Issues & Analysis: Proponents say time is ripe to consider new nuclear power plants

Spheres about the size of tennis balls may power the next generation of nuclear power plants, called pebble bed reactors. Conventional power plants use nuclear fuel rods clad in metal and cooled by water. The next generation of nuclear power plants will have a graphite lined silo reactor stuffed with 400,000 of the balls and cooled by helium. Exelon Corp. of Philadephia is developing the pebble bed technology with Eskom, a South African utility.


By Ann de Rouffignac
OGJ Online

Spheres about the size of tennis balls may power the next generation of nuclear power plants called pebble bed reactors. Conventional power plants use nuclear fuel rods clad in metal and cooled by water. The next generation of nuclear power plants will have a graphite lined silo reactor stuffed with 400,000 of the balls and cooled by helium. Exelon Corp. of Philadephia is developing the pebble bed technology with Eskom, a South African utility that is conducting feasibility studies to build one in that country.

HOUSTON, Mar. 26�As electricity prices rise, nuclear power is back on the table.

Now, companies are looking beyond extending the life of existing plants through license renewals. For decades out of favor because of risk, public opposition, high costs, and waste disposal issues, nuclear power is being revived by a what proponents say is a new cheaper safer design giving the industry hope for new power plant construction.

�Prior to this energy crisis we were supposed to be extinct,� said Thelma Wiggins, spokeswoman for the Nuclear Energy Institute. �New polls say people think new nuclear plants should be built in this country. We are in a Renaissance period.�

Nuclear power proponents are looking to so-called "pebble bed" reactors as an alternative to existing nuclear plant design. Conventional power plants use nuclear fuel rods clad in metal cooled by water and took up to a decade to build.

Pebble bed reactors can be built cheaply in less than 3 years, say proponents of the technology. But experts say similar technology was tried and discarded in the 1980s. Critics say cheap nuclear power is an old promise that has been broken before. And the crucial issue of disposing of nuclear waste has yet to be solved.

Pebble bed development work is under way in South Africa and at the Massachusetts Institute of Technology. Developers say total production costs are competitive with natural gas-fired power plants. The technology employs nuclear fuel in graphite-coated spheres cooled by an inert gas instead of water. Meltdown of the core is impossible, developers say.

Eskom, a South African utility, and Philadelphia-based Exelon Corp. are developing a reactor design they say can be manufactured in 100 Mw modules, tiny by most nuclear plant standards. Exelon has invested $7.5 million for a 12.5% equity stake in the design development. If feasibility studies pan out, the company is ready to boost its investment, sources say.

South Africa's government still has not given the go-ahead nor have feasibility studies been completed, but a decision is expected by yearend.

Exelon Corp. is the main US proponent of new nuclear plants. The company operates 17 nuclear reactors and together with British Energy Co. PLC operates three others through Amergen Energy Co., a US joint venture. Corbin McNeill, Exelon�s CEO, met with officials of the US Nuclear Regulatory Commission (NRC) in January about the design certification process for a pebble bed reactor.

�Exelon came in to say it was interested and wanted to keep the commission abreast of developments,� said Victor Dricks, spokesman for the NRC. �At this point, they asked what might be required to process an application.�

New plant possible
Exelon is ready to build a new nuclear plant if it could be done in a flexible, cost effective, and safe manner, says Exelon spokesman Bill Jones. �As early as mid-2002 we could ask the NRC for an early siting permit,� Jones says. �Common sense would tell you it would be on an existing site."

Exelon is not the only energy company to express interest in a new generation of nuclear plants. Entergy Corp., Dominion Resources Inc., and Southern Co. joined a task force formed by the Nuclear Energy Institute late last year to investigate what it would take to build a new nuclear plant. But publicly the companies are holding their cards close.

Entergy, the second largest US nuclear operator behind Exelon, is interested in the future of pebble bed technology and says it is mostly keeping tabs on the technology.

�We at Entergy are not talking about a plant now. No action is planned at all for at least 5 years and even further out,� said Carl Crawford, spokesman for Entergy. �We are in the business of buying existing plants and there is plenty to do there.�

�It�s important to have a place at the table to look at what needs to be done,� said Rick Zuercher, spokesman for Dominion Energy, a unit of Dominion Resources. �Participating in a panel doesn�t mean we will build a nuclear plant.�

Southern Co., which operates 6 nuclear units, is just taking a look, said spokesman Mike Jones. �Could anyone even do it? Could it be done?� said Jones. �We are not further along than that.�

Analysts say such reticence is not surprising given the negative view many still hold toward the technology. �I would say a new nuclear plant would add a lot of risk to the equation. We would have to evaluate such a move very carefully,� said Dan Pickering, chief analyst with Simmons & Co. International.

Exelon and Eskom are pursuing the development of the pebble bed reactor or a high temperature helium-cooled reactor with a direct cycle gas turbine. The reactor core is cooled by helium which transfers the energy to a closed cycle gas turbine and generator.

Because the reactor is cooled by gas the risk of accidents resulting from a cooling fluid loss is reduced. The coolant, helium, is inert and can be used at very high temperatures without any concerns about corrosion. Leakage to the outside is minimized and the helium doesn�t become contaminated with radioactivity.

If the coolant circuit breaks in a conventional water-cooled reactor, the reactor is cooled by steam and air. The power plant can overheat catastrophically and meltdown is possible. Water is also corrosive, leading to expensive maintenance procedures to keep the cooling system functioning safely.

The pebble bed fuel consists of uranium elements, the so-called pebbles, to form spheres about the size of tennis balls. About 400,000 fuel balls lie within a graphite-lined silo that is 30 ft high and 10 ft in diameter.

Technological issues
The helium is introduced into the top of the reactor and passes around the fuel balls. It leaves the reactor at the bottom at about 900�C. This hot helium gas then turns turbines for compressors and a generator that produces electricity.

The gas is reprocessed and reintroduced at the top of the reactor to start over again. The design means the reactor can be constructed in modules. The fuel can withstand high temperatures because the use of graphite is integral to the fuel. This rules out meltdown of the core.

�You can�t melt the fuel,� said Ronald Ballinger, associate professor of nuclear engineering at Massachusetts Institute of Technology. �You are safe to pull the switch and walk away from it.� Ballinger and Professor Andrew Kadak are working on a pebble bed reactor design that will be utilized in a research reactor to be built in Idaho.

Conventional reactors have additional safety systems to shut down the reactor in the event of an accident and utilize a containment system that keeps radioactive materials separated (contained) from the atmosphere.

Unlike the Eskom reactor design, the MIT version of the reactor will insert an intermediate heat exchanger to isolate the gas circulating in the reactor from the gas circulating in the power conversion unit. With funding from the US Department of Energy, Ballinger is currently working to answer key questions about the reactor, especially issues affecting the gas driven turbines and heat exchanger.

Proponents claim the pebble bed reactor can be built without safety backup systems or a containment system reducing costs. The NRC�s Dricks cautioned the NRC would look very closely at any design without containment or safety backup systems.

The pebble bed reactor can be built for about $1million/Mw, says Exelon�s Jones. If the reactors are assembled from manufactured modules without containment or backup safety systems, costs are comparable to a new coal-fired power plant and even gas-fired generation, says MIT�s Ballinger.

�The South Africans say the total cost of capital and operation and maintenance over a 40-year life of the plant will be 1.6�/kw-hr. MIT estimates those same costs at 3.5�/kw-hr,� he says. �Adding a containment system would up the cost another penny to 4.5�/kw-hr.�

Eskom advertises on its web site the pebble bed reactor will be �cheap to build and economical to operate.� Critics, however, say they have heard such claims before.

The famous �too cheap to meter" claim of nuclear power proponents in the mid-50s has haunted the industry for decades, says Jim Riccio, nuclear power expert with Public Citizen in Washington. Why would this new technology work out to be cheap when none ever has, he asks.

Other versions of the high temperature gas-cooled reactor have been built in the US and in Germany. These plants were shut down because of complications. The US version at Fort St. Vrain in Colorado was in service from 1976-1989.

It was decommissioned because of high costs and a high outage rate. A new version of this reactor received research support from the DOE but lost its funding in 1995. Problems with fuel and fuel production were cited as the biggest difficulties, according to the National Academy of Sciences.

The German version is closest to the one proposed by Eskom and Exelon. In Germany, the THTR-300, a version of the pebble bed reactor, was ordered in 1970, according to a 1999 report, by Steve Thomas, senior research fellow with the Energy Policy Program at the UK's University of Sussex.

The German pebble bed reactor began generating electricity in 1983 and was shut down 6 years later. German officials cited problems with fuel circulation and damage to the gas ducts, the report says. Safety concerns and the unwillingness of plant owners, including the government to continue to provide subsidies, resulted in the plant being permanently shuttered in 1990, according to Thomas.

The NRC says a lot of questions about what happened to the German reactor will need to be answered before going forward with the pebble bed design. �Until those issues are resolved, nobody is going to submit an application,� says the NRC�s Dricks.

The manufacture of fuel and the commercial production of the turbine units are major stumbling blocks to the reactor, Thomas says. There is no commercial gas-driven turbine in production. Even if these aspects of the technology can be resolved economically, critics point to the most serious inherent problem of nuclear power�waste disposal. Nuclear power creates dangerous waste that endures for thousands of years. The waste disposal problem has not been solved safely or economically, critics say.

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