Category Archives: Power Generating Technology – Nuclear

Thorium: What’s Old is New Again

Development of the uranium-thorium fuel cycle in the U.S began in the late 1940s, encouraged by the abundance of thorium, the ability to convert thorium into fissile uranium during reactor operation, and the prospects for a closed fuel cycle with good economics.  The commercial potential of thorium has yet to be realized.

Today, there is renewed interest in thorium as an abundant, cheap nuclear fuel source that can be employed in the context of a variety of proliferation-resistant nuclear fuel cycles.

1. In the beginning:

Alvin Weinberg is generally considered in the U.S. to be “father” of the pressurized water reactor (PWR), which has become the dominant type of nuclear reactor employed in commercial power generation and in naval reactors.  On18 September 1944, Weinberg first described the basis for a PWR, with ordinary water as both coolant and moderator operating at high pressure, and producing steam for power production.

Dr. Alvin Weinberg. Source: Oak Ridge National Laboratory

On 10 April 1946, Weinberg and F. H. Murray (Oak Ridge, Clinton Laboratory) published, “High-Pressure Water as a Heat-Transfer Medium in Nuclear Power Plants,” in which the design characteristics of a water-cooled and moderated PWR were presented.  Interestingly, this PWR concept had a thorium-converter core, which used 233U as the fissile “seed” and thorium as the fertile “blanket” to breed more 233U during reactor operation.  This was similar in concept to the thorium-breeder core installed in the Shippingport commercial power reactor nearly 30 years later under the Department of Energy’s (DOE) Light Water Breeder Reactor (LWBR) Program.

The neutron absorption and decay chains for converting natural thorium (232Th) into fissile uranium (233U and 235U) are shown in the following diagram.

Source:  WAPD-TM-1387

Production of 233U through the neutron irradiation of 232Th invariably produces small amounts of 232U as an impurity (not shown in the above diagram), because of parasitic (n,2n) reactions on 233U itself, or on Pa233(protactinium), or on 232Th. The decay chain of 232U quickly yields strong gamma radiation emitters.  This characteristic is one aspect of the proliferation resistance of thorium fuel cycles.

2. Early commercial power reactors with thorium-converter cores

 In the U.S., thorium-converter cores were operated in five commercial power reactors between 1962 and 1989:

  • Indian Point 1 PWR
  • Elk River boiling water reactor (BWR)
  • Shippingport LWBR
  • Peach Bottom 1 high-temperature gas-cooled reactor (HTGR)
  • Fort St. Vrain HTGR

A brief overview of these commercial power reactors follows.  In retrospect, none would be judged as commercial successes.

Indian Point 1 thorium-converter Core 1 (1962 – 1974)

The first commercial use of a thorium-converter “seed-and-blanket” core was in the Indian Point 1 pressurized water reactor designed by Babcock & Wilcox. Construction started in New York in May 1956 and the plant was commissioned in October 1962.

Indian Point 1, circa 1963. Source: USDOE,

Indian Point 1 nuclear plant cross-section.   Source: Atomic Power Review,

Indian Point 1 was one of very few nuclear plants to incorporate fossil fired superheat to supplement the reactor power. In the cross-section view above, you can see the two oil-fired superheaters placed between the reactor and the turbine generator.  In its original configuration, Indian Point 1 had a net electrical output of 255 MWe, of which 104 MWe was derived from the fossil-fired superheaters.

Core 1 was rated at 585 MWt.  This was the only thorium converter core; highly-enriched (93%) 235U was used as the seed material. This core consisted of 120 fuel assemblies arranged in three concentric zones, each with differing UO2– ThO2ratios.  The central zone had the lowest uranium content.  Core loading was about 1,300 kg (2,425 pounds) of UO2(1,100 kg of U-235) and 17,207 kg (37,935 pounds) of ThO2.

The zoned core and fuel element layout are shown below.

Source:  Directory of Nuclear Reactors, Volume IV, Power Reactors, International Atomic Energy Agency, 1962

Subsequent cores used low-enriched UO2fuel and were rated at a somewhat higher power, 615 MWt.  Core 2 was installed between the last quarter of 1965 and the first quarter of 1966, after three years of operation on the thorium-converter Core 1. With the all-UO2Core 2, the plant’s net electrical output was raised to 265 MWe.

Seventeen tons of stainless steel-clad thorium oxide pellet fuel from Core 1 were reprocessed at the privately owned and operated Nuclear Fuel Services plant at West Valley, New York.  This was the first commercial spent fuel reprocessing plant in the U.S.

The Indian Point 1 nuclear plant was shutdown in October 1974, after 12 years of operation.

Elk River thorium-converter core (1964 – 1968)

This small boiling water reactor (BWR) demonstration plant was developed by Allis-Chalmers and built in Minnesota. The reactor core, which was rated at 58.2 MWt, was a highly-enriched (93%) 235U / thorium converter.  Core loading was about 208 kg (459 pounds) of UO2and 4,300 kg (9,480 pounds) of ThO2in 148 fuel assemblies.

Like Indian Point 1, Elk River incorporated fossil fired superheat to supplement the reactor power.  The plant’s total thermal power was 73 MWt, yielding a net electrical output of 22 MWe. The general plant layout is shown below.


The Elk River nuclear plant only operated from 1 July 1964 to 1 February 1968.  Subsequently, the plant was decommissioned. Some of the spent nuclear fuel was sent to the Trisaia facility in southern Italy for reprocessing as part of a thorium fuel cycle research program supported by the Italian National Committee for Nuclear Energy.  This pilot plant was operated during 1970s to process the uranium-thorium cycle fuels

Shippingport Light Water Breeder Reactor (LWBR, 1977 – 1982)

The LWBR Program, which was run for the Department of Energy (DOE) by the Office of Naval Reactors, was conducted to demonstrate the capability of the 233U/ thorium fuel system for use in a breeder reactor core that could be deployed in conventional light water reactor plants.  The LWBR core was installed in the Shippingport reactor and started operation in the fall of 1977.  Operation with the LWBR core finished on October 1, 1982.

Considerable experience was gained in fabricating the fuel for the LWBR core. This reactor used 233U / thorium instead of 235U / thorium as used in the Indian Point 1 and Elk River thorium converter cores.  The 233U needed for the LWBR was recovered from previously irradiated thorium using existing PUREX reprocessing equipment, which was designed for recovering uranium, but was not suitable for thorium recovery.  About 1,100 kg (2,425 pounds) of 233U was processed in pilot-plant scale equipment at Oak Ridge National Laboratory (ORNL) to produce the reactor-grade UO2needed for the LWBR core.  Fortunately, the 232U content of the uranium (note: 232U is a byproduct formed during thorium irradiation) was less than 10 ppm and remotely operated facilities with heavy shielding were not required to protect against high-energy gamma radiation from the 232U decay chain.

The basic LWBR seed-and-blanket core layout is shown in the following diagram:

Source:  INEEL/EXT-98-00799, Rev. 1, “Fuel Summary Report: Shippingport Light Water Breeder Reactor,” January 1999

LWBR fuel modules consisted of a hexagonal seed module inside an annular blanket module. The movable seed modules started life below the blanket modules and traveled vertically upward through the hexagonal passages in the blanket modules during core life. Core reactivity was controlled by changing the axial position of seed modules within the surrounding blanket modules, thus eliminating parasitic loss of neutrons to conventional poison control rods.

In the March 1986 report, “Shippingport Operations With the Light Water Breeder Reactor Core,”WAPD-TM-1542, Bettis Atomic Power Laboratory reported the following results:

“The Shippingport Station during LWBR operation demonstrated flexibility and load change response characteristics superior to those found in non-nuclear steam generating stations and the availability of the LWBR reactor compared very favorably with conventional light water reactors. The core operated for five years accumulating 29,047 effective full power hours (EFPH), far beyond the design goal of 15,000 EFPH. At the end of this period, the core was removed and the spent fuel shipped to the Naval Reactors Expended Core Facility in Idaho for a detailed examination to verify core performance, including an evaluation of breeding characteristics.”

Westinghouse reported the breeding performance of the reactor as follows (WAPD-T-3007, October 1993):

“Nondestructive assay of 524 fuel rods and destructive analysis of 17 fuel rods determined that 1.39% more fissile fuel was present at the end of core life than at the beginning, thereby establishing that breeding had occurred. Successful LWBR power operation to over 160% of design lifetime demonstrated the performance capability of this fuel system.”

The LBWR spent fuel was not reprocessed.

High-temperature Gas-Cooled Reactors (HTGRs, 1967 – 1989)

Three U.S. HTGRs and two German HTGRs have operated with U-Th coated particle fuel.

  • Peach Bottom 1 (1967 – 1974)
    • 40 MWe General Atomics HTGR operated in Pennsylvania
    • Used highly-enriched 235U / thorium fuel in the form of microspheres of mixed thorium-uranium carbide coated with pyrolytic carbon. These microspheres were embedded in annular graphite segments that were arranged into fuel elements.
  • Fort St. Vrain (1976 – 1989)
    • 330 MWe General Atomics HTGR operated in Colorado
    • Used highly-enriched 235U / thorium fuel in the form of TRISO and BISO microspheres coated with pyrolytic carbon, which were embedded in a graphite matrix and placed in prismatic graphite fuel elements.  The TRISO fuel particles were highly-enriched 235U and the BISO fuel particles were thorium.
    • Almost 25 tonnes (25,000 kg, 55,155 pounds) of thorium was used in fuel for the reactor.
  • Thorium High Temperature Reactor (THTR, 1983 – 1989)
    • 300 MWe pebble-bed reactor operated in Germany.
  • AVR (1967 – 1988)
    • 15 MWe pebble-bed reactor operated in Germany.
    • AVR was the first reactor based on the circa 1945 – 46 concept of the “Daniels Pile” by Farrington Daniels, the inventor of pebble bed reactors.

In the U.S., General Atomics originally planned to have HTGR spent fuel reprocessed to recover useful material, including 233U, which would have been recycle in HTGR fuel. The planned back-end of the fuel cycle included a step to separate the TRISO and BISO particles, thereby simplifying the downstream reprocessing steps for uranium and thorium.

No commercial HTGRs were built in the U.S. after Fort St. Vrain and the back-end of the HTGR U-Th fuel-cycle was never developed.  Spent fuel from the operating U.S. HTGRs was not reprocessed. DOE took title to the spent fuel and became responsible for managing its temporary storage at the Fort St. Vrain site.

3. Reprocessing spent uranium – thorium fuel *

By the early 1950s, several kilograms of purified 233U had been recovered from experimental lots of irradiated thorium, and two chemical processing flowsheets based on solvent extraction techniques had been developed and tested in small-scale operations.

The THOREX process was developed in the mid-1950s for reprocessing 233U – thorium fuel.  By the mid-to-late 1950s, the THOREX Pilot Plant Demonstration Program had been completed, and 35 tons of irradiated thorium metal had been processed in a facility with a throughput of 150 to 200 kg of thorium per day to recover 55 kg of purified 233U. The principal emphasis was on demonstrating the THOREX flowsheet, defining flowsheet capabilities, and identifying problem areas in the reprocessing of spent U-Th fuel.

During the 1960s, approximately 870 tons of thorium (primarily as ThO2) was irradiated. This thorium was then processed in production scale equipment to recover 1.4 tons of purified233U. The large-scale programs at Savannah River Plant (SRP) and Hanford utilized either the THOREX Flowsheet or a modified version of it (i.e., the Acid THOREX flowsheet) to effect the separation and recovery of 233U and thorium.

In the late 1970s, a total of 28 metric tons of fabrication scrap generated during the preparation of LWBR fuel was recycled in large-scale solvent extraction facilities to recover the 233U. The ability to dissolve advanced ThO2-containing fuels was an important step in demonstrating the reprocessing of spent fuel in a U-Th fuel cycle.

The DOE HTGR Fuel Recycle Program supported research and development for reprocessing HTGR fuel, focusing on small, engineering-scale tests.  No pilot- or full-scale reprocessing facility was built.

In April 1977, President Carter terminated federal support for reprocessing in an attempt to limit the proliferation of nuclear weapons material. The U.S. nuclear fuel cycle became the once-through fuel cycle we have today.

*          Source: “THOREX Reprocessing Characterization,” International Nuclear Fuel Cycle Evaluation (INFCE), 1978

4. The Radkowsky Thorium Reactor (RTR) concept

 Alvin Radkowsky, who was recruited by Admiral Rickover in 1947, later served as the Chief Scientist of the Naval Reactors program. He was responsible for originating and assisting in the development of two reactor concepts for which he was awarded the Navy’s Distinguished Civilian Award (the highest non-military award) in 1954 and the Atomic Energy Commission (AEC) Citation (1963):

  • Burnable poison, which is important to all nuclear power plants for managing long-term reactivity control, and is especially important for enabling very long life naval reactor cores.
  • Seed and blanket reactor core, which consists of a highly enriched fuel “seed” section surrounded by a “blanket” of fertile natural uranium. The blanket generates more than half of the reactor power and has a very long life relative to the “seed” section, which is replaced more frequently.

Alvin Radkowsky receives award from Admiral Hyman Rickover.  A diagram of the Shippingport reactor with a seed-and-blanket core is in the background. Source:  Thorium Power, Inc.

With the encouragement of Edward Teller, Alvin Radkowsky developed a long-standing interest in the use of thorium in nuclear reactors as a means to improve resistance to the proliferation of nuclear material suitable for making weapons. He held several patents in the field, which he assigned to the company he helped found in 1992, Thorium Power, Inc.

The Radkowsky Thorium Reactor concept developed by Alvin Radkowsky and Thorium Power makes use of a seed-and-blanket geometry with low-enriched (< 20%) 235U as the initial fissile seed material and thorium as the fertile blanket material.  Unlike Indian Point 1 and the LWBR, which separated the seed and blanket elements into zones in the core, the RTR implements the seed-and-blanket concept at the level of individual fuel assemblies that are designed to replace the fuel assemblies in existing reactors, but require a complex process to manage fuel during refueling outages. Radkowsky described his RTR fuel design concept as follows:

“Basically, seeds are treated similarly to the standard PWR assemblies. i.e., approximately one-third of seeds are replaced annually by “fresh” seeds, and the remaining two-thirds (partially depleted) seeds are reshuffled. Each seed is loaded into an “empty” blanket, forming a new fuel type. These new fuel type (fresh) assemblies are reshuffled together with partially depleted SBU (seed-blanket) assemblies to form a reload configuration for the next cycle.……..the Th-blanket in-core residence time is quite long (about 10 years), while the uranium part of the SBU (seed) is replaced on a annual (or 18 month) basis, similar to standard PWR fuel management practice.”

You can read his paper entitled, “Thorium Fuel for Light Water Reactors – Reducing Proliferation Potential of Nuclear Power Fuel Cycle,”here:

The RTR seed-and-blanket fuel assembly concept and the simpler zoned seed-and-blanket core concept are well illustrated in the following figure from an article by Mujid S. Kazimi entitled, “Thorium Fuel for Nuclear Energy.”  The RTR core and the seed-and-blanket arrangement of the fuel rods in an individual fuel assembly are shown at the top of the diagram.  A more conventional seed-and-blanket core with separate seed and blanket assemblies is shown at the bottom of the diagram.

You can read Mujid Kazimi’s complete article on the American Scientist website here:

The September / October 1997 issue of the The Bulletin of the Atomic Scientists contains an article by John S. Friedman entitled, “More power to thorium?” in which the author offered the following comments on the RTR:

“The Radkowsky design avoids recycling by envisioning a complex fuel core in which uranium “seeds” enriched to about 20 percent uranium 235 are kept separate from a surrounding thorium-uranium “blanket.” The uranium 235 produces the neutrons that sustain the chain reaction while slowly creating uranium 233 in the blanket. As burnup continues, the newly created uranium 233 picks up an increasingly greater share of the fission load.”

“As in any uranium-fuel reactor, the uranium portion of the core would produce plutonium, but in lesser quantities than in a conventional reactor and with far higher isotopic contamination (from Pu-238, which is a strong alpha radiation emitter). The latter characteristic would make the plutonium even less desirable for weapons than is ordinary reactor-grade plutonium, argues Radkowsky. That would make his reactor exceptionally unattractive to would-be weapons makers. Although uranium 233 can be used for weapons, it too would be isotopically contaminated (from U-232, which is a strong, high-energy gamma radiation emitter), making its use in weapons unlikely.”

“The main selling point of the Radkowsky concept, according to Grae, is that the reactor ‘helps sever the link between nuclear power generation and nuclear weapons.’ The new reactor, he says, will help fulfill the mandate of the Nuclear Non-Proliferation Treaty, which calls not only for a halt in the proliferation of nuclear weapons, but also for the transfer of peaceful nuclear technology.”

You can read John Friedman’s complete article here:

Thorium Power, Inc. has worked with Kurchatov Institute, Brookhaven National Laboratory and others to design and analyze the use of hexagonal RTR-type thorium-plutonium fuel assemblies that could replace the standard fuel assemblies in Russian-designed VVER-1000 PWRs.  Analysis in 2001 indicated that large quantities of weapons-grade plutonium could be consumed over the 40 year operating life of a VVER-1000 reactor.

5. Molten salt thorium reactors

Molten salt reactors (MSRs) use molten fluoride salts as the primary coolant.  The main MSR concept is to have the fuel dissolved in the coolant as a fuel salt that is continuously circulated through the primary system and into a “reactor vessel” where a controlled criticality is maintained to produce useful power. The system operates at high temperature and low pressure.  The MSR concept could include provisions for on-line cleanup and reprocessing of the circulating fuel salt.

In the U.S., the DOE conducted an MSR program from 1957 to 1976. The small 8 MWt test reactor known as Molten Salt Reactor Experiment (MSRE) ran two campaigns at ORNL; the first campaign (1965 – 68) ran with 235U and the second campaign (1968 – 1969) ran with imported (not bred) 233U.  Thorium was not used in MSRE.

MSRE demonstrated the feasibility of the MSR concept and provided the technical basis for designing an MSR breeder using thorium with a graphite moderator in a core operating on thermal neutrons.  The MSR breeder never got past the study phase.

The Generation IV (Gen IV) International Forum, which was initiated by the U.S. Department of Energy in 2000, has been promoting a fast-spectrum molten salt reactor (MSFR) with dissolved 233U and thorium fuel. The Gen IV MSR power system concept is shown in the following diagram.  Construction and operation of any Gen IV reactor concept is decades away.

Source:  Gen IV International Forum.

In August 2017, the Salt Irradiation Experiment (SALIENT) began operation at the Petten High Flux Reactor in the Netherlands.  This is the first in-reactor experiment with molten salt in about 40 years. SALIENT will conduct tests on thorium molten salt in an actual reactor environment. The results of the SALIENT tests are intended to support future development of a European MSR thorium breeder reactor. You can read the Petten announcement here:

6. India’s thorium fuel plan

 India is the only country in the world that has established a fully committed thorium program.  Because India is outside the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) due to its nuclear weapons program, it was for 34 years largely excluded from trade in nuclear plants and materials, which hampered its development of civil nuclear energy. Due to this trade ban and lack of indigenous uranium, India has been developing a unique nuclear fuel cycle to exploit its reserves of thorium. India has the second largest known reserve of thorium in the world (Australia is #1). In September 2008, the international Nuclear Suppliers Group (NSG) issued a waiver, which allowed India to commence international nuclear trade.  This has secured access to a uranium supply chain and opened the Indian nuclear market to various LWR commercial power plants from international suppliers.

India has developed a three-stage thorium fuel plan that involves three types of reactors and a closed nuclear fuel cycle.

  • Stage 1: Deployment of indigenous pressurized heavy-water reactors (PHWRs) to produce plutonium.
    • The PHWR designed by Bhabha Atomic Research Centre (BARC) is a horizontal pressure tube / calandria reactor using natural uranium dioxide (UO2) fuel and heavy water as moderator and coolant.
    • India currently operates 18 PHWRs power plants, with generating capacities between 100 to 540 MWe.
    • Four 700 MWe PHWRs are under construction.
    • At least 16 more 700 MWe PHWRs are planned.
    • In the mid-1990s, India began using thorium in fuel assemblies in PHWR initial cores to even out the core power distribution (flux flattening) to allow the reactor to operate at full power in its initial phase of operation.

You’ll find a detailed description of India’s PHWR here:

  • Stage 2: Deployment of indigenous fast-neutron reactors with blankets containing uranium and thorium to breed new fissile material (Pu and 233U).
    • The Prototype Fast Breeder Reactor (PFBR) designed by the Indira Gandhi Centre for Atomic Research is a sodium-cooled pool-type reactor rated at 500 MWe.
    • The PFBR initially will be fueled with a plutonium-uranium mixed oxide (PuO2– UO2) fuel.
    • PFBR is nearing completion at the Madras Atomic Power Station in Kalpakkam. Commissioning is expected in early-to-mid 2018 and commercial power generation may occur by end of 2018.
    • The Indian government in 2013 approved construction at Kalpakkam of fuel cycle facilities to recover plutonium and uranium, to be ready in time to process the first used fuel from the PFBR.
    • After PFBR, India plans to build six larger fast breeder reactors rated at 600 MWe.

You’ll find a description of the PFBR and the fast reactor fuel cycle at the following links:


  • Stage 3: Deployment of advanced heavy-water reactors (AHWR) designed by BARC to demonstrate commercial utilization of thorium.
    • The AHWR is a 300 MWe, vertical pressure tube type, boiling light water cooled, heavy water moderated reactor.
    • The fuel material will use Th-Pu MOX and Th-U MOX, where the uranium may be 233U or LEU 235U.  Development of Th-Pu and 233U-Th MOX fuels was initiated in 2001.
    • The reactor is configured to obtain a significant portion of power by fission of 233U derived from in-situ conversion from 232Th. On an average, about 39% of the power will be obtained from thorium.
    • One AHWR prototype currently is planned.  Start of construction has been delayed several times since it was first announced in 2004.  Start of construction in 2018 is possible.
    • BARC claims that the AHWR will have a one hundred year design life.

You’ll find more information on the AHWR at the following links:


7. Summary

So, there you have it.  Early experience with thorium fuel provided a technical proof-of-concept demonstration of thorium fueled reactors, but was not a commercial success.  A complete closed fuel cycle with thorium has never been demonstrated.

The key factor driving the resurgence of international interest in thorium is the proliferation resistance of the Th-U and Th-Pu fuel cycles.  The key factors driving India’s interest in thorium are the abundance of thorium and shortage of uranium in that nation coupled with India’s three-stage thorium fuel plan, which was developed to counter its long-term isolation from international trade in nuclear plants and materials as a consequence of not signing the NPT.

Work in Russia on Radkowsky Thorium Reactor (RTR) fuel elements and renewed work on a thorium molten salt reactor (MSR) in Europe certainly are encouraging.  However, there’s a long road (decades) from where these projects stand today and actual thorium utilization in a commercial nuclear power plant.  The most promising near-term (within a decade) demonstration of commercial utilization of thorium will be India’s AHWR and the associated thorium closed fuel cycle.

Additional resources on thorium:

“Nuclear Power in India”, World Nuclear Association

CHEUK WAH LAU, “Improved PWR Core Characteristics with Thorium-containing Fuel”, Thesis for the Degree of Doctor of Philosophy, 2014!/Improved%20PWR_Cheuk%20Wah%20Lau.pdf

Michael J. Higatsberger, “The Non-Proliferative Commercial Radkowsky Thorium Fuel Concept,”November 1999



The Importance of Baseload Generation and Real-Time Control to Grid Stability and Reliability

On 23 August 2017, the Department of Energy (DOE) issued a report entitled, “Staff Report to the Secretary on Energy Markets and Reliability.” In his cover letter, Energy Secretary Rick Perry notes:

“It is apparent that in today’s competitive markets certain regulations and subsidies are having a large impact on the functioning of markets, and thereby challenging our power generation mix. It is important for policy makers to consider their intended and unintended effects.”

Among the consequences of the national push to implement new generation capacity from variable renewable energy (VRE) resources (i.e., wind & solar) are: (1) increasing grid perturbations due to the variability of the output from VRE generators, and (2) early retirement of many baseload generating plants because of several factors, including the desire of many states to meet their energy demand with a generating portfolio containing a greater percentage of VRE generators. Grid perturbations can challenge the reliability of the U.S. bulk power systems that comprise our national electrical grid. The reduction of baseload capacity reduces the resilience of the bulk power system and its ability dampen these perturbations.

The DOE staff report contains the following typical daily load curve. Baseload plants include nuclear and coal that operate at high capacity factor and generally do not maneuver in response to a change in demand. The intermediate load is supplied by a mix of generators, including VRE generators, which typically operate at relatively low capacity factors. The peak load generators typically are natural gas power plants that can maneuver or be cycled (i.e., on / off) as needed to meet short-term load demand. The operating reserve is delivered by a combination of power plants that can be reliably dispatched if needed.

The trends in new generation additions and old generation retirements is summarized in the following graphic from the DOE staff report.

Here you can see that recent additions (since 2006) have focused on VRE generators (wind and solar) plus some new natural gas generators. In that same period, retirements have focused on oil, coal and nuclear generators, which likely were baseload generators.

The DOE staff report noted that continued closure of baseload plants puts areas of the country at greater risk of power outages. It offered a list of policy recommendations to reverse the trend, including providing power pricing advantages for baseload plants to continue operating, and speeding up and reducing costs for permitting for baseload power and transmission projects.

Regarding energy storage, the DOE staff report states the following in Section 4.1.3:

“Energy storage will be critical in the future if higher levels of VRE are deployed on the grid and require additional balancing of energy supply and demand in real time.”

“DOE has been investing in energy storage technology development for two decades, and major private investment is now active in commercializing and the beginnings of early deployment of grid-level storage, including within microgrids.”

Options for energy storage are identified in the DOE staff report.

You can download the DOE staff report to the Secretary and Secretary Perry’s cover letter here:

Lyncean members should recall our 2 August 2017 meeting and the presentation by Patrick Lee entitled, “A fast, flexible & coordinated control technology for the electric grid of the future.” This presentation described work by Sempra Energy and its subsidiary company PXiSE Energy Solutions to address the challenges to grid stability caused by VRE generators.   An effective solution has been demonstrated by adding energy storage and managing the combined output of the VER generators and the energy storage devices in real-time to match supply and demand and help stabilize the grid. This integrated solution, with energy storage plus real-time automated controls, appears to be broadly applicable to VRE generators and offers the promise, especially in Hawaii and California, for resilient and reliable electrical grids even with a high percentage of VRE generators in the state’s generation portfolio.

You can download Patrick Lee’s 2 August 2017 presentation to the Lyncean Group of San Diego at the following link:





Energy Literacy

I was impressed in 2007 by the following chart in Scientific American, which shows where our energy in the U.S. comes from and how the energy is used in electricity generation and in four consumer sectors. One conclusion is that more than half of our energy is wasted, which is clearly shown in the bottom right corner of the chart. However, this result shouldn’t be surprising.

2007 USA energy utilizationSource: Scientific American / Jen Christiansen, using LLNL & DOE 2007 data

The waste energy primarily arises from the efficiencies of the various energy conversion cycles being used. For example, the following 2003 chart shows the relative generating efficiencies of a wide range of electric power sources. You can see in the chart that there is a big plateau at 40% efficiency for many types of thermal cycle power plants. That means that 60% of the energy they used is lost as waste heat. The latest combined cycle plants have demonstrated net efficiencies as high as 62.22% (Bouchain, France, 2016, see details in my updated 17 March 2015 post, “Efficiency in Electricity Generation”).

Comparative generation  efficiencies-Eurelectric 2003Source: Eurelectric and VGB PowerTech, July 2003

Another source of waste is line loss in electricity transmission and distribution from generators to the end-users. The U.S. Energy Information Administration (EIA) estimates that electricity transmission and distribution losses average about 6% of the electricity that is transmitted and distributed.

There is an expanded, interactive, zoomable map of U.S. energy data that goes far beyond the 2007 Scientific American chart shown above. You can access this interactive map at the following link:

The interactivity in the map is impressive, and the way it’s implemented encourages exploration of the data in the map. You can drill down on individual features and you can explore particular paths in much greater detail than you could in a physical chart containing the same information. Below are two example screenshots. The first screenshot is a top-level view. As in the Scientific American chart, energy sources are on the left and final disposition as energy services or waste energy is on the right. Note that waste energy is on the top right of the interactive map.

Energy literacy map 1

The second screenshot is a more detailed view of natural gas production and utilization.

Energy literacy map 2

As reported by Lulu Chang on the website, this interactive map was created by Saul Griffith at the firm Otherlab ( You can read her post at the following link:

I hope you enjoy exploring the interactive energy literacy map.

Quadrennial Energy Review

On 9 January 2014 the Administration launched a “Quadrennial Energy Review” (QER) to examine “how to modernize the Nation’s energy infrastructure to promote economic competitiveness, energy security, and environmental responsibility…” You can read the Presidential Memorandum establishing the QER at the following link:

You can get a good overview of the goals of the QER in a brief factsheet at the following link:

On April 21, 2015, the QER Task Force released the “first installment” of the QER report entitled “Energy Transmission, Storage, and Distribution Infrastructure.” The Task Force announcement stated:

“The first installment (QER 1.1) examines how to modernize our Nation’s energy infrastructure to promote economic competitiveness, energy security, and environmental responsibility, and is focused on energy transmission, storage, and distribution (TS&D), the networks of pipelines, wires, storage, waterways, railroads, and other facilities that form the backbone of our energy system.”

The complete QER 1.1 report or individual chapters are available at the following link:

QER 1.1 contents are listed below:

QER 1.1 contentOn January 6, 2017, the QER Task Force released the “second installment” of the QER report entitled “Transforming the Nation’s Electricity System.” The Task Force announcement stated:

“The second installment (QER 1.2) finds the electricity system is a critical and essential national asset, and it is a strategic imperative to protect and enhance the value of the electricity system through modernization and transformation. QER 1.2 analyzes trends and issues confronting the Nation’s electricity sector out to 2040, examining the entire electricity system from generation to end use, and within the context of three overarching national goals: (1) enhance economic competitiveness; (2) promote environmental responsibility; and (3) provide for the Nation’s security.

The report provides 76 recommendations that seek to enable the modernization and transformation of the electricity system. Undertaken in conjunction with state and local governments, policymakers, industry, and other stakeholders, the recommendations provide the building blocks for longer-term, planned changes and activities.”

The complete QER 1.2 report or individual chapters are available at the following link:

QER 1.2 contents are listed below:

QER 1.2 contentI hope you take time to explore the QERs. I think the Task Force has collected a great deal of actionable information in the two reports. Converting this information into concrete actions will be a matter for the next Administration.

NuScale Submits First Ever Design Certification Application (DCA) for a Small Modular Reactor (SMR)

For all the talk about SMRs over the past two decades or more, there have been no SMR license applications submitted to the U.S. Nuclear Regulatory Commission (NRC) until now. On 31 December 2016, NuScale Power, Portland, OR made the first ever request to the NRC to initiate a licensing review of an SMR. On 12 January 2017, NuScale made the formal submittal to NRC of all the required DCA documents for an SMR power plant comprised of 12 individual NuScale Power ModulesTM.

An NPM is a small pressurized water reactor (PWR) with an integrated primary system and many passive features for normal modes of operation and for safe shutdown in response to abnormal or accident conditions. NuScale claims that the passive safety features enable shutdown and self-cooling with no operator action, no AC or DC power, and no external water.

You’ll find a good 2013 overview of the NuScale Power ModuleTM on the IAEA’s (International Atomic Energy Agency’s) ARIS (Advanced Reactor Information System) website at the following link:

More information is available on the NuScale Power website at the following link:

The basic, factory-manufactured NPM is rated at 160 MWt, which could deliver about 45 MWe. A power plant with 12 NPMs would have a combined output of 1,920 MWt and about 540 MWe. A single NPM is shown below.

NuScale moduleSource: NuScale Power

NuScale Power anticipates a 42-month licensing process as outlined in the following chart. If this schedule can be achieved, then the NRC could issue a Design Certification (DC) as soon as July 2020. At that time, the standard design of a modular NuScale power plant with up to 12 NPMs will have NRC approval independent of an application to construct or operate a specific plant. A design certification is valid for 15 years from the date of issuance and can be renewed.

NuScale licensing scheduleSource: NuScale Power

A license application for an actual plant will focus on site-specific issues and should not need to re-open issues already covered in the NRC’s DC review. This greatly de-risks construction of a new nuclear power plant based on the NPM standard design approved in the DC. NuScale forecasts that the first NPM could go into operation as soon as 2024.



New Safe Confinement Structure Moved into Place at Chernobyl Unit 4

Following the Chernobyl accident on 26 April 1986, a concrete and steel “sarcophagus” was built around the severely damaged Unit 4 as an emergency measure to halt the release of radioactive material into the atmosphere from that unit. For details on the design and construction of the sarcophagus, including many photos of the damage at Unit 4, visit the website at the following link:

The completed sarcophagus is shown below, at left end of the 4-unit Chernobyl nuclear plant. In 1988, Soviet scientists announced that the sarcophagus would only last 20–30 years before requiring restorative maintenance work. They were a bit optimistic.

Sarcophagus overview photoThe completed sarcophagus at left end of the 4-unit Chernobyl nuclear plant. Source:

Sarcophagus closeup photoClose-up of the sarcophagus. Source:

Inside-sarcophagusCross-section of the sarcophagus. Source:

The sarcophagus rapidly deteriorated. In 2006, the “Designed Stabilization Steel Structure” was extended to better support a damaged roof that posed a significant risk if it collapsed. In 2010, it was found that water leaking through the sarcophagus roof was becoming radioactively contaminated as it seeped through the rubble of the damaged reactor plant and into the soil.

To provide a longer-term remedy for Chernobyl Unit 4, the  European Bank of Reconstruction and Development (EBRD) funded the design and construction of the New Safe Confinement (NSC, or New Shelter) at a cost of about €1.5 billion ($1.61 billion) for the shelter itself. Total project cost is expected to be about €2.1 billion ($2.25 billion).

Construction by Novarka (a French construction consortium of VINCI Construction and Bouygues Construction) started in 2012. The arched NSC structure was built in two halves and joined together in 2015. The completed NSC is the largest moveable land-based structure ever built, with a span of 257 m (843 feet), a length of 162 m (531 feet), a height of 108 m (354 feet), and a total weight of 36,000 tonnes.

NSC exterior viewNSC exterior view. Source: EBRD

NSC cross section

NSC cross-section. Adapted from

Novarka started moving the NSC arch structure into place on 14 November 2016 and completed the task more than a week later. The arched structure was moved into place using a system of 224 hydraulic jacks that pushed the arch 60 centimeters (2 feet) each stroke. On 29 November 2016, a ceremony at the site was attended by Ukrainian president, Petro Poroshenko, diplomats and site workers, to celebrate the successful final positioning of the NSC over Chernobyl Unit 4.

EBRD reported on this milestone:

“Thirty years after the nuclear disaster in Chernobyl, the radioactive remains of the power plant’s destroyed reactor 4 have been safely enclosed following one of the world’s most ambitious engineering projects.

Chernobyl’s giant New Safe Confinement (NSC) was moved over a distance of 327 meters (1,072 feet) from its assembly point to its final resting place, completely enclosing a previous makeshift shelter that was hastily assembled immediately after the 1986 accident.

The equipment in the New Safe Confinement will now be connected to the new technological building, which will serve as a control room for future operations inside the arch. The New Safe Confinement will be sealed off from the environment hermetically. Finally, after intensive testing of all equipment and commissioning, handover of the New Safe Confinement to the Chernobyl Nuclear Power Plant administration is expected in November 2017.”

You can see EBRD’s short video of this milestone, “Unique engineering feat concluded as Chernobyl arch reaches resting place,” at the following link

The NSC has an expected lifespan of at least 100 years.

The NSC is fitted with an overhead crane to allow for the future dismantling of the existing sarcophagus and the remains of Chernobyl Unit 4.

International Energy Agency (IEA) Assesses World Energy Trends

The IEA issued two important reports in late 2016, brief overviews of which are provided below.

World Energy Investment 2016 (WEI-2016)

In September 2016, the IEA issued their report, “World Energy Investment 2016,” which, they state, is intended to addresses the following key questions:

  • What was the level of investment in the global energy system in 2015? Which countries attracted the most capital?
  • What fuels and technologies received the most investment and which saw the biggest changes?
  • How is the low fuel price environment affecting spending in upstream oil and gas, renewables and energy efficiency? What does this mean for energy security?
  • Are current investment trends consistent with the transition to a low-carbon energy system?
  • How are technological progress, new business models and key policy drivers such as the Paris Climate Agreement reshaping investment?

The following IEA graphic summarizes key findings in WEI-2016 (click on the graphic to enlarge):


You can download the Executive Summary of WEI-2016 at the following link:

At this link, you also can order an individual copy of the complete report for a price (between €80 – €120).

You also can download a slide presentation on WEI 2016 at the following link:

World Energy Outlook 2016 (WEO-2016)

The IEA issued their report, “World Energy Outlook 2016,” in November 2016. The report addresses the expected transformation of the global energy mix through 2040 as nations attempt to meet national commitments made in the Paris Agreement on climate change, which entered into force on 4 November 2016.

You can download the Executive Summary of WEO-2016 at the following link:

At this link, you also can order an individual copy of the complete report for a price (between €120 – €180).

The following IEA graphic summarizes key findings in WEO-2016 (click on the graphic to enlarge):


Climate Change and Nuclear Power

In September 2016, the International Atomic Energy Agency (IAEA) published a report entitled, “Climate Change and Nuclear Power 2016.” As described by the IAEA:

“This publication provides a comprehensive review of the potential role of nuclear power in mitigating global climate change and its contribution to other economic, environmental and social sustainability challenges.”

An important result documented in this report is a comparative analysis of the life cycle greenhouse gas (GHG) emissions for 10 electric power generating technologies. The IAEA authors note that:

“By comparing the GHG emissions of all existing and future energy technologies, this section (of the report) demonstrates that nuclear power provides energy services with very few GHG emissions and is justifiably considered a low carbon technology.

In order to make an adequate comparison, it is crucial to estimate and aggregate GHG emissions from all phases of the life cycle of each energy technology. Properly implemented life cycle assessments include upstream processes (extraction of construction materials, processing, manufacturing and power plant construction), operational processes (power plant operation and maintenance, fuel extraction, processing and transportation, and waste management), and downstream processes (dismantling structures, recycling reusable materials and waste disposal).”

The results of this comparative life cycle GHG analysis appear in Figure 5 of this report, which is reproduced below (click on the graphic to enlarge):

IAEA Climate Change & Nuclear Power

You can see that nuclear power has lower life cycle GHG emissions that all other generating technologies except hydro. It also is interesting to note how effective carbon dioxide capture and storage could be in reducing GHG emissions from fossil power plants.

You can download a pdf copy of this report for free on the IAEA website at the following link:

For a link to a similar 2015 report by The Brattle Group, see my post dated 8 July 2015, “New Report Quantifies the Value of Nuclear Power Plants to the U.S. Economy and Their Contribution to Limiting Greenhouse Gas (GHG) Emissions.”

It is noteworthy that the U.S. Environmental Protection Agency’s (EPA) Clean Power Plan (CPP), which was issued in 2015, fails to give appropriate credit to nuclear power as a clean power source. For more information on this matter see my post dated 2 July 2015,” EPA Clean Power Plan Proposed Rule Does Not Adequately Recognize the Role of Nuclear Power in Greenhouse Gas Reduction.”

In contrast to the EPA’s CPP, New York state has implemented a rational Clean Energy Standard (CES) that awards zero-emissions credits (ZEC) that favor all technologies that can meet specified emission standards. These credits are instrumental in restoring merchant nuclear power plants in New York to profitable operation and thereby minimizing the likelihood that the operating utilities will retire these nuclear plants early for financial reasons. For more on this subject, see my post dated 28 July 2016, “The Nuclear Renaissance is Over in the U.S.”  In that post, I noted that significant growth in the use of nuclear power will occur in Asia, with use in North America and Europe steady or declining as older nuclear power plants retire and fewer new nuclear plants are built to take their place.

An updated projection of worldwide use of nuclear power is available in the 2016 edition of the IAEA report, “Energy, Electricity and Nuclear Power Estimates for the Period up to 2050.” You can download a pdf copy of this report for free on the IAEA website at the following link:

Combining the information in the two IAEA reports described above, you can get a sense for what parts of the world will be making greater use of nuclear power as part of their strategies for reducing GHG emissions. It won’t be North America or Europe.

Current Status of the Fukushima Daiichi Nuclear Power Station (NPS)

Following a severe offshore earthquake on 11 March 2011 and subsequent massive tidal waves, the Fukushima Daiichi NPS and surrounding towns were severely damaged by these natural events. The extent of damage to the NPS, primarily from the effects of flooding by the tidal waves, resulted in severe fuel damage in the operating Units 1, 2 and 3, and hydrogen explosions in Units 1, 3 and 4. In response to the release of radioactive material from the NPS, the Japanese government ordered the local population to evacuate. You’ll find more details on the Fukushima Daiichi reactor accidents in my 18 January 2012 Lyncean presentation (Talk #69), which you can access at the following link:

On 1 September 2016, Tokyo Electric Power Company Holdings, Inc. (TEPCO) issued a video update describing the current status of recovery and decommissioning efforts at the Fukushima Daiichi NPS, including several side-by-side views contrasting the immediate post-accident condition of a particular unit with its current condition. Following is one example showing Unit 3.

Fukushima Unit 3_TEPCO 1Sep16 video updateSource: TEPCO

You can watch this TEPCO video at the following link:

This video is part of the TEPCO Photos and Videos Library, which includes several earlier videos on the Fukushima Daiichi NPS as well as videos on other nuclear plants owned and operated by TEPCO (Kashiwazaki-Kariwa and Fukushima Daini) and other TEPCO activities. TEPCO estimates that recovery and decommissioning activities at the Fukushima Daiichi NPS will continue for 30 – 40 years.

An excellent summary article by Will Davis, entitled, “TEPCO Updates on Fukushima Daiichi Conditions (with video),” was posted on 30 September 2016 on the ANS Nuclear Café website at the following link:

For additional resources related to the Fukushima Daiichi accident, recovery efforts, and lessons learned, see my following posts on Pete’s Lynx:

  • 20 May 2016: Fukushima Daiichi Current Status and Lessons Learned
  • 22 May 2015: Reflections on the Fukushima Daiichi Nuclear Accident
  • 8 March 2015: Scientists Will Soon Use Natural Cosmic Radiation to Peer Inside Fukushima’s Mangled Reactor



China is Developing Floating Nuclear Power Plants

Various reports in 2016 indicate that China has designed and is constructing its first indigenous floating nuclear power plant. This mobile power plant is intended for deployment to remote coastal locations and to islands being developed by China in the South China Sea. According to China General Nuclear Power Corporation (CGN), this floating nuclear power plant is intended to operate as a combined energy supply platform that is capable of delivering electric power, low-temperature process heat, and fresh water as needed by the particular application. Construction of the first unit started in 2015 and is scheduled to be completed in 2018 and operational by 2020. It also has been reported that China Shipbuilding Industry Corporation (CSIC) is building the first floating nuclear power plant, with plans to build a total of 20 for deployment in the South China Sea.

The availability of ample supplies of electric power, low-temperature process heat, and fresh water will enable more rapid development in remote regions, including construction of new infrastructure for harbors, airports, defense and commercial activities such as oil exploration and oil field exploitation and other marine resource development.

CGN reports that the nuclear steam supply system (NSSS) for the first floating nuclear power plant is a single “small modular offshore reactor” ACPR50S, which is a compact two-loop pressurized water reactor (PWR). China’s National Development and Reform Commission (NDRC) recently approved this reactor design as part of the 13th Five-Year Plan for innovative energy technologies. The ACPR50S is rated at 200 MWt, with an electrical output of 60 MWe.

In comparison, the first Russian floating nuclear power plant, Akademik Lomonosov, has 2 x KLT-40S modular PWRs that will provide 70 MWe net electrical output and low-temperature process heat for shore installations. Akademik Lomonosov is schedule for its initial core load at the Baltiisky Zavod shipyard in St. Petersburg, Russia in late 2016. After completing reactor testing, it is expected that Akademik Lomonosov will depart St. Petersburg in October 2017 and be towed along the north coast of Siberia to the Arctic port of Pevek, where it will be moored and connected to the grid.

The physical layout if the ACPR50S is shown below. The major components of the NSSS are the reactor vessel, two steam generators and primary pumps, and one pressurizer.


The primary system is housed within a containment structure that is protected against damage from a ship collision (similar to design features in NS Savannah and other early commercial nuclear powered vessels). Active and passive safety systems provide for core and containment cooling during an accident. Severe (beyond design basis) accident mitigation measures include opening safety plugs to submerge the NSSS in seawater to ensure continued core cooling. The physical arrangement of the NSSS within the vessel is shown below.

ACPR50S shipboard arrangementAPR50S physical arrangement in the vessel. Source: CGN

The floating nuclear power plant is designed for on-ship refueling and pre-treatment of radioactive waste. When the floating nuclear power plant is deployed in a remote location, a visiting offshore engineering services vessel will provide logistics and maintenance services as needed.

The following figure shows how a floating nuclear power plant might look moored to a pier and delivering electric power, process heat and fresh water to a shore installation.

China Floating NPP moored at shore installationSource: CGN

The floating nuclear power plant also could be deployed to support one or many oil drilling platforms as shown below.

China Floating NPP at oil platformSource: CGN

A important issue related to China’s deployment of floating nuclear power plants is that they may be deployed to support military development of islands in contested areas of the South China Sea. Time will tell how this scenario plays out.