactive caustic soda plant. Using liquid
sodium as coolant made life too interesting. Cleaning it all up is
still ongoing:

https://www.neimagazine.com/features/featuresodium-success-story-at-
dounreays-pfr-9408761/
Sodium cooled FBR\'s now in the planning stage:
https://www.terrapower.com/our-work/natriumpower/

I did a lot of testing of shaft seals for sodium pumps for the
subsequently canceled Clinch River FBR in \'74-75 while I was a full
time lab tech at the Stein Seal Co. & part time engineering student.
Safely pumping hot pressurized radioactive sodium is now a long solved
problem, although those who solved the problem last time are either
retired or dead now.

I thought they would use electromagnetic pump so it would be a close
system with no shafts or seals

That method was also tested by GE during Clinch River FBR design, standard
induction motor drive with a non-magnetic can in the air gap between rotor
and stator (as commonly used in sealless circ pumps), with the entire
rotor assy in sodium and the stator in air. There are pros and cons both
ways, as far as I know GE did not decide which method to use before the
project was canceled. The canned rotor design put the entire motor in the
high radiation part of the plant, while the shaft with seal design put the
motor and seal on the low radiation side of an 8-foot thick shield. The
seal design was double buffered, with multiple low probability failures
required to allow any sodium leakage, while the canned rotor will leak
into the presumably sealed and pressurized motor stator housing with any
failure of the necessarily thin can. (I never saw the details of the
canned rotor design, just going on description from GE engineer.)

 

[John Walliker]

On Monday, 12 September 2022 at 22:02:27 UTC+1, Glen Walpert wrote:

On Mon, 12 Sep 2022 11:20:19 -0700 (PDT), Lasse Langwadt Christensen
wrote:
mandag den 12. september 2022 kl. 17.16.07 UTC+2 skrev Glen Walpert:
On Mon, 12 Sep 2022 15:24:24 +0100, Martin Brown wrote:

On 12/09/2022 14:12, upsid...@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the
coolant pumps full bore and the amount of power needed is within
what emergency backup generators can supply. ISTR most have two
independent grid connections so that cooling can be maintained even
if one link fails. That\'s how its done in the UK anyway. I don\'t
think anyone considered the possibility of having a full scale war
raging round a nuclear plant.

At least in some countries they run dedicated direct high voltage
lines from a nearby hydroelectric plant. The hydros are considered
foolproof.

That assumes you have one nearby. Most UK nuclear sites do not. The
only one that might have was the experimental reactor at Dounreay
home of the worlds only radioactive caustic soda plant. Using liquid
sodium as coolant made life too interesting. Cleaning it all up is
still ongoing:

https://www.neimagazine.com/features/featuresodium-success-story-at-
dounreays-pfr-9408761/
Sodium cooled FBR\'s now in the planning stage:
https://www.terrapower.com/our-work/natriumpower/

I did a lot of testing of shaft seals for sodium pumps for the
subsequently canceled Clinch River FBR in \'74-75 while I was a full
time lab tech at the Stein Seal Co. & part time engineering student.
Safely pumping hot pressurized radioactive sodium is now a long solved
problem, although those who solved the problem last time are either
retired or dead now.

I thought they would use electromagnetic pump so it would be a close
system with no shafts or seals
That method was also tested by GE during Clinch River FBR design, standard
induction motor drive with a non-magnetic can in the air gap between rotor
and stator (as commonly used in sealless circ pumps), with the entire
rotor assy in sodium and the stator in air. There are pros and cons both
ways, as far as I know GE did not decide which method to use before the
project was canceled. The canned rotor design put the entire motor in the
high radiation part of the plant, while the shaft with seal design put the
motor and seal on the low radiation side of an 8-foot thick shield. The
seal design was double buffered, with multiple low probability failures
required to allow any sodium leakage, while the canned rotor will leak
into the presumably sealed and pressurized motor stator housing with any
failure of the necessarily thin can. (I never saw the details of the
canned rotor design, just going on description from GE engineer.)

Wouldn\'t there be massive eddy current losses if the rotor was flooded with
molten sodium?

John

 

[Lasse Langwadt Christensen]

mandag den 12. september 2022 kl. 23.02.27 UTC+2 skrev Glen Walpert:

On Mon, 12 Sep 2022 11:20:19 -0700 (PDT), Lasse Langwadt Christensen
wrote:
mandag den 12. september 2022 kl. 17.16.07 UTC+2 skrev Glen Walpert:
On Mon, 12 Sep 2022 15:24:24 +0100, Martin Brown wrote:

On 12/09/2022 14:12, upsid...@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the
coolant pumps full bore and the amount of power needed is within
what emergency backup generators can supply. ISTR most have two
independent grid connections so that cooling can be maintained even
if one link fails. That\'s how its done in the UK anyway. I don\'t
think anyone considered the possibility of having a full scale war
raging round a nuclear plant.

At least in some countries they run dedicated direct high voltage
lines from a nearby hydroelectric plant. The hydros are considered
foolproof.

That assumes you have one nearby. Most UK nuclear sites do not. The
only one that might have was the experimental reactor at Dounreay
home of the worlds only radioactive caustic soda plant. Using liquid
sodium as coolant made life too interesting. Cleaning it all up is
still ongoing:

https://www.neimagazine.com/features/featuresodium-success-story-at-
dounreays-pfr-9408761/
Sodium cooled FBR\'s now in the planning stage:
https://www.terrapower.com/our-work/natriumpower/

I did a lot of testing of shaft seals for sodium pumps for the
subsequently canceled Clinch River FBR in \'74-75 while I was a full
time lab tech at the Stein Seal Co. & part time engineering student.
Safely pumping hot pressurized radioactive sodium is now a long solved
problem, although those who solved the problem last time are either
retired or dead now.

I thought they would use electromagnetic pump so it would be a close
system with no shafts or seals
That method was also tested by GE during Clinch River FBR design, standard
induction motor drive with a non-magnetic can in the air gap between rotor
and stator (as commonly used in sealless circ pumps), with the entire
rotor assy in sodium and the stator in air. There are pros and cons both
ways, as far as I know GE did not decide which method to use before the
project was canceled. The canned rotor design put the entire motor in the
high radiation part of the plant, while the shaft with seal design put the
motor and seal on the low radiation side of an 8-foot thick shield. The
seal design was double buffered, with multiple low probability failures
required to allow any sodium leakage, while the canned rotor will leak
into the presumably sealed and pressurized motor stator housing with any
failure of the necessarily thin can. (I never saw the details of the
canned rotor design, just going on description from GE engineer.)

I was thinking EM pumps with no moving parts, current is run through
the sodium and it is moved through pipes with magnetism

 

[Martin Brown]

On 12/09/2022 21:00, Jeroen Belleman wrote:

On 2022-09-12 15:12, upsidedown@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the coolant
pumps full bore and the amount of power needed is within what emergency
backup generators can supply. ISTR most have two independent grid
connections so that cooling can be maintained even if one link fails.
That\'s how its done in the UK anyway. I don\'t think anyone considered
the possibility of having a full scale war raging round a nuclear plant.

At least in some countries they run dedicated direct high voltage
lines from a nearby hydroelectric plant. The hydros are considered
foolproof.

I do not know if they have hydros in Ukraine (it is quite flat), but
according to the news, they just repaired some auxiliary line to allow
removing the decay heat. Is it just a connection to the national grid
or do they have some external facility ?


If they have 200MWth available even with the reactor shut down, why
did no one think of using that to drive a few smaller auxiliary
turbines with that? What madness brought them to designing a plant
that cannot be shut down and kept in a safe state on its own?

I think what Glen said in response to my earlier post is probably right.

That they do have enough fast start emergency diesel electric generators
on site to run the pumps continuously even when disconnected from the
grid and would have started out with a full reserve fuel tank.

But they now have an uncertain amount of fuel remaining after being
forced to use it when off grid and/or pilfering by Russian forces.

It seems unlikely that the Russians would top up their reserve fuel
diesel tanks but they might well be tempted to use it up.

--
Regards,
Martin Brown

 

[Jasen Betts]

On 2022-09-12, Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

I thought they would use electromagnetic pump so it would be a close
system with no shafts or seals
That method was also tested by GE during Clinch River FBR design, standard
induction motor drive with a non-magnetic can in the air gap between rotor
and stator (as commonly used in sealless circ pumps), with the entire
rotor assy in sodium and the stator in air. There are pros and cons both
ways, as far as I know GE did not decide which method to use before the
project was canceled. The canned rotor design put the entire motor in the
high radiation part of the plant, while the shaft with seal design put the
motor and seal on the low radiation side of an 8-foot thick shield. The
seal design was double buffered, with multiple low probability failures
required to allow any sodium leakage, while the canned rotor will leak
into the presumably sealed and pressurized motor stator housing with any
failure of the necessarily thin can. (I never saw the details of the
canned rotor design, just going on description from GE engineer.)

I was thinking EM pumps with no moving parts, current is run through
the sodium and it is moved through pipes with magnetism

Magnetohydrodynamic



--
Jasen.

 

[Jeroen Belleman]

On 2022-09-13 10:10, Martin Brown wrote:

On 12/09/2022 21:00, Jeroen Belleman wrote:
On 2022-09-12 15:12, upsidedown@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the
coolant pumps full bore and the amount of power needed is
within what emergency backup generators can supply. ISTR most
have two independent grid connections so that cooling can be
maintained even if one link fails. That\'s how its done in the
UK anyway. I don\'t think anyone considered the possibility of
having a full scale war raging round a nuclear plant.

At least in some countries they run dedicated direct high
voltage lines from a nearby hydroelectric plant. The hydros are
considered foolproof.

I do not know if they have hydros in Ukraine (it is quite flat),
but according to the news, they just repaired some auxiliary line
to allow removing the decay heat. Is it just a connection to the
national grid or do they have some external facility ?


If they have 200MWth available even with the reactor shut down,
why did no one think of using that to drive a few smaller
auxiliary turbines with that? What madness brought them to
designing a plant that cannot be shut down and kept in a safe state
on its own?

I think what Glen said in response to my earlier post is probably
right.

That they do have enough fast start emergency diesel electric
generators on site to run the pumps continuously even when
disconnected from the grid and would have started out with a full
reserve fuel tank.

But they now have an uncertain amount of fuel remaining after being
forced to use it when off grid and/or pilfering by Russian forces.

It seems unlikely that the Russians would top up their reserve fuel
diesel tanks but they might well be tempted to use it up.

Well, that\'s my point: Why use diesel, which may run out, if you
have several 100 MW of steam power ready for the taking. When that
runs out, the need for it is gone too.

By the way, the primary circuit pumps are real beasts. In a traditional
Westinghouse-type PWR, there are three 5 MW pumps. When a PWR is
started up from the cold state, the waste heat and the churn of these
pumps are what brings the reactor to the hot stopped state.

Jeroen Belleman

 

[server]

On Mon, 12 Sep 2022 22:00:38 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

On 2022-09-12 15:12, upsidedown@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the coolant
pumps full bore and the amount of power needed is within what emergency
backup generators can supply. ISTR most have two independent grid
connections so that cooling can be maintained even if one link fails.
That\'s how its done in the UK anyway. I don\'t think anyone considered
the possibility of having a full scale war raging round a nuclear plant.

At least in some countries they run dedicated direct high voltage
lines from a nearby hydroelectric plant. The hydros are considered
foolproof.

A hydro plant can be quite foolproof, but the HV line might not be.

In some cases, at the nuclear site, they had only a single voltage
measurement transformer connected between two phases. If this
measurement shows normal voltages, it was assumed that the feed from
the hydro was OK.

However, there gas been cases, in which two phases were OK, but the
third phase was down, but no one noticed this situation for several
months. If this feed would have to be used to run the emergency
pumps, the motors would not start . Essentially only a single
phase feed to the delta connected motor. To start a three phase
motor, you need all three phases.

After this scary situation, they now monitor the voltages on all three
phases on the external feed.

I do not know if they have hydros in Ukraine (it is quite flat), but
according to the news, they just repaired some auxiliary line to allow
removing the decay heat. Is it just a connection to the national grid
or do they have some external facility ?


If they have 200MWth available even with the reactor shut down, why
did no one think of using that to drive a few smaller auxiliary
turbines with that?

There can be multiple reason for a reactor shutdown. One is a leak in
the tubing. How could you trust that steam with correct temperature
and pressure would be available to drive the smaller turbine if some
tubing is broken ?

What madness brought them to designing a plant
that cannot be shut down and kept in a safe state on its own?

Jeroen Belleman

 

[Martin Brown]

On 13/09/2022 09:33, Jasen Betts wrote:

On 2022-09-12, Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

I thought they would use electromagnetic pump so it would be a close
system with no shafts or seals
That method was also tested by GE during Clinch River FBR design, standard
induction motor drive with a non-magnetic can in the air gap between rotor
and stator (as commonly used in sealless circ pumps), with the entire
rotor assy in sodium and the stator in air. There are pros and cons both
ways, as far as I know GE did not decide which method to use before the
project was canceled. The canned rotor design put the entire motor in the
high radiation part of the plant, while the shaft with seal design put the
motor and seal on the low radiation side of an 8-foot thick shield. The
seal design was double buffered, with multiple low probability failures
required to allow any sodium leakage, while the canned rotor will leak
into the presumably sealed and pressurized motor stator housing with any
failure of the necessarily thin can. (I never saw the details of the
canned rotor design, just going on description from GE engineer.)

I was thinking EM pumps with no moving parts, current is run through
the sodium and it is moved through pipes with magnetism

Magnetohydrodynamic

Astronomers and some brave mechanical/chemical engineers have been
playing with rapidly stirred spheres of molten sodium as an analogue
model of the processes that generate suns magnetic field.

https://ui.adsabs.harvard.edu/abs/2006APS..DPPBP1094K/abstract

I used to know one of the players in this game. It seems with some
success. I find bulk molten sodium more than a little bit scary. YMMV
(potassium would be worse)

--
Regards,
Martin Brown

 

[Martin Brown]

On 16/09/2022 18:14, John Walliker wrote:

On Friday, 16 September 2022 at 14:51:40 UTC+1, bill....@ieee.org wrote:
On Friday, September 16, 2022 at 10:05:29 PM UTC+10, a a wrote:
On Sunday, 11 September 2022 at 14:57:04 UTC+2, Fred Bloggs wrote:

--- Chernobyl released a bunch of radioactive clouds that blanketed all of western Europe

fake
radioactive clouds never blanketed any country of western Europe
since no rise in radiation was detected by network of radiation detectors at weather station control points

It was first detected on on the Swedish/Finnish border.
Contemporaneous report from the Finnish MOD here:

https://inis.iaea.org/collection/NCLCollectionStore/_Public/19/001/19001530.pdf

They saw readings as high as 200 Bequerels(counts per second) per cubic
metre at sea level and two orders of magnitude higher at altitude.

IOW *YOU* ARE A LIAR
(oh it is shit for brains \"A A\" again - why am I not surprised)

That\'s not the way I remember it.

Nor me. There was fallout in the UK afterwards. Areas with high rainfall were
affected most as Caesium 137 was washed out of the atmosphere. This meant that
sheep in some parts of Wales have been monitored ever since. Fortunately,
the Caesium has now mostly decayed (the half life is about 30 years) or been
washed out of the ground.

Annoyingly it wasn\'t - at least not for a very long time. The heather
and sphagnum moss proved remarkably good at hanging onto strontium and
caesium. It extended the lifetime of Welsh sheep considerably as they
were not deemed fit for human consumption through being too
radioactively hot (and for a long while after).

The initial hope was that high rainfall in these areas would wash it
deeper into the ground and no longer accessible in the food chain.

Import of Haggis was banned in Japan for nearly a decade as a result.

There was also contamination in London. A friend who was a radiation
protection physicist measured the activity of the filters in the main air conditioning
system at a large hospital and found that the filters would need to be handled
as medium level radioactive waste. Most of the activity in the filters was
from iodine 131 which had been adsorbed onto fine airborne soil particles.
Iodine 131 decays very quickly as the half-life is only about 8 days.

At the time I worked for the UK\'s leading mass spectrometer maker.

We were absolutely horrified to see a radio isotope lead signature in
carpark rainwater puddles and various other non-natural short lived
fission product species. We knew what to look for since our machines
were being used to analyse official monitoring air filter samples.

Tiny ion peaks sat on masses where no natural stable isotopes exist was
a bit of a give away that this was fallout from Chernobyl.

--
Regards,
Martin Brown

 

[server]

On Sun, 11 Sep 2022 01:52:46 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

OK, I\'ll imagine there are some energy needs that the plant couldn\'t
self satisfy when disconnected from their grid. So, reconnection
enabled them to shutdown the remaining active reactor:
\"preparations are under way for its cooling and transfer to a cold state\"

The site has six VVER-1000 reactors. Each has 3000 MWth and 950 MWe.

When a nuclear reactor has been running for more than a year and then
stop the chain reaction, the thermal power doesn\'t drop to zero
immediately, but only drops slowly to \"cold\" state, when the short
half life isotopes have decayed. Immediately after shutdown, the
thermal power is still 7 % of the full thermal power, in the VVER-1000
case 210 MWth.

This 210 MW *MUST* be transferred out from the reactor to the
environment for a few days and slightly lower for a week or two. If
this emergency cooling fails, most likely the core _will_ melt. For
this reason, multiple power sources, including multiple diesels are
used to pump out this heat. In Fukushima all these emergency cooling
systems failed, when the diesels were submerged by the tsunami only
after a while after the reactor shutdown (due to the earthquake) and
the result we all know.

In Ukraine if the emergency cooling systems would fail (e.g. due
grenades), shutting the reactor is too late and the reactor core will
melt, if less than a week or two has elapsed since the reactor
shutdown.

Better shut down the reactor now and hope that no grenades will hit
the emergency cooling system in the next week or two. After that, the
reactor is in \"cold\" state and in a more safe state. Of course hitting
the reactors itself with fuel rods inside will spill some radio active
material into the environment, but the contamination is much less
severe than exploding a hot reactor.

 

[Fred Bloggs]

On Sunday, September 11, 2022 at 4:52:58 AM UTC-4, Don Y wrote:

OK, I\'ll imagine there are some energy needs that the plant couldn\'t
self satisfy when disconnected from their grid. So, reconnection
enabled them to shutdown the remaining active reactor:
\"preparations are under way for its cooling and transfer to a cold state\"

But, how does that reduce the risk of \"a nuclear disaster\"? The
plant hasn\'t been decommissioned so fissile material still remains
on the premises. Or, is it just the fact that the *pressure* has
been reduced thereby making venting of radiation less likely in
the event of a containment breach (e.g., due to exploding ordinance)?

https://www.nuclear-power.com/nuclear-power/reactor-physics/reactor-operation/reactor-cooling/

I.e., with the reactor in \"a cold state\", does it cease to be an issue on
the battlefield?

Cold state means the rods have been separated and cooled down, usually submerged in a pool of water, so that radioactive decay of the fissionable material is minimum. The nuclear power plant is just a 19th century vintage steam power kluge that\'s of course very inefficient. Only about 20-30% of the input energy is actually captured in the form of electrical output. So for every 1MW rated output about 5MW , or thereabouts, equivalent heat from nuclear fission was used to make it. This waste needs to be removed from the coolant and expelled to the external environment in order to maintain a controlled, mainly rate of energy production control, in the reactor. So now you know why they\'re always located near high volumetric flow rate rivers or humongous surface area reservoirs of water. Assuming the plant is functioning properly, the most significant environmental damage done by nuclear power is thermal pollution of the local environment, and it is in fact very damaging to the local ecosystem. Getting back to this heat producing kluge, there are a bunch of components used to safely maintain and control the reaction- not the least of which is the containment chamber. If they lose control of the reactor, it runs away from them, producing too much heat, more heat than the cooling can handle. Everything has a melting point, so eventually the whole housing assembly and its components turn to soup, and all the radioactive materials spill all over the place- the atmosphere, the ground, the ground water, the nearby flowing river, you name it. So they end up with an unholy mess that in effect lasts forever, which is what happened at Chernobyl. And this stuff travels. Chernobyl released a bunch of radioactive clouds that blanketed all of western Europe and Scandinavia. Dumps like Hanford in the U.S. have contaminated the Columbia River which happily transports the material to the ocean to poison the entire northwest coast. There are many, many more, especially in the former Soviet Union, vodka and nuclear power don\'t mix well. The stupid Russians are endangering their home population by disrupting this Ukraine power plant. This hysterical stuff about an accidental formation of a critical mass, self-multiplying and very rapid fission reactions, resulting in a nuclear detonation type of explosion is about as likely as the entire Earth exploding from all the radioactive elements in its core- not gonna happen iow.
https://en.wikipedia.org/wiki/Criticality_accident

 

[Fred Bloggs]

On Sunday, September 11, 2022 at 4:52:58 AM UTC-4, Don Y wrote:

OK, I\'ll imagine there are some energy needs that the plant couldn\'t
self satisfy when disconnected from their grid. So, reconnection
enabled them to shutdown the remaining active reactor:
\"preparations are under way for its cooling and transfer to a cold state\"

But, how does that reduce the risk of \"a nuclear disaster\"? The
plant hasn\'t been decommissioned so fissile material still remains
on the premises. Or, is it just the fact that the *pressure* has
been reduced thereby making venting of radiation less likely in
the event of a containment breach (e.g., due to exploding ordinance)?

https://www.nuclear-power.com/nuclear-power/reactor-physics/reactor-operation/reactor-cooling/

I.e., with the reactor in \"a cold state\", does it cease to be an issue on
the battlefield?

Looks like the idiots are powering up the cooling system, which usually requires a few thousand HP of water pumps among other things, from the gird. When they shut the plant down, they lose grid energy. That\'s why they had to wait until the grid was powered back up by external sources to initiate the shutdown. They do have emergency generator backup to power up the cooling system but apparently they don\'t want to rely on that. You can check them on the map, the plant is located adjacent to the Dnipro River, which looks kind of massive of course.
https://en.wikipedia.org/wiki/Dnieper
The Black Sea is only about 100 miles downstream, so it\'s a major contamination risk.
Northern Balkans and Central Europe will catch all the airborne stuff. Looks like the prevailing winds in that part of the world are mostly easterly.
http://wdc.org.ua/atlas/en/4080100.html#:~:text=In%20the%20north%2C%20east%2C%20and,the%20southwest%20%E2%80%93%20southerly%20and%20southeasterly.
http://wdc.org.ua/

It\'s about 500 miles south of Chernobyl.

 

[Don Y]

On 9/11/2022 4:49 AM, upsidedown@downunder.com wrote:

This 210 MW *MUST* be transferred out from the reactor to the
environment for a few days and slightly lower for a week or two. If
this emergency cooling fails, most likely the core _will_ melt. For
this reason, multiple power sources, including multiple diesels are
used to pump out this heat.

So, the single reactor wouldn\'t be able to generate enough power WHILE
shutting down to cool itself? Or, the available diesels aren\'t
enough to get this done? (i.e., why the need for external power
to do this)

In Fukushima all these emergency cooling
systems failed, when the diesels were submerged by the tsunami only
after a while after the reactor shutdown (due to the earthquake) and
the result we all know.

In Ukraine if the emergency cooling systems would fail (e.g. due
grenades), shutting the reactor is too late and the reactor core will
melt, if less than a week or two has elapsed since the reactor
shutdown.

So, the \"threat\" isn\'t directly froma containment breach causing
a radiation leak but, rather, from the reactor eating itself.

[I thought these containment structures were REALLY \"hard\";
not the sort of thing to fail from \"grenades\" or even missiles
(unless a concerted attack). Is the cooling system \"left exposed\",
relatively speaking?]

Better shut down the reactor now and hope that no grenades will hit
the emergency cooling system in the next week or two. After that, the
----------------^^^^^^^^^^^^^^
reactor is in \"cold\" state and in a more safe state. Of course hitting
the reactors itself with fuel rods inside will spill some radio active
material into the environment, but the contamination is much less
severe than exploding a hot reactor.

 

[server]

upsidedown@downunder.com wrote:

On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the coolant
pumps full bore and the amount of power needed is within what emergency
backup generators can supply. ISTR most have two independent grid
connections so that cooling can be maintained even if one link fails.
That\'s how its done in the UK anyway. I don\'t think anyone considered
the possibility of having a full scale war raging round a nuclear plant.

At least in some countries they run dedicated direct high voltage
lines from a nearby hydroelectric plant. The hydros are considered
foolproof.

If I read news report correcty Zaporizhzhia had 4 independent connections
to the grid + dedicated connection to nearby thermal power plant.
Possibly journalists exaggerated and connection to thermal plant
was counted among 4 connections. Anyway, there was a lot of redundancy.

> I do not know if they have hydros in Ukraine (it is quite flat),

There are. But backup plant for Zaporizhzhia is thermal one.

but
according to the news, they just repaired some auxiliary line to allow
removing the decay heat. Is it just a connection to the national grid
or do they have some external facility ?

IIUC they repaired connection to nearby thermal power plant.

--
Waldek Hebisch

 

[server]

upsidedown@downunder.com wrote:

On Thu, 15 Sep 2022 18:53:45 -0000 (UTC), antispam@math.uni.wroc.pl
wrote:

upsidedown@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the coolant
pumps full bore and the amount of power needed is within what emergency
backup generators can supply. ISTR most have two independent grid
connections so that cooling can be maintained even if one link fails.
That\'s how its done in the UK anyway. I don\'t think anyone considered
the possibility of having a full scale war raging round a nuclear plant.

At least in some countries they run dedicated direct high voltage
lines from a nearby hydroelectric plant. The hydros are considered
foolproof.

If I read news report correcty Zaporizhzhia had 4 independent connections
to the grid + dedicated connection to nearby thermal power plant.
Possibly journalists exaggerated and connection to thermal plant
was counted among 4 connections. Anyway, there was a lot of redundancy.

I do not know if they have hydros in Ukraine (it is quite flat),

There are. But backup plant for Zaporizhzhia is thermal one.

Unless the thermal plant is guarantied to be running 24/365 it is
useless for nuclear plant emergency operations.

If the thermal plant is down and you have to restart it, it takes
several hours and by that time the nuclear site has already melted

I do not know details here, but normal thermal power plant has
several generators. Generators routinely are shut down for
maintanence or due to low demand, but shutting down the whole
plant is unusual. So it is reasonable to assume that backup
thermal plant will be running in absence of some catastrophic
event.

Second, Zaporizhzhia is able to operate on its own power for
few hours, so there is time to restart thermal plant.

Concerning \"guarantied\", we are talking here about low probablity
evants. The only guarantied thing is that _some_ such event
_sometimes_ will happen. All we can do is to lower probablity
of such events. But estimating low probabilities is tricky,
one can make significant mistake in such estimates.

Anyway, in Zaporizhzhia case thermal plant proved to be
useful backup: it allowed orderly shutdown (orderly meaning
they still had diesel generators as a buckup) despite
losing all normal connection to the grid. Otherwise
they would have to shutdown quite early during conflict
or take more risc.

--
Waldek Hebisch

 

[Glen Walpert]

On Mon, 12 Sep 2022 14:10:33 -0700 (PDT), John Walliker wrote:

On Monday, 12 September 2022 at 22:02:27 UTC+1, Glen Walpert wrote:
On Mon, 12 Sep 2022 11:20:19 -0700 (PDT), Lasse Langwadt Christensen
wrote:
mandag den 12. september 2022 kl. 17.16.07 UTC+2 skrev Glen Walpert:
On Mon, 12 Sep 2022 15:24:24 +0100, Martin Brown wrote:

On 12/09/2022 14:12, upsid...@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the
coolant pumps full bore and the amount of power needed is within
what emergency backup generators can supply. ISTR most have two
independent grid connections so that cooling can be maintained
even if one link fails. That\'s how its done in the UK anyway. I
don\'t think anyone considered the possibility of having a full
scale war raging round a nuclear plant.

At least in some countries they run dedicated direct high voltage
lines from a nearby hydroelectric plant. The hydros are
considered foolproof.

That assumes you have one nearby. Most UK nuclear sites do not.
The only one that might have was the experimental reactor at
Dounreay home of the worlds only radioactive caustic soda plant.
Using liquid sodium as coolant made life too interesting. Cleaning
it all up is still ongoing:

https://www.neimagazine.com/features/featuresodium-success-story-
at-
dounreays-pfr-9408761/
Sodium cooled FBR\'s now in the planning stage:
https://www.terrapower.com/our-work/natriumpower/

I did a lot of testing of shaft seals for sodium pumps for the
subsequently canceled Clinch River FBR in \'74-75 while I was a full
time lab tech at the Stein Seal Co. & part time engineering student.
Safely pumping hot pressurized radioactive sodium is now a long
solved problem, although those who solved the problem last time are
either retired or dead now.

I thought they would use electromagnetic pump so it would be a close
system with no shafts or seals
That method was also tested by GE during Clinch River FBR design,
standard induction motor drive with a non-magnetic can in the air gap
between rotor and stator (as commonly used in sealless circ pumps),
with the entire rotor assy in sodium and the stator in air. There are
pros and cons both ways, as far as I know GE did not decide which
method to use before the project was canceled. The canned rotor design
put the entire motor in the high radiation part of the plant, while the
shaft with seal design put the motor and seal on the low radiation side
of an 8-foot thick shield. The seal design was double buffered, with
multiple low probability failures required to allow any sodium leakage,
while the canned rotor will leak into the presumably sealed and
pressurized motor stator housing with any failure of the necessarily
thin can. (I never saw the details of the canned rotor design, just
going on description from GE engineer.)

Wouldn\'t there be massive eddy current losses if the rotor was flooded
with molten sodium?

John

Good point, although I am not sure how massive the losses would be with a
very thin layer of whatever the conductivity of liquid sodium is in a
multi-megawatt motor. Likely they were planning to keep the air gap
sodium liquid free with inert gas pressure with vertical shaft, pump on
bottom arrangement used in conventional pumps in similar applications
(taking a guess). The conventional pump with seal kept the liquid sodium
~10 feet below the seal with gas pressure, and kept sodium vapor away from
the seals with continuous gas purge, in above a labyrinth and out below
with sodium recovery on the bleed.

Glen

 

[Glen Walpert]

On Mon, 12 Sep 2022 14:14:00 -0700 (PDT), Lasse Langwadt Christensen
wrote:

mandag den 12. september 2022 kl. 23.02.27 UTC+2 skrev Glen Walpert:
On Mon, 12 Sep 2022 11:20:19 -0700 (PDT), Lasse Langwadt Christensen
wrote:
mandag den 12. september 2022 kl. 17.16.07 UTC+2 skrev Glen Walpert:
On Mon, 12 Sep 2022 15:24:24 +0100, Martin Brown wrote:

On 12/09/2022 14:12, upsid...@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:


Once it has cooled down enough you don\'t need to be running the
coolant pumps full bore and the amount of power needed is within
what emergency backup generators can supply. ISTR most have two
independent grid connections so that cooling can be maintained
even if one link fails. That\'s how its done in the UK anyway. I
don\'t think anyone considered the possibility of having a full
scale war raging round a nuclear plant.

At least in some countries they run dedicated direct high voltage
lines from a nearby hydroelectric plant. The hydros are
considered foolproof.

That assumes you have one nearby. Most UK nuclear sites do not.
The only one that might have was the experimental reactor at
Dounreay home of the worlds only radioactive caustic soda plant.
Using liquid sodium as coolant made life too interesting. Cleaning
it all up is still ongoing:

https://www.neimagazine.com/features/featuresodium-success-story-
at-
dounreays-pfr-9408761/
Sodium cooled FBR\'s now in the planning stage:
https://www.terrapower.com/our-work/natriumpower/

I did a lot of testing of shaft seals for sodium pumps for the
subsequently canceled Clinch River FBR in \'74-75 while I was a full
time lab tech at the Stein Seal Co. & part time engineering student.
Safely pumping hot pressurized radioactive sodium is now a long
solved problem, although those who solved the problem last time are
either retired or dead now.

I thought they would use electromagnetic pump so it would be a close
system with no shafts or seals
That method was also tested by GE during Clinch River FBR design,
standard induction motor drive with a non-magnetic can in the air gap
between rotor and stator (as commonly used in sealless circ pumps),
with the entire rotor assy in sodium and the stator in air. There are
pros and cons both ways, as far as I know GE did not decide which
method to use before the project was canceled. The canned rotor design
put the entire motor in the high radiation part of the plant, while the
shaft with seal design put the motor and seal on the low radiation side
of an 8-foot thick shield. The seal design was double buffered, with
multiple low probability failures required to allow any sodium leakage,
while the canned rotor will leak into the presumably sealed and
pressurized motor stator housing with any failure of the necessarily
thin can. (I never saw the details of the canned rotor design, just
going on description from GE engineer.)

I was thinking EM pumps with no moving parts, current is run through the
sodium and it is moved through pipes with magnetism

Got it, inverse of a MHD. Has such a pump ever been used in any practical
application? The Nuke industry would never consider any pump design
without a long track record of high reliability use in power plants, when
the have options with established reliability and high efficiency. I have
never heard of a catastrophic seal failure of any primary cooling pump
shaft seal; if any occurred it was after I retired or not in the US. They
are routinely replaced on hours run well before wearing out.

Glen

 

[Anthony William Sloman]

On Tuesday, September 20, 2022 at 9:52:01 AM UTC+10, Glen Walpert wrote:

On Mon, 12 Sep 2022 14:14:00 -0700 (PDT), Lasse Langwadt Christense wrote:
mandag den 12. september 2022 kl. 23.02.27 UTC+2 skrev Glen Walpert:
On Mon, 12 Sep 2022 11:20:19 -0700 (PDT), Lasse Langwadt Christensen wrote:
mandag den 12. september 2022 kl. 17.16.07 UTC+2 skrev Glen Walpert:
On Mon, 12 Sep 2022 15:24:24 +0100, Martin Brown wrote:
On 12/09/2022 14:12, upsid...@downunder.com wrote:
On Mon, 12 Sep 2022 09:34:20 +0100, Martin Brown <\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

<snip>

I was thinking EM pumps with no moving parts, current is run through the
sodium and it is moved through pipes with magnetism.

Got it, inverse of a MHD. Has such a pump ever been used in any practical
application?

I thought that it was a standard solution, in use (in odd places ) for decades.

https://www.sciencedirect.com/science/article/pii/S0306454918305413

Linear synchronous motors were popular back in the 1970\'s.

https://en.wikipedia.org/wiki/Eric_Laithwaite

liked them, which didn\'t help.

<snip>

--
Bill Sloman, Sydney