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Significant incidents at Japanese nuclear power plants and nuclear fuel facilities

(Jan. 2003 - Dec. 2003)
DATE Operator Facility Name Type Short Description of Incidents
Feb. 7 JNFL (Japan Nuclear Fuel Limited) Rokkasho Reprocessing Plant Reprocessing Plant Leak detected at fuel assembly transfer pit
Feb. 12 Kansai-EPCO Takahama-1 Pressurized Water Reactor (PWR) During periodic inpection crack found at neutron flux monitor nozzle (made of Inconel 600) mounted to reactor vessel bottom
Feb. 18 Shikoku-EPCO Ikata-1 PWR Leak detected at chemical volume control tank outlet piping
Feb. 27 JAPC (Japan Atomic Power Company) Tsuruga-1 Boiling Water Reactor (BWR) Reactor manually shut down due to leak detected at mechanical seals of recirculation pumps (B and C)
Feb. 27 Tokyo-EPCO Kashiwazaki-Kariwa-3 BWR Cracks found at welds of primary loop recirculation system piping (made of SUS316L) during planned stoppage
Feb. 28 Tokyo-EPCO Fukushima I-3 BWR Control rod interlock cancelation found at 'one control rod draw check' during periodic inspection
March 4 Tokyo-EPCO Fukushima I-3 BWR A control rod insertion delayed at 'control rod insertion/draw examination' during periodic inspection
March 5 Tokyo-EPCO Fukushima II-1 BWR Foreign metal material found at the top of a nuclear fuel assembly during periodic inspection
March 10 Chubu-EPCO Hamaoka-3 BWR Cracks found at welds of core shroud (made of SUS316L) middle and lower region during periodic inspection; cracks found at inside surface of H4 position, at outside surface of H6a position, at inside surface of H7 position, etc.
March 27 Tokyo-EPCO Kashiwazaki-Kariwa-4 BWR Cracks found at 6 welds of primary loop recirculation system piping (made of SUS316L) during periodic inspection
April 16 Tokyo-EPCO Fukushima II-1 BWR Cracks found at a weld between reactor pressure vessel nozzle safe-end pipe (made of SUS316L) and primary loop recirculation system piping (made of SUS304L) during periodic inspection
April 17 Chubu-EPCO Hamaoka-3 BWR Cracks found at welds of primary loop recirculation system piping (made of SUS316L) during periodic inspection
April 17 Chubu-EPCO Hamaoka-4 BWR Cracks found at welds of primary loop recirculation system piping (made of SUS316L) during periodic inspection
April 29 Chugoku-EPCO Shimane-2 BWR Cracks found at welds of core shroud (made of SUS316L) middle region during periodic inspection; cracks found at inside surface of H4 position
May 8 Kansai-EPCO Mihama-2 PWR Generator power reduced due to leak at 5th high pressure feed water heater
May 12 Tokyo-EPCO Kashiwazaki-Kariwa-5 BWR Cracks found at welds of primary loop recirculation system piping (made of SUS316L) during periodic inspection
May 15 Kyushu-EPCO Sendai-1 PWR Damage to 15 steam generator tubes during periodic inspection
May 20 Tokyo-EPCO Kashiwazaki-Kariwa-5 BWR Cracks found at welds of core shroud (made of SUS316L) middle region during periodic inspection; cracks found at inside surface of H4 position and of V14 position
May 21 Kansai-EPCO Mihama-3 PWR Cracks found at reactor vessel bottom mounted conduit tube during periodic inspection
May 22 Kansai-EPCO Takahama-4 PWR Damage to 2 steam generator tubes during periodic inspection
May 26 Tohoku-EPCO Onagawa-3 BWR Reactor automatically shutdown due to 'large ground acceleration' signal set off by an earthquake (magnitude 7.0)
May 28 Tokyo-EPCO Fukushima II-3 BWR Cracks found at guide roller installed area of a control rod handle during periodic inspection
June 9 Tohoku-EPCO Onagawa-2 BWR Cracks found at welds of core shroud (made of SUS316L) middle region and lower region during periodic inspection; cracks found at outside surface of H3 position and at inside surface of H7a position
June 10 Chubu-EPCO Hamaoka-1 BWR Cracks found at a weld of core shroud (made of SUS304) lower region during periodic inspection; cracks found at inside surface of H7b position
June 14 Tokyo-EPCO Fukushima II-3 BWR Fuel assemblies installation operation stopped due to lack of a control rod at a fuel cell during periodic inspection
June 16 Chubu-EPCO Hamaoka-1 BWR Cracks found at upper region of a weld of the core shroud (made of SUS304) during periodic inspection; crack found near upper lattice plate base
June 23 Tohoku-EPCO Onagawa-2 BWR Cracks found at a weld of primary loop recirculation system piping (made of SUS316L) during periodic inspection
June 24 JAPC Tsuruga-1 BWR Cracks found at surface of control rod blades during periodic inspection
July 4 JNC (Japan Nuclear Cycle Development Institute) Fugen Advanced Thermal Reactor Fire alarm set off at waste treatment building; window of low-level radioactive waste incinerator broken due to explosion and 460 million bequerels of radioactive ash leaked
July 8 JNC Joyo Experimental Fast Reactor Reactor automatically shut down due to 'neutron flux high' signal
July 15 Tokyo-EPCO Fukushima II-2 BWR Cracks found at welds of primary loop recirculation system piping (made of SUS316L) during periodic inspection
July 24 Tokyo-EPCO Fukushima I-2 BWR Leak found at instrumentation outlet of residue heat removal system during periodic inspection
July 29 Hokuriku-EPCO Shika-1 BWR Cracks found at welds of primary loop recirculation system piping (made of SUS316L) during periodic inspection (also on Aug. 26 and on Sep. 3)
July 31 Tokyo-EPCO Fukushima II-2 BWR Cracks found at welds of core shroud (made of SUS316L) middle region during periodic inspaction; cracks found at outside surface of H4 position
Aug. 1 Tohoku-EPCO Onagawa-2 BWR Cracks found at welds of primary loop recirculation system piping (made of SUS316L) during periodic inspection
Sep. 7 Hokkaido-EPCO Tomari-2 PWR Leak found at regenerated heat exchanger; reactor manually shut down for inspection on Sep. 11
Sep. 10 JAPC Tsuruga-2 PWR Build up of boric acid powder and cracks found at welds of pressurizer relief valve nozzle and of pressurizer safety valve nozzle during periodic inspection
Oct. 6 Tohoku-EPCO Onagawa-2 BWR Leak detected at containment vessel sump; damage found at mechanical seals of recirculation inlet pump and of recirculation outlet pump during periodic inspection
Oct. 6 Tokyo-EPCO Fukushima II-4 BWR Cracks found at guide roller installed area of control rod handles and at surface of control rod blades during periodic inspection
Oct. 7 Tokyo-EPCO Kashiwazaki-Kariwa-7 BWR Cracks found at impellers of reactor internal pumps during periodic inspection
Oct. 9 - Nov. 7 Tokyo-EPCO Fukushima I-1,2,3,4,6 BWR Various foreign materials (scaffolding members, clamps, vinyl sheet chips, vinyl tape chips, ropes, spanner, pen, etc.) found in suppression chambers during periodic inspection
Oct. 14 Chugoku-EPCO Shimane-1 BWR Spacers slippage found at fuel assemblies during periodic inspection
Oct. 14 - Nov. 7 Tokyo-EPCO Kashiwazaki-Kariwa-1,2,3,5,7 BWR Various foreign materials (vinyl sheet chips, ropes, electromoved grinder, pliers, dust mask, video tape, boot, heat insulating materials, etc.) found in suppression chambers during periodic inspection
Oct. 16 - Nov. 7 Tokyo-EPCO Fukushima II-1,2,3,4 BWR Various foreign materials (vinyl sheet chips, vinyl tape chips, ropes, spanner, pen, etc.) found in suppression chambers during periodic inspection
Oct. 17 Shikoku-EPCO Ikata-3 PWR Emergency diesel generator activation failed at start-up operation
Oct. 22 Kansai-EPCO Takahama-2 PWR Reactor manually shut down due to steam leak from 3rd low-pressure turbine inlet flange during conditioning operation
Oct. 22 Tokyo-EPCO Fukushima II-4 BWR Crack found at weld of primary loop recirculation system piping (made of SUS316L) during periodic inspection
Nov. 5 Tokyo-EPCO Kashiwazaki-Kariwa-2 BWR One part of cleaning device fell into reactor vessel during core shroud cleaning test operation during periodic inspection
Nov. 6 Tohoku-EPCO Onagawa-2 BWR Various foreign materials (wire, vinyl sheet chips, vinyl tape chips, ropes, miniature lamp, etc.) found in suppression chambers during periodic inspection
Nov. 9 Kansai-EPCO Mihama-2 PWR Reactor manually shut down due to primary coolant leak found at cap of bent line attached to pressurizer spray piping
Nov. 18 Tokyo-EPCO Fukushima I-6 BWR One part of cleaning device fell into reactor vessel during control rod drive mechanism housing tub tube cleaning operation during periodic inspection
Nov. 19 Chubu-EPCO Hamaoka-2 BWR SCRAM signal set off accidentally due to ocsillation in value indicated by average power range monitor
Nov. 22 Chubu-EPCO Hamaoka-1 BWR One part of cleaning device fell into reactor vessel during core shroud support cylinder cleaning operation during periodic inspection
Nov. 25 Chubu-EPCO Hamaoka-1 BWR Cracks found at welds of core shroud support cylinder and of core shroud support legs during periodic inspection
Dec. 2 Chugoku-EPCO Shimane-1 BWR A worker exposed due to inhalation of 917 bequerels of cobalt-60 during containment vessel head installation operation
Dec. 5 Kansai-EPCO Ohi-1 PWR Reactor manually shut down due to leak from mechanical seal of primary coolant pump
Dec. 5 Tokyo-EPCO Fukushima I-6 BWR Leak found at water level gauge tube opening during periodic inspection
Dec. 18 Chubu-EPCO Hamaoka-1 BWR Cracks found at welds of jet pumps during periodic inspection
Dec. 19 JAPC Tsuruga-1 BWR Reactor automatically shut down due to lightning
Dec. 20 Tokyo-EPCO Fukushima I-6 BWR Stress reduction device stopped during operation to reduce stress on control rod drive mechanism housing stub tubes during periodic inspection
Dec. 26 JAPC Tsuruga-1 BWR Leak detected at mechanical seal of recirculation pump; reactor manually shut down on Dec. 28
*Please note: The entries in bold type indicate either (1) that the incident was a reportable incident under
The Regulation of Nuclear Reactors and Related Matters Act, or (2) that CNIC judged it to be an especially significant incident.

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