US Government Accountability Office pours cold water on advanced reactor concepts
Nuclear Monitor #810, 9 Sept 2015, ‘US Government Accountability Office pours cold water on advanced reactor concepts’, https://www.wiseinternational.org/nuclear-monitor/810/us-government-accountability-office-pours-cold-water-advanced-reactor-concepts
The US Government Accountability Office (GAO) has released a report on the status of small modular reactors (SMRs) and other new reactor concepts in the US.
Let’s begin with the downbeat conclusion of the GAO report:
“While light water SMRs and advanced reactors may provide some benefits, their development and deployment face a number of challenges. Both SMRs and advanced reactors require additional technical and engineering work to demonstrate reactor safety and economics, although light water SMRs generally face fewer technical challenges than advanced reactors because of their similarities to the existing large LWR [light water] reactors. Depending on how they are resolved, these technical challenges may result in higher-cost reactors than anticipated, making them less competitive with large LWRs or power plants using other fuels. …
“Both light water SMRs and advanced reactors face additional challenges related to the time, cost, and uncertainty associated with developing, certifying or licensing, and deploying new reactor technology, with advanced reactor designs generally facing greater challenges than light water SMR designs. It is a multi-decade process, with costs up to $1 billion to $2 billion, to design and certify or license the reactor design, and there is an additional construction cost of several billion dollars more per power plant.
“Furthermore, the licensing process can have uncertainties associated with it, particularly for advanced reactor designs. A reactor designer would need to obtain investors or otherwise commit to this development cost years in advance of when the reactor design would be certified or available for licensing and construction, making demand (and customers) for the reactor uncertain. For example, the price of competing power production facilities may make a nuclear plant unattractive without favorable rates set by a public authority or long term prior purchase agreements, and accidents such as Fukushima as well as the ongoing need for a long-term solution for spent nuclear fuel may affect the public perception of reactor safety. These challenges will need to be addressed if the capabilities and diversification of energy sources that light water SMRs and advanced reactors can provide are to be realized.”
Many of the same reasons explain the failure of the Next Generation Nuclear Plant Project. Under the Energy Policy Act of 2005, the US Department of Energy (DoE) was to deploy a prototype ‘next generation’ reactor using advanced technology to generate electricity, produce hydrogen, or both, by the end of fiscal year 2021. However, in 2011, DoE decided not to proceed with the deployment phase of the project.
Small modular reactors
Four companies have considered developing SMRs in the US in recent years. NuScale has a cost-sharing agreement such that the DoE will pay as much as half of NuScale’s costs − up to $217 million (€194m) over five years − for SMR design certification. NuScale expects to submit a design certification application to NRC in late 2016, and may begin operating its first SMR in 2023 or 2024. (However the timeframe is unrealistic, and the project may be abandoned − as other SMR projects have.)
The other three companies are a long way behind NuScale:
- mPower, a subsidiary of Babcock & Wilcox, enjoyed a cost-sharing agreement with the DoE but in 2014 scaled back its R&D efforts because of a lack of committed customers and a lack of investors.
- Holtec says it is continuing R&D work, but does not have a detailed schedule.
- In 2014 Westinghouse suspended its efforts to certify its SMR design, because of a lack of committed customers (and the lack of a DoE cost-sharing agreement).
The GAO report states that the development of light water SMRs may proceed without serious difficulties as they are based on existing light water reactor technology. That said, standardization is a key pillar of SMR rhetoric, and members of an expert group convened by the GAO noted that component standardization has proven challenging for the construction of the larger Westinghouse AP1000 that has some modular components.
Another pillar of SMR rhetoric is mass production (to make them economic), and the development of a massive construction chain to allow for mass production is a radically different proposition to NuScale’s plan to build just one reactor over the next decade.
Not-so-advanced reactor concepts
According to the GAO report, SMRs and new reactor concepts “face some common challenges such as long time frames and high costs associated with the shift from development to deployment − that is, in the construction of the first commercial reactors of a particular type.”
The report notes the US government’s generous financial support for utilities developing SMRs and advanced reactor concepts − DoE provided US$152.5 million (€137m) in fiscal year 2015 alone. Advanced reactor concepts attracting DoE largesse are the high temperature gas cooled reactor, the sodium cooled fast reactor, and to a lesser extent the molten salt reactor (specifically, a sub-type known as the fluoride salt cooled high temperature reactor).
DoE and Nuclear Regulatory Commission (NRC) officials do not expect applications for advanced reactors for at least five years. In other words, an application may (or may not) be submitted some time between five years and five centuries from now.
Advanced reactor designers told the GAO that they have been challenged to find investors due to the lengthy timeframe, costs, and uncertainty. Advanced reactor concepts face greater technical challenges than light water SMRs because of fundamental design differences. Thus designers have significantly more R&D issues to resolve, including in areas such as materials studies and fuel certification, coolant chemistry studies, and safety analysis. Some members of the expert group convened by the GAO noted a potential need for new test facilities to support this work. Furthermore, according to reactor designers, certifying or licensing an advanced reactor may be particularly time-consuming and difficult, adding to the already considerable economic uncertainty for the applicants.
The process of developing and certifying a specific reactor design can take 10 years or more for design work and nearly 3.5 years, as a best case, for NRC certification. Even that timeframe is more hope than expectation. Recent light water reactor design certifications, for the Westinghouse AP1000 and the GE Hitachi ESBWR, have taken about 15 and 11 years respectively. Both the AP1000 and ESBWR are modifications of long-established reactor types, so considerably longer timeframes can be expected for advanced concepts.
The cost to develop and certify a design can range from US$1−2 billion (€0.9−1.8b). Developers hope that costs can be reduced as they move from certification to the construction of a first-of-a-kind plant to the construction of multiple plants. But the GAO report notes that those hopes may be unfounded:
“[S]ome studies suggest that existing, large LWRs have not greatly benefitted from industry-wide standardization or learning to date for reasons including intermittent development and production. In fact, some studies have found that “reverse or negative learning” occurs when increased complexity or operation experience leads to newer safety standards. On a related point, another reactor designer said that the cost and schedule difficulties associated with building the first new design that has been certified by the NRC and started construction in the United States in three decades − the Westinghouse AP1000, a recently designed large LWR − have made it harder for light water SMRs to obtain financing because high-profile problems have made nuclear reactors in general less attractive. … The AP1000 was the first new design that has been certified by the NRC and started construction in the United States in three decades. However, construction problems, including supply chain and regulatory issues, have resulted in cost and schedule increases.”
US Government Accountability Office, July 2015, ‘Nuclear Reactors: Status and challenges in development and deployment of new commercial concepts’, GAO-15-652, www.gao.gov/assets/680/671686.pdf
(Written by Nuclear Monitor editor Jim Green.)
French government agency sceptical about Gen IV reactors
Nuclear Monitor #803, 7 May 2015, ‘French government agency sceptical about Gen IV reactors’, https://www.wiseinternational.org/nuclear-monitor/803/french-government-agency-sceptical-about-gen-iv-reactors
The French Institute for Radiological Protection and Nuclear Safety (IRSN) has produced an important critique of Generation IV nuclear power concepts.1 IRSN is a government authority with 1,790 staff under the joint authority of the Ministries of Defense, the Environment, Industry, Research, and Health.
There are numerous critical analyses of Generation IV concepts by independent experts2, but the IRSN critique is the first from the government of a country with an extensive nuclear industry.
The IRSN report focuses on the six Generation IV concepts prioritised by the Generation IV International Forum (GIF), which brings together 12 countries with an interest in new reactor types, plus Euratom. France is itself one of the countries involved in the GIF.
The six concepts prioritised by the GIF are:
- Sodium cooled Fast Reactors (SFR);
- Very High Temperature Reactors, with thermal neutron spectrum (VHTR);
- Gas-cooled Fast Reactors (GFR);
- Lead-cooled Fast Reactors (LFR) or Lead-Bismuth (LB) cooled Fast Reactors;
- Molten Salt Reactors (MSR), with fast or thermal neutron spectrum; and
- SuperCritical Water Reactors (SCWR), with fast or thermal neutron spectrum.
The report states: “There is still much R&D to be done to develop the Generation IV nuclear reactors, as well as for the fuel cycle and the associated waste management which depends on the system chosen.”
IRSN considers the SFR system to be the only one to have reached a degree of maturity compatible with the construction of a reactor prototype during the first half of this century − and even the development of an SFR prototype would require further preliminary studies and technological developments.
Only SFR and VHTR systems can boast operating experience. IRSN states: “No operating experience feedback from the other four systems studied can be put to direct use. The technological difficulties involved rule out any industrial deployment of these systems within the time frame considered [mid century].”
The report says that for LFR and GFR systems, small prototypes might be built by mid-century. For MSR and SCWR systems, there “is no likelihood of even an experimental or prototype MSR or SCWR being built during the first half of this century” and “it seems hard to imagine any reactor being built before the end of the century”.
IRSN notes that it is difficult to thoroughly evaluate safety and radiation protection standards of Generation IV systems as some concepts have already been partially tried and tested, while others are still in the early stages of development.
IRSN is sceptical about safety claims: “At the present stage of development, IRSN does not notice evidence that leads to conclude that the systems under review are likely to offer a significantly improved level of safety compared with Generation III reactors, except perhaps for the VHTR …” Moreover the VHTR system could bring about significant safety improvements “but only by significantly limiting unit power”.
The report notes that the safety of fast reactors can be problematic because of high operating temperatures and the toxicity and corrosive nature of most coolants considered. It says that issues arising from the Fukushima disaster require detailed examination, such as: choice of coolant; operating temperatures and power densities (which are generally higher for Generation IV concepts); and in some cases, fuel reprocessing facilities that present the risk of toxic releases.
The report is unenthusiastic about research into transmutation of minor actinides (long-lived waste products in spent fuel), saying that “this option offers only a very slight advantage in terms of inventory reduction and geological waste repository volume when set against the induced safety and radiation protection constraints for fuel cycle facilities, reactors and transport.” It notes that ASN, the French nuclear safety authority, has recently announced that minor actinide transmutation would not be a deciding factor in the choice of a future reactor system.
The reports findings on the six GIF concepts are briefly summarised here:
Sodium-cooled Fast Reactors (SFR)
The main safety advantage is the use of low-pressure liquid coolant. The normal operating temperature of this coolant is significantly lower than its boiling point, allowing a grace period of several hours during loss-of-cooling events. The advantage gained from the high boiling point of sodium, however, must be weighed against the fact that the structural integrity of the reactor cannot be guaranteed near this temperature.
The use of sodium also comes with a number of drawbacks due to its high reactivity not only with water and air, but also with MOX fuel.
It seems possible for SFR technology to reach a safety level at least equivalent to that of Generation III pressurised water reactors, but IRSN is unable to determine whether it could significantly exceed this level, in view of design differences and the current state of knowledge and research.
Very High
Temperature Reactors (VHTR)
The
VHTR benefits from the operating experience feedback obtained from High
Temperature Reactors (HTR).
This technology is intrinsically safe with respect to loss of cooling, which
means that it could be used to design a reactor that does not require an active
decay heat removal system. The VHTR system could therefore bring about
significant safety improvements compared with Generation III reactors,
especially regarding core melt prevention.
VHTR safety performance can only be guaranteed by significantly limiting unit power.
The feasibility of the system has yet to be determined and will chiefly depend on the development of fuels and materials capable of withstanding high temperatures; the currently considered operating temperature of around 1000°C is close to the transformation temperature of materials commonly used in the nuclear industry.
Lead-cooled Fast Reactors (LFR)
Unlike sodium, lead does not react violently with water or air.
The thermal inertia associated with the large volume of lead used and its very high density results in long grace periods in the event of loss of cooling.
In addition, the high boiling point at atmospheric pressure is a guarantee of high margins under normal operating conditions and rules out the risk of coolant boiling.
The main drawback of lead-cooled (or lead-bismuth cooled) reactors is that the coolant tends to corrode and erode stainless steel structures.
LFR safety is reliant on operating procedures, which does not seem desirable in a Generation IV reactor.
The
highly toxic nature of lead and its related products, especially polonium-210,
produced when lead-bismuth is used, raises the problem of potential
environmental impact.
IRSN is unable to determine whether the LFR system could guarantee a
significantly higher safety level than Generation III reactors.
Various technical hurdles need to be overcome before a reactor of this type could be considered.
Gas-cooled Fast Reactors (GFR)
Given the current state of GFR development, construction of an industrial prototype reactor would not be technically feasible. GFR specifications are highly ambitious and raise a number of technological problems that are still a long way from being solved.
From the safety point of view, the GFR does not display any intrinsic quality likely to lead to a significant improvement over Generation III reactors.
Molten Salt Reactors (MSR)
The MSR differs considerably from the other systems proposed by the GIF. The main differences are that the coolant and fuel are mixed in some models and that liquid fuel is used.
The MSR has several advantages, including its burning, breeding and actinide-recycling capabilities.
Its intrinsic neutron properties could be put to good use as, in theory, they should allow highly stable reactor operation. The very low thermal inertia of salt and very high operating temperatures of the system, however, call for the use of fuel salt drainage devices. System safety depends mainly on the reliability and performance of these devices.
Salt has some drawbacks − it is corrosive and has a relatively high crystallisation temperature.
The reactor must also be coupled to a salt processing unit and the system safety analysis must take into account the coupling of the two facilities.
Consideration must be given to the high toxicity of some salts and substances generated by the processes used in the salt processing unit.
The feasibility of fuel salt processing remains to be demonstrated.
SuperCritical-Water-cooled Reactors (SCWR)
The SCWR is the only system selected by GIF that uses water as a coolant. The SCWR is seen as a further development of existing water reactors and thus benefits from operating experience feedback, especially from boiling water reactors. Its chief advantage is economic.
While the use of supercritical water avoids problems relating to the phase change from liquid to vapour, it does not present any intrinsic advantage in terms of safety.
Thermal inertia is very low, for example, when the reactor is shut down.
The use of supercritical water in a nuclear reactor raises many questions, in particular its behaviour under neutron flux.
At the current stage of development, it is impossible to ascertain whether the system will eventually become significantly safer than Generation III reactors.
References:
1. IRSN, 2015, ‘Review of Generation IV Nuclear Energy Systems’, www.irsn.fr/EN/newsroom/News/Pages/20150427_Generation-IV-nuclear-energy-systems-safety-potential-overview.aspx
Direct download: www.irsn.fr/EN/newsroom/News/Documents/IRSN_Report-GenIV_04-2015.pdf
2. See for example: International Panel on Fissile Materials, 2010, ‘Fast Breeder Reactor Programs: History and Status’, www.ipfmlibrary.org/rr08.pdf
Helmut Hirsch, Oda Becker, Mycle Schneider and Antony Froggatt, April 2005, ‘Nuclear Reactor Hazards: Ongoing Dangers of Operating Nuclear Technology in the 21st Century’, www.greenpeace.org/international/press/reports/nuclearreactorhazards
OECD: Generation IV R&D “a growing challenge”
Nuclear Monitor #860, 10 May 2018, ‘Generation IV R&D “a growing challenge”‘, https://www.wiseinternational.org/nuclear-monitor/860/nuclear-news-nuclear-monitor-860-10-may-2018
The OECD Nuclear Energy Agency noted in its March 2018 monthly bulletin that “maintaining existing facilities operational is a growing challenge” for members of the Generation IV International Forum (GIF).1
The Nuclear Energy Agency was reporting on a February meeting of the Forum’s new task force, established to identify R&D facilities needed for the development of Generation IV systems. Presentations were made by the representatives of the six systems that GIF member countries are exploring ‒ gas-cooled fast reactors, sodium-cooled fast reactors, lead-cooled fast reactors, molten salt reactors, supercritical water-cooled reactors, and very high temperature reactors ‒ highlighting existing R&D capabilities and also gaps.
Filling those gaps will presumably be difficult if, as the Nuclear Energy Agency states, just maintaining existing facilities operational is a growing challenge.
Industry bodies such as the Nuclear Energy Agency are typically more bullish about Generation IV prospects. However the timelines are repeatedly deferred: Generation IV reactors were 20 years away 20 years ago, they are 20 years away now, and they will likely be 20 years away 20 years from now.
The Generation IV International Forum states: “It will take at least two or three decades before the deployment of commercial Gen IV systems. In the meantime, a number of prototypes will need to be built and operated. The Gen IV concepts currently under investigation are not all on the same timeline and some might not even reach the stage of commercial exploitation.”2
The International Atomic Energy Agency states: “Experts expect that the first Generation IV fast reactor demonstration plants and prototypes will be in operation by 2030 to 2040.”3 A 2015 report by the French government’s Institute for Radiological Protection and Nuclear Safety (IRSN) states: “There is still much R&D to be done to develop the Generation IV nuclear reactors, as well as for the fuel cycle and the associated waste management which depends on the system chosen.”4
The World Nuclear Association noted in 2009 that “progress is seen as slow, and several potential designs have been undergoing evaluation on paper for many years.”5
1. OECD Nuclear Energy Agency, ‘Generation IV research and development’, NEA Monthly News Bulletin – March 2018, www.oecd-nea.org/general/mnb/2018/march.html
2. www.gen-4.org/gif/jcms/c_41890/faq-2
3. Peter Rickwood and Peter Kaiser, 1 March 2013, ‘Fast Reactors Provide Sustainable Nuclear Power for “Thousands of Years”‘, www.iaea.org/newscenter/news/2013/fastreactors.html
4. Institute for Radiological Protection and Nuclear Safety, 2015, ‘Review of Generation IV Nuclear Energy Systems’, www.irsn.fr/EN/newsroom/News/Pages/20150427_Generation-IV-nuclear-energy-systems-safety-potential-overview.aspx
Direct download: www.irsn.fr/EN/newsroom/News/Documents/IRSN_Report-GenIV_04-2015.pdf
5. World Nuclear Association, 15 Dec 2009, ‘Fast moves? Not exactly…’, www.world-nuclear-news.org/NN_France_puts_into_future_nuclear_1512091.html