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Small Modular Reactors

TUK020
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Small Modular Reactors

#458290

Postby TUK020 » November 15th, 2021, 6:16 pm

I have read a number of things that I am trying to get my head around:

RR are leading a project to develop SMRs, and have got matching funding for this pilot from the UK gov.

RR are well positioned for this activity, given that they make small nuclear reactors to power submarines etc.

The UK Navy nuclear reactors use high enriched uranium, that would be suitable for further refinement into weapons grade.

France has also committed funds for Aveva?Framatome? to develop SMRs

The French Navy nuclear reactors use low enriched reactors.

Question? Does this makes them less efficient (larger?) but also means they are likely to be considerably less of a headache both from a security and waste perspective?

Anyone able to put this in perspective?

mc2fool
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Re: Small Modular Reactors

#458295

Postby mc2fool » November 15th, 2021, 6:45 pm

Some answers here: https://world-nuclear.org/information-library/non-power-nuclear-applications/transport/nuclear-powered-ships.aspx

They [naval reactors] deliver a lot of power from a very small volume and therefore most run on highly-enriched uranium (>20% U-235, originally c 97% but apparently now 93% in latest US submarines, c 20-25% in some western vessels, 20% in the first and second generation Russian reactors (1957-81)*, then 21% to 45% in 3rd generation Russian units (40% in India's Arihant). Newer French reactors run on low-enriched fuel.

They have long core lives, so that refuelling is needed only after 10 or more years, and new cores are designed to last 50 years in carriers and 30-40 years (over 1.5 million kilometres) in most submarines, albeit with much lower capacity factors than a nuclear power plant (<30%).


The long core life is enabled by the relatively high enrichment of the uranium and by incorporating a 'burnable poison' such as gadolinium – which is progressively depleted as fission products and actinides accumulate and fissile material is used up. These accumulating poisons and fissile reduction would normally cause reduced fuel efficiency, but the two effects cancel one another out.

However, the enrichment level for newer French naval fuel has been dropped to 7.5% U-235, the fuel being known as 'Caramel', originally developed for research reactors and providing the possibility for greater fuel density, so helping to minimize the increased size of an LEU-fuelled core. It needs to be changed every ten years or so, but avoids the need for a specific military enrichment line, and some reactors will be smaller versions of those on the Charles de Gaulle. In 2006 the Defence Ministry announced that Barracuda class submarines would use fuel with "civilian enrichment, identical to that of EdF power plants," about 5% enriched, and certainly marks a major change there.


A core life of 50 years in carriers and 30-40 years in subs is essentially for the expected lifetime of the vessel, so in effect they never have to be refuelled. I note that RR say their SMRs will have a lifetime of 60 years, but I've not seen anything on their site about refuelling frequency.

I have no idea which would be more of a headache from the security and waste aspects; more lower enriched fuel being changed more frequently or less higher enriched fuel being changed less frequently ...

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Re: Small Modular Reactors

#458335

Postby Spet0789 » November 15th, 2021, 10:48 pm

mc2fool wrote:Some answers here: https://world-nuclear.org/information-library/non-power-nuclear-applications/transport/nuclear-powered-ships.aspx

They [naval reactors] deliver a lot of power from a very small volume and therefore most run on highly-enriched uranium (>20% U-235, originally c 97% but apparently now 93% in latest US submarines, c 20-25% in some western vessels, 20% in the first and second generation Russian reactors (1957-81)*, then 21% to 45% in 3rd generation Russian units (40% in India's Arihant). Newer French reactors run on low-enriched fuel.

They have long core lives, so that refuelling is needed only after 10 or more years, and new cores are designed to last 50 years in carriers and 30-40 years (over 1.5 million kilometres) in most submarines, albeit with much lower capacity factors than a nuclear power plant (<30%).


The long core life is enabled by the relatively high enrichment of the uranium and by incorporating a 'burnable poison' such as gadolinium – which is progressively depleted as fission products and actinides accumulate and fissile material is used up. These accumulating poisons and fissile reduction would normally cause reduced fuel efficiency, but the two effects cancel one another out.

However, the enrichment level for newer French naval fuel has been dropped to 7.5% U-235, the fuel being known as 'Caramel', originally developed for research reactors and providing the possibility for greater fuel density, so helping to minimize the increased size of an LEU-fuelled core. It needs to be changed every ten years or so, but avoids the need for a specific military enrichment line, and some reactors will be smaller versions of those on the Charles de Gaulle. In 2006 the Defence Ministry announced that Barracuda class submarines would use fuel with "civilian enrichment, identical to that of EdF power plants," about 5% enriched, and certainly marks a major change there.


A core life of 50 years in carriers and 30-40 years in subs is essentially for the expected lifetime of the vessel, so in effect they never have to be refuelled. I note that RR say their SMRs will have a lifetime of 60 years, but I've not seen anything on their site about refuelling frequency.

I have no idea which would be more of a headache from the security and waste aspects; more lower enriched fuel being changed more frequently or less higher enriched fuel being changed less frequently ...


From a security perspective, they’re much of a muchness. Even the HEU for reactors isn’t sufficiently highly enriched to be used for a bomb so either way you would need to further enrich it, which immediately puts you beyond terrorists into nation state territory. Both are equally nasty in terms of radioactivity and therefore as material in a dirty bomb. Ditto from a waste perspective.

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Re: Small Modular Reactors

#458446

Postby TUK020 » November 16th, 2021, 11:18 am

mc2fool wrote:Some answers here: https://world-nuclear.org/information-library/non-power-nuclear-applications/transport/nuclear-powered-ships.aspx

It needs to be changed every ten years or so, but avoids the need for a specific military enrichment line, and some reactors will be smaller versions of those on the Charles de Gaulle. In 2006 the Defence Ministry announced that Barracuda class submarines would use fuel with "civilian enrichment, identical to that of EdF power plants," about 5% enriched, and certainly marks a major change there.[/i]

A core life of 50 years in carriers and 30-40 years in subs is essentially for the expected lifetime of the vessel, so in effect they never have to be refuelled. I note that RR say their SMRs will have a lifetime of 60 years, but I've not seen anything on their site about refuelling frequency.


thanks for the link, very enlightening site.
And I think you summarised the refuelling/enrichment trade off well

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Re: Small Modular Reactors

#458673

Postby TUK020 » November 17th, 2021, 8:48 am

Overview of SMRs
Link courtesy of Ody2k on the Musk Gigapost
https://www.youtube.com/watch?v=yofGtxEgpI8

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Re: Small Modular Reactors

#458709

Postby 88V8 » November 17th, 2021, 10:57 am

TUK020 wrote:Overview of SMRs
Link courtesy of Ody2k on the Musk Gigapost https://www.youtube.com/watch?v=yofGtxEgpI8

Jolly interesting.
Umpteen designs in progress.
This seems rather like the grid-scale battery storage problem... umpteen different designs of unknown merit.

Hard for the know-nothing politicos to make a decision, and for sure whatever decision they make by the time it comes online it will be apparent that it wasn't the best decision.

I read somewhere that Rolls Royce had a modular design way back in 1989...

V8

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Re: Small Modular Reactors

#459288

Postby mc2fool » November 19th, 2021, 1:40 pm

Yes, interesting video. Here's another, more US-centric, one: https://www.youtube.com/watch?v=cbrT3m89Y3M

The Small Isn't Always Beautiful (Safety, Security, and Cost Concerns about Small Modular Reactors) report referenced in the first video can be found at: https://www.ucsusa.org/sites/default/files/2019-10/small-isnt-always-beautiful.pdf

I note from the first video that "Small" Modular Reactors are defined as less than 300MWe, whereas the Rolls Royce one is 470MWe.
https://www.rolls-royce.com/innovation/small-modular-reactors.aspx/
https://www.rolls-royce-smr.com/

You'd think that then it would be an MMR (Medium Modular Reactor) but that acronym has been registered by the Ultra Safe Nuclear Corporation (wonder how long it took marketing to come up with that name!) for their Micro Modular Reactor of 5-10MWe. https://usnc.com/mmr/

I am somewhat bemused that one of their safety features is that the reactor is "Self Protecting": Once powered on, the reactor becomes self-protecting due to its radiation. Attempting to approach the reactor vessel or handle its fuel elements would quickly incapacitate the attacker. :!:

One of the things from the first video that did surprise me was the amount of solid radioactive waste that has been generated (worldwide) so far: 35,000,000 cubic metres. That's a square kilometres of waste 35 metres high! It says 28,000,000m^3 has been permanently disposed of (buried) but the rest is in "interim" storage awaiting disposal, some since the 1940s...

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Re: Small Modular Reactors

#459329

Postby mc2fool » November 19th, 2021, 4:07 pm

A further point on that "what is small" matter: the UK currently has 7 nuclear power stations but only one of those, Sizewell B, has a single reactor (1195MWe). The others have two reactors each, being Hinkley Point B (2 x 425MWe), Hunterston B (2 x 460MWe), Hartlepool (2 x 595MWe), Heysham A (2 x 585MWe), Torness (2 * 595MWe), and Heysham B (2 x 610MWe).

So, the 470MWe Rolls Royce "small" modular reactor is actually bigger, power wise, than the reactors in some of our existing nuclear power stations and not far short of most of the rest.

Maybe they mean physically small? Well, RR do show it on the back of a truck and their brochure says it will "Sit within a power station that would be roughly five and half times the size of the pitch at Wembley, which is just one-tenth the size of a typical large-scale reactor site (40,000m2 vs 400,000m2).

Uh? Well ok, smaller than a typical reactor site, but still, why so big? After all, these things come from reactors on submarines, and clearly they don't need even one times the size of the pitch at Wembley!

And then "modular" ... I'd imagined that meant that each reactor was a module and you could (figuratively speaking) bolt together as many modules as you wanted to get the size of power plant desired. However, RR in their video describes the SMR as a "factory built nuclear power plant, transported to site as modules, and assembled in a specially designed on-site factory".

In fact, they don't seem to be selling just the reactor but an entire power plant, with a futuristic looking building and designed even down to the landscaping. And their "twin" solution, far from just adding a second reactor etc in the existing plant, appears to be to build another entire power plant next door. So that's 11 times the size of the pitch at Wembley ...!

RR are targeting a UK market of 7GWe, which is actually around the amount of nuclear power we currently have (and all of which is due to be shut down in the next 14 years, half of it in the next 3). While it might be more efficient to put the SMRs close to the users, I can't see many communities being happy with a nuclear plant being plonked into them, so I suspect, if any, they'll go onto existing nuclear power sites, which are already quite popular with the community (jobs, etc).

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Re: Small Modular Reactors

#459655

Postby 88V8 » November 20th, 2021, 5:28 pm

mc2fool wrote:.....due to be shut down in the next 14 years, half of it in the next 3...

But I bet it won't be.
That can will be kicked down the road.

V8

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Re: Small Modular Reactors

#459665

Postby mc2fool » November 20th, 2021, 6:05 pm

88V8 wrote:
mc2fool wrote:.....due to be shut down in the next 14 years, half of it in the next 3...

But I bet it won't be.
That can will be kicked down the road.

V8

That can has already been kicked down the road, in some cases several times. Four out of our seven nuclear power stations are already in "life extension" and some aren't going to quite make it to their extended life.

E.g. in 2012 Hinkley Point B and Hunterston B were given seven-year extensions to their 2016 decommissioning dates, to remain in use until "at least 2023".
https://www.independent.co.uk/news/business/news/edf-extends-life-of-two-nuclear-power-stations-8381256.html

But in fact Hinkley Point B will stop generating electricity and start defuelling in just a few months time.
https://www.edfenergy.com/media-centre/news-releases/uks-most-productive-nuclear-power-station-move-decommissioning-july-2022


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