The problems caused by a turbo pump when a supervision test was being carried out at the Ascó I nuclear power plant (Tarragona), they have led the plant to start the sequence for the shutdown of the nuclear reactor up to the technical level called “hot stop” event “with no impact on workers, the public or the environment”.
The Nuclear Safety Council (CSN) reported this Friday that the incident was classify with level 0 on the International Nuclear and Radiological Event Scale (INES).
The CSN indicates that on April 15, “with the plant at 100% nominal power, the reactor protection system automatically activated due to a failure of an electronic card that caused the automatic stop of the same”.
“During this event,” says the nuclear supervisor, “the automatic start-up of the auxiliary feed water occurred, but the auxiliary feed water turbopump stopped a protection of the equipment due to overspeed. actual turbo water pump failure auxiliary power supply was classified as level 1 on the INES scale “.
Those responsible for the plant, after reviewing the equipment, made several starts and on April 19, in a new start-up test, “failed again due to overspeed”.
After this new ruling, he stresses, the central declared “the equipment inoperable, according to the ETFs, which give a period of 72 hours to recover the operability of the equipment or stop the plant, up to a mode of operation in which the turbopump is not required to be operable “.
Since that day, according to the CSN, several automatic start-ups of the turbopump were carried out “and it has been fix the detected problem, considering in the end that the failure came from the control system of the VN-3072 valve, of steam control to the turbopump “.
As a consequence, he adds, it was decided to regulator replacement and the actuating piston of the regulation system of said VN-3072 valve.
On April 22, the surveillance procedure called PV-65 was carried out, with automatic start, to return operational capacity to the turbopump, “with satisfactory result”.
Additionally, the Council has an impact, a additional supervision by means of a program of tests that had to be carried out “to verify its behavior” and once “the problem had been solved, declaring the turbopump operable”.
“Finally, the CSN specifies, during the test carried out this Friday within the supervision program, the turbopump has stopped again due to overspeed, so the holder, in compliance with the ETFs, has started the load descent to mode 4 (Hot stop) “.
The CSN specifies that those responsible for the plant have agreed to that shutdown “due to the turbopump inoperability of auxiliary feed water greater than 72 hours “.
The event, underlines the CSN, “has had no impact on workers, the public or the environment. “