Reassessing the Reactor

["JOHN JACOBUS" <JENDAY1@EMAIL.MSN.COM>]

The following appeared in last week;s Washington Post.  I think it is still

a timely article.

-- John



John Jacobus, MS

Certified Health Physicist

3050 Traymore Lane

Bowie, MD 20715-2024

jenday1@email.msn.com (H)



Reassessing the Reactor

For Nuclear Power, New Emphasis and Old Doubts



By Guy Gugliotta

Washington Post Staff Writer

Sunday, June 10, 2001; Page A03



At 4 a.m. on March 28, 1979, a pump malfunction set off an alarm at the

Three Mile Island Unit 2 nuclear power plant outside Harrisburg, Pa. Within

nine seconds, equipment failures and human error caused a dramatic drop in

the reactor core water level, setting off the worst nuclear accident in U.S.

history.



No one was injured, but the partial meltdown at Three Mile Island, and the

far worse meltdown and explosion at Chernobyl seven years later, left deep

scars on the American psyche about the dangers of nuclear power. Not a

single plant has been ordered since 1973.



Now, however, the Bush administration's plan to increase energy supplies --

including nuclear generation -- has focused attention on whether the United

States might once again turn to the atom to fulfill its electricity needs.



The nuclear power industry thinks it's ready. Since Chernobyl, engineers

have designed a new generation of nuclear plants they believe will sharply

reduce the risk of another Three Mile Island.



Three simpler -- and therefore cheaper and safer -- versions of the power

plants currently in use have been approved by the Nuclear Regulatory

Commission (NRC), a crucial vote of confidence for any interested utility.



Moreover, an international consortium has designed a new type of plant that

uses hundreds of thousands of billiard-ball-sized "pebbles" of nuclear

material instead of a conventional reactor core. It does not have enough

radioactive fuel in a confined space to generate the temperatures necessary

for the pebbles to explode. In theory, it is meltdown-proof.



But none of these advances has enticed a U.S. utility to order a nuclear

plant, and many obstacles persist.



Polls show that public dread endures. About 40,000 tons of radioactive waste

from existing reactors are piling up around the country because the Energy

Department has not found a permanent repository.



Critics of nuclear power remain skeptical of the new plants' safety. And

although the economics are good today, who's to say how long that will last?

Even if a utility decided to build a reactor tomorrow, it would take a

snag-free minimum of six to 10 years to bring it on line.



"There's renewed interest, but people are still skeptical that the public

will allow nuclear [plants] to be built again," said Stephen T. Lee of the

Electric Power Research Institute, the utility industry's research and

development arm. "Also, the financial risk is quite large. The private

investor will always take the lowest-risk, highest-return option, which, for

now, is still gas generation."



U.S. utilities in 31 states operate 103 commercial reactors, which provide

about 20 percent of the nation's electricity.



All U.S. plants are either "boiling water reactors" or "pressurized water

reactors" that use uranium-rich fuel rods in a reactor core to create a

controlled nuclear chain reaction. The resulting heat changes water into

steam that drives the turbo-generators. "Control rods," usually made of

boron, are inserted or withdrawn from the core to regulate the pace of the

reaction by soaking up excess neutrons.



As with any boiler, the integrity of a nuclear core depends on the ability

of operators and instruments to keep the system from overheating. But while

a conventional boiler may blow up in a cloud of fire and soot when it gets

too hot, a nuclear core can also spew deadly radioactivity.



The keys to avoiding trouble are many: adequate operator training, fail-safe

shutdown measures and careful monitoring of valves, gauges and instruments.

This can be difficult, partly because of the machinery's intrinsic

complexity, but mostly because U.S. plants are all one-of-a-kind designs

with modifications added along the way. Every operating and safety regime

had to be tailor-made to the idiosyncrasies of a specific reactor.



In recent years, utilities have markedly improved safety records with better

training and by upgrading plant equipment, monitoring procedures and video

displays. Between 1987 and 1999, the number of automatic shutdowns per plant

dropped from 3.6 per year to 0.6 per year, according to the NRC. The number

of safety system failures per plant was cut in half, to 0.8 per year.



In the meantime, the industry prepared three new reactor designs and

obtained NRC certification for them. The object was standardization: "Right

now there's a lot of highly skilled construction -- it's like airports,"

said James Lake, president of the American Nuclear Society. "We're looking

for a way to change to building airplanes. If you can build in one place on

an assembly line, it's much, much cheaper."



The three designs -- one by General Electric and two by Westinghouse -- are

based on traditional technology. GE simplified safety systems, reduced the

amount of hardware and made the plant easier to operate.



"It's still concrete, steel, welding, pumps and valves," said Steven A.

Hucik, GE's general manager for nuclear plant projects. "But when you

simplify the design, there's much less of it. You can reduce the size of the

building, and that means savings."



GE has built two 1,350-megawatt "advanced boiling water reactors" in Japan

and has six under construction: four in Japan and two in Taiwan. The two

operating plants took four years and three months to build, and "we're

predicting 54 months [4 1/2 years] in the United States," Hucik said.



Neither of Westinghouse's two designs, both pressurized water reactors, has

been built. The System 80-plus, also 1,350 megawatts, is projected to be

South Korea's next-generation reactor, and existing plants there have

incorporated features of the new system.



The Westinghouse 600-megawatt "AP600" departs more from tradition because it

incorporates "passive" safety features based on gravity and other natural

forces. Many safety devices are activated without human intervention.



Obtaining certification for the passive safety system was "a fundamental

issue" for Westinghouse, said Howard Bruschi, the company's chief technology

officer, because the system will allow off-site, modular construction that

can be finished in three years.



Critics acknowledge that standardization and simplicity make new-generation

plants safer, but reactors "are inherently dangerous, so while it's a

question of properly managing the risk, you can't make it zero," said David

Lochbaum, a nuclear safety engineer with the Union of Concerned Scientists.



The only truly innovative design on the horizon for the U.S. market is the

pebble bed reactor. Instead of fuel rods, the pebble bed reactor uses tiny

particles of uranium dioxide encased in layers of graphite and silicon

carbide and shaped into spheres. These pebbles -- 320,000 of them -- are

poured into a 65-foot cylindrical hopper that is lined with graphite bricks

and has a hollow column in the middle. The shape, called an annulus, is like

an elongated angel food cake mold.



Once in place, the pebbles initiate a chain reaction. But instead of making

steam, the plant pumps helium into the top of the hopper and extracts the

heated gas at the bottom, where it drives the turbines.



To shut down the reactor, control rods are inserted through conduits in the

graphite bricks. Because the rods cannot run straight through the pebble

bed, the reactor must be small -- 110 to 130 megawatts, vs. 1,000 megawatts

or more for a water reactor. But its proponents see small size as an

advantage.



"You can build it in a modular fashion and locate it close to transmission

lines where you need generation," said Oliver Kingsley, president and chief

nuclear officer of the U.S. utility Exelon Corp.



Also, added nuclear engineer Andrew Kadak, who leads a Massachusetts

Institute of Technology team developing a pebble bed reactor, smaller makes

sense for utilities reluctant to make monster investments.



"What's best: Spend $3 billion, get the plant in five or six years, or $100

or $200 million and get it in 2 1/2 to three years?" Kadak said. Utilities

"want to grow incrementally. Our idea is to build a lot of them quickly and

get economies of scale that way."



Finally, small size should make the reactor virtually accident-proof.

Computer modeling shows that the plant can't generate enough heat to melt

the pebbles -- even if helium flow is stopped and the control rods are

withdrawn.



"You can't have a runaway accident, and that's one thing that's very

attractive," Lochbaum said. "But the jury's still out. Graphite can catch on

fire, like it did at Chernobyl."



A joint venture that includes Exelon, the South African utility Eskom,

British Nuclear Fuel and the South African government, is planning to build

a prototype in South Africa and will seek NRC authorization to build a plant

in the United States. But the company and the NRC agree it could not come on

line before 2007.



"It offers a great deal of possibility," Kingsley said, "but it's still on

paper."



© 2001 The Washington Post Company







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