Damages corner the Laguna Verde nuclear plant

View of the Laguna Verde Nuclear Power Plant, Veracruz, Mexico COURTESY

The Laguna Verde Nuclear Power Plant (CNLV), the only one in Mexico, began 2021 as it ended the previous year, with operational problems that have placed it in a technical strike according to versions of workers and documents consulted by EL PAÍS.

Unit 2 is shut down as its uranium recharge is more than 21 days late while Unit 1 needs repairs to correct some damage.

These failures mean that the Federal Electricity Commission (CFE), owner of the plant located in the municipality of Alto Lucero (Veracruz), does not have the 810 megawatts produced by each reactor, which represents 4% of the installed electrical capacity. of Mexico and 2% of the country's total generation.

A spokesperson for the CFE has denied the flaws.

The most recent incident occurred on January 20, when Unit 1 suffered an emergency shutdown (

scram

) that put the station back at risk orange, a level prior to the maximum, red, which implies that it cannot function as its safety is not guaranteed.

This fact was reported in three reports that have been consulted by EL PAÍS.

The trigger for the problem was the loss of the auxiliary transformer T11 due to degraded and corroded secondary cables, according to this newspaper in four photographs.

This drawback, caused by the acceleration of a turbine that intervened in the transformer ignition, implies that the nuclear power plant has only three emergency diesel generators to feed the generator in case of losing internal fluid.

In the early morning of January 21, a fuel leak was also recorded when testing the emergency diesel generator II, according to the plant's condition report 106688.

"Compensatory actions and contingency plans are carried out" and "the organization is notified in order to remain in this condition for the shortest time possible," the document states.

"There was a lot of unusual movement at the plant, there was tension and it was immediately known that there was this emergency in Unit 1," said a worker at the plant on condition of anonymity.

The diesel generator that failed received maintenance in the fourth quarter of 2020. The National Commission for Nuclear Safety and Safeguards (CNSNS), the sector's Mexican regulator and attached to the Ministry of Energy, found at least seven failures, according to the inspection report. OR-03/20-LV l, prepared to verify the safety activities during the 20th nuclear refueling of Unit 1 carried out between August and September of last year.

Luis Bravo, the CFE Communication coordinator, denies "categorically and categorically" that there have been any failures.

"The Laguna Verde Nuclear Power Plant is in a process of refueling as part of the maintenance that is scheduled long in advance, in accordance with the standards and safety protocols established by national and international regulations," he said in a email.

EL PAÍS published in December that the plant presented a risk situation for 13 hours due to the work of a contractor carried out during the uranium replacement operation.

Among the damages affecting the plant, two diesel leaks were also identified.

The CNSNS reported that the verification of the generator concluded with "satisfactory results."

During the first four months of 2020, Unit 2 was in yellow risk due to the unavailability of that generator.

"As the contracts were given quickly, the contractors came in in a hurry, because they were assigned during the refueling.

It is possible that the connection (of the generator) was loose, ”a station worker tells EL PAÍS, who is part of a group of 150 employees who disagrees with the decisions made by the management, led by Héctor López Villarreal.

During its normal operation and refueling process, the plant uses color monitoring that indicates the degrees of danger of core melt or disconnected components.

This system is adapted to the standards used by the United States Nuclear Regulatory Commission.

In the second half of 2020, Laguna Verde has registered at least one orange alarm for failures in several systems.

In September, the operators carried out work to change the mechanisms of the reactor control rods despite being prohibited by the administrative procedure Risk Assessment and Management before carrying out maintenance work on U-1 and U-2 of the CNLV.

In the dark

The generating plant remained in an emergency situation on December 20 for more than two hours due to a massive blackout in Unit 2. The notification of reportable event 2-13 / 20, consulted by EL PAÍS, indicates that the power outage was It was due to human error from wrong work on electrical panels.

The blunder caused the AT3 electrical autotransformer, one of the plant's vital power supplies, to accelerate.

Around midnight, at 11:51 p.m., there was an increase in the operation of the auxiliary transformer T2T22, so Laguna Verde declared an emergency due to an unusual event.

The generators went into operation as backup.

Unusual events are considered unpredictable: earthquakes, roadblocks near the plant and fires.

Therefore, the aforementioned building suffered a blackout while the workers completed maneuvers to install the steam dryer - a device that improves steam quality by reducing humidity - in the vessel that surrounds the core and suspended the drainage of the dry well - the cavity. between the reactor and its concrete containment.

Consequently, Unit 2 was left without the access control program and without the air conditioning and ventilation system.

This disabled the checkpoints that allow verifying that workers are not contaminated with radiation.

The chain of events occurred while a standby transformer was offline for maintenance.

The emergency ended at 02.10 on Monday 21. The AT3 transformer has previously registered problems.

In the first four months of 2020, both units of the plant were in a yellow risk condition due to emerging jobs in that system, according to a condition report consulted by EL PAÍS.

A similar situation was repeated in the second four-month period of this year, as reflected in RC 101104. Edwin Lyman, director of Nuclear Energy Security of the Union of Concerned Scientists, of the United States, told EL PAÍS that “it could be serious if emergency provisioning does not start or malfunctions before external power restarts.

If that happens, then the plant will suffer a total loss of alternating current.

If electricity is not restored within a few hours, then the radioactive fuel in the reactor core could overheat and eventually melt, as happened in three reactors at the Fukushima Daiichi plant in Japan after a major earthquake and tsunami ", which occurred in 2011 The expert pointed out that the plant is "more vulnerable to a severe accident" when external electricity is not available if another type of accident occurs, "such as the rupture of a pipe."

Between 2012 and 2020, the Laguna Verde registered 33 unusual events, according to data from the CFE, which estimates that it loses approximately one million dollars per day of unemployment.

The nuclear power plant started operations of Reactor I in 1990 and Reactor II in 1995, with an estimated useful life of 40 years each and with a power of 2,027 thermal megawatts (Mwt).

In July, the Ministry of Energy renewed the CNLV's operating license for another 30 years, after the nuclear regulator reviewed its safety conditions, in a process that began in 2015. In its 2018 report, the World Association of Operators Nucleares (WANO), the club of atomic plant owners and to which the CFE belongs, assigned Unit 2 a score of 87 points in its performance index, to place it in 30th place out of 36 plants evaluated.

Unit 1 obtained 74.8 –step 32–.

The evaluation placed the Mexican nuclear power plant in the worst performance quartile along with seven other US generators.

”Corporate performance is marginal with a stable track record.

Corporate measures have been ineffective in influencing Laguna Verde's performance.

The plant has been under observation since June 2018, ″ reads a WANO summary from September 2019.

Since 2014, Laguna Verde has performed below the average of the plants supervised by WANO.

In 2019, it was more than 20 points below the average.

“In some cases, a loss of external power is unavoidable, as with natural disasters that cause a failure in the power grid.

But the equipment failures that could cause that loss are preventable with rigorous inspections and maintenance, "said Lyman.

The expert warned: if the power failure occurs, the possibility of a subsequent blackout can be reduced by strengthening the plant against such incidents.

In October, the Secretary of Energy, Rocío Nahle, assured in the Senate that the generator operates without problems after an investment in maintenance of 4,000 million pesos.

"It is very good, it has the highest safety norms and standards," said the official.

The CFE's own records tell another story.