The Laguna Verde Nuclear Power Plant (CNLV), the only one operating in Mexico, suffered serious malfunctions on October 30 that led to its temporary stoppage, according to documents obtained by EL PAÍS. This time, Unit 2, one of the station’s two reactors, suffered a loss of external electricity (LOOP) due to the inoperability of one of the generator’s main electrical transformers.

Condition report 112,318, a document that details failures that have arisen in the plant and consulted by EL PAÍS, indicates that at 7:53 p.m. on Saturday, October 30, the transformer “trip” (acceleration) occurred that triggered the LOOP and therefore the three emergency diesel generators that it owns came into operation green lagoon. “The operators had to use flashlights and their cell phones to work. A lot of radioactive contamination was generated, ”a worker told EL PAÍS who, for safety reasons, requested anonymity.

Likewise, the air control instruments (CIA), which provide pressurized air to operate safety-related equipment in the reactor building, and all the emergency systems, vital for the safety of the reactor, were shut down. the plant, they ran out of power.

The LOOP caused the unavailability of the document search and printing program, such as manuals, procedures and diagrams, “a vital setback for the recovery of the unit’s systems”, for which “it was impossible for us to be efficient” during the contingency. reveals the condition report 112,357, obtained by EL PAÍS.

After the strike, CNLV personnel detected a spill of contaminated water at 9:00 p.m. from the drainage systems of equipment and radioactive waste on three levels of the U2 building and whose radioactivity measurement shows high levels, according to the condition report 112,322 , consulted by EL PAÍS. Therefore, radiation protection technicians proceeded to reduce pollution.

It is the second time in less than a year that the CNLV has suffered a similar failure, since last December it registered a LOOP due to the operation of an auxiliary transformer, which regulates current of the electrical system into and out of the nuclear power plant. The failure caused an electrical autotransformer – one of the plant’s vital sources of power supply – to accelerate, causing the alert to turn orange.

During its normal operation and the uranium recharge process, the plant uses color monitoring that indicates the degrees of danger melting of the core or disconnected components (a nomenclature that adapts the standards used by the Nuclear Regulatory Commission of the United States). Green means the systems are running smoothly. But the red color indicates an operation with a high degree of insecurity.

The US NRC notes that a LOOP is a major contributor to the overall risk at atomic stations. In addition, it can have a negative impact on the ability of a plant to achieve and maintain safe shutdown conditions. Physicist Rubén Dorantes, a researcher at the Autonomous University of Mexico (UAM), tells EL PAÍS that it is a serious incident. “Those events are of high concern. Every time the plant coughs, it is to worry, because it is a plant of more than 40 years. The maintenance it receives is very worrying due to budget cuts ”.

The transformation equipment of Laguna Verde, which has two reactors that each generate 810 megawatts and which represents 4% of the installed electrical capacity of Mexico and 2% of the total generation of the country, accumulate a history of damage.

Faulty system

In the third quarter of 2019, a main transformer was out of operation, for which both reactors of the station were in a yellow hazard condition, according to the inspection file OR-04/19-LVl, reviewed by EL PAÍS. On June 25, 2020, a “trip” of a main transformer of U2 occurred, for which an emergency diesel generator came into operation, as stated in the inspection file OR-02/20-LV2, consulted by EL PAÍS . Last July, U2 registered an emergency stop due to the rise in temperature above 65 degrees Celsius in the primary container, as reported by a digital medium from Veracruz.

The breakdown occurs almost two months after Héctor López Villarreal will pass from the management from the plant to nuclear coordination, a position suggested by the World Association of Nuclear Operators (WANO), the club of atomic power plant owners and to which the Federal Electricity Commission (CFE) belongs. Despite several attempts to contact, the CFE did not respond to EL PAÍS’s query.

As if that were not enough, the U2 accumulated 10 days of unscheduled stoppage due to vibrations of a turbo pump and failure of the cooling system of the dry well – the area between the core vessel and the primary concrete container that protects it -, according to a blog unemployment rate on November 1, reviewed by EL PAÍS.

The damage is added to the gallery of failures that the generator has suffered since September 2020, as in a pump of the Nuclear Service Water System, which supplies the station with liquid; loss of external electricity and diesel leakage in an emergency generator. These breakdowns implied that the CNLV fell into three orange alerts.

As of last August, U2 was close to matching the record of reportable events for 2020 –12 against 13– while U1’s report is 12 and 8, in that order, according to data obtained from access to public information. The CFE assumed to achieve in 2021 “a performance of excellence” and to place itself in the best quartile of the plants evaluated by WANO, goals that, from the perspective of the results shown, are still far away.

The CNLV, to which the Ministry of Energy extended the operating license in July 2020, during the pandemic, for another 30 years, is among the worst evaluated by that private association, due to the number of unscheduled shutdowns, levels of efficiency, forced energy losses and the exposure of workers to radiation.

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