In message ,
David Paste writes
Hello all,

Reading an article in the Guardian (yes, I know) about a looming
electricity shortage, one of the reasons cited was the phasing
out of coal-fired generating capacity:

http://www.theguardian.com/environme...ers-warn-of-lo
oming-uk-energy-gap

How much of a pain / why can't coal plants be converted to gas if
they are cleaner on the emmissions front?

From very limited knowledge and roughly 40 years ago.... we looked at
converting oil fired boilers to gas and found they would need to be
hugely derated because the gas flame for the same energy would be too
long and hit the back of the burner tube. I guess coal, which may be
powdered before injection, might have a raft of similar issues.

An expert will be along shortly:-)

--
Tim Lamb

On 26/01/2016 20:42, Tim Lamb wrote:
In message ,
David Paste writes
Hello all,

Reading an article in the Guardian (yes, I know) about a looming
electricity shortage, one of the reasons cited was the phasing
out of coal-fired generating capacity:

http://www.theguardian.com/environme...ers-warn-of-lo
oming-uk-energy-gap

How much of a pain / why can't coal plants be converted to gas if
they are cleaner on the emmissions front?

From very limited knowledge and roughly 40 years ago.... we looked at
converting oil fired boilers to gas and found they would need to be
hugely derated because the gas flame for the same energy would be too
long and hit the back of the burner tube. I guess coal, which may be
powdered before injection, might have a raft of similar issues.

An expert will be along shortly:-)

Apart from this, even if you can get the flame to work in a boiler
designed for coal, you will only get the 40% thermal efficiency of a
coal plant. Whereas, if you burn it first in a gas turbine and then heat
steam with the exhaust you have approaching 60% thermal efficiency.
Although we used to think of "jet engines" as being expensive, high tech
kit they are now mature technology.

On 26/01/2016 20:58, newshound wrote:

Apart from this, even if you can get the flame to work in a boiler
designed for coal, you will only get the 40% thermal efficiency of a
coal plant. Whereas, if you burn it first in a gas turbine and then heat
steam with the exhaust you have approaching 60% thermal efficiency.
Although we used to think of "jet engines" as being expensive, high tech
kit they are now mature technology.

I think they probably count as mature, expensive, high tech kit :-)

In article ,
Tim Lamb wrote:
In message ,
David Paste writes
Hello all,

Reading an article in the Guardian (yes, I know) about a looming
electricity shortage, one of the reasons cited was the phasing
out of coal-fired generating capacity:

http://www.theguardian.com/environme...ers-warn-of-lo
oming-uk-energy-gap

How much of a pain / why can't coal plants be converted to gas if
they are cleaner on the emmissions front?

From very limited knowledge and roughly 40 years ago.... we looked at
converting oil fired boilers to gas and found they would need to be
hugely derated because the gas flame for the same energy would be too
long and hit the back of the burner tube. I guess coal, which may be
powdered before injection, might have a raft of similar issues.

An expert will be along shortly:-)

I suspect power plants use gas turbines rather than heating water to create
steam - but, as you say, an expert will be along soon.

--
from KT24 in Surrey, England

On 26/01/2016 21:12, charles wrote:
In article ,
Tim Lamb wrote:
In message ,
David Paste writes
Hello all,

Reading an article in the Guardian (yes, I know) about a looming
electricity shortage, one of the reasons cited was the phasing
out of coal-fired generating capacity:

http://www.theguardian.com/environme...ers-warn-of-lo
oming-uk-energy-gap

How much of a pain / why can't coal plants be converted to gas if
they are cleaner on the emmissions front?

From very limited knowledge and roughly 40 years ago.... we looked at
converting oil fired boilers to gas and found they would need to be
hugely derated because the gas flame for the same energy would be too
long and hit the back of the burner tube. I guess coal, which may be
powdered before injection, might have a raft of similar issues.

An expert will be along shortly:-)

I suspect power plants use gas turbines rather than heating water to create
steam - but, as you say, an expert will be along soon.

CCGT uses *both*

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

On 26/01/2016 21:00, Clive George wrote:
On 26/01/2016 20:58, newshound wrote:

Apart from this, even if you can get the flame to work in a boiler
designed for coal, you will only get the 40% thermal efficiency of a
coal plant. Whereas, if you burn it first in a gas turbine and then heat
steam with the exhaust you have approaching 60% thermal efficiency.
Although we used to think of "jet engines" as being expensive, high tech
kit they are now mature technology.

I think they probably count as mature, expensive, high tech kit :-)

Except the fuel they burn costs many times the hardware that burns it!

On 27/01/16 02:09, Fredxxx wrote:
On 26/01/2016 21:00, Clive George wrote:
On 26/01/2016 20:58, newshound wrote:

Apart from this, even if you can get the flame to work in a boiler
designed for coal, you will only get the 40% thermal efficiency of a
coal plant. Whereas, if you burn it first in a gas turbine and then heat
steam with the exhaust you have approaching 60% thermal efficiency.
Although we used to think of "jet engines" as being expensive, high tech
kit they are now mature technology.

I think they probably count as mature, expensive, high tech kit :-)

Except the fuel they burn costs many times the hardware that burns it!
I missed the original post somehow, but FRedxxx has it pretty much spot
on as far as I am concerned.

To be economic a gas power station needs to be combined cycle - due to
the price of gas mainly. Just about the only part of a coal power
station that is usable would be the alternators.


It would make more sense to convert a coal plant to nuclear. You aren't
concerned much with efficiency, with nuclear. Uranium is dirt cheap.


--
You can get much farther with a kind word and a gun than you can with a
kind word alone.

Al Capone

I've long been suggesting building nuclear steam raising plant alongside the coal boilers. The turbines, switchgear, control room, cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station boiler bears much resemblance to a domestic or even an industrial unit. If you contact your nearest station and ask if they have an open day coming up or if you could be attached to an organised tour I'm sure they would oblige. I toured Drax in the 1970s with one of the station engineers and it's an impressive site. Everything from the "merry go round" coal delivery system to the 400kv switchfarm gates. Even thinking of shutting it is just plain crazy.

In message ,
writes
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial unit.
If you contact your nearest station and ask if they have an open day
coming up or if you could be attached to an organised tour I'm sure
they would oblige. I toured Drax in the 1970s with one of the station
engineers and it's an impressive site. Everything from the "merry go
round" coal delivery system to the 400kv switchfarm gates. Even
thinking of shutting it is just plain crazy.

Umm.. Nuclear plant seems to be sited next to a good source of cooling
water. Coal sited close to the fuel source.

--
Tim Lamb

In article ,
Tim Lamb wrote:
In message ,
writes
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial unit.
If you contact your nearest station and ask if they have an open day
coming up or if you could be attached to an organised tour I'm sure
they would oblige. I toured Drax in the 1970s with one of the station
engineers and it's an impressive site. Everything from the "merry go
round" coal delivery system to the 400kv switchfarm gates. Even
thinking of shutting it is just plain crazy.

Umm.. Nuclear plant seems to be sited next to a good source of cooling
water. Coal sited close to the fuel source.

Coal fired sites also need water. Rivers: like the Trent are good. Think
Battersea & Bankside for Thames water or others close to the sea. Coal
was/is brought by train

--
from KT24 in Surrey, England

"charles" wrote in message
...
In article ,
Tim Lamb wrote:
In message ,
writes
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial unit.
If you contact your nearest station and ask if they have an open day
coming up or if you could be attached to an organised tour I'm sure
they would oblige. I toured Drax in the 1970s with one of the station
engineers and it's an impressive site. Everything from the "merry go
round" coal delivery system to the 400kv switchfarm gates. Even
thinking of shutting it is just plain crazy.

Umm.. Nuclear plant seems to be sited next to a good source of cooling
water. Coal sited close to the fuel source.

Coal fired sites also need water. Rivers: like the Trent are good. Think
Battersea & Bankside for Thames water or others close to the sea. Coal
was/is brought by train

Power stations need two things: good source of fuel and good source of
cooling water. All the power stations I can think of are beside rivers so
the river water can be pumped to the power station to cool the recirculating
clean water, with some of the river water going up the cooling towers as
steam and the majority (once it has been cooled to an environmentally
friendly temperature) being pumped back into the river further downstream.

On 27/01/2016 08:50, wrote:
I've long been suggesting building nuclear steam raising plant alongside the coal boilers. The turbines, switchgear, control room, cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station boiler bears much resemblance to a domestic or even an industrial unit. If you contact your nearest station and ask if they have an open day coming up or if you could be attached to an organised tour I'm sure they would oblige. I toured Drax in the 1970s with one of the station engineers and it's an impressive site. Everything from the "merry go round" coal delivery system to the 400kv switchfarm gates. Even thinking of shutting it is just plain crazy.


Except that 40 year old turbo alternators, CW systems, switchgear etc
are coming to the end of their life.

In article , NY
wrote:
"charles" wrote in message
...
In article , Tim Lamb
wrote:
In message ,
writes
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial
unit. If you contact your nearest station and ask if they have an
open day coming up or if you could be attached to an organised tour
I'm sure they would oblige. I toured Drax in the 1970s with one of
the station engineers and it's an impressive site. Everything from
the "merry go round" coal delivery system to the 400kv switchfarm
gates. Even thinking of shutting it is just plain crazy.

Umm.. Nuclear plant seems to be sited next to a good source of cooling
water. Coal sited close to the fuel source.

Coal fired sites also need water. Rivers: like the Trent are good.
Think Battersea & Bankside for Thames water or others close to the sea.
Coal was/is brought by train

Power stations need two things: good source of fuel and good source of
cooling water. All the power stations I can think of are beside rivers so
the river water can be pumped to the power station to cool the
recirculating clean water, with some of the river water going up the
cooling towers as steam and the majority (once it has been cooled to an
environmentally friendly temperature) being pumped back into the river
further downstream.

There are seaside ones, too. Most of the Nuclear ones are by the sea, but
Longannet, in Fife is seaside. There are probably others.

--
from KT24 in Surrey, England

Most of the plant has been regularly maintained during planned unit outtages. Every thing can be refurbished if required and is not beset by eco loons objecting at every stage of the planning process for a new station.

Most of the plant has been regularly maintained during planned unit outtages. Every thing can be refurbished if required and is not beset by eco loons objecting at every stage of the planning process for a new station.

On 27/01/2016 03:17, The Natural Philosopher wrote:

the price of gas mainly. Just about the only part of a coal power
station that is usable would be the alternators.



The most valuable part is the massive iron-cored transformer. The one
from Didcot was salvaged and taken back to the Siemens factory in
Germany (*) for a refurb and it will then be installed in one of the
many brown-coal fired stations that the Germans are building.

(*) Was pictured on ITV meridian on a special low-loader, using a route
that avoided bridges, on its way to a ferry somewhere near Bristol.

En el artículo ,
newshound escribió:

Except that 40 year old turbo alternators, CW systems, switchgear etc
are coming to the end of their life.

That's true. I watched a TV programme (Power to the People) recently
about Ferrybridge C (coal-burning) station. 50 years old, due to close
in March this year. They're basically keeping it running on string and
sealing wax. The large metal baskets in the maintenance area showing
ancient, obsolete, motors, valves etc. for repair said it all.

http://www.bbc.co.uk/programmes/b06q4z6j

--
(\_/)
(='.'=) Bunny says: Windows 10? Nein danke!
(")_(")

On 27/01/2016 09:37, newshound wrote:
On 27/01/2016 08:50, wrote:
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial
unit. If you contact your nearest station and ask if they have an open
day coming up or if you could be attached to an organised tour I'm
sure they would oblige. I toured Drax in the 1970s with one of the
station engineers and it's an impressive site. Everything from the
"merry go round" coal delivery system to the 400kv switchfarm gates.
Even thinking of shutting it is just plain crazy.


Except that 40 year old turbo alternators, CW systems, switchgear etc
are coming to the end of their life.

Easy to refurbish though. New bearings in the generators etc.

The DRAX merry-go-round came to an end recently when the last deep mine
closed. Now all the fuel is imported.

On 27/01/2016 13:14, Andrew wrote:
On 27/01/2016 09:37, newshound wrote:
On 27/01/2016 08:50, wrote:
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial
unit. If you contact your nearest station and ask if they have an open
day coming up or if you could be attached to an organised tour I'm
sure they would oblige. I toured Drax in the 1970s with one of the
station engineers and it's an impressive site. Everything from the
"merry go round" coal delivery system to the 400kv switchfarm gates.
Even thinking of shutting it is just plain crazy.


Except that 40 year old turbo alternators, CW systems, switchgear etc
are coming to the end of their life.

Easy to refurbish though. New bearings in the generators etc.

The DRAX merry-go-round came to an end recently when the last deep mine
closed. Now all the fuel is imported.

Not from the industry, are you, Andrew Mike and John.

Ever tried running an old car? Eventually there are so many failing bits
that it just isn't worth the effort, assuming you have the option to
replace it with something.

On Tuesday, 26 January 2016 20:43:05 UTC, Tim Lamb wrote:
In message ,
David Paste writes
Hello all,

Reading an article in the Guardian (yes, I know) about a looming
electricity shortage, one of the reasons cited was the phasing
out of coal-fired generating capacity:

http://www.theguardian.com/environme...ers-warn-of-lo
oming-uk-energy-gap

How much of a pain / why can't coal plants be converted to gas if
they are cleaner on the emmissions front?

From very limited knowledge and roughly 40 years ago.... we looked at
converting oil fired boilers to gas and found they would need to be
hugely derated because the gas flame for the same energy would be too
long and hit the back of the burner tube. I guess coal, which may be
powdered before injection, might have a raft of similar issues.

An expert will be along shortly:-)

--
Tim Lamb

Yes.
We tried ceramic "targets" in the path of the flame. Not very successful.

On Wednesday, 27 January 2016 13:52:31 UTC, newshound wrote:
On 27/01/2016 13:14, Andrew wrote:
On 27/01/2016 09:37, newshound wrote:
On 27/01/2016 08:50, wrote:
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial
unit. If you contact your nearest station and ask if they have an open
day coming up or if you could be attached to an organised tour I'm
sure they would oblige. I toured Drax in the 1970s with one of the
station engineers and it's an impressive site. Everything from the
"merry go round" coal delivery system to the 400kv switchfarm gates.
Even thinking of shutting it is just plain crazy.


Except that 40 year old turbo alternators, CW systems, switchgear etc
are coming to the end of their life.

Easy to refurbish though. New bearings in the generators etc.

The DRAX merry-go-round came to an end recently when the last deep mine
closed. Now all the fuel is imported.

Not from the industry, are you, Andrew Mike and John.

Ever tried running an old car? Eventually there are so many failing bits
that it just isn't worth the effort, assuming you have the option to
replace it with something.

We took had taken out a boiler that was absolutely shagged.
I thought they'd cut it up on site, but no.
Carefully removed.

They'd sold it to some place in Pakistan.

On 27/01/16 09:06, Tim Lamb wrote:
In message ,
writes
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial
unit. If you contact your nearest station and ask if they have an open
day coming up or if you could be attached to an organised tour I'm
sure they would oblige. I toured Drax in the 1970s with one of the
station engineers and it's an impressive site. Everything from the
"merry go round" coal delivery system to the 400kv switchfarm gates.
Even thinking of shutting it is just plain crazy.

Umm.. Nuclear plant seems to be sited next to a good source of cooling
water. Coal sited close to the fuel source.

In fact that's merely marginally accidental. Both need decent supplies
of cooling somehow, and it turns out that transporting uranium by sea
upsets less shrinking violets.

Drax uses the Ouse for cooling purposes. many nukes in France are on Rivers.

For a given power a conventional steam turbine needs the same amount of
coolant whatever heat source feeds its boilers.


--
"What do you think about Gay Marriage?"
"I don't."
"Don't what?"
"Think about Gay Marriage."

On 27/01/16 09:37, newshound wrote:
On 27/01/2016 08:50, wrote:
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial
unit. If you contact your nearest station and ask if they have an open
day coming up or if you could be attached to an organised tour I'm
sure they would oblige. I toured Drax in the 1970s with one of the
station engineers and it's an impressive site. Everything from the
"merry go round" coal delivery system to the 400kv switchfarm gates.
Even thinking of shutting it is just plain crazy.


Except that 40 year old turbo alternators, CW systems, switchgear etc
are coming to the end of their life.

Some are, some arent, And they can be refurbed


--
The biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.

On 27/01/16 13:52, newshound wrote:
On 27/01/2016 13:14, Andrew wrote:
On 27/01/2016 09:37, newshound wrote:
On 27/01/2016 08:50, wrote:
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial
unit. If you contact your nearest station and ask if they have an open
day coming up or if you could be attached to an organised tour I'm
sure they would oblige. I toured Drax in the 1970s with one of the
station engineers and it's an impressive site. Everything from the
"merry go round" coal delivery system to the 400kv switchfarm gates.
Even thinking of shutting it is just plain crazy.


Except that 40 year old turbo alternators, CW systems, switchgear etc
are coming to the end of their life.

Easy to refurbish though. New bearings in the generators etc.

The DRAX merry-go-round came to an end recently when the last deep mine
closed. Now all the fuel is imported.

Not from the industry, are you, Andrew Mike and John.

Ever tried running an old car? Eventually there are so many failing bits
that it just isn't worth the effort, assuming you have the option to
replace it with something.


Cost benefit rules, BUT its more akin top repairing a classic car.
remember every power station is a 'one off' so mass production only goes
so far top bring the costs down. To refurb an old boiler is often
cheaper than building a new one.

Same goes for condensers and alternators. Maybe the steam turbines get
replaced now and again.

Nukes die from neutron bombardment eventually, at that point they are
truly beyond repair.



--
The biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.

On 27/01/2016 17:25, The Natural Philosopher wrote:
On 27/01/16 13:52, newshound wrote:
On 27/01/2016 13:14, Andrew wrote:
On 27/01/2016 09:37, newshound wrote:
On 27/01/2016 08:50, wrote:
I've long been suggesting building nuclear steam raising plant
alongside the coal boilers. The turbines, switchgear, control room,
cooling towers, grid connections and workforce are already in place.
To the OP don't imagine a pulverised fuel coal fired power station
boiler bears much resemblance to a domestic or even an industrial
unit. If you contact your nearest station and ask if they have an open
day coming up or if you could be attached to an organised tour I'm
sure they would oblige. I toured Drax in the 1970s with one of the
station engineers and it's an impressive site. Everything from the
"merry go round" coal delivery system to the 400kv switchfarm gates.
Even thinking of shutting it is just plain crazy.


Except that 40 year old turbo alternators, CW systems, switchgear etc
are coming to the end of their life.

Easy to refurbish though. New bearings in the generators etc.

The DRAX merry-go-round came to an end recently when the last deep mine
closed. Now all the fuel is imported.

Not from the industry, are you, Andrew Mike and John.

Ever tried running an old car? Eventually there are so many failing bits
that it just isn't worth the effort, assuming you have the option to
replace it with something.


Cost benefit rules, BUT its more akin top repairing a classic car.
remember every power station is a 'one off' so mass production only goes
so far top bring the costs down. To refurb an old boiler is often
cheaper than building a new one.

Same goes for condensers and alternators. Maybe the steam turbines get
replaced now and again.

Nukes die from neutron bombardment eventually, at that point they are
truly beyond repair.



Well I suppose you can refurbish anything at a price. I agree it comes
down to cost benefit. It's sometimes worth reblading steam turbines, in
part because new manufacturing processes and CFD let you push the
efficiency. But it is not just "big lumps" in a thermal power station.
There's lots of pipework, valves, pumps, heat exchangers, and C&I. If
you have a car with rotten bodywork it is not (generally) worth getting
a new shell and transferring over not only the engine and transmission,
but the wiring, plumbing, hydraulics, glass, trim, etc.

If you are moving from coal to gas, the sensible thing is to go to CCGT
and the old T/A set is simply not re-useable.

It's not only the neutron flux which degrades nuclear plant, there are
also thermal ageing processes, not to mention accumulation of creep and
fatigue damage. And all of these processes apply to parts of coal fired
plant too.

And IIRC some "nuke" pressure vessels (overseas) have been annealed to
reduce the effects of radiation embrittlement.

En el artículo ,
newshound escribió:

It's not only the neutron flux which degrades nuclear plant, there are
also thermal ageing processes, not to mention accumulation of creep and
fatigue damage. And all of these processes apply to parts of coal fired
plant too.

I read an interesting article recently that said material
wear/fatiguing/embrittlement has to be treated differently in a nuclear
environment because of the intense radiation causing subtle changes in
the atomic structure of materials.

I've had a hunt and can't find it again, but this Wonkypedia page covers
the basics:

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

--
(\_/)
(='.'=) Bunny says: Windows 10? Nein danke!
(")_(")

On 28/01/2016 17:14, Mike Tomlinson wrote:
En el artículo ,
newshound escribió:

It's not only the neutron flux which degrades nuclear plant, there are
also thermal ageing processes, not to mention accumulation of creep and
fatigue damage. And all of these processes apply to parts of coal fired
plant too.

I read an interesting article recently that said material
wear/fatiguing/embrittlement has to be treated differently in a nuclear
environment because of the intense radiation causing subtle changes in
the atomic structure of materials.

I've had a hunt and can't find it again, but this Wonkypedia page covers
the basics:

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

All true, but the doses to materials are not all that high in UK gas
cooled reactors. Gamma doses are much higher in parts of the Sellafield
reprocessing plant, for example. Neutron doses are higher in PWR
pressure vessels, and very much higher in fast reactor internals, and
also in fusion research facilities.

They are regularly taken into account in safety cases, but so are
thermal ageing, creep, and fatigue.

Trawsfynydd was shut down early because of concerns over irradiation
embrittlement to welds, but the general view afterwards (and after
assessing more experimental data) was that this decision had been
unnecessarily cautious.