Press Release

Press Release

Power Adjustments Begin at Hamaoka Nuclear Power Station Reactor No. 4

February 03, 2011
Chubu Electric Power Co.,Inc.

Chubu Electric Power began the 12th regular inspection of Hamaoka Nuclear Power Station Reactor No. 4 (boiling water reactor; rated electric output 1,137 MW) on October 14, 2010. As part of this process, plant equipment has been thoroughly checked.


At present, all equipment checking tasks that are performed while the reactor is shut down, as well as all regular business inspections, are scheduled to be completed today.

Following their completion, Chubu Electric will prepare for reactor startup. The reactor is expected to recommence operation as early as tomorrow, after which power adjustments will commence.


During power adjustments, output will be gradually ramped up and equipment inspection and tests performed using steam generated by the reactor. Upon finishing these checks, the reactor will undergo one final inspection, the General Load Performance Inspection by the government of Japan.


In the event that any irregularities occur during power adjustments, Chubu Electric will perform whatever repairs are necessary. It may also be necessary to shut down the reactor again depending on the repair procedures involved.


In addition, during the present periodic inspection, it was decided to postpone the implementation of our Pluthermal Plan in Reactor No. 4, which was scheduled to be put into effect from FY2010.

(Reported on December 06, 2010)


In future, we will expend every effort in attempting to achieve early realization of the Pluthermal Plan, and with the safe operation of the Hamaoka Nuclear Power Station as our highest priority, we will strive to operate a facility that inspires complete confidence in local residents.



Major Inspections and Work Performed During Periodic Inspection at Hamaoka Nuclear Power Station Reactor No. 4

1. Major inspections

(1) Reactor

Inspection of reactor pressure vessel, structures inside reactor, and fuel

(2) Reactor cooling system equipment

Inspection of pipes, heat exchangers, pumps and valves

(3) Measurement and control system equipment

Inspection of control rod drive hydraulic control system; inspection and calibration of various measurement devices

(4) Radiation control equipment

Inspection and calibration of various radiation control measurement devices

(5) Reactor containment equipment

Seal testing of reactor building, containment equipment

(6) Steam turbine

Opening and inspection of condensers; inspection of auxiliary equipment

(7) Other

Inspection of scrapped equipment, fuel equipment, emergency backup generator equipment, electrical equipment, etc.


2. Major work

(1) Replacement of fuel assemblies

Of the total 764 fuel assemblies in the reactor, 184 have been replaced. Reserve uranium fuel was used instead of MOX fuel in the case of the 28 assemblies that had been scheduled to be loaded with MOX fuel. The MOX fuel that was scheduled to have been loaded is being stored in a fuel storage pool.

(2) Results of measures in relation to inspection plans and inspection records for devices for which the inspection period had been exceeded

Of the 320 devices for which the inspection period had been exceeded, disassembly and other inspections have been conducted on the 319 that were scheduled for inspection during the current inspection period, and no abnormalities have been detected.
The remaining device is presently undergoing a disassembly inspection as a normal periodic inspection that is carried out while the reactor is in operation. This inspection is scheduled to be completed within February.

(3) Results of measures in relation to phenomena observed in welded areas not included in the in-service inspection

An in-service inspection was conducted of the welds on the mounts for the supporting members of the reactor isolation cooling system pumps, and no abnormalities were detected.

(4) Results of measures in relation to omission of procedures based on the High Pressure Gas Safety Law

Application for permission was made to the Shizuoka Prefecture administration on January 13, 2011 in relation to two valves in Reactor No. 4 for which procedures based on the High Pressure Gas Safety Law had been omitted. Certification of completed inspection was received on January 26.

(5) Measures in relation to increased monitoring of shaft vibration in main turbine

On June 04, 2010, a slight increase in the shaft vibration value of the main turbine was detected. Monitoring was enhanced, and the cause of the phenomenon was investigated. In order to investigate the cause of the phenomenon, during the periodic inspection the coupling between the shafts of low-pressure turbine (C) and the generator was dismantled, and it was discovered that the shafts were very slightly off-center.
The shafts were therefore adjusted in order to realign them. The shaft vibration value will be checked during power adjustment operation.

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