One of the most ancient metals gets a 21st century focus

In the 19th century lead, which had it major cultural identification in the bullets of the U.S. Civil War, found a new emphasis with the invention of the Linotype Machine. For the first time since Guttenberg deployed his printing press, newspapers and books saw a huge leap in the ability of their publishers to put media products into the hands of consumers. In the 21st century a surprising development is that one of the six so-called reference designs of the Generation IV advanced nuclear reactor program, lead cooled reactors, has attracted development commitments from U.S. and Russian firms.

In the U.S. Westinghouse Electric Company announced that it is seeking to collaborate with the U.S. Department of Energy (DOE) on the next clean-energy innovation: a Westinghouse lead-cooled fast reactor (LFR) that will be designed to achieve new levels of energy affordability, safety and flexibility.

Westinghouse submitted its project proposal for the DOE’s upcoming investment in advanced reactor concepts that can be demonstrated in the 2035 timeframe. The Westinghouse-led project team includes members of the national laboratory system, universities and the private sector with expertise in areas essential to the design and commercialization of an advanced LFR plant. The team will evolve Generation IV reactor technology and power it with a new type of nuclear to create a Generation V plant that is economically competitive.

Rosatom has approved the results of a study of the SVBR 100 project. In a press statement the agency said;

“Experts have confirmed there are no scientific or technical issues that would prevent completion of the project and obtaining a construction licence.”

The SVBR is modular lead-bismuth-cooled fast neutron reactor from Gidropress. Rosatom set up joint stock company AKME-Engineering in 2009 to develop and commercialize the SVBR-100. The reactor, to be built in Dimitrovgrad in Russia’s Ulyanovsk region, is expected to enter pilot operation in 2017 or 2018. This puts it almost two decades ahead of the Westinghouse effort.

Westinghouse lead cooled reactor not just another R&D sandbox

One of the criticisms of the GEN IV program is that it has evolved over time to be a sandbox for nuclear scientists, but has not produced any commercially viable designs.  What appears to be different about the Westinghouse effort to design and deploy a lead-cooled reactor is that it has the attention of the firm’s CEO. According to a company press statement, he said;

“Nuclear energy is a critical part of today’s energy mix, and will play an even larger role in the future to satisfy global demand for energy that is clean, safe, reliable and economical,” said Westinghouse President and CEO Danny Roderick.

“Westinghouse’s vision is to be the first to innovate the next technology, and we believe an LFR plant will be the next advanced reactor technology to be deployed. Westinghouse and our partners have the experience and technical capability to bring it to market.”

The firm said in its press statement that beyond electricity generation, the Westinghouse LFR applications would include hydrogen production and water desalination. Additionally, the plant’s load-following capabilities would further support the increased use of renewable energy sources such as solar and wind.

Russian effort moving towards commercial prototype

According to the World Nuclear Association, two of Russia’s foremost new reactor plans are for the 300 MWe BREST fast reactor, also lead-cooled, and the 100 MWe SVBR, cooled by a lead-bismuth combination.  Demonstration units of both are almost ready to start construction.

WNN reports that the pilot production unit is to be built by AKME-engineering, a joint venture between Rosatom and private company Irkutsenergo. The SVBR-100 is a small, modular, fast-neutron reactor using lead-bismuth cooling with a net output of 100MWe. The prototype SVBR-100 unit is scheduled to start operating in 2019.

According to a recent report by Nuclear Engineering International (NEI), in September, Vyacheslav Pershukov, deputy director general and director for innovations management at Rosatom, told journalists that the initial costing plans for the SVBR-100 project “turned out to be more optimistic than it is in actual fact”, adding the project participants were not happy with this cost.

In October 2014, NEI reports he said the total cost had increased to RUB36bn ($532m). However, Rosatom also said it is not seeking new partners to implement the project, but was in discussions with Irkutskenergo on next steps.

In August, Akme-engineering received a patent from the USA for the SVBR-100 nuclear reactor trademark. The company said it wanted to protect its intellectual property in preparation for construction of a prototype SVBR-100 unit at the Research Institute for Atomic Reactors (NIIAR) in Dimitrovgrad in the Ulyanovsk region. The trademark has already been registered in the European Union and South Korea.

Profile of lead cooled reactor designs

According to the Roadmap of the Gen IV program, lead cooled reactors have the following characteristics.

LFRs are Pb or Pb-Bi-alloy-cooled reactors operating at atmospheric pressure and at high temperature because of the very high boiling point of the coolant (lead up to 1749C; lead-bismuth-eutectic at 1670C).

The core is characterized by a fast-neutron spectrum due to the scattering properties of lead. Pb and Pb-Bi coolants are chemically inert and possess several attractive properties:

• There is no exothermic reaction between lead and water or air. The high boiling point of lead eliminates the risk of core voiding due to coolant boiling.

• The high density of the coolant contributes to fuel dispersion instead of compaction in case of core destruction.

• The high heat of vaporization and high thermal capacity of lead provide significant thermal inertia in case of loss-of-heat-sink.

• Lead shields gamma-rays and retains iodine and cesium at temperatures up to 600°C, thereby reducing the source term in case of release of volatile fission products from the fuel.

• The low neutron moderation of lead allows greater spacing between fuel pins, leading to low core pressure drop and reduced risk of flow blockage.

• The simple coolant flow path and low core pressure drop allow natural convection cooling in the primary system for shutdown heat removal.

However, according to the Gen IV technology roadmap, several drawbacks must be overcome, including the need for coolant chemical (oxygen) control for prevention of lead erosion- corrosion effects on structural steels at high temperatures and flow rates, and seismic/structural issues because of the weight of the coolant.

The opacity of lead, in combination with its high melting temperature, presents challenges related to inspection and monitoring of reactor in-core components as well as fuel handling. In particular, in the case of reactor system cooled by pure Pb, the high melting temperature of lead (327°C) requires that the primary coolant system be maintained at temperatures adequately high to prevent the solidification of the lead coolant.

The roadmap notes that although Pb-Bi reactors have been operated successfully in some of the Russian submarine programs, this experience cannot be easily extrapolated to the LFR since the propulsion reactors were small, operated at low capacity factors, featured an epithermal (not fast) neutron spectrum and operated at significantly lower temperatures than those anticipated in Gen-IV lead-cooled fast reactors.

An additional issue with the lead-bismuth cooled reactors is related to the accumulation of volatile Polonium-210 which is a strong alpha emitters. In the Russian Federation, techniques to trap and remove 210Po have been developed.

Summary of the Gen IV program

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 program set up by regulators aims to develop multinational regulatory standards for Generation IV reactors.

The designs include These include the:  Gas-cooled Fast Reactor (GFR),Lead-cooled Fast Reactor (LFR), Molten Salt Reactor (MSR), Supercritical Water-cooled Reactor (SCWR),Sodium-cooled Fast Reactor (SFR) and Very High Temperature Reactor (VHTR).

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