New Nuclear Reactor Technologies

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Most current nuclear power stations use Uranium fuel in solid form in rods, with water or heavy water as coolant. Neutrons produced by the nuclear reactions are slowed down to "thermal spectrum" velocities which affects the range of nuclear reactions they produce. Reactors are large in order to produce high power outputs, but are consequently complex in order to ensure safety through multiple redundant control systems, and expensive to build. Major components including the huge pressure and containment vessels are built on-site. In most cases even reactors of the same nominal design vary from one instance to another.

Many other reactor designs are possible, and a few are being actively developed. Some build on existing water-cooled Uranium-fuelled designs but shrink and simplify the designs to make them cheaper and quicker to build with the aim of building most of the reactor itself in factories where production-line economies can be gained. Physically smaller designs can more easily be made "walk away safe", averting the risk of the sort of overheating which lead to the melt-downs at Fukushima, using only passive cooling systems. Thus although the smaller designs have lower power output they may achieve lower cost per power output and bigger power stations can simply use multiple Small Modular Reactors to give higher outputs. Because the capital cost of each SMR is much lower than that of conventional reactors the bigger power stations can be built gradually with income from completed SMR modules helping pay for expansion of the station.

Other designs differ more radically from current generation reactors: Helium is used instead of water as a heat transfer medium in High Temperature Gas Reactors, liquid sodium is used in many "breeder" reactors operating in the "fast" neutron spectrum, and Molten Salt Reactors (MSRs) use molten Fluoride or Chloride salts of Sodium or Lithium (and sometimes other elements) as coolants, and as solutions in which fuel is dissolved. There are also reactor designs - particularly MSRs - which use Thorium rather than Uranium as fuel, and some which are designed to burn existing used nuclear fuel (which still contains much of the theoretically burnable Uranium it started with) or Plutonium (such as now-surplus nuclear bomb material).


Advanced Reactor Infromation System (ARIS)

The ARIS database includes technical information about Advanced Reactor Designs that is provided by the responsible design organizations and/or reactor plant vendors. According to the definitions established by the IAEA, an advanced reactor design consists of both Evolutionary and Innovative reactor technologies. Evolutionary reactor designs are reactor designs that improve on existing designs through small or moderate modifications with a strong emphasis on maintaining proven design features to minimize technological risk. While innovative reactor designs incorporate radical changes in the use of materials and/or fuels, operating environments and conditions, and system configurations. Advanced reactors can be classified in terms of coolant, neutron spectrum, temperature or purpose. With regards to purpose, the reactors can be sorted in terms of experimental, demonstration or prototype, and commercial.

Generation III reactor Wikipedia

Generation IV reactor Wikipedia

Generation IV Nuclear Reactors World Nuclear Association ; Jul 2016

  • An international task force is developing six nuclear reactor technologies for deployment between 2020 and 2030. Four are fast neutron reactors.
  • All of these operate at higher temperatures than today's reactors. In particular, four are designated for hydrogen production.
  • All six systems represent advances in sustainability, economics, safety, reliability and proliferation-resistance.
  • Europe is pushing ahead with three of the fast reactor designs.
  • A separate programme set up by regulators aims to develop multinational regulatory standards for Generation IV reactors.

The Advanced Nuclear Industry Samuel Brinton; Third Way; 15 Jun 2015

has comprehensive list of fission & fusion developments, comparison of technology types, and references

Tomorrow’s Nuclear Reactors are Closer Than You Think Laura Scheele, Idaho National Laboratory;; 1 Mar 2016

Advanced Reactor Nuclear Power Resurgence in the U.S.; 29 Jan 2016

White House strikes a blow for advanced nuclear reactors Richard Martin; MIT Technology Review; 20 Nov 2015

U.S. Department of Energy has announced a new program to help facilitate and finance innovation in nuclear power. Called the Gateway for Accelerated Innovation in Nuclear, the program will “provide the nuclear energy community with access to the technical, regulatory, and financial support necessary to move new or advanced nuclear reactor designs toward commercialization.”
There are nearly 50 companies in North America working on advanced nuclear reactor technologies, backed by more than $1.3 billion in private capital, according to Third Way, a Washington, D.C.-based research organization focused on energy, climate change, and national security (see “Experiments Start on a Meltdown-Proof Nuclear Reactor” and “Advanced Reactor Gets Closer to Reality”). But a lack of support from the DOE and an expensive, time-consuming licensing process under the Nuclear Regulatory Commission have presented hurdles that are all but insurmountable for startups (see “Advanced Nuclear Industry to Regulators: Give Us a Chance”).
The Gateway program, announced at the Summit on Nuclear Energy held last week at the White House, is the clearest signal to date of the Obama administration’s support for new nuclear technology. The DOE also announced it would broaden its $12.5 billion loan guarantee program for innovative nuclear technologies. These initiatives will give advanced nuclear companies access to the national laboratories, a single point of contact for collaboration with DOE experts, and help in “understanding and navigating the regulatory process for licensing new reactor technology.”

A retrospective analysis of funding and focus in US advanced fission innovation A Abdulla, M J Ford, M G Morgan, D G Victor; IOP science; 10 Aug 2017

Deep decarbonization of the global energy system will require large investments in energy innovation and the deployment of new technologies. While many studies have focused on the expenditure that will be needed, here we focus on how government has spent public sector resources on innovation for a key carbon-free technology: advanced nuclear. We focus on nuclear power because it has been contributing almost 20% of total US electric generation, and because the US program in this area has historically been the world's leading effort. Using extensive data acquired through the Freedom of Information Act, we reconstruct the budget history of the Department of Energy's program to develop advanced, non-light water nuclear reactors. Our analysis shows that—despite spending $2 billion since the late 1990s—no advanced design is ready for deployment. Even if the program had been well designed, it still would have been insufficient to demonstrate even one non-light water technology. It has violated much of the wisdom about the effective execution of innovative programs: annual funding varies fourfold, priorities are ephemeral, incumbent technologies and fuels are prized over innovation, and infrastructure spending consumes half the budget. Absent substantial changes, the possibility of US-designed advanced reactors playing a role in decarbonization by mid-century is low.

Analysis highlights failings in US's advanced nuclear program IOP Publishing; AAAS EurekAlert; 9 Aug 2017

Despite repeated promises over the past 18 years, the US Office of Nuclear Energy (NE) is unlikely to deliver on its mission to develop and demonstrate an advanced nuclear reactor by the mid-21st century.
That is the conclusion of a new study from the University of California, San Diego and Carnegie Mellon University, published today in the journal Environmental Research Letters, which used data obtained through the Freedom of Information Act to reconstruct the program's budget history.
Lead researcher Dr Ahmed Abdulla, from UC San Diego, said: "In theory, advanced, non-light water reactors are a promising carbon-free technology, which could complement or replace light water reactors. Some of these reactors would operate at higher temperatures, providing energy services that existing reactors cannot. Others, meanwhile, could reduce future nuclear waste burdens by operating for decades without refuelling, burning up more of their fuel and generating smaller volumes of waste.
"However, despite repeated commitments to non-light water reactors, and substantial investments by NE (more than $2 billion of public money), no such design is remotely ready for deployment today."
The researchers investigated how effectively those resources were allocated, and how NE has performed as a steward of nuclear technology innovation. What they found was an office beset by problems and violating much of the wisdom about how to effectively run an applied energy research program.
Dr Abdulla said: "There were often inconsistencies in the annual budget documents. The budget itself varies significantly over the period of study, which is fine if these variations are part of a coherent vision that is being pursued, but that is not the case. At all levels, NE favours existing technologies and fuels over innovation, and, where it does support truly innovative research, it is prone to changing priorities before any concrete progress has been made.

Next Steps for Nuclear Innovation in the UK Stephen Tindale, with Katherine Chapman and Suzanna Hinson; Weinberg Next Nuclear; Apr 2016

Nuclear energy makes a major contribution to UK energy security. Existing civil nuclear reactors provide clean, low carbon energy, mitigating the problems of air pollution and climate change. But they have high upfront capital costs, and are not sufficiently flexible to back up wind and solar power. Significant progress on advanced nuclear energy technologies over the next ten years would address these drawbacks and contribute substantially to a more secure and sustainable UK energy system. However, advanced nuclear should be pursued as well as - not instead of - new nuclear facilities using existing nuclear technology. Advanced nuclear is not yet ready to fill the entire gap created as current UK nuclear facilities reach the end of their design life.
Advanced nuclear reactors could deliver energy that is even lower-carbon than energy from existing nuclear designs. They could be inherently and passively safe and have a significantly reduced proliferation risk. They would be cheaper to build than the EPR, and very probably cheaper than any existing nuclear design. They could be a means of re-using spent fuel and reducing the UK’s plutonium stockpile.
Includes summary of some new generation designs
Charles Barton's comments on Weinberg report:
Next Step for Nuclear innovation in the UK is a deeply flawed document prepared for the British Government by the Weinberg Institute as a policy guide intended to assist the Government of the UK on future choices regarding advanced nuclear technology. Unfortunately, the Weinberg Institute lacks the Depth of Alvin Weinberg, the famous Nuclear Scientist for which it is named. Below is a link to this document. I will focus here of the criteria by which this document suggests future nuclear decisions should be based. Next Step places two Safety and proliferation prevention above other categories. But Generation III + reactors are already highly safe, indeed safer than renewable generation technologies, and minimal safety standards for Generation IV reactors are in some cases even safer. Efficiency requirements might well produce generation IV reactors that meet absurdly safe standards. So why make safety more important than other considerations. The second standard is the prevention of nuclear proliferation. Yet we are talking her about Reactors to be built in the UK, the United States and Canada. The first two countries are already nuclear powers, while the third country has possessed the ability to build nuclear weapons since WW II, but has refrained to do so. The reactors built in these three countries are very unlikely to cause nuclear proliferation, and one way to avoid proliferation from Generation IV technology built in any of these countries, is an agreement between the three of them to not sell Generation IV reactors to any State that is likely to embark on nuclear weapons programs. A further consideration is that the Chinese are working on development projects involving 3 different types of Generation IV reactor technology. Unless brought into proliferation prevention arrangements, China could sell Generation IV reactors to countries known to pose proliferation risks. Clearly there are problems with this study.

Floating reactors

Are Floating Reactors The Future Of Nuclear Energy? Vanand Meliksetian; OilPrice; 8 Dec 2018

The future of nuclear energy is either gloomy or promising depending on the country or region in question. In the developed world nuclear power is in decline. Especially after the disaster at Fukushima in Japan, the nuclear power industry is fighting an uphill battle. Tokyo became the world’s largest importer of LNG following the closure of several of its nuclear facilities. Germany is planning to decommission all of its 22 plants until 2022. Also, heavyweight France which derives 75 percent of its energy from nuclear, has announced the decommissioning of 14 of its 58 plants. Only the UK intends to construct a new power plant with Chinese and French help.
In other parts of the world, however, nuclear energy is a highly sought-after prize. Russia’s state-owned Rosatom has emerged as the global leader when it comes to constructing nuclear power plants. The company has an international order book worth $300 billion spread over 12 countries in the developing world. Traditional plants take over a decade to build and are definitively fixed to the grid, but Rosatom intends to provide alternative technologies to overcome these liabilities.
In order to maintain its competitive edge, the company has invested approximately $400 million in developing a unique kind of nuclear power plant, a floating one. The secretive nature of the project in the first years of its development didn’t help assure critics concerning the safety of the facility. In recent years, Rosatom has disclosed some of the construction methods in order to prove to potential customers the value and safety of its technological breakthrough.
Besides Russia, others also intend to develop floating nuclear power plants of their own. Two Chinese state-owned companies are developing the necessary technology to start constructing up to 20 facilities over the coming years. American scientists are also at it, but according to Jacopo Buongiorno, a professor of nuclear engineering at Massachusetts Institute of Technology “the Russians are light-years ahead of us”.


Bohai Shipbuilding Industry to build China’s first offshore nuclear platform Jason Jiang; Splash 24/7; 20 Apr 2016

China Shipbuilding Industry Corporation (CSIC) has confirmed that it will construct the first offshore nuclear platform at its affiliate yard Bohai Shipbuilding Industry. Currently Bohai Shipbuilding Industry is collaborating with China General Nuclear Power Corporation (CGN) for the preliminary works of the project. CSIC-No.719 Research and Development Institute has completed two designs for the platform, one is a floating platform and the other is a submersible platform. CGN has been developing a small modular nuclear reactor called the ACPR50S for maritime use, which would be able to provide power to offshore oil and gas exploration and production. The investment on the project is about RMB3bn ($464m), and the first platform is expected to start a trial in 2019. China also made plans to build 20 offshore nuclear platforms in the near future. Bohai Shipbuilding is one of China’s more secretive yards, tasked with plenty of military contracts as well as commercial vessel construction.

China Plans A Floating Nuclear Power Plant James Conca; Forbes; 18 Jan 2016

A 200MW light water reactor for electrical power, desalination etc.

Lloyd's Register to help Chinese develop floating SMR World Nuclear News; 26 Oct 2015

Lloyd's Register of the UK announced today it has signed a framework agreement with the Nuclear Power Institute of China (NPIC) to support the design and development of a floating nuclear power plant utilizing a small modular reactor (SMR).
Under the framework agreement, Lloyd's Register and NPIC - a subsidiary to China National Nuclear Corporation (CNNC) - will cooperate on the development of the "first-of-a-kind floating nuclear vessel" which will be used in Chinese waters to supply electrical power to offshore installations.
Lloyd's Register said the first contract under the framework agreement is to develop new safety regulations, safety guidelines, and nuclear code and standards for the floating vessel, that are consistent with Offshore and International Marine Regulations and the International Atomic Energy Agency (IAEA) nuclear safety standards.


Russia to Build World's First Floating Nuclear Power Plant Next Year The Moscow Times; 21 Apr 2015

Russia starts work on Arctic dock for 1st-ever floating nuclear power plant RT; 7 Oct 2016

The world’s first floating nuclear power plant is set to start producing power and heat in 2019. While the plant is already being tested, construction of the dock has begun on the Arctic coast in Russia’s Far East. The construction works on the dock, which will host the floating nuclear power plant ‘Akademik Lomonosov’, kicked off Wednesday in the bay of the city of Pevek, Chukotka, RIA Novosti reports.

Russia's Floating Nuclear Power Plant Has Hit the Sea Jennings Brown; Gizmodo; 30 Apr 2018

Russia launched the world’s first floating nuclear power plant on Saturday. The 70-megawatt vessel, christened the Akademik Lomonosov, was towed away from St. Petersburg by two boats. It is currently coasting through the Baltic Sea to the town of Murmansk for fuel, and is then supposed to embark for the Arctic town of Pevek in 2019, according to a release from the state-run firm that built the rig.

Both reactors on Rosatom’s floating nuclear plant now operational Charles Digges; Bellona; 7 Dec 2018

Both reactors on the Akademik Lomonosov, Russia’s controversial floating nuclear power plant, are now operational, and its starboard side reactor has been brought up to 10 percent of its total power, Rosatom, Russia’s state nuclear corporation, said in a release.
The reactor start, which occurred at Atomflot, Russia’s nuclear icebreaker port in Murmansk, passed without incident, according to the release, and will be followed by a number of reactor tests, which are expected to last several months.
After completing these tests, the Akademik Lomonosov – essentially a large barge atop which sit the reactors – will be towed through the Arctic to the far eastern Siberian port of Pevek, a town of 100,000 people in Chukotka, were it is slated to go online in the summer of 2019.
The plant is expected to replace the energy supplied by the Bilibino nuclear power plant – the world’s four northernmost commercial reactors – which Rosatom will begin decommissioning in 2021.

Washington State SMRs

Washington State continues looking into small modular reactors nuScale, mPower

Advanced Boiling Water Reactor

One step closer to building an Advanced Boiling Water Reactor (ABWR) in the UK The Alvin Weinberg Foundation

Travelling Wave Reactor / TerraPower

Traveling Wave Reactor Wikipedia


Bill Gates explains why China will build the first fourth generation nuclear plant

Fast Breeder reactors *


Thorium fuel cycle — Potential benefits and challenges International Atomic Energy Agency; May 2005

Thorium is three times more abundant in nature compared to uranium and occurs mainly as ‘fertile’ 232Th isotope. From the inception of nuclear power programme, the immense potential of 232Th for breeding human-made ‘fissile’ isotope 233U efficiently in a thermal neutron reactor has been recognized. Several experimental and prototype power reactors were successfully operated during the mid 1950s to the mid 1970s using (Th, U)O2 and (Th, U)C2 fuels in high temperature gas cooled reactors (HTGR), (Th, U)O2 fuel in light water reactors (LWR) and Li7 F/BeF2/ThF4/UF4 fuel in molten salt breeder reactor (MSBR). 232Th and 233U are the best ‘fertile’ and ‘fissile’ materials respectively for thermal neutron reactors and ‘thermal breeding’ has been demonstrated for (Th, U)O2 fuel in the Shippingport light water breeder reactor (LWBR). ThO2 has also been successfully used as blanket material in liquid metal cooled fast breeder reactor (LMFBR) and for neutron flux flattening of the initial core of pressurized heavy water reactor (PHWR) during startup. So far, thorium fuels have not been introduced commercially because the estimated uranium resources turned out to be sufficient. In recent years, there has been renewed and additional interest in thorium because of: (i) the intrinsic proliferation resistance of thorium fuel cycle due to the presence of 232U and its strong gamma emitting daughter products, (ii) better thermo-physical properties and chemical stability of ThO2, as compared to UO2, which ensures better in-pile performance and a more stable waste form, (iii) lesser long lived minor actinides than the traditional uranium fuel cycle, (iv) superior plutonium incineration in (Th, Pu)O2 fuel as compared to (U, Pu)O2 and (v) attractive features of thorium related to accelerated driven system (ADS) and energy amplifier (EA). However, there are several challenges in the front and back end of the thorium fuel cycles. Irradiated ThO2 and spent ThO2-based fuels are difficult to dissolve in HNO3 because of the inertness of ThO2. The high gamma radiation associated with the short lived daughter products of 232U, which is always associated with 233U, necessitates remote reprocessing and refabrication of fuel. The protactinium formed in thorium fuel cycle also cause some problems, which need to be suitably resolved. The information on thorium and thorium fuel cycles has been well covered in the IAEATECDOC-1155 (May 2000) and IAEA-TECDOC-1319 (November 2002). The objective of the present TECDOC is to make a critical review of recent knowledge on thorium fuel cycle and its potential benefits and challenges, in particular, front end, applying thorium fuel cycle options and back end of thorium fuel cycles.

Dutch satirical news show on why we need to break the taboo around nuclear energy (comment) Reddit;

warning, nuclear physicist talking.
Anything you watch or read when they talk about Thorium, do the Protactinium test: Ctrl+F "Protactinium".
If you've heard about Thorium, you might remember that 232Th is not a nuclear fuel per se, it must be turn into the good stuff 233U; thats the one that will fission and give you your energy from fission, to turn into heat, steam, etc. Think of it like a recipe, you have butter and flower, you mix them to get the shortbread that you want. See how easy it is for everybody to get some shortbread?
Except everybody also like to gloss over that between the "butter/flower" step and the "shortbread" step, there's a "white phosphorous neurotoxic napalm" step that might make things a bit more complicated the kitchen. That's your 233Pa.
So it goes 232Th+n -> 233Pa -> 233U.
This is when you say: "but wait 233c, this is just like 239Pu is produced from 238U: 238U+n -> 239Np -> 239Pu, this is happening all the time in normal nuclear power plants. What's the difference?". The difference is the same as between 2 and 27.
239Np (the step between Uranium 238 and Plutonium 239) has a half life of 2 days, while 233Pa (the thing between Thorium and Uranium 233) has one of 27 days. If you leave 239Np in the core it will quickly turn into 239Pu, but you can't leave 233Pa in the core for a month or it will capture more neutrons and turn into something else than 233U. (there's also a matter of cross section: 233Pa has a much higher probability of capturing neutrons than 239Np). If you leave your butter and flower too long in the over you'll get a brick rather than a shortbread.
If you want to use Thorium, you must: expose your Th; extract your 233Pu; let it decay into 233U; feed the 233U back to your reactor.
By now you should understand why liquifying the fuel make so much more sense for Th than for U. It's not "MSR work so well with Thorium", it "if you want to continuously extract your 233Pa, you'd better do it with a liquid fuel".
this is where you say "Ok, but still don't see the issue, you just pump and filter your fuel to recover the 233Pa, and let it decay in a tank, and pump/filter the 233U back in for it to fission".
I'm going to assume that you know what a Becquerel and a Sievert are.
Remember the 27 days? with the density of 233Pa, that translates into 769TBq/g (Tera is for 1012 , that's a lot), and because of the high energy gamma from our friend 233Pa, that also means a dose rate at 1m from a 1g teardrop of 233Pa of 20,800mSv/h. Starting to get a picture?
Notice how all the numbers I've use are not "engineering limits" that few millions in R&D can bend, those are hardwired physical constants of Nature: half life, density, neutron capture cross section, gamma energy. Good luck changing those by throwing $ at them.
Now try to imagine technicians working in those plants, like doing some maintenance, replacing a pump (I haven't even touched the complex chemical separation system you need to extract your 233Pa from your fuel or 233U from your 233Pa, which will definitely need maintenance). Let's put it this way: if there is 1mg of 233Pa left in the component they are working on, they'll reach their annual dose limit in 1h.

A safer route to a nuclear future?; 13 Jun 2012

discussion of recycling actinides as fuel, safety problems with multiple cycles with U fuel that Th fuel could solve, Ben Lindley, Cambridge Enterprises

Thorium-Fuelled Molten Salt Reactors Report for the All Party Parliamentary Group on Thorium Energy; The Weinberg Foundation; Jun 2013

Thorium-fuelled Molten Salt Reactors (MSRs) offer a potentially safer, more efficient and sustainable form of nuclear power. Pioneered in the US at Oak Ridge National Laboratory (ORNL) in the 1960s and 1970s, MSRs benefit from novel safety and operational features such as passive temperature regulation, low operating pressure and high thermal to electrical conversion efficiency. Some MSR designs, such as the Liquid Fluoride Thorium Reactor (LFTR), provide continuous online fuel reprocessing, enabling very high levels of fuel burn-up. Although MSRs can be fuelled by any fissile material, the use of abundant thorium as fuel enables breeding in the thermal spectrum, and produces only tiny quantities of plutonium and other long-lived actinides.
Current international research and development efforts are led by China, where a $350 million MSR programme has recently been launched, with a 2MW test MSR scheduled for completion by around 2020. Smaller MSR research programmes are ongoing in France, Russia and the Czech Republic. The MSR programme at ORNL concluded that there were no insurmountable technical barriers to the development of MSRs. Current research and development priorities include integrated demonstration of online fuel reprocessing, verification of structural materials and development of closed cycle gas turbines for power conversion.

Thor-bores and uro-sceptics: thorium's friendly fire Jim Green − Nuclear Monitor editor; Nuclear Monitor Issue: #8014458; 9 Apr 2015

Many Nuclear Monitor readers will be familiar with the tiresome rhetoric of thorium enthusiasts − let's call them thor-bores. Their arguments have little merit but they refuse to go away.

The U.S. government lab behind China's nuclear power push Reuters; 20 Dec 2013

Thorium molten salt reactors in EenVandaag - Dutch Public Television 20151105 Gijs Zwartsenberg

Thorium Energy Report website with pages of reports on work on Thorium reactors from:

Thorium can give humanity clean, pollution free energy Kirk Sorensen; TEDxColoradoSprings

Thorium Energy World - papers

127 mostly quite technical papers presented during the Thorium Energy World conference
Grouped by subject area. Links to full papers where author(s) permit.

Small Modular Reactors *

Molten Sodium Reactors

Some Fast Breeder Reactors, and TerraPower's Traveling Wave Reactor use molten sodium as coolant.

Sodium safety

Metal Fires in Fast Reactors: Part I Tara J. Olivier, Ross F. Radel, Steven P. Nowlen, Thomas K. Blanchat, John C. Hewson; Nuclear Green Revolution; 23 Feb 2015

Refers to report by Sandia Labs

Criticism of Sodium-cooled reactor designs by Robert Steinhaus

The Short of Why I do not like the Terrapower TWR pool style SFR
(Safety Concern) - Sodium Cooled Fast Reactors like the Terrapower TWR contain a lot of reactive sodium coolant.
The French Superphenix used 5500 metric tons of sodium (3300 tons in the primary reactor vessel) for a 1.2 GWe reactor - exact figures have not so far been provided for other mature SFR designs like GE PRISM, BN-800, or the Terrapower TWR so scaling the Superphenix numbers is about the best analysts can do given the reticence of current SFR designers to reveal to the public and decision makers the numbers that would allow fair and accurate analysis of the potential hazard of their SFR designs.
Sodium Safety - Sodium reacts exothermically with liquid water or steam to generate sodium hydroxide and hydrogen:
Na + H2O -> NaOH + 1/2H2 + heat Heat of reaction: ~ 162kJ/mole-Na (around 7.05MJ/kg-Na)
Hydrogen tends to accumulate in the roof area of a reactor containment building and if the conditions are right, hydrogen air mixtures can detonate.
Reference – G. Manzini and F. Parozzi “Sodium Safety” (Intrinsically safer nuclear technology exits)-
A 1 GWe Pu-239 fueled Sodium Cooled Reactor, like the Terrapower TWR, fissions about 1 ton of Pu-239 fuel while producing about 1 ton (1000 kilograms) of fission products a year. The Terrapower TWR is designed to retain spent fuel inside the reactor and "shuffle fuel" while operating. One effect of this arrangement is that over the designed lifetime of the reactor, more and more fission products accumulate.After 60 years of operation, some of the early produced fission products inside the TWR will have decayed to lower levels of activity - becoming less radioactive. On the other hand, depending on the specific arrangements of the fuel shuffling system used in the TWR, old fission products which are exposed to neutrons will continue to absorb neutrons and become further neutron activated, in some instances making them more radioactive. A more complex modeling of 60 year isotopic inventory of a Terrapower TWR would need to be made with a code like ORIGEN-S to give a reliable and accurate assessment of radioactivity of the fission product isotopic inventory after 60 years of operation. Still, I think it can be fairly stated that the radiological inventory of a sodium cooled TWR would be very large indeed and the chemical stored energy in Sodium coolant also very large which means that the potential is there for a really large accident (INES-7) if any of the SFR engineered safety systems (like the Argon cover gas over the main reactor sodium pool) is ever even momentarily lost as the result of an air leak..
Safer reactor coolants than hot reactive sodium exist (I like Molten Salts or helium).

Molten Salt Reactors *

High Temperature Gas-cooled / Pebble Bed Reactors


HTR-10 Wikipedia

China plans to open 1st ‘meltdown-free’ nuclear power plant by 2017 Chinese High Temperature Pebble Bed Reactor

China Could Have a Meltdown-Proof Nuclear Reactor Next Year Richard Martin; MIT Technology Review; 11 Feb 2016

Two high-temperature, gas-cooled reactors under construction in Shandong will make up the first commercial-scale plant of its type in the world.
In what would be a milestone for advanced nuclear power, China’s Nuclear Engineering Construction Corporation plans to start up a high-temperature, gas-cooled pebble-bed nuclear plant next year in Shandong province, south of Beijing. The twin 105-megawatt reactors—so-called Generation IV reactors that would be immune to meltdown—would be the first of their type built at commercial scale in the world.
Construction of the plant is nearly complete, and the next 18 months will be spent installing the reactor components, running tests, and loading the fuel before the reactors go critical in November 2017, said Zhang Zuoyi, director of the Institute of Nuclear and New Energy Technology, a division of Tsinghua University that has developed the technology over the last decade and a half, in an interview at the institute’s campus 30 miles south of Beijing. If it’s successful, Shandong plant would generate a total of 210 megawatts and will be followed by a 600-megawatt facility in Jiangxi province. Beyond that, China plans to sell these reactors internationally; in January, Chinese president Xi Jinping signed an agreement with King Salman bin Abdulaziz to construct a high-temperature gas-cooled reactor in Saudi Arabia.

China's HTGR fuel production line starts up World Nuclear News; 29 Mar 2016

A pilot production line of fuel elements for China's Shidaowan HTR-PM - a high-temperature gas-cooled reactor (HTGR) demonstration project - has started in Baotou, Inner Mongolia. The first tank of uranium dioxide powder was slowly poured into the dissolution tank on 27 March, marking formal entry into production of the HTGR fuel line, China National Nuclear Corporation announced the following day. Earlier this month, the National Nuclear Security Administration approved an operating licence for the fuel production line. The production line will have an annual capacity of 300,000 spherical fuel elements. The National Nuclear Security Administration issued a permit for its construction in February 2013 and an opening ceremony was held the following month. The installation of equipment was completed in September 2014.

Progress Report on HTGR reactors in China and U.S. 9 Neutron Bytes; Apr 2016

Development of the a high temperature gas cooled reactor (HTGR), a concept with more than three decades of history behind it, in 2016 has had several new breakout milestones in China and the U.S.
  • In March 2016 China installed the first of two reactor pressure vessels for a demonstration high temperature, gas cooled (HTGR) (Pebble Bed) reactor that is under construction at Shidaowan in Shandong province.
  • In January 2016 the U.S. Department of Energy announced that X-energy, located in the Maryland suburbs of Washington, DC, has won a $40 million grant to develop the Xe-100 pebble bed High Temperature Gas-Cooled reactor (HTGR). The development grant includes $6M in FY2016, which will be supplemented with additional investor funding from X-energy.
  • The Next Generation Nuclear Plant alliance (NGNP) continues its work on development of the Areva Antares HTGR, a prismatic block design. The NGNP alliance has published a business plan with the objective of building a prototype at the U.S. site in the 2020s.

Will China convert existing coal plants to nuclear using HTR-PM reactors? Rod Adams; Atomic Insigts; 21 Nov 2016

It would be a huge benefit to the earth’s atmosphere if China, India, Brazil and the US could reduce direct coal burning while still making use of much of the capital that they have invested in building coal fired power plants. It would make an even larger difference in reducing air pollution in the areas downwind of the coal stations.
Converting coal-burning supercritical steam plants to nuclear power plants by replacing the furnaces and boilers with high temperature gas cooled reactors might become a routine power plant improvement in the relatively near future. The High Temperature Reactor – Power Module (HTR-PM) project is aimed at demonstrating the feasibility of this evolutionary concept.
At the recent High Temperature Reactor 2016 (HTR2016), held in Las Vegas, NV, Prof. Zhang Zuoyi, Director of China’s Institute of Nuclear and New Energy Technologies (INET), briefed his colleagues in the international community of high temperature gas reactor enthusiasts on the current status of the HTR-PM. That project is one of the more intriguing clean air projects underway in the world today.

China Advances HTGR Technology Abby L. Harvey; Power; 1 Nov 2017

China’s State Nuclear Power Technology Corp. (SNPTC) has completed the installation of its high-temperature gas-cooled reactor (HTGR) project, the joint venture told the International Atomic Energy Agency (IAEA).

NGNP Alliance




Meet A Startup Making A New Kind Of Safer, Smaller Nuclear Reactor X-energy PBR

Urenco U-battery

Miniature nuclear power stations available within decade Tereza Pultarova; E&T Magazine; 7 Oct 2016

uranium enrichment firm URENCO has decided to go even further and develop a miniature nuclear power plant so small and cheap that it could power a single village or a factory
“A single unit would occupy an area the size of two squash courts,” explained Paul Harding of URENCO, overseeing the project called U-Battery. “The footprint of each unit is about the penalty area of a football pitch. Each unit is designed to give 10 megawatts of thermal output of which around 40 per cent can be converted into electricity, so you can get four megawatts of electricity from a single installation.”
Unlike the larger SMRs, U-battery is a high temperature gas cooled reactor akin to currently developed generation IV nuclear reactors. It uses grain-like TRISO fuel that is not designed for reprocessing but spent after one use.
“The U-Battery is designed to operate at about 700℃ and you do not challenge integrity of the fuel to at least 1600℃ so there is a great margin,” Harding said. “TRISO fuel is inherently safe. It consists of grains of uranium oxide that are coated in three layers of ceramic material, which ensures that fission products do not escape from the inner kernel.”
The remotely controlled U-battery was designed with renewable energy generation in mind and the team envisions it could serve as a back-up power generator for solar and wind power plants.
The team is already negotiating with authorities of the Canadian province of Ontario to have U-Batteries tested in some of the remote northern communities that are not connected to the utility grid.

Swiiming Pool / District Heating reactors

CNNC completes design of district heating reactor World Nuclear News; 7 Sep 2018

The preliminary design of the Yanlong swimming pool-type low-temperature reactor for district heating has been completed, China National Nuclear Corporation (CNNC) announced yesterday.
CNNC launched its independently researched and developed Yanlong reactor (referred to as the DHR-400) for district heating in November 2017. The move came shortly after the "49-2" pool-type light-water reactor developed by the China Institute of Atomic Energy continuously supplied heat for 168 hours.
CNNC said the Yanlong reactor - which an output of 400 MWt - has been developed based upon the company's safe and stable operation of pool-type experimental reactors over the past 50 years. It said the Yanlong is a "safe, economical and green reactor product targeting the demand for heating in northern cities". The reactor can be operated under low temperatures and normal pressures. It can be constructed near urban areas due to the zero risk of a meltdown and lack of emissions. In addition, the reactor is easy to decommission. The Yanlong "represents a relatively modest investment", according to CNNC.
"It's an effective way to improve China's energy resource structure by utilising nuclear energy for district heating, and to ease the increasing pressures on energy supplies," CNNC said. "Nuclear energy heating could also reduce emissions, especially as a key technological measure to combat haze during winter in northern China. Thus, it can benefit the environment and people's health in the long run."
The company added, "It can be constructed either inner land or on the coast, making it an especially good fit for northern inland areas, and it has an expected lifespan of around 60 years. In terms of costs, the thermal price is far superior to gas, and is comparably economical with coal and combined heat and power (CHP)."

Nuclear batteries

Scientists are turning nuclear waste into super-efficient diamond batteries PETER DOCKRILL; Science Alert; 29 NOV 2016

Scott's team has so far demonstrated a prototype diamond battery that uses an unstable isotope of nickel (nickel–63) as its radiation source. Nickel 63 has a half-life of approximately 100 years, meaning the researchers' prototype device would still hold about 50 percent of its 'charge' in 100 years' time.
But the scientists say there's an even better source they could work with – and doing so would end up providing a solution for the UK's massive stockpiles of nuclear waste. The first generation of Magnox nuclear reactors in the UK produced during the 1950s through to the 1970s used graphite blocks to help sustain the nuclear reactions, but the technique comes at a cost. During the process, the graphite blocks themselves become radioactive, generating an unstable carbon isotope, carbon–14. The last of these Magnox reactors was retired in 2015, but after decades of nuclear power generation, there's an awful lot of waste byproduct left over, with almost 95,000 tonnes of these graphite blocks needing to be safely stored and monitored while they remain radioactive. And that could be a pretty long time, given that carbon–14 has a half-life of about 5,730 years.
"Carbon–14 was chosen as a source material because it emits a short-range radiation, which is quickly absorbed by any solid material," says one of the researchers, Neil Fox. "This would make it dangerous to ingest or touch with your naked skin, but safely held within diamond, no short-range radiation can escape. In fact, diamond is the hardest substance known to man, there is literally nothing we could use that could offer more protection."
According to the researchers, carbon–14 batteries would only be good for low-power applications – but their endurance would be on a whole different scale. "An alkaline AA battery weighs about 20 grams, has an energy density storage rating of 700 Joules/gram, and [uses] up this energy if operated continuously for about 24 hours," Scott told Luke Dormehl at Digital Trends. "A diamond beta-battery containing 1 gram of C14 will deliver 15 Joules per day, and will continue to produce this level of output for 5,730 years — so its total energy storage rating is 2.7 TeraJ."

Fusion *


Carbon nanotubes shown to protect metals against radiation damage David Szondy; Gizmag; 5 Mar 2016

An international team of scientists led by MIT has discovered that adding small amounts of carbon nanotubes to metals makes them much more resistant to radiation damage. Though currently only proven in low-temperature metals like aluminum, the team says that the ability of the nanotubes to slow the breakdown process could improve the operating lifetimes of research and commercial reactors.