Hamaoka (Japan)

Map of Hamaoka

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1 * BWR 515 MW
1 * BWR 810 MW
2* 1100 MW BWR
1* ABWR 1350 MW
all units by Toshiba

Facilities in Hamaoka

plantreactor typconstruction startoperation startshut down

In Hamaoka 1&2 during a periodic inspection, cracks were found in the pass-through section of a common exhaust stack of Unit 1 and 2 (specifically, the sampling pipe designed for monitoring purposes). A tube will be installed to surround the pass-through section and the pass-through section of the sampling pipe at the stack monitor will be included in the inspection plan of the exhaust stack.


"In Hamaoka-4 during adjustment operation, the reactor was shutdown manually in response to a large CUW differential flow alert in the reactor coolant cleanup system. Operators confirmed abnormal noise in the regenerated heat exchanger room. Cause: According to Chubu Electric, the setting for detection of large CUW (reactor cleanup water system) differential flow was incorrect."


"During adjustment operation, an alarm signalized inoperability of reactor average power-monitor-B. At the same time, one of the signals showing rapid reduction of reactor coolant flow rate was also excluded. Power output was reduced to less than 75%. A component in the central processing unit (CPU) used to measure reactor power was damaged."
(source: http://cnic.jp/english)


Cracks found at welds of primary loop recirculation system piping during periodic inspection of Hamaoka-4.
(source: http://cnic.jp/english/)


Cracks found at welds of primary loop recirculation system piping during former periodic inspection at Unit 1 and at Unit 3.
(source: http://cnic.jp/english/)


"Cracks found at welds of core shroud (made of SUS316L) lower region during periodic inspection"
(source: http://cnic.jp/english/)


A small amount of radioactive water has leaked from the nuclear plant, but no radiation has so far reached the outside environment, the prefectural government announced.
The leakage was discovered in a water feed pump valve in the No. 4 reactor of the Hamaoka Nuclear Power Station by an employee.


After the discovery of a radioactive water leak, the No 2 reactor was shut down. The leak occurred 24 hours after the company reached "understanding" with local residents who had in April filed a temporary injunction to force the suspension of operations of four reactors at the nuclear power plant.


"Reactor manually shut down due to water leak from residual heat removal system low pressure injection pipe isolation valve drain piping weld during reactor start-up operation."
(source: http://cnic.jp/english/)


Reactor Hamaoka-1 coolant leak due to crack of stub tube welding attached to control rod drive mechanism housing.
(source: http://cnic.jp/english/)


An emergency core cooling system (ECCS) pipe ruptured, which was located in the residual heat removal system (RHRS) which is connected to the high pressure coolant injection system (HPCI). The rupture occurred during a regular monthly test to confirm the HPCI´s performance. The previous test was done on October 3rd, when no problem was found. That means, that there was no sign of a possible incident. The pipe is covered with insulation materials, thus it is difficult to find cracks. The ruptured pipe was put in place as a replacement in 1993. The Agency for Nuclear and Industrial Safety (ANIS) will conduct an emergency inspection of all BWR 4 type reactors that began operation around the same time (1976).


Residents opposed to adding Hamaoka 5
In the Sakura district, residents agreed with little dissent to the construction of the four previous reactors, but they decided to oppose the 5th in March 1995, saying that they had done enough already to further national policy.
In spite of this the mayor and the council of Hamaoka Town in June this year decided in a closed-door meeting to enter into negotiations with Chubu Electric. Opposition to this unrepresentational and autocratic behavior from local residents has spread from the Sakura district to other districts, and on August 5th petitions with the signatures of 3.417 people demanding a complete withdrawal of the plan for Hamaoka 5 and of 3.020 people asking for a referendum on the issue, were handed to the town mayor.


Reactor manually stopped due to increased water discharge from containment cooler.


Fire in turbine building.


Radioactivity leak from fuel rod found during inspection, sipping tests revealed a leaking fuel element; Follow up analysis of all 368 fuel assemblies showed that a total of 78 had been more or less damaged caused by a combination of the effects of water chemistry and fuel cladding material loaded in 1984 and 1986 that was more sensitive to corrosion. It is the first time that fuel clad corrosion has resulted in failure and that flaking has been found on Japanese BWRs. The reloads from 1984 and 1986 will be removed.


Abnormal vibration of HPCI pump due to a clogged adhesive tape strip: a roll of adhesive tape inadvertently left inside a pump by a maint. worker damaged the turbine axis of a HPI pump.


Stress corrosion cracking found during outage in the traversing in core probe system: 13 mm crack in the upper part of the tube, which vertically penetrates the 140 mm thick bottom of the reactor pressure vessel electrical. Tube was sleeved and expanded to close the gap between its outer surface and the inner vessel wall. Leak of small amount of primary coolant through the crack.


Leakage in ECCS drain piping; 17 workers exposed to contaminated water.


Common mode failure of both recirculation pumps, due to a relay failure in power line, Scram failed. Power was manually reduced ,