Hanuwon Co., Ltd. Hanul Nuclear Power HQ said, “On February 25 (Thursday), the electrical bypass valve of the Hanul Unit 4 turbine protection system (pressurized light water reactor type, 1 million kW) was shut down. closed. It announced that it had resumed electricity production on Friday February 26 at 1:44 p.m.
In this regard, the Hanul Nuclear Power Plant Civilian Environmental Monitoring Organization announced the investigation data of the “Hanul Nuclear Power Plant Suspension Summary” on its website. According to the monitoring agency, The reason for the power output suspension was found to be “failure of valve operation due to extraneous (approximate) case of the electric bypass valve”. Here is the survey data revealed by the Hanul Nuclear Power Plant Environmental Monitoring Organization.
– Summary of the suspension of Unit 4 of the Hansuwon Hanul nuclear power plant
-Cause: Malfunction of the valve due to foreign housing (approximate) of the electric bypass valve.
Summary Summary of incidents
25 (preview) On February 25, at around 10:43 a.m., ’21 (Thursday), Hanul 4 nuclear power plant (pressurized light water reactor type, 1 million kW class) was operating normally(100% reactor, generator 1,057 MWe) Turbine protection system 1) Periodic test (6 months)After completing the electrical overspeed shutdown test, return the electrical bypass valve (ELV) 2 to the normal position. In the process of return, the spool 3) controls the flow of control oil from the valve Because of this there was a problem (sticking),
Finally, the normal return of the bypass valve is delayed (about 10 minutes, Usually within 1 to 2 seconds), the signal “check oil pressure low” is displayed by turning off the check oil pressure. This happened and the turbine / alternator was shut down, and the reactor power rapidly declined in accordance with the reactor design.The foot system (RPCS) works and is automatically reduced by about 45%
1) Turbine protection system: when abnormal signals related to the turbines (composed of 13 signals including manual shutdowns) occur during plant operation Immediately turn off the turbine / generator to prevent damage to the turbine / generator and related installations
2) Electric bypass valve: A valve is used to test the turbine safety system during normal operation without stopping the turbine. 3) Spool valve: As a spool valve with several grooves on the outside of a valve body, the spool is in the axial direction.Going out in the sun controls the road of the oil flow
Loss This case complies with the rules for reporting and disclosing accidents or breakdowns at nuclear facilities (Korean National Security Agency notice number 2020-3), No detailed report or rating assessment is required on the original invoice as this is a power plant suspension other than a nuclear reactor suspension.
❍ (environmental impact) in this case, monitoring center Real-time environmental radiation monitoring (ERMS) 4) Signal values, etc. As a result of the investigation, it was confirmed that they are all within normal limits and that there is no leakage of radioactivity to the outside.
4) Status of the installation of environmental radiation in real time near the Hanul nuclear power plant (11 points within a radius of 6 km):
Within the power station (between 1 and 2, Shin Hanul 1, Shin Hanul 2, Weather Station, Gomok-Ri, Shinhwa-Ri, Southwest Hill, Gugi-Song Observation Station) Relative to the power station (Bugu Bridge, Hansuwon House (Nagok), Zookebon Elementary School)
And (power generation measurements and revitalization) companies should perform repeatable tests, etc. due to the failure of the electric bypass valve. As was finally confirmed, the replacement of the defective valve with a new one, performance testing and the future plan[전문기관을 통한 전기적우회밸브 오동작 상세 원인분석 및 터빈보호계통 전면개선(국산화_진행중)] Lamp installation is complete, and development resumes the next day (2.24) (3) at 3:47 p.m.% / h), reaching full power at 8:45 p.m. the same day
Written by: monitoring center /
Data = provided by Hanulwon Civil Environmental Monitoring Organization