Problem-Ridden A-Plant Hopes for Restart in May

The cooling towers that jut majestically from the valley floor belie Rancho Seco’s hardening reputation as one of the least reliable nuclear power plants in the nation.

It has been shut down 321 of the 438 days between Jan. 1, 1985, and March 14, plunging the Sacramento Municipal Utility District into a multimillion-dollar deficit that may soon force a rate hike, said plant spokesman Kerry Shearer.

SMUD financial forecasts indicate that the plant, idle continuously since Dec. 26, apparently will not start up again until about mid-May as it recovers from an overcooling incident. Shearer said the restart date is not firm, however.

One of the Worst Records

Federal investigators have called the overcooling the most serious of the problems that have given Rancho Seco one of the worst operating records of any U.S. nuclear power plant, while SMUD officials point out that there was no damage to major components and that they are moving swiftly to prevent any repeat of the incident.

Operators were unable to halt a rapid temperature decline in the reactor vessel during the overcooling, which unfolded amid a cacophony of alarms that even warned--falsely--of both a fire and an earthquake, investigators said.

Before it was over, Rancho Seco had vented a reportedly harmless amount of radioactive steam into the air over Sacramento Valley pastures, about 25 miles southeast of the California Capitol.

Since the 913-megawatt plant, built 11 years ago at a cost of $364 million, generates more than half the power to satisfy SMUD’s electrical demand, the utility has been forced at times to buy power from outside utilities or government agencies.

Utility officials estimated this week that SMUD is losing about $260,000 each day the plant is inactive. If Rancho Seco restarts May 15, the loss from the current shutdown would be approximately $28 million, they said.

SMUD had counted on the plant this year to thwart any need for increasing rates. But despite two separate rate hikes of 14% last year, the utility has posted a $9.2 million deficit for 1985.

Officials at SMUD have attributed the loss to poor performance at Rancho Seco, which was shut down five times last year for a total of 248 days.

But SMUD officials believe the utility is better off with the plant than without it.

Although Rancho Seco has cost SMUD $1.1 billion since it opened, the electricity it has generated would have cost $1.9 billion if purchased from outside sources, they say. Shearer said that despite problems, the plant has generated 70% of Sacramento’s total needs since start-up in April, 1975.

“We’re not happy with the capacity factor of the plant and we’re doing everything we can to change that. We’ve made management changes and hired consultants. . . . We’re very, very hopeful that when it restarts, it will remain on line for some time,” Shearer said.

Plant manager George Coward said in a memorandum to employees in January that he thought Rancho Seco has been treated unfairly by the news media.

“Somehow, all the hard work and thousands of things we do right every day seem to be totally forgotten when the media makes a negative news story out of things that are not newsworthy in any other industry,” Coward said.

Plant Called Unreliable

But Rancho Seco has proven so troubled in recent months that another utility, sensitive to nuclear power woes, has taken actions branding the plant as unreliable.

Pacific Gas & Electric Co. officials said earlier this month that they had begun withholding millions of dollars in payments because Rancho Seco operates only 11% of the time, compared to the industry average of more than 60% for the country’s 98 working reactors.

The payments had ensured that SMUD, which serves more than 380,000 customers in Sacramento County, would reserve electricity needed during power shortages in the PG&E; system, which serves most of the surrounding Northern California area.

SMUD has filed a complaint with the Federal Energy Regulatory Commission in Washington, claiming that PG&E;’s action violates a longstanding power-sharing contract between the two utilities.

Officials at SMUD said that the lost payments could total about $22 million this year, compounding the total costs tied to Rancho Seco problems.

Utility officials also worry that budget deficits could affect the district’s bond rating, which could drive up the cost of borrowing money for construction projects and ultimately mean even more rate hikes.

Federal investigators said the latest shutdown of the plant, Rancho Seco’s third overcooling incident, came in the pre-dawn hours the day after Christmas with the failure of a low-voltage, direct-current power supply that caused the “integrated control system” panel in the control room to go dead.

Pumps Slowed Automatically

Operators no longer were able to use the panel to control pumps and valves that send cold water into the reactor and let out hot water and steam, used to generate electricity.

Automatically, due to a built-in safety feature, valves went to a half-open position and pumps to mid-speed.

Reactor temperature climbed for 16 seconds because less water was being pumped in.

Triggered by the heat, another automatic safety feature went into action--control rods plunged around the core to halt fission in the reactor vessel.

Then, as water continued to flow into the core, the reactor cooled too quickly. Workers were dispatched through the plant to close valves by hand, but one would not budge even with a wrench.

Cooling such a steel vessel too quickly can cause cracks, which could drain the water that acts as a coolant and trigger a meltdown. The overcooling at Ranch Seco did not last long enough to threaten a meltdown, but during one 24-minute period, the plant cooled by 180 degrees--well beyond the approved 100 degrees an hour.

‘Off’ Switches Overlooked

Four workers independently looked for the problem with the “integrated control system,” since its reactivation would have made a controlled shutdown much easier. But all four failed to see that two circuit-breaker switches had tripped to the “off” position.

A senior operator, who collapsed later in the incident due to hyperventilation, noticed the two switches and flipped them back on, restoring remote control over water flows 26 minutes after the power failure.

Then a pump, left running after the flow to it was cut off by hand, burned out and spilled 450 gallons of water contaminated by radioactive isotopes onto the floor inside the reactor containment building. None of the water reached the outside environment but a trace of water evaporated through vents, carrying too little radiation outside the plant to be a hazard.

2 Workers Exposed

Two workers who entered the area were exposed to radiation, but at a level well below the annual amount permitted to nuclear employees.

A Nuclear Regulatory Commission investigative team has concluded that operators were not trained to handle the type of electrical outage that forced the rapid cool-down.

Frank Hebdon, head of the team, also said that written emergency procedures maintained by SMUD did not take such an electrical failure into account. Therefore, he said, the plant’s operators were taken by surprise when the plant cooled at a rapid pace following the failure.

The investigative team said that poor design in the direct current power supply made it vulnerable to small electrical changes that would cause it to turn off, as it did Dec. 26.

No Lubrication in 12 Years

The attempt at manually slowing the pace of cool-down also was hampered by the fact that some valves had received no lubrication since their installation 12 years ago, the team’s report said.

Investigators said operators forgot that they had an auxiliary control panel which, if properly used, would have averted the scurrying to turn valves manually.

The team also reported a backup system that was to have been installed in 1984 was never added to the plant.

In another aspect of the incident, plant spokesmen have conceded that operators did not fully follow procedures for notifying surrounding counties of the development, which federal investigators said was properly declared an “unusual event”--the lowest emergency category.

SMUD officials said they have taken steps to assure notification procedures are followed in the future.

Single Manufacturer

The utility also says it is working closely with the Nuclear Regulatory Commission in resolving concerns in order to secure federal approval for a restart.

There have been several failures of similar systems, which are unique to plants built by Babcock & Wilcox Inc., the federal report said. The Nuclear Regulatory Commission has ordered a review of the other B&W; plants, which are especially vulnerable to over-cooling incidents, but have allowed them to continue operating.

Earlier this month, the Union of Concerned Scientists, an independent, nonprofit group, said that the commission has failed to correct major safety flaws at the eight U.S. plants, including Rancho Seco, designed by the company.

The flaws involve the pressure in the reactors’ steam generation systems and the failure of those systems to compensate for the plants’ “inherent instability,” the group said.

The seven other plants are Arkansas 1 near Russelville, Ark.; Crystal River near Crystal River, Fla.; Davis-Besse near Toledo, Ohio; Oconee 1, 2 and 3 near Greenville, S.C.; and Three Mile Island No. 1, near Harrisburg, Pa.

The company also designed the Three Mile Island reactor No. 2 that had the nation’s most serious nuclear accident in March, 1979.