Small modular nuclear reactors

[Mogster]

Nukes are a planning, regulatory and security nightmare. We already have sites that meet those requirements, if we need them we should build them on, or close to those existing sites. Those sites were chosen carefully for sound reasons.

I’m yet to see any compelling evidence that small reactors have advantages over large ones. Thermodynamics always favours bigger volumes, a bigger kettle is more efficient than a small one. Anyone that thinks we are going to have container sized nukes scattered across the country anytime soon is living in fantasy land. FWIW naval military nukes aren’t suitable as civilian electricity generators, way too low output, expensive and designed for different criteria.

 

[najaB]

I’m yet to see any compelling evidence that small reactors have advantages over large ones. Thermodynamics always favours bigger volumes, a bigger kettle is more efficient than a small one.

Yes, thermodynamics favours a larger plant, but:

Nukes are a planning, regulatory and security nightmare.

The advantages of the small modular reactor are that they are small - meaning that they require much less land take and contain much less fissile material which helps with the planning and security aspects, and they are modular, which means that they can be type rated rather than each being almost a custom build. This should cut down the regulatory burden considerably.

They can also be sited a lot closer to where the power is needed, and so don't need huge grid connections, nor do they need to run flat out for years at a time to provide base load for tens of thousands of premises.

 

[tomuk]

Nukes are a planning, regulatory and security nightmare. We already have sites that meet those requirements, if we need them we should build them on, or close to those existing sites. Those sites were chosen carefully for sound reasons.

I’m yet to see any compelling evidence that small reactors have advantages over large ones. Thermodynamics always favours bigger volumes, a bigger kettle is more efficient than a small one. Anyone that thinks we are going to have container sized nukes scattered across the country anytime soon is living in fantasy land. FWIW naval military nukes aren’t suitable as civilian electricity generators, way too low output, expensive and designed for different criteria.

The small in SMR is becoming a bit of a misnomer, the Rolls design at 470MW and Holtec 300MW and others are gravitating towards a size closer to old coal fired units. The modular part is the key with standardised off site manufacture of components.

 

[Mogster]

Yes, thermodynamics favours a larger plant, but:

The advantages of the small modular reactor are that they are small - meaning that they require much less land take and contain much less fissile material which helps with the planning and security aspects, and they are modular, which means that they can be type rated rather than each being almost a custom build. This should cut down the regulatory burden considerably.

They can also be sited a lot closer to where the power is needed, and so don't need huge grid connections, nor do they need to run flat out for years at a time to provide base load for tens of thousands of premises.

I can see the rationale for remote locations. Otherwise connections already exist if you build on or close to existing sites. You have a willing and trained workforce to scale from also.

Isn’t one of the current requirements to have a trained senior reactor operator on site at all plants? How would that work for smaller sites? The security and regulatory issues seem to be a huge problem. Environmentalists seem to be fairly neutral on SMRs so far, I suspect this is only because they don’t exist…

I do believe nukes are the way forward. Just the bigger the better.

 

[AndrewE]

Yes there is evidence that rivers can supply it, the decades they supplied all the now closed coal\oil fired stations.
The classic 500MW based plants, preceeded by smaller and late larger units too.
01 West Burton Nottinghamshire 2,000 MW
02 Ferrybridge C West Yorkshire 2,000 MW
03 Eggborough North Yorkshire 2,000 MW
04 Kingsnorth Kent 2,000 MW Oil fired
05 Fawley Hampshire 2,000 MW Oil fired
06 Aberthaw B South Wales 1,500 MW
07 Ironbridge B Shropshire 1,000 MW
08 Fiddlers Ferry Cheshire 2,000 MW
09 Ratcliffe Nottinghamshire 2,000 MW
10 Cottam[8] Nottinghamshire 2,000 MW
11 Pembroke South West Wales 2,000 MW Oil fired
12 Rugeley B Staffordshire 1,000 MW
13 Didcot A Oxfordshire 2,000 MW
14 Ince B Cheshire 1,000 MW Oil Fired

You must realise that a load (half?) of those are coastal or on estuaries? And since the others closed it is a fair bet that the river water quality has improved...

"S" MRs scattered around the country aren't going to all have access to big rivers for cooling (even if they were allowed to nowadays) and there is evidence that water temperatures are already doing harm:
http://news.bbc.co.uk/1/hi/wales/south_east/8687538.stm says

The team said stream temperatures had increased over the study period by 0.5C to 0.7C in summer and 0.7C to 1C in winter.

The researchers said water temperature was known to affect the growth of the fish and their susceptibility to disease,

and https://www.ukrivers.net/climate.html says

direct climate change impacts on rivers will occur through rising temperatures... and
"major pollution episodes (either chemical or thermal) sufficient to wipe-out entire fish stocks from stretches of river."

 

[dcbwhaley]

Why not, specifically?

It was a sarcastic comment anticipating the reaction of local residents to having a mini nuclear power station in their town.
The River Thames is a good source of water so do you think that we will see SMR near Westminster?

== Doublepost prevention - post automatically merged: 7 Feb 2025 ==

Yes, thermodynamics favours a larger plant, but:

The advantages of the small modular reactor are that they are small - meaning that they require much less land take and contain much less fissile material which helps with the planning and security aspects, and they are modular, which means that they can be type rated rather than each being almost a custom build. This should cut down the regulatory burden considerably.

They can also be sited a lot closer to where the power is needed, and so don't need huge grid connections, nor do they need to run flat out for years at a time to provide base load for tens of thousands of premises.

Also they can be manufactured in factories and delivered to site rather than being built on site. Which, amongst other advantages, means quality control is much easier.

 

[Yew]

And since the others closed it is a fair bet that the river water quality has improved...

It is probably best for our discussion if we ensure we're dealing with verified facts here, could you a) prove that with some evidence, and b) provide some proof that any improvement in water quality is a direct consequence of changes in power generation, rather than other initiatives?

 

[Three-Nine]

There is a potential human factor risk with designs based on naval vessel reactors - which includes many full-size nuclear reactors which were essentially upscaled versions of submarine reactors - which is that the people in charge may be trained to react a certain way to issues, such as ex-submarine crew (who may be hired exactly because of their experience with that type of reactor) which may not be the optimal reaction outside of a naval environment. This was a factor in the Three Mile Island incident, for example.

 

[najaB]

There is a potential human factor risk with designs based on naval vessel reactors - which includes many full-size nuclear reactors which were essentially upscaled versions of submarine reactors - which is that the people in charge may be trained to react a certain way to issues, such as ex-submarine crew (who may be hired exactly because of their experience with that type of reactor) which may not be the optimal reaction outside of a naval environment. This was a factor in the Three Mile Island incident, for example.

What kind of behaviours did you envisage?

 

[Three-Nine]

Going by an actual nuclear engineers account of the incident, and without the full text to hand from memory, the person in question - an ex nuclear submariner - was trained to react in a certain way to a certain problem that could occur with a nuclear reactor; however because the Three Mile Island reactor was essentially a much bigger submarine reactor, their actions turned out not to be the correct response as the reactor did not act in quite the same way as a smaller one.

There were several other factors in play, as there usually are, including the layout of the control room instruments which made working out exactly what was happening harder than it should have been. Of course, I’ve just realised that I’ve kind of approached this backwards as we are discussing submarine size reactors to start with…!

 

[AndrewE]

It is probably best for our discussion if we ensure we're dealing with verified facts here, could you a) prove that with some evidence, and b) provide some proof that any improvement in water quality is a direct consequence of changes in power generation, rather than other initiatives?

There is remarkably little data on this, I suspect that the funders of research (and the EA) have studiously looked the other way...
However https://journals.sagepub.com/doi/full/10.1177/0309133314550669

River water temperature in the United Kingdom: Changes over the 20th century and possible changes over the 21st century​

says​

Heated effluent from power plants and other point sources may have a profound warming impact (e.g. Maderich et al., 2008). The thermal effects of reservoirs are well documented for the UK, the USA and elsewhere (e.g. Webb and Walling, 1997; Olden and Naiman, 2010; and more recently Casado et al., 2013, who report increases in temperature minima and decreases in temperature maxima at a range of spatial scales).

It's inconceivable that the closure of thermal power stations hasn't reduced the thermal stress on watercourses. Maybe you can prove that not dumping cooling water into a river has no effect on the water temperature?
p.s. and https://www.researchgate.net/public...on-tidal_reaches_to_the_freshwater_tidal_zone has

In the catchment, traditional industries such as textiles and iron and steel have declined, while the chemical and petrochemical industries are thriving, as is the power industry. The largest concentration of electricity-generating power stations in the UK is located along the river Trent (Jarvie et al., 2000 ), largely coal-fired, directcooled stations. A number of other direct-cooled power stations are situated on the tidal rivers entering the estuary. ...
... The largest concentration of electricity-generating power stations in the UK is located along the river Trent (Jarvie et al., 2000 ). These are principally direct-cooled coal-fired stations, and have contributed to the river's high annual average water temperature. ...

and Geographhttps://www.geograph.ie/article/The-River-Trent---The-Derbyshire-and-Leicestershire-Trent (admittedly not a prime source) says

The Trent Vale was noted for the number of coal burning power stations giving it the nickname 'Megawatt Valley' and led to higher water temperatures.