An operational incident occurred again at the Sutian Bay Nuclear Power Plant. Did it cause any casualties?

On March 24, 2021, the official website of the National Nuclear Safety Administration announced that on March 9, 2021, Unit 2 of the Tianwan Nuclear Power Plant underwent its twelfth refueling overhaul. The unit has been shut down. The cooling boric acid concentration reached has been established. The control rods are in mechanical support positions at the bottom of the core while the reactor cools down. As the regulating performance of the regulator's spray pipe regulating valve decreases, the pressure in the main circuit fluctuates greatly. At 14:43, the steam side isolation signal of the No. 2 steam generator is triggered, the hot section temperature of the primary circuit is higher than 146°C, the pressure of the steam generator is lower than 4.9MPa, and the saturation between the primary and secondary circuits The temperature difference is greater than 75°C. ?Close the main steam rapid isolation valve of the steam generator and isolate the steam side of the No. 2 steam generator.

After the accident, the operation organization conducted a cause analysis, replaced the faulty regulating valve, and then carried out overhaul work as planned. Ten months later, this was the first operational accident at Jiangsu Tianwan Nuclear Power Plant. According to the notice, an event is defined as an event that results in the automatic or manual triggering of the reactor shutdown protection system and special safety facilities in accordance with Article 22 of the Nuclear Safety Reporting Rules of the Nuclear Power Plant Operating Organization, Guideline (6). During the incident, the reactor protection system responded normally and all three safety barriers remained intact. There are no radiological consequences, no human exposure, and no environmental contamination. Incidents with operational deviations but no impact on safety are classified as level 0. This event level has no impact on nuclear safety, the health of power plant employees, the public and the environment in nearby areas.

Jiangsu Nuclear Power Co., Ltd. is the operating unit of Tianwan Nuclear Power Plant and is responsible for the construction and management of Tianwan Nuclear Power Plant and its commercial operation after completion. The company's shareholder composition and shareholding ratio are: China National Nuclear Corporation 50%, State Power Investment Corporation 30%, and Jiangsu Guoxin Asset Management Group Co., Ltd. 20%. In May 2020, during the refueling overhaul of Unit 1 of the Tianwan Nuclear Power Plant, it was discovered that one of the pipe welds of the low-pressure safety injection system had an excessive defect. Thereafter, all the same types of welds in Unit 1 were inspected and found to show eight substandard defects, which is a Level 0 nuclear power operation event.

Tianwan Nuclear Power Plant is located in Lianyungang District, Lianyungang City, Jiangsu Province. The base plans to build an 8-million-kilowatt pressurized water reactor nuclear power plant. According to the plan, after the completion of these eight units, the total installed capacity will exceed 9 million kilowatts, and the annual power generation capacity will be approximately 70 billion kilowatt hours. The nuclear power plant is by far the largest technical and economic cooperation project between China and Russia. Units 1 to 4 use Russia's VVER-1000 nuclear power units, units 5 and 6 use China National Nuclear Corporation's independent M31 improved model, and units 7 and 8 are planned to use Russia's advanced VVER-1200 third-generation nuclear power plant. generation nuclear power plant.