SMRs and MSRs
The similarity of the acronyms is confusing, but the two nuclear reactor concepts are quite different.
Small Modular Reactors are seen as an alternative to the large water reactors now being built. It is argued that ever-larger reactors with their complex safety structure and systems, are examples of diseconomies of scale – the larger the reactor, the less competitive it becomes.
The IAEA defines SMRs as “advanced reactors that produce electric power up to 300 MW(e), designed to be built in factories and shipped to utilities for installation as demand arises”. The aim is to reduce construction times. SMR designs include water-cooled reactors, high temperature gas cooled reactors, as well as liquid metal cooled reactors with fast neutron spectrum.”
The advantage of SMRs is that they would be much easier to finance, and , with construction times of 2-3 years they could be mass produced and installed as single units or with several grouped together in series over a period of time to form power stations with outputs comparable to today’s large reactors. SMRs safety features include the potential for underground siting, autonomous refuelling systems and natural circulation for cooling. Thorium could also be used as a fuel.
SMRs are being developed in most nuclear countries. Reactors are now under construction in the Argentine, China, and Russia. In the UK The Energy Technologies Institute (ETI) has awarded a £200K contract to Mott MacDonald, to identify the characteristics of alternative small-scale thermal and nuclear plant power generation technologies.
Almost now forgotten are the 4 small 62 MW thermal co-generation graphite/boiling water reactors which have been producing steam for district heating and 11 MW electricity in a remote corner of Siberia since 1976, without any problems and cheaper than fossil fuelled alternatives in this Arctic region. Other early reactors – Magnox natural uranium/graphite reactors, Canadian heavy water reactors could also be regarded as SMR’s.
One criticism of SMR’s is that without a fundamental change in the operational regime, their operations and maintenance will be subject to same regulatory regime as for a large nuclear plant but this would be charged against a smaller power output. Against this it is claimed that because of their increased inherent and passive safety systems SMRs will require fewer operators or little supervision.
The case for SMRs has been convincingly argued by Owen Paterson, the retiring Environment Secretary. Small factory built units located within 20 to 40 miles of demand centres could supply both electric power and process heat, using the heat that would otherwise be wasted through cooling towers. According to Rolls Royce factory-built SMRs installed at the rate of one a month could add to the capacity at a rate of 1.8 GW per year. There are, Paterson said, simply not enough suitable sites, or sufficient time to build the large nuclear plants that are otherwise needed.
Molten salt reactors are quite different. They were first developed at Oak Ridge National Laboratory in the 1950’s and this work continued into the 60’s and 70’s, but the technology was then abandoned when the USA concentrated on PWR and BWR systems, which have now established a world-wide dominance – the independent development of gas-cooled graphite reactors in the UK also came to an end when the PWR was chosen for Sizewell B the last nuclear reactor to be built here which began operating in 1995.
To overcome the limitations of water reactors tied to the steam cycle and when
the spent fuel discharged from the reactor still contains 96% of the original
uranium as well as radioactive fission products – the much feared
‘nuclear waste’ – bold claims are made for molten salt reactors which can run on spent nuclear fuels and depleted uranium to deliver cheap, safe, clean energy for tens of thousands of years.
There then is, or should be, a strong incentive to develop and introduce more efficient systems. On the other hand the existing water reactors have, or could have a life span of up to 50 or even 70 years, and with a heavy initial capital cost, but low running costs, the companies which have built them will seek to keep them in operation for the longest possible time and be reluctant, indeed unlikely, to introduce any alternative rival system.
These alternatives are now being explored, albeit at low level, by national authorities or some small private companies. An international study group of 12 countries together with Euratom initiated in 2000 – The Generation IV – selected 7 reactor technologies as worthy of further development. Four of these are fast reactors cooled by gas, lead, sodium, or molten salt; three are high temperature thermal reactors 2 of which are cooled by gas and 1 by molten salt. In January 2014 a GIF review considered that the Gen IV technologies most likely to be deployed first are the sodium-cooled fast reactor, the lead- cooled fast reactor and the very high temperature reactor technologies; the molten salt reactor and the gas-cooled fast reactor were believed to be furthest from demonstration phase.
Despite this a later review by the WNA (August 2014) considered that “Compared with solid-fuelled reactors, MSR systems have lower fissile inventories, no radiation damage constraint on fuel burn-up, no requirement to fabricate and handle solid fuel or solid used fuel, and a homogeneous isotopic composition of fuel in the reactor. These and other characteristics may enable MSRs to have unique capabilities and competitive economics for actinide burning and extending fuel resources.” But the GIF 2014 Roadmap also said that much work needed to be done on molten salt systems before demonstration reactors were operational, and suggested 2025 as the end of the viability R&D phase. Yet bold claims are now being made for molten salt reactors which can run on spent nuclear fuels and use depleted uranium to deliver cheap, safe, clean energy for tens of thousands of years and also use the radioactive isotopes in nuclear waste as fuel– an answer to the parrot question of “yes but what about the waste?”
Molten salt reactor technology comes into two distinct lines; one uses the molten salt solely as the coolant (the fuel is then in block form) and the other has fuel mixed with the coolant, as part of the molten salt (the fuel is a molten mixture of lithium and beryllium fluoride salts with dissolved enriched uranium, plutonium, thorium or U-233 fluorides). The fission products dissolve in the salt and are removed continuously in an online reprocessing plant and replaced with new fuel or fertile material. Actinides remain in the reactor until they fission or are converted to higher actinides, which also then fission.
One of the attractions of MSR’s is in their capability to burn thorium fuel. This is a particular advantage for India, which has little uranium, but large potential supplies of thorium.
In addition to their participation in the international GIF study a number of countries also have their own programmes.
China which is furthest advanced in developing MSRs has however recently pushed back the completion date of the test 2MW thorium molten salt reactor being built at the TMSR center of the Chinese Academy of Science from 2017 to 2020. In other countries there is a growing interest in his technology, but as yet little serious commitment.
In the US a small research company Transatomic Power, started by two former MIT graduates has now raised some $3.5 million from private-investor funds to develop a molten salt reactor. The company makes some bold claims – it will turn nuclear waste into a safe, clean, and scalable source of electricity, generating emission free electric power, mass producing reactors to meet the growing energy demand. But it will be some years and millions of dollars more before these claims can be realised. It will be the same for another US initiative, Flibe Energy, which was founded in 2011 to develop a 20-50 MW liquid fuelled thorium reactor (LFTR) reactor using the thorium fuel cycle with a fluoride- based, molten, liquid salt for fuel.
MSR’s are also being proposed in Canada by Terrestrial Energy which claims their IMSR design offers a “walk away safe level of assurance, with Zero operator intervention, even with a total loss of site power. Moreover, the MSR consumes one-sixth the fuel to produce the same amount of electricity, and can also be designed to consume the spent fuel of today’s fleet of conventional nuclear reactors.” Their estimates indicate that the IMSR “will demonstrate the lowest Lifetime Cost of Energy of any known technology, and by some margin”. But all this is some way off, Terrestrial energy are now seeking license approval for its IMSR design from the Canadian Nuclear Safety Commission.
In the UK there are a number of independent or competing projects none of which will be able to get far without a very substantial support of at least millions of pounds which can only realistically come from the Govenrment. But the government is, or last year was, not enthusiastic. In the House of Lords on Feb 14th 2013 Baroness Verma, Parliamentary Under-Secretary of State for Energy and Climate Change, linking MSR’s to thorium, said “We maintain an interest in the global potential of thorium and have, for the longer term, commissioned a wider analysis of nuclear fuel cycle scenarios which are open to the UK, among which is the reactor design fuelled by molten thorium salts. However, previous studies show that there are still significant risks to resources to develop thorium fuel to commercial deployment. In these difficult economic times, we need to concentrate on potential technologies that compete for the same investment.”
Despite this a small team – Energy Process Developments – has been granted
£75,000 by another government body – Technology Strategy Board to carry out an
eight-month feasibility study of costs, regulatory, public acceptance and site
issues for building and licensing a pilot-scale demonstration reactor in the
UK. The aim is to prepare the ground for a full engineering design for the
chosen option, to present to potential investors. This seems to be a new
venture for the TSB – now called Innovate UK which was set up in 2007 to
“accelerate economic growth by stimulating and supporting businessled
innovation – bringing together business, research and the public sector,
supporting and accelerating the development of innovative products and
services to meet market needs, tackle major societal challenges and help build
the future economy.” They seem to have supported a very wide range of projects
and have no experience of energy or nuclear technology.
The need for a much larger investment in money and time to get from an initial concept and feasibility study to a working reactor is emphasised in another (rival?) UK proposal for a “Simple Molten Sat Reactor” ,from Ian Scott of Moltex Energy. “The first stage will cost around £1bn, to get through the regulatory process and build a prototype. Realistically, only the government can do this.”
There is already a range of interests in molten salt technology at the universities and the NNL, but these seem to be mainly directed to nuclear fuel reprocessing which could become redundant if MSRs are successfully developed.
The U battery: Small is beautiful
In a new venture for the fuel enrichment company Urenco – the UK, Dutch, German enrichment company – believing (like Owen Paterson )that nuclear reactors have become too large is funding the Universities of Manchester and Delft to develop what it has called a ‘U-Battery to produced heat and electricity.
The initial conceptual design for a 1.8 m diameter, 4MWe/10MWth reactor was completed in 2012. Unlike the established water-cooled reactors, the U- Battery is a gas-cooled graphite-moderated reactor but rather than the AGR It is more akin to the German pebble bed modular reactor. The prismatic reactor core comprises thousands of micro-fuel particles, – SiC ceramic-coated uranium spheres known as TRISO (tristructural-isotropic), embedded in the graphite matrix to bed cooled by helium or nitrogen. A secondary gas circuit would drive the turbine to produce electricity. It is expected that refuelling will be required every five years.
To finalise the design and build a prototype Urenco is working with UK industry partners such as Atkins and Amec to build a prototype in the UK which would to prove the concept works and to confirm that the costs initially would be lower than now expected for Hinkley point. It is claimed that later models should be at below €100/MWh (£78/MWh). But it would take 8 years for a first protype and full-sized U-battery would not be operational until 2022 at the earliest and at a cost of at least some £130 million.
The UK government however is now seeking to sell off its share in Urenco believing that an immediate capital gain is preferable to a potential long- term income. The benefits if this is successful would go elsewhere.
It is not widely known, indeed the green lobby would have us believe otherwise, but in 2012 nuclear power was the major source of primary energy produced within the 28 EU countries when it met 28.7% of total domestic production. Solid fuels (mainly coal) met 20.9%, natural gas 16.8%, oil 8.9% and renewables 22.3%. Again contrary to the green image, of the share taken by renewables the greater part, approximately 65% came from biomass and 20% from Hydro, 20% from geothermal, 10% from solar, and only 5% from wind turbines which are always portrayed as the future for green renewable energy.
But this should be considered against the worrying trend of an increasing
dependence on imported fossil fuels from less than 40 % of gross energy
consumption in the 1980s to reach 53.4 % by 2012 when imports of primary
energy exceeded exports by some 922.8 million toe. The security of the EU’s
primary energy supplies could also be at risk if a high proportion of imports
are concentrated among relatively few partners. We already have the threats of
sanctions disputes with Russia over developments in the Ukraine. Yet In 2012
Russia was the main supplier to the EU of fossil fuel, followed by Colombia and the United States. More than three quarters (76.8 %) of the EU-28’s imports of natural gas in 2012 came from Russia, Norway or Algeria followed by Qatar
For electricity generation in 2012 the nuclear share of European output fell slightly meeting 26.7 % of the total, but this was still well above the so- called renewables with wind at 6.5%, solar at 2.2%; 0.2 came from geothermal; hydropower met 11.6%, but most generation, 52.6 %, came from power stations using combustible fuels (such as natural gas, coal and oil); much of this fuel would have been imported.
Nuclear power makes a significant contribution to electricity supply in 14 of the 28 EU countries; percentage figures for 2013 show : France 73.3, Belgium 52, Slovakia 51.7, Hungary 50.7, Sweden 42.7, Czech Rep 35.9, Slovenia 33.6, Finland 33.3, Bulgaria 30.7, Romania 19.8, Spain 19.7, UK 18.3, Germany 15.4 (still!), Netherlands 2.8. In addition new nuclear stations are now being planned for Bulgaria, Czech Republic, Finland, France, Hungary, Lithuania, Poland and the United Kingdom.
It is then not surprising that in a letter to the EU commission (25th June) the Czech government, writing on behalf of Bulgaria, France, Hungary, Lithuania, Poland, Romania, Slovakia, Slovenia and the United Kingdom, expressed their common view that nuclear power will have an important role in the future of the EU’s energy mix.
“Well diversified energy systems are essential if we want to ensure energy security. We need an energy mix that will affordably meet our decarbonization objectives and meet energy demand. In the last decade the European Union has faced a continuous decline in its domestic energy production. This could be decelerated in the medium term by increasing the use of renewables according to EU policy and maintaining or developing nuclear energy according to policies of individual Member States. Nuclear energy’s significant role in the European energy mix should be clearly recognized.”
Since markets alone may not be able to offer the sufficient security required to stimulate investment on a purely commercial basis, national support mechanisms, may be needed, and the letter pointed out that the Commission itself had recognised, in November 2013, that such intervention might be necessary to secure a level playing field, overcome market failures, foster technology and innovation deployment and, more generally, support the market in delivering appropriate investment signals.
It also emphasised that Nuclear power stations, bring significant benefits in providing electricity free from greenhouse gas emissions, energy security and ensuring economic growth. In this respect, the European leadership in nuclear industry should be preserved, and the long-term capital intensive and long- term investment, should be supported by market mechanisms to create a predictable investment. It is crucial that the EU adopts a technology neutral approach in creating a level playing field for all low-emission sources.
The US company Lockheed Martin has claimed that the compact nuclear fusion reactor (CFR), for which they are developing a protoype, could be built in 5 years time and be readily used within a decade.
This is in striking contrast to the international JET project for which a first prototype is now being built in the South of France at an estimated cost of $20 billion and for which the first 15,000 cubic metres of concrete has just been poured. Jet expects to begin experiments in 2020, though the fusion fuel – the heavy isotopes of hydrogen: deuterium and tritium – will not be fed into the reactor until 2027 and then should only be able to generate 500MW of energy for several minutes at a time. A full scale commercial reactor is not expected before the 2040s
Lockheed Martin claims that their compact fusion concept combines several alternative magnetic confinement approaches, taking the best parts of each and offers a 90% size reduction over previous concepts. This small size enables them to build and test prototypes within a relatively few years.
Sceptics can point to the claims for cold fusion put forward in 1989 by two scientists, Pons and Fleischman, which were later disabused. But these have been revived with reports that NASA is developing an alternative cheap, clean, low-energy nuclear reaction technology (LENR)
Further developments of the rival fusion claims and projects should be interesting!
A paper by Dr Capell Aris, published jointly by the Adam Smith Institute and the Scientific Alliance reveals the limitations of wind power as a reliable source of electricity for a modern society.
Wind is, by its nature, intermittent and so the extent to which this affects the output of the fleet of wind turbines in a typical year is crucial in determining how much conventional generating capacity is needed by way of backup and thus what the overall system costs are. A rigorous quantitative assessment of wind variability and intermittency, based on nine years of hourly measurements of wind speed on 22 sites across the country, shows for a model UK wind fleet of 10 GW nominal capacity that the power output has the following pattern over a year:
- Power exceeds 90 % of available power for only 17 hours
- Power exceeds 80 % of available power for 163 hours
- Power is below 20 % of available power for 3,448 hours (20 weeks)
- Power is below 10 % of available power for 1,519 hours (9 weeks)