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?

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.

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

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." rel="nofollow" target="_blank">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.

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.

On 11/09/2022 09:52, 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)?

It is more that operational nuclear reactors need ancillary power
available to run just in case they have to shutdown. The coolant pumps
must run for a considerable time afterwards otherwise you can get a TMI
or worse a Chernobyl style bang.

The core remains thermally hot for quite a while after you do a quick
shutdown. Plenty of short lived fission product radioisotopes still
merrily decaying in there on timescales of hours and days.

Snag is that without the pumps moving that heat out of the core it is
far too easy for stagnation to take the core coolant to boiling point
and a massive internal pressure increase. Very bad thing...

> <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?

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.

I think the reactor containment is supposed to be good enough to survive
everything except a deliberate direct hit with the right sort of armour
piercing ordinance. We may yet find out if that really is the case.

--
Regards,
Martin Brown

On 9/12/2022 1:34 AM, Martin Brown 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.

^^^^ this

> I think the reactor containment is supposed to be good enough to survive
> everything except a deliberate direct hit with the right sort of armour
> piercing ordinance. We may yet find out if that really is the case.

Much (all?) infrastructure is designed to address *accidents*,
not malevolent actors. And, even so, often not very well
("Who'da thought a tsunami would flood the generators/pumps located
in the basement?!")

If the pumps must continue in perpetuity (even when "cold"), one has to wonder
how vulnerable *they* are to being compromised. And, with "repair crews" not
just a phone call away...

On Monday, September 12, 2022 at 5:08:19 AM UTC-4, Don Y wrote:
> On 9/12/2022 1:34 AM, Martin Brown 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.
> ^^^^ this
> > I think the reactor containment is supposed to be good enough to survive
> > everything except a deliberate direct hit with the right sort of armour
> > piercing ordinance. We may yet find out if that really is the case.
> Much (all?) infrastructure is designed to address *accidents*,
> not malevolent actors. And, even so, often not very well
> ("Who'da thought a tsunami would flood the generators/pumps located
> in the basement?!")
>
> If the pumps must continue in perpetuity (even when "cold"), one has to wonder
> how vulnerable *they* are to being compromised. And, with "repair crews" not
> just a phone call away...

It's not reactor, it's reactors, this place has 6. They already shut 5 of the 6 down into "cold state" and the sixth was kept operational to generate enough electricity to power its own cooling system as well as maintenance cooling for the cold state reactors. They referred to this mode of operation as "island mode." As of Saturday they restored the Ukraine national grid power to the plant site enabling them to initiate shutdown of the 6th reactor into the cold state, using the external grid to power the requisite cooling loads. They say the shut down is a 30 hour process, so it should be in cold state by now. Having all the reactors now in the cold state has eliminated any chance for a Chernobyl type of disaster. And the cold state maintenance cooling would be a light load for the auxiliary power generation in the event it's ever needed. Underloading the generations should mean the fuel consumption is greatly reduced, one would think, so it would be less of a crisis to keep them fully fueled.
Of course the media is greatly disappointed and scrambling to find some other story to shock and awe the populace, which is all about viewership and charging top dollar for advertisements.

On 9/12/2022 2:38 AM, Fred Bloggs wrote:
> On Monday, September 12, 2022 at 5:08:19 AM UTC-4, Don Y wrote:
>> On 9/12/2022 1:34 AM, Martin Brown 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.
>> ^^^^ this
>>> I think the reactor containment is supposed to be good enough to
>>> survive everything except a deliberate direct hit with the right sort of
>>> armour piercing ordinance. We may yet find out if that really is the
>>> case.
>> Much (all?) infrastructure is designed to address *accidents*, not
>> malevolent actors. And, even so, often not very well ("Who'da thought a
>> tsunami would flood the generators/pumps located in the basement?!")
>>
>> If the pumps must continue in perpetuity (even when "cold"), one has to
>> wonder how vulnerable *they* are to being compromised. And, with "repair
>> crews" not just a phone call away...
>
> It's not reactor, it's reactors, this place has 6.

Yes, it's not uncommon to have more than one reactor at a site.
TMI had two, Chernobyl 4, Fukishima 6, etc.

But, that doesn't change the fact that only the containment
vessel is "hardened". I imagine there are lots of "soft targets"
(e.g., for a malevolent actor -- like a military!) to attack
that can effectively compromise the entire facility. Esp if
getting repairs isn't easy (due to the local conditions).

> They already shut 5 of the 6 down into "cold state" and the sixth was kept
> operational to generate enough electricity to power its own cooling system
> as well as maintenance cooling for the cold state reactors. They referred to
> this mode of operation as "island mode." As of Saturday they restored the
> Ukraine national grid power to the plant site enabling them to initiate
> shutdown of the 6th reactor into the cold state, using the external grid to
> power the requisite cooling loads. They say the shut down is a 30 hour
> process, so it should be in cold state by now. Having all the reactors now
> in the cold state has eliminated any chance for a Chernobyl type of
> disaster. And the cold state maintenance cooling would be a light load for
> the auxiliary power generation in the event it's ever needed. Underloading

Unless *it* becomes compromised.

As I said, these things were designed to tolerate *accidents*,
not deliberate hostile actors.

This is true of most infrastructure that "society" relies upon for
its normal functioning.

[We had a natural gas *shortage* caused by excessive demand.
As a result, appliances (furnaces, etc.) couldn't maintain ignition.
Nothing you could do about it -- other than disconnecting legitimate
customers from the supply (so everyone else could use the supply
that remained).]

It's scary to think about what *your* neighborhood relies upon
and the measures taken (or not!) to ensure it's continued
viability!

> the generations should mean the fuel consumption is greatly reduced, one
> would think, so it would be less of a crisis to keep them fully fueled. Of
> course the media is greatly disappointed and scrambling to find some other
> story to shock and awe the populace, which is all about viewership and
> charging top dollar for advertisements.

On Monday, September 12, 2022 at 6:30:58 AM UTC-4, Don Y wrote:
> On 9/12/2022 2:38 AM, Fred Bloggs wrote:
> > On Monday, September 12, 2022 at 5:08:19 AM UTC-4, Don Y wrote:
> >> On 9/12/2022 1:34 AM, Martin Brown 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.
> >> ^^^^ this
> >>> I think the reactor containment is supposed to be good enough to
> >>> survive everything except a deliberate direct hit with the right sort of
> >>> armour piercing ordinance. We may yet find out if that really is the
> >>> case.
> >> Much (all?) infrastructure is designed to address *accidents*, not
> >> malevolent actors. And, even so, often not very well ("Who'da thought a
> >> tsunami would flood the generators/pumps located in the basement?!")
> >>
> >> If the pumps must continue in perpetuity (even when "cold"), one has to
> >> wonder how vulnerable *they* are to being compromised. And, with "repair
> >> crews" not just a phone call away...
> >
> > It's not reactor, it's reactors, this place has 6.
> Yes, it's not uncommon to have more than one reactor at a site.
> TMI had two, Chernobyl 4, Fukishima 6, etc.
>
> But, that doesn't change the fact that only the containment
> vessel is "hardened". I imagine there are lots of "soft targets"
> (e.g., for a malevolent actor -- like a military!) to attack
> that can effectively compromise the entire facility. Esp if
> getting repairs isn't easy (due to the local conditions).
> > They already shut 5 of the 6 down into "cold state" and the sixth was kept
> > operational to generate enough electricity to power its own cooling system
> > as well as maintenance cooling for the cold state reactors. They referred to
> > this mode of operation as "island mode." As of Saturday they restored the
> > Ukraine national grid power to the plant site enabling them to initiate
> > shutdown of the 6th reactor into the cold state, using the external grid to
> > power the requisite cooling loads. They say the shut down is a 30 hour
> > process, so it should be in cold state by now. Having all the reactors now
> > in the cold state has eliminated any chance for a Chernobyl type of
> > disaster. And the cold state maintenance cooling would be a light load for
> > the auxiliary power generation in the event it's ever needed. Underloading
> Unless *it* becomes compromised.
>
> As I said, these things were designed to tolerate *accidents*,
> not deliberate hostile actors.

Russia is not deliberately attacking the containment structure- the most they're doing is maybe shelling switching station gear. Of course that doesn't preclude the existence of a Russian lunatic thinking it would be real cool to put a hole in the containment building.

>
> This is true of most infrastructure that "society" relies upon for
> its normal functioning.
>
> [We had a natural gas *shortage* caused by excessive demand.
> As a result, appliances (furnaces, etc.) couldn't maintain ignition.
> Nothing you could do about it -- other than disconnecting legitimate
> customers from the supply (so everyone else could use the supply
> that remained).]
>
> It's scary to think about what *your* neighborhood relies upon
> and the measures taken (or not!) to ensure it's continued
> viability!
> > the generations should mean the fuel consumption is greatly reduced, one
> > would think, so it would be less of a crisis to keep them fully fueled. Of
> > course the media is greatly disappointed and scrambling to find some other
> > story to shock and awe the populace, which is all about viewership and
> > charging top dollar for advertisements.

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 ?

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/
>
> 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 ?

I think most UK nuclear sites have (at least) two independent feeds off
different subgrids so that no one line failure or grid segment collapse
(other than near total national blackout) can take both down at once.

They are more likely to have a (dedicated) gas turbine standby backup
somewhere nearby if all else fails.

--
Regards,
Martin Brown

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.
>> 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 ?
>
> I think most UK nuclear sites have (at least) two independent feeds off
> different subgrids so that no one line failure or grid segment collapse
> (other than near total national blackout) can take both down at once.
>
> They are more likely to have a (dedicated) gas turbine standby backup
> somewhere nearby if all else fails.

All Nuke plants I know of in the US use on-site diesel generators for
backup power, tested monthly for ability to reach full load from a cold
start in under a minute. I have heard several reports than the problem
Ukraine reactor has had to use backup diesel power several times and thus
has an unknown but not full amount of diesel fuel remaining.

On 9/12/2022 4:04 AM, Fred Bloggs wrote:
> On Monday, September 12, 2022 at 6:30:58 AM UTC-4, Don Y wrote:
>> On 9/12/2022 2:38 AM, Fred Bloggs wrote:
>>> On Monday, September 12, 2022 at 5:08:19 AM UTC-4, Don Y wrote:
>>>> On 9/12/2022 1:34 AM, Martin Brown 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.
>>>> ^^^^ this
>>>>> I think the reactor containment is supposed to be good enough to
>>>>> survive everything except a deliberate direct hit with the right
>>>>> sort of armour piercing ordinance. We may yet find out if that
>>>>> really is the case.
>>>> Much (all?) infrastructure is designed to address *accidents*, not
>>>> malevolent actors. And, even so, often not very well ("Who'da thought
>>>> a tsunami would flood the generators/pumps located in the
>>>> basement?!")
>>>>
>>>> If the pumps must continue in perpetuity (even when "cold"), one has
>>>> to wonder how vulnerable *they* are to being compromised. And, with
>>>> "repair crews" not just a phone call away...
>>>
>>> It's not reactor, it's reactors, this place has 6.
>> Yes, it's not uncommon to have more than one reactor at a site. TMI had
>> two, Chernobyl 4, Fukishima 6, etc.
>>
>> But, that doesn't change the fact that only the containment vessel is
>> "hardened". I imagine there are lots of "soft targets" (e.g., for a
>> malevolent actor -- like a military!) to attack that can effectively
>> compromise the entire facility. Esp if getting repairs isn't easy (due to
>> the local conditions).
>>> They already shut 5 of the 6 down into "cold state" and the sixth was
>>> kept operational to generate enough electricity to power its own cooling
>>> system as well as maintenance cooling for the cold state reactors. They
>>> referred to this mode of operation as "island mode." As of Saturday they
>>> restored the Ukraine national grid power to the plant site enabling them
>>> to initiate shutdown of the 6th reactor into the cold state, using the
>>> external grid to power the requisite cooling loads. They say the shut
>>> down is a 30 hour process, so it should be in cold state by now. Having
>>> all the reactors now in the cold state has eliminated any chance for a
>>> Chernobyl type of disaster. And the cold state maintenance cooling would
>>> be a light load for the auxiliary power generation in the event it's
>>> ever needed. Underloading
>> Unless *it* becomes compromised.
>>
>> As I said, these things were designed to tolerate *accidents*, not
>> deliberate hostile actors.
>
> Russia is not deliberately attacking the containment structure- the most

Yet!

> they're doing is maybe shelling switching station gear. Of course that
> doesn't preclude the existence of a Russian lunatic thinking it would be
> real cool to put a hole in the containment building.

Or, someone beating their chest in a silly display of bravado.
(Or, someone with nothing to lose after having lost it all, already!)

People have done crazy things in the past (fly planes into buildings)...

Glen Walpert <nospam@null.void> wrote:

> 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.

That still leaves hot radioactive fuel rods to store forever that only
have 0.5% to 0.7% of their energy used, and some kind of fault that
produces a meltdown, such as a fire or earthquake.

The solution is Thorium Molted Salt Reactors. These operate at atmospheric
pressure and at 1250F to 1400F, temperatures that pressurized water
reactors cannot reach. This increases thermal efficiency and allows liquid
CO2 to transfer the heat to drive turbines, which can be much smaller and
fit on a tabletop.

The reactors cannot melt down since they are already molten. They a
walk-away safe, since any fault will melt a frozen drain plug and drain
the salt into a holding tank.

These reactors use virtually 100% of the energy available. There is enough
thorium to last for thousands of years.

The tiny amount of radioactive waste only remains hot for a very short
time, about 300 years compared to the millennia of pressurized water
reactors.

TMSR's do not have to be situated near water like PWR's. China is building
one in the desert.

There is a lot of information and misinformation on the web. One of the
best sources is Kirk Sorenson of Flibe Energy;

Molten-Salt Reactor Choices - Kirk Sorensen of Flibe Energy
https://www.youtube.com/watch?v=mz49CB8XGQo

A bit of encouragement:

Thorium Lifters Could Power Civilization for BILLIONS of Years!
https://www.youtube.com/watch?v=74iiaXIVtZI

China's Molten Salt Reactor Program and the Thorium Fuel Cycle/U233
https://www.youtube.com/watch?v=smI7NdmQ7gc

--
MRM

Mike Monett VE3BTI <spamme@not.com> wrote:

> The solution is Thorium Molted Salt Reactors.

Typo. s/b Molten

--
MRM

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

> >> 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 ?
> >
> > I think most UK nuclear sites have (at least) two independent feeds off
> > different subgrids so that no one line failure or grid segment collapse
> > (other than near total national blackout) can take both down at once.
> >
> > They are more likely to have a (dedicated) gas turbine standby backup
> > somewhere nearby if all else fails.
> All Nuke plants I know of in the US use on-site diesel generators for
> backup power, tested monthly for ability to reach full load from a cold
> start in under a minute. I have heard several reports than the problem
> Ukraine reactor has had to use backup diesel power several times and thus
> has an unknown but not full amount of diesel fuel remaining.

they keep the coolant and oil hot 24-7 or use turbines?

piston engines don't like full power before they are warmed up, turbines don't really care

On Monday, September 12, 2022 at 2:20:25 PM UTC-4, lang...@fonz.dk 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
> > >> 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 ?
> > >
> > > I think most UK nuclear sites have (at least) two independent feeds off
> > > different subgrids so that no one line failure or grid segment collapse
> > > (other than near total national blackout) can take both down at once.
> > >
> > > They are more likely to have a (dedicated) gas turbine standby backup
> > > somewhere nearby if all else fails.
> > All Nuke plants I know of in the US use on-site diesel generators for
> > backup power, tested monthly for ability to reach full load from a cold
> > start in under a minute. I have heard several reports than the problem
> > Ukraine reactor has had to use backup diesel power several times and thus
> > has an unknown but not full amount of diesel fuel remaining.
> they keep the coolant and oil hot 24-7 or use turbines?
>
> piston engines don't like full power before they are warmed up, turbines don't really care

They use engine block heaters:
"the National Fire Protection Agency (NFPA) requires that standby generators be heated as necessary to ensure the system will start and carry the full emergency loads within ten seconds after loss of primary power from the utility service."
The block heaters should be thermostatically controlled to keep the block above 60oF is all that's needed most of the time. It doesn't need to be "hot."

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?

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

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

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.)

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

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

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