Hansuwon Hanul Central Nuclear Power Unit 4 Power Generation Suspension Summary .. Low Oil Pressure Signal Generation Control, Turbine / Generator Shutdown: National Safety Newspaper

▲ A view of the 2nd and 3rd rounds of the Hanul Nuclear Power Plant © Editorial Department

Hansuwon Co., Ltd. Hanul Nuclear Power Headquarters said: “On February 25 (Thursday), Hanul Unit 4 (pressurized light water reactor type, 1 million kW) stopped the electrical bypass valve of the system. turbine protection. It announced that it had resumed power generation at 1:44 am on Friday, February 26.

In this regard, the Hanul Nuclear Power Plant Civil Environmental Monitoring Organization announced the survey data on the “Hanul 4 Nuclear Power Plant Suspension Summary” through its website. According to the watchdog agency, The cause of the suspension of power generation was found to be “Valve malfunction due to (estimated) foreign matter from electrical bypass valve.” The following are the survey data released by Hanul Nuclear Power Plant Environmental Monitoring Organization.

– Summary of the suspension of unit 4 of the Hansuwon Hanul Nuclear Power Plant

-Cause: Valve malfunction due to foreign matter (estimated) from electrical bypass valve-

□ Summary of incidents

❍ (Overview) Around 10:43 on February 25, ’21 (Thursday), Hanul 4 nuclear power plant (pressurized light water reactor type, 1 million kW class) is operating normally(100% reactor, 1,057 MWe generator) Turbine protection system 1) Periodic test (6 months)After completing the electrical overspeed shutdown test, return the electric bypass valve (ELV) 2) to the normal state. In the return process, the spool 3) that controls the flow of the valve control oil There was a malfunction (stuck) caused by this,

Eventually, the normal return of the bypass valve is delayed (approximately 10 minutes, Normally within 1 to 2 seconds), the “ control oil pressure low ” signal is displayed when the control oil pressure is turned off. It happened and the turbine / generator stopped, and the reactor output decreased rapidly in accordance with the reactor design.The foot system (RPCS) works and is automatically reduced to approximately 45%

1) Turbine protection system: when abnormal turbine-related signals (composed of 13 signals, including manual stop) occur during power plant operation. Quickly stop the turbine / generator to avoid damage to the turbine / generator and related facilities

2) Electric Bypass Valve – Valve used to test the turbine protection system without stopping the turbine during normal operation. 3) Spool valve: As a valve with several grooves on the outside of a valve body, the spool is in the axial direction.Controls the path of the oil flow moving towards the incense

▮ This case is in accordance with the notification and disclosure regulations in the event of accidents or breakdowns at nuclear facilities. A detailed report or qualification assessment is not required on the original invoice as it is a power plant suspension that is not a nuclear reactor suspension.

❍ (Environmental impact) In this case, the monitoring center Real-time environmental radiation monitoring (ERMS) 4) indication values, etc. As a result of the verification, it was confirmed that all of them are within the normal range and there is no leakage of radioactivity to the outside.

4) Status of the installation of the real-time environmental radiation monitors in the area around the Hanul nuclear power plant (11 points within a radius of 6 km):

-Inside the power station (between 1 and 2, Shin Hanul 1, Shin Hanul 2, weather station, Gomok-ri, Shinhwa-ri, Southwest Hill, Gugi-sang observation station) -In addition to the power plant (Bugu Bridge, Hansuwon House (Nagok), Jukbyeon Elementary School)

❍ (Measurements and resumption of power generation) Businesses should conduct reproducibility tests, etc. due to the failure of the As finally confirmed via, after replacing the faulty valve with a new one, the performance test and the future plan[전문기관을 통한 전기적우회밸브 오동작 상세 원인분석 및 터빈보호계통 전면개선(국산화_진행중)] The establishment of the lamps was completed and development resumed at 01:44 the next day (2.26) (3% / h), reaching maximum power at 20:45 on the same day

Written by: Monitoring Center /

Data = provided by Hanulwon Civil Environmental Monitoring Organization

▲ KHNP Hanul Nuclear Power Plant Unit 4 Power Generation Suspension Summary-Cause: Valve malfunction due to foreign matter (estimated) from electrical bypass valve-Data = provided by Hanulwon Civil Environmental Monitoring Organization ©