Thursday, June 1, 2017

Next gen nuclear: will it happen?

Nuclear power may be having problems with its current range of Generation III reactor types, most of which are upgrades of standard water-cooled and moderated uranium reactors. There have been long deployment delays and crippling cost escalations for some of them- the EPR especially.  But, as ever, is is claimed that new nuclear technologies, the so-called Generation IV, will come to the rescue. They include revamped fast-neutron plutonium breeder reactors and molten salt reactors using thorium, along with helium- gas cooled high temperature reactors, all being developed on both the large and small scale. 

However, none yet actually exist and it will take time to develop commercial scale plants, or even prototypes. For example, in an interesting exchange of views in a debate on Thorium run by The Engineer, Fiona Rayment, director of fuel cycle solutions at the UK’s National Nuclear Laboratory, said ‘To develop radical new reactor designs, specifically designed around thorium, would take at least 30 years’:

She may be proved wrong, or other options may step in, but it is early days as yet, with, on the one hand, plenty of room for all types and scales, while on the other, it being unclear whether any of these ideas will prosper beyond prototypes. To some extent, the Generation IV technologies seem to be at the same stage as many renewables were twenty years or so ago, seeking to step beyond some historical precedents. Renewables of various types have managed that. It remains to be seen if Generation IV can. 

Some estimates of hoped for progress were produced in 2014 by the Generation IV International Forum (GIF), as below. On the basis of the industries past performance, they may be optimistic. GIF noted that the Fukushima disaster had led to some slow downs.

GIF Generation IV progress estimates
The Generation IV International Forum ‘Technology Roadmap Update for Generation IV Nuclear Energy Systems’ measures progress according to three (pre-commercialisation) phases:
*The viability phase, when basic concepts are tested under relevant conditions and all potential technical show-stoppers are identified and resolved;
*The performance phase, when engineering-scale processes, phenomena and materials capabilities are verified and optimised under prototypical conditions; and
*The demonstration phase, when detailed design is completed and licensing, construction and operation of the system are carried out, with the aim of bringing it to commercial deployment stage.
Its 2014 projections were as below, with demonstration phases presumably to follow on after:
·       Gas-cooled fast reactor: end of viability phase 2022; end of performance phase 2030.
·       Molten salt reactor: end of viability phase 2025; end of performance phase 2030.
·       Sodium-cooled fast reactor: end of viability phase 2012; end of performance phase 2022.
·       Supercritical-water-cooled reactor: end of viability phase 2015; end of performance phase 2025.
·       Very-high-temperature reactor: end of viability phase 2010; end of performance phase 2025.
·       Lead-cooled fast reactor: end of viability phase 2013; end of performance phase 2021.

Certainly, even on these estimates, there is still a long way to go before commercialization. GIF’s 2014 update to its 2002 Technology Roadmap review noted that ‘the development of technologies and associated system designs to the point of commercialisation for each of the six systems, as identified in the original Technology Roadmap, would have required considerable investment and international commitment. Since the “starting point” and R&D funding of the different Generation IV systems were not equivalent, the degree of technical progress over the past decade has not been uniform for all systems. A number of participating countries devoted significant resources to the development of the SFR and VHTR, for example, in large part due to the considerable historical effort associated with these technologies. More limited resources were dedicated to the other systems’:

A more recent review, from a US perspective, the ‘Advanced Demonstration and Test Reactor Options Study’ carried out by the Argonne, Idaho and Oak Ridge National Labs, looked at basically the same six Gen-IV advanced reactor technology concepts. It concluded, a little more optimistically, that ‘the modular High Temperature Gas-Cooled Reactor (HTGR) and sodium-cooled fast reactor (SFR) have high enough technology readiness levels to support a commercial demonstration in the near future’. It went on ‘These technologies are considered mature as a result of several successful demonstrations brought about through billions of dollars of public and private investment in the U.S. over more than fifty years. These systems are also being built internationally, further confirming the high level of maturity of these systems as evaluated in this study’.

By contrast it said that ‘the fluoride-cooled high-temperature reactor (FHR) and lead-cooled fast reactor (LFR) are less mature and require additional research and development (R&D) and engineering demonstration in the near future. International and U.S. technology development activities are underway to mature these technologies, and technology demonstrations are planned. Other options examined (e.g., gas-cooled fast reactor) were even lower in maturity or did not have significant U.S. commercial interest (e.g., super-critical water-cooled reactor)’.

On this basis it suggested that HTGRs and SFRs ‘are mature enough to enable deployment of their first modules at commercial scale (the commercial demonstration step) in the early 2030s with additional commercial offerings soon thereafter,’ while the less-mature technologies, FHR and LFR, ‘are facing a longer technology development path to commercial offerings because they need a combination of both the engineering demonstration step and the performance demonstration step through 2040, prior to commercial offerings in ~2050’: ART TDO Documents/Advanced Demonstration and Test  Reactor Options Study/ADTR_Options_Study_Rev3.pdf

It will be interesting to see if any of these quite long term predictions prove to be correct.
As we have seen, not everyone is optimistic about the potential for significant gains, with a range of doubt being expressed. In a recent an interview-based review of advanced nuclear prospects in North America, Eaves looks at both sides of the debate, reporting on the enthusiasm expressed by some practitioners, but she also quotes former US Nuclear Regulatory Commission Chairman Allison Macfarlane as saying ‘I do not see past experience pointing at a positive direction’ :

Macfarlane was talking about High Temperature Reactors, but as we have seen, that comment might also be applicable, in the view of many critics, to most of the new nuclear options. Certainly, there are multiple challenges. Breakthroughs are always possible, and as one the the nuclear enthusiast that Eaves interviewed said ‘if we believe that nothing new can happen and everything is really hard, then it will be. That’s not to minimize the challenge, but it’s to say, if you start out thinking something is impossible, it’s very unlikely to happen.’
However, given the past history of nuclear power, and the multiple challenges, a degree of caution seems wise.

The above is extracted from a new book for the IoP ‘Nuclear Power: past, present and future’, which looks at the early days of nuclear power and how some of the ideas that emerged then are being re-explored as Generation IV:
As for beyond that, Generation V, if you have hopes for fusion, see this:’re-cracked-be10699

Saturday, April 1, 2017

Small Nuclear

Small Modular Reactors (SMRs) of up to a few hundred megawatts capacity are being touted by some as the way ahead for nuclear power since they are expected to be quicker to build than large gigawatt scale plants and so less costly to finance, with mass production also reducing unit costs. They might also be located in or near cities so that the waste heat they produce could be fed to district heating networks, the use of this extra output offsetting their cost further. It may also be possible, it is claimed, that their power output could be more easily varied, so that they could play a role in grid balancing, though, as with large nuclear plants, that would undermine their economics- it is best to run them flat out.

There has certainly been much enthusiasm expressed for the idea, with various vendors offering their wares, for example   Estimates of costs vary, but in the US context it has been claimed by NuScale that ‘first of kind’ SMRs might generate at around 101cents/MWh, falling to 90c/MWh on mass production, cheaper than new large advanced nuclear plants at 96c/MWh, and also cheaper that coal fired plants, but not competitive with unabated combined cycle gas plants (64-66c) or wind plants (80c) or hydro (85c).
Some of the designs for SMRs are quite exotic, based on the use of fuel dissolved in molten salt which then acts as both reaction medium/moderator and heat transfer /coolant medium. Terrestial Energy amongst others is pushing this Molten Salt Reactor idea, and is seeking US government backing: It may take a while to happen- this is new ground. But some of the less radical ideas might be faster to develop. The UKs Energy Technologies Institute says SMRs could be up and running in the UK by 2030 if R&D work gets underway soon and should be designed to be able to run in CHP mode, so that they can provide heat as well as electricity:

Although much work will have to be done to modify the technology for civil power (and possibly heat), it is claimed that civil SMRs can be based on existing nuclear submarine propulsion technology, which is well established, with companies like Rolls Royce being well placed to develop suitable units: However the submarine and civil contexts are very different, with very different operational requirements and operating regimes. Safety and reliability is obviously a key issue in all contexts, but even in the closely managed military environment things can go wrong:  And spreading SMRs around in urban areas could pose safety and security risks, with local public acceptability potentially being a big issue.

In the USA however, the Tennessee Valley Authority (TVA) claims that SMRs could be put close to population zones and it is looking to reduce the risk of issues such as emergency
planning evacuation zones slowing operating project approval. They say that, given safety
upgrades, ‘based upon the preliminary information which we've received from the four vendors, we are confident that all of them can be supported by a two-mile emergency plan [zone] and at least one has capability of site [only] boundary’ i.e. no safety zoning beyond the plant site. That compares with 10 miles typically required for a large reactor.

That seems a little provocative. Will anyone accept mini nukes in their backyards? And what about security?  SMRs will pressumably be sealed modular units, making access to the fissile material hard, but, unless they are very carefully guarded, they might still provide an enticing and convenient target for terrorist attack. In terms of safety, the US Union for Concerned Scientists says that ‘Multiple SMRs may actually present a higher risk than a single large reactor, especially if plant owners try to cut costs by reducing support staff or safety equipment per reactor.’ It adds that some proponents have suggested siting SMRs underground as a safety measure. However, underground siting is a double-edged sword- it reduces risk in some situations (such as earthquake) and increases it in others (such as flooding). It can also make emergency intervention more difficult. And it increases cost.’
There are thus a range of technical, economic, safety and security issues to face, not least the issue of social acceptance, with there being no clear indication that they can be resolved:

From the industry side however, enthusiasm remains strong, and there is much debate about exactly how to proceed and on what basis. For example, should SMRs replace large nuclear plants in any future programme?  In the UK context, ETI’s 2015 report on The role for nuclear within a low carbon energy system’ said that contrary to the claim SMRs might be better than large nuclear plants, large reactors are best suited for baseload electricity production’. However, it notes that, based on using existing (nuclear) sites for them, there is ‘an upper capacity limit in England and Wales to 2050 from site availability of around 35 GWe,’ while there could be room for at least 21GW of SMRs in the UK, given that more sites could be available for them, including near cities, where the heat option offered a key economic compensation. So, although SMRs ‘may be less cost effective for baseload electricity production, SMRs could fulfil an additional role in a UK low carbon energy system by delivering combined heat and power (CHP) - a major contribution to the decarbonisation of energy use in buildings’, assuming the necessary district heating infrastructure was available, with SMRs delivering heat into cities ‘via hot water pipelines up to 30km in length’.
In this context it is interesting that, more recently, the Newcastle-based SMR enthusiasts Penultimate Power thinks SMRs will work best as ‘complementary to, rather than competing with’ the large-scale nuclear plants:

A SMR assessment programme has been launched by the UK government, and SMR programmes are going ahead in the USA and elsewhere: is all in a context where, according to the UK National Nuclear Laboratory, the potential market for SMRs might be up to 85 GWe by 2035:   That may be optimistic. The OECD says ‘up to 21 GWe of SMRs could be added globally by 2035’.  And there is no shortage of critical comment on the whole idea:

It’s not a new idea: in addition to the small units developed for the US military in 1940’s, (for planes and ships) there were may attempts to build small civilian nuclear plants in the USA in the 1950s, mostly with poor results: The current flurry of enthusiasm for SMRs seems to be mainly driven by the failure of conventional nuclear to expand as fast as the industry would like.  It’s stalled or declining in many parts of the world, due to poor economics and local opposition, and the existence of better, cheaper renewable alternatives. However, SMRs may not offer much help in changing this situation. There will no doubt be some prototype projects around the world in selected sites, and some projects may be suited to specialised applications, for example in remote sites or for some industrial processes:
However, in terms of widespread use for public power and heat production, given the practical problems of finding acceptable sites and the uncertain economics, plus all the usual problems with nuclear, including what to do with the radioactive wastes that are produced, it could be that SMRs may not prove to be that significant. But it’s also possible that they may boom, if a wider market emerges and/or if there are some major technological breakthroughs:

All this and much more is covered in Dave Elliott’s new book for the Institute of Physics: ‘Nuclear Power: Past, present and Future’, out soon.