MADRID, Oct 24 (Reuters) - Spain's 1,000-megawatt Cofrentes nuclear plant was halted on Friday for maintenance work while power was being stepped down at the 1,000-MW Asco II plant prior to refuelling, operators and technicians said.
That leaves just five of Spain's eight nuclear power plants working normally, as the 1,000 MW Vandellos II plant has been halted almost continually for two months.
Data from national grid operator REE showed that nuclear plants were supplying 5,179 MW by 1140 GMT, or 14.6 percent of demand. That compares to about 7,300 MW when all eight plants are working normally.
Technicians at Cofrentes said they aimed to complete checks on valves at the Iberdrola-owned plant over the weekend with a view to starting up again on Monday.
Cofrentes, which is close to the eastern port of Valencia, had been running at about 90 percent of power since last weekend for maintenance and went off line at about 0530 GMT on Friday.
Asco II nuclear power station is scheduled to halt at 2200 GMT on Friday for refuelling work expected to take 33 days, a statement from the plant's operators said.
A technician at Asco II, which is near to the northeastern port of Tarragona, added that output from the plant began to fall at about 1000 GMT.
The statement added that refuelling and associated maintenance would cost 11.5 million euros ($14.47 million).
Spain's number-two utility Endesa has an 85-percent stake in the plant, and top utility Iberdrola has the remaining 15 percent.
NUCLEAR FUTURE IN DOUBT
Cuts in supply of relatively cheap nuclear power tend to force up the wholesale price of power for prompt delivery
Technicians at Vandellos II have said that tests at the plant began on Wednesday, after the plant failed to start up on Tuesday, and are expected to take about a week.
Vandellos II had been halted since Aug. 24 when one of its generators caught fire.
The fire and other unscheduled stoppages, coupled with a controversial radioactive leak, prompted watchdog CSN last month to tell plants that renewing their operating permits would depend on their implementing tighter safety procedures.
Permits for seven plants expire between 2009-11, or within the mandate of the Socialist government, which has pledged to phase out nuclear power amidst a boom in renewable energy.
Industry Minister Miguel Sebastian recently said the government was open to renewing permits if operators made sufficient investments in safety.
Spain has the capacity to generate more than twice as much power from wind than from nuclear. However, on average nuclear plants provide more power as they work more consistently.