Undated (AP) _ A vote by the main owner of the debt-ridden Seabrook nuclear power plant to default on loan payments is the latest in a series of blows suffered by the nuclear industry.

Here is a brief look at some other nuclear power projects that have been beset by safety questions or financial and technical problems.

WPPSS

The biggest default in the history of the municipal bond market occurred when the Washington Public Power Supply System, a consortium of 16 Washington state public utilities, failed to make payments on $2.25 billion in bonds used to finance two nuclear power plants.

WPPSS, with headquarters in Richland, Wash., attempted to build five nuclear power plants in the 1970s to serve Northwest customers. Of those, only one plant is operating after starting up in late 1984. Two others were terminated and two were mothballed after $4.5 billion had been invested in them.

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Three Mile Island

The nation's worst commercial nuclear accident happened March 28, 1979, at the Three Mile Island Unit 2 reactor in Middletown, Pa.

The accident, which caused some radioactive gases to be released into the atmosphere, was caused by a combination of human and mechanical errors that led to protective cooling water being drained from the reactor.

An estimated $1 billion cleanup at the plant is expected to be completed in late 1988. About half the damaged nuclear fuel and debris has been removed from inside the reactor thus far.

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Zimmer

The Zimmer plant, on the Ohio River about 28 miles east of Cincinnati, was plagued by problems after being announced as a single-unit, $240 million nuclear station in September 1969.

In November 1982, the federal Nuclear Regulatory Commission ordered a halt to all safety-related construction at Zimmer because of questions about welding deficiencies and quality assurance problems.

In January 1984, the three Ohio utilities that own the plant announced plans for an unprecedented conversion to a coal-fired facility, costing about $3.4 billion when completed in 1991.

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Perry

The Nuclear Regulatory Commission issued a full-power operating license for the Perry nuclear power plant near Cleveland in November 1986, despite efforts by the state and an anti-nuclear group to block Perry's operation.

Opponents questioned evacuation plans around the Ohio plant and whether Perry can withstand another earthquake like a Jan. 31, 1986, temblor centered 10 miles from the plant. The NRC said the plant sustained no major damage.

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Diablo Canyon

Diablo Canyon's Unit 1 reactor was brought up to full power in April 1985 following nine years of delays and arrests of thousands of protesters at the site along the central California coast.

Contributing to the delays were were legal and technical problems, including the discovery of an offshore earthquake fault, design errors, and federal licensing disputes.

Both reactors are now in operation.

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Midland

Consumers Power Co., Michigan's largest utility, spent $4.2 billion on the nuclear power plant at Midland, in east-central Michigan, 20 miles west of Saginaw Bay, before regulatory and financing problems scuttled the project in 1984.

The Midland Cogeneration Venture plans a $600 million conversion to a gas- fired plant that will generate steam and 1,370 megawatts of electricity.

Regulatory problems included disputes relating to inadequately compacted soil inspectors said led to excessive settling of safety-related structures. Financing dried up and Consumers Power ordered work halted.

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Marble Hill

Indiana's Marble Hill nuclear power plant was canceled in 1984 after $2.7 billion was spent on construction. Public Service Indiana is working under a four-year agreement that allows the utility to increase rates and write off part of its loss on the plant.

The company had been near default before the agreement, but creditors granted PSI a reprieve after the agreement was approved.

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Shoreham

The Shoreham nuclear power plant on eastern Long Island, N.Y., operated by the Long Island Lighting Co., has been awaiting an operating license from the Nuclear Regulatory Commission.

The licensing proceedings have been delayed by local and New York State officials, including Gov. Mario Cuomo, who refused to participate in an emergency plan because they contend a safe evacuation is impossible because of Long Island's unique geography and dense population.

The $5 billion plant, about 75 miles east of New York City, was completed in 1983, 10 years behind schedule and more than 10 times over budget.