UConn prof writes clear PBMR overview

Pelindaba, South Africa, pebble bed work site

Professor Lee Langston writes in Mechanical Engineering
University of Connecticut retired professor Lee Langston has just published a very clear, readable history of the pebble bed modular reactor project underway in South Africa. Pebbles Making Waves is the feature article in the April, 2008, issue of Mechanical Engineering, published by the American Society of Mechanical Engineers.

I encourage you to read this overview of the history and status of the Pebble Bed Modular Reactor project in South Africa.

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.

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.

ADVANTAGES

• 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.

DISADVANTAGES

• 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.

DARTMOUTH COLLEGE ILEAD
ENERGY POLICY AND ENVIRONMENTAL CHOICES:
RETHINKING NUCLEAR POWER

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 http://rethinkingnuclearpower.googlepages.com.

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

Syllabus

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

Vernon

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

Nuclear powered cars are emissions free

or or
Some ways to generate electricity for electric cars

Electric cars are emissions free, unless the electric power they use comes from coal power plants. Electric cars are becoming available, and more are planned.


2010 Chevrolet Volt Electric Vehicle

Chevrolet will produce the Volt EV in the 2010-2012 time frame. It is powered by electricity from batteries that will allow the car to travel 40 miles on a single overnight charge. It also has a range extending internal combustion engine designed to run on gasoline, E85, or biodiesel fuels. The engine will give the drivers the confidence to venture out in a electric car, knowing they can drive even if the batteries run out. The turbo-charged three-cylinder engine provides 71 hp, and the electric motor can provide 161 hp. If you commute only 40 miles a day you can save 500 gallons of gasoline a year, saving $1200 after netting out the cost of electricity against $3 gasoline.


2008 Tesla Roadster Electric Car

This sports car can do 0-60 in about 4 seconds. Tesla Motors estimates 250 miles per charge, at a cost for electricity of about 1 cent per mile. Costing $92,000 it will not attract enough consumers to solve the US energy crisis, but it will be fun to drive.



2007 Toyota Prius plug-in hybrid shown to Bush

Consumers can today buy aftermarket conversion kits and batteries to allow cars such as the Toyota Prius to travel 20 miles on electric power alone. California is leading the nation in promoting plug-in hybrid vehicles.


Buying Nuclear Power for Cars

Originally conceived to lower energy costs through competition, electric deregulation has allowed consumers the choice of energy suppliers, and many choose "green" sources like wind power, or cow power (methane generated). Consumers pay a premium of about $0.04 per kilowatt-hour.

"Inconvenient Truth" Al Gore was criticized for the high energy consumption at his residence mansion, but his retort was that all his energy was purchased from "green" sources, so that he was not contributing to global warming. Providing a nuclear power purchasing option can similarly benefit the nuclear power industry, particularly if some electric vehicle fleets could be promoted as using clean, safe nuclear power.

I'd like to drive a car with a "Nuclear Powered" sign. Consumers today can not choose nuclear power. Nuclear power plant operators should file the necessary tariffs and enter into contracts with distribution utilities so that a consumer could indeed buy nuclear power for recharging his vehicle.

Melt-down-proof pebble bed reactors may be the power source for the future US automobile fleet.

Germany built the first pebble bed reactor

Demonstration of inherently safe AVR shutdown

The pebble bed reactor is an intrinsically safe because the chain reaction diminishes as the fuel temperature rises. This has been demonstrated. The experimental Arbeitsgemeinschaft Versuchsreaktor (AVR) was built in Germany in 1960. Dr. Rudolf Schulten was the originator of the pebble bed reactor design. The experimental AVR at the Julich Research Center operated at 46 megawatt thermal power, about 13 negawatt electric. The safety test was performed in 1970 by stopping the cooling and preventing the control rods from activating. The temperature rose, Doppler broadening absorbed neutrons in U238, the chain reaction slowed, temperatures fell, and the unit stabilized at 300 kilowatts.

HTR-300 Cooling Tower

Germany also built a second pebble bed reactor, the THTR-300, which generated 300 megawatts when it achieved full power operation in 1989. THTR stands for Thorium High Temperature Reactor; it uses thorium to enrich the uranium fuel. Thorium is fertile in that it is not itself very radioactive but can be transformed into uranium fuel. The Th232 absorbs a neutron from the chain reaction of U235 decay, and then the Th233 decays into U233, which is a fissile element that participates in the chain reaction. Thorium is three times as plentiful as uranium in the earth's crust.

In 1986 an operator error caused some of the pebbles to be fractured and the helium gas lock to be jammed. An unknown amount of radioactive materials were released. The THTR-300 was shut down in 1989 following public concerns arising from the Chernobyl accident. Since then Germany has decided to shut down all its nuclear power plants.