UPDATE 1-Spain's Vandellos II nuclear plant halted for tests

(Adds details, background)

MADRID Oct 23 (Reuters) - Spain's 1,000-megawatt Vandellos II nuclear power station has been disconnected from the grid to undertake tests prior to being reconnected, a technician said on Thursday.

Speaking from the plant, which is near to the northeastern port of Tarragona, the technician added that the plant had been disconnected on Wednesday and the tests could take a week.

Vandellos II had been reconnected on Tuesday after a two-month halt prompted by a generator having caught fire, but did not reach full power.

Spain's other seven nuclear plants were working normally and supplying 6,231 MW by 1110 GMT, according to data from nuclear watchdog CSN and national grid operator REE (REE.MC). That compares to about 7,300 MW when all are working normally.

Spain's number-two utility Endesa (ELE.MC) has a 72-percent stake in Vandellos II, while the biggest utility Iberdrola (IBE.MC) owns the other 28 percent.

Prompt power prices <SP/BASE> tend to rise when less nuclear electricity is available, as the grid depends more on relatively expensive gas-fired generators. (Reporting by Martin Roberts; editing by James Jukwey)