Wednesday, March 19, 2008

Pebble fuel grains pass performance testing

INL Advanced Test Reactor test site

An earlier post described the start of testing of the multiple-layer-coated fuel grains that form the billiard-ball-sized fuel pebbles in the pebble bed reactor. Idaho National Laboratory used its Advanced Test Reactor to expose these test fuel grains to radiation levels much higher than in an operational PBR, thus simulating years of exposure in a few months. The multiple, coated layers of silicon carbide and ceramic graphite contain the radioactive products of fission. These tested fuel grains have not failed, at the level of 9% burn-up of the uranium within. Tests will continue to see if a 12-14% burnup can be achieved by year-end.

Tuesday, March 4, 2008

Energy Policy and Environmental Choices: Rethinking Nuclear Power

Will the public rethink nuclear power?

I have not posted anything to this blog about pebble bed reactors for months. I have been busy developing a way to educate the general public about the broader issues of nuclear power.

Most people to whom I have presented the pebble bed reactor have been encouraging and supportive. The most common query I receive is "what about the waste?".

I now think public acceptance of nuclear power will depend on reprocessing to burn up the most hazardous radioactive waste. Also, reprocessing will wondrously provide a century of power just from the existing spent fuel inventories at nuclear power plant sites. Not only can non-fissile U-238 be bred into plutonium fuel, but abundant thorium can also be bred into U-233 fuel. We can have fuel that meets all our energy needs for thousands of years and waste that decays in a few hundred.

I have tried to rethink the advantages and disadvantages of pebble bed reactor technology. which I summarize below.

  • Passive safety makes core meltdown impossible.
  • Modularity allows smaller plants, with less capital investment risk, and distributed siting.
  • Small size permits factory mass production and on-site assembly.
  • High temperature, air cooled reactor needs no water for cooling.
  • 50% efficiency means 2/3 the fuel use.
  • High temperature permits direct hydrogen production.
  • Multi-layer pebbles containing all reaction waste products are ready for burial.

  • Technology learning curve not yet fully traversed.
  • Licensing in the US will require new NRC skills and knowledge.
  • US needs more nuclear power now, from already approved designs.
  • Fuel supply will be strained at the proposed one-unit-per-week installation schedule.
  • Reprocessing fuel in the hard pebbles will be difficult.



This is an 8-week course developed for the Dartmouth Ilead continuing education department. The course meets 2 hours a week beginning March 31, 2008, at Dartmouth College in Hanover NH. More information is available at

The PowerPoint slides and audio of the talks will be posted after each session.


Global warming continues. The world consumes oil and gas faster than finding it. We import oil from unstable countries. Producing ethanol from corn consumes almost as much energy as the ethanol delivers. Sites for wind and hydro power are limited. Can more nuclear power help? Are the health risks acceptable? One theme will be how many? How many acres of corn? How many power plants? How many windmills? How many tons of uranium? How many tons of CO2?

1. Introduction

Energy units, uses, sources
Social benefits, demand growth, conservation, developing world
Periodic table, nuclear fission, nuclear power plants

2. Fear

Chernobyl, Three Mile Island
Radiation, health, safety, waste
Nuclear weapons proliferation

3. Environmental choices

Oil and gas depletion
Global warming, mining, coal, oil shale, tar sands
Wind, hydro, solar
Corn, sugarcane, cellulosic ethanol, biodiesel
Uranium and thorium availability

4. Current technology

Submarines and ships
Operating nuclear power plants, industry structure, NRC
Current products: GE, Westinghouse, Toshiba, Areva

5. Nuclear power plant visit


6. New technologies

High temperature gas reactors, liquid metal reactors
Hydrogen production, hydrocarbon synthesis, coal-to-liquid, electric cars

7. Global Nuclear Energy Partnership

Integral fast reactor, waste reprocessing
Fuel supply for non-nuclear nations
Current public awareness, funding, activities

8. Debate

Antinuclear activism, Union of Concerned Scientists, Caldecott
Public opinion, NEI, environmentalist shifts
Congressional and presidential candidate's views