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Information
Post-quake status of the Kashiwazaki-Kariwa Nuclear Power Station (Report #13)
- Results and current status of reactor opening and in-core inspections -Tokyo Electric Power Company has completed the in-core inspections of all reactor
units today (February19), when a Phase 3 inspection on Unit 3 was concluded.This
Report #13 explains the implementation details and outcome of in-core inspections, aswell as the results of other inspections and the status of non-conformity management.
The Report also provides an overview of the “International Symposium on Seismic
Safety of Nuclear Power Plants and Lessons learned from the Niigataken Chuetsu-oki
Earthquake”, scheduled for next week.
1. Status of main inspections and restoration work
(1) In-core inspections
The attachment summarizes a series of work implemented from reactor opening
to fuel transfer and in-core inspection (Phases 1 to 3) and their respective current
status.
Several non-conformities have been identified, as listed below, in the course of
the applicable work, but none of them represented an event that could seriously
impact the plants’ performance or safety.No other abnormalities such as “damage,deformation and dislodgment” have been identified.
ａ．Unit 1:Deformation of the steam-water separator at the legs for temporary
placement○ On September 27 last year, an inspection on the steam-water separator, which
was placed in a temporary storage pool at the time, identified deformation at its
legs for temporary placement (4 out of 4 legs) and guide pins for determining
the device’s position during installation inside the reactor (2 out of 2 pins).
○ The temporary placement legs and guide pins are auxiliary fittings of the steamwater separator, and do not affect its functions or structure.The deformation of
the legs scratches the floor of the temporary storage pool, but no water leakage
has been reported from this location.
ｂ．Unit 5:Shutdown of the refueling machine’s automatic operation during fueltransfer due to abnormal loading○ On November 11 last year, during fuel transfer, an alarm was sounded,
indicating that the refueling machine is becoming overloaded, and shutting down
the machine’s automatic operation.An underwater camera was subsequently
used to inspect the outside of the applicable fuel assemblies, and found that theyhad become dislodged from support fittings that keep the assemblies in thecorrect position.
○ The applicable fuel assemblies and their support fittings show no major
deformation or other visual abnormality, and the iodine concentration of thereactor water also showed no significant change.This indicated that there was nodamage to the fuel loaded in the reactor.
○ The dislodgment of the applicable fuel assemblies has been attributed toincorrect loading for unknown reason at the time of outage (May last year),which triggered dislodgment when the assemblies became subject to earthquake
tremors or other factors.

○ The fuel assembly that could not be removed during the in-core inspection, was

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placed in the support fittings (in the correct position) on November 20, before
being transferred to the spent fuel storage pool.Once the in-core inspection iscompleted, the distortion of the channel boxes will be measured to determine thecause of the incident in more details.
ｃ． Unit 5:Displacement of a wedge for the jet pump (No.1)○ On November 29 last year, on one of 20 jet pumps, the wedge, inserted from the
top to control the vibration of the inlet mixer during its operation, was founddisplaced.
○ The inlet mixer is securely affixed to the riser pipe with an upper beam, and thedisplacement of the applicable wedge causes no safety issues.At the time of theearthquake, Unit 5 was in the shutdown state for outage.
○ Subsequent inspections of the remaining 19 jet pumps did not identify any
similar abnormality.TEPCO plans to look into the cause of the displacement.
d． Units 6 and 7:Inability to retrieve control rods [Unrelated to the Chuetsu-oki
Earthquake]○ Issues with control rod removal were reported at Unit 7 for one of its control
rods on October 18 last year during fuel transfer, and at Unit 6 for two of its
control rods on November 23 and 25 last year during fuel transfer.In all of thecases, the control rods were successfully retrieved according to the pre-defined
restoration procedure.
○ An inspection on the control rod drive mechanisms, control rods and reactorside equipment identified no events (foreign matter, damage, etc.) that could beattributable to the nonconformity.
○ A subsequent study to identify common factors between Units 6 and 7 pointed toextended halt of water feeding for the prevention of foreign matter entry.Thehalt, which lasted longer than at the time of regular plant shutdown, is suspectedof having increased the entry of cladding materials (rust and other metalimpurities), and temporarily raised friction resistance within the control rod
drive mechanisms, causing rod removal difficulty.
○ Even if a similar event develops in the future, it can be rectified with a scram
operation, etc.Also, interference from cladding materials would not compromise
the control rod drive mechanism’s rod insertion function.
e． Unit 7:Detection of drain water from the reactor well liners○ In regard to water identified on October 8 last year in the level gauge connectedto the well liner, minor damage that could lead to leakage was found at twolocations on November 7.It was subsequently confirmed that there was minor
damage that could lead to leakage at a total of two locations (3mm and 2mm inlength).The sections were covered with stainless steel sheets (leakage preventioncovers) as temporary repair work.
○ An investigation into the cause of the incident found that the damage occurred in
the liner’s welded section.Since the locations presented structural difficulty for
welding work, the welding material may not have fully melted during welding
work at the time of plant construction (for incomplete welding).Also, the use ofa grinder as finishing work for welded sections removed extra weld forreinforcement, reducing the thickness of the remaining metal.It is believed that,
following the Niigata Chuetsu-oki Earthquake, a slot plug struck the area near
the applicable locations, causing penetration cracks.
○ The section cut out for the causal investigation (on the main unit of the liner)
will be repaired through welding by February 26, 2008.Leakage from the reactor
well will be checked when filling the well next time.
(2) Other inspection result
An ultrasonic test was conducted from January 22 to February 13 to examine thecracks (1 coupling) identified in the previous inspection on the recirculation systempiping at Unit 3.The test did not find any new damage that would classify as cracks.

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2. Status of non-conformity management (associated with the Chuetsu-okiEarthquake)
TEPCOdefines the management status of non-conformities at power stations into
six grades (As – Not applicable) and regularly releases the information.The
screening status of non-conformities as of the end of January is as follows.There arejust under 3,300 earthquake-related non-conformities, and most of them areclassified as minor events of Grade C or below.

(*1)
As:Reportable event as stipulated by law or Safety Regulations (events that have aserious impact on plant performance and safety)
A :Serious non-conformity against quality assurance requirements (events that have aserious impact on outage schedule) etc.
B :Non-conformity pointed out in a government inspection (events that require
enhanced operation monitoring, etc.)
C :Minor non-conformities against quality assurance requirements, etc.
D :Events within the scope of normal maintenance, etc.
N/A:Replacement of a consumable and equivalent events, etc.
(*2) Unit 7:Detection of drain water from the reactor well liners(*3) Unit 7:Water leakage inside the reactor building (radiologically controlled area) (2cases:See Report #11)(*4) Unit 5:Shutdown of the refueling machine’s automatic operation during fueltransfer due to abnormal loading(*5) Unit 5:Displacement of a wedge for the jet pump (No.1)
3. Outlines of the International Symposium on Seismic Safety of Nuclear PowerPlants and Lessons Learned from the Niigataken Chuetsu-oki Earthquake
The Niigata Chuetsu-oki Earthquake presented numerous challenges involved inoperating nuclear power stations in an earthquke-prone country like
Japan.Currently, TEPCO is undertaking inspections, restoration work andgeological surveys, while the government investigates into facts on specific effectsof the earthquake on the Kashiwazaki Kariwa Nuclear Power Station, anddeliberates on future tasks and responses in light of the earthquake.
In the given situation, the Japan Atomic Industrial Forum (JAIF), CentralResearch Institute of Electric Power Industry (CRIEPI) and JANTI have banded
together to organize an international symposium in the local community of theKashiwazaki Kariwa Nuclear Power Station with focus on integrity assessment ofplant equipment affected by an earthquake, influence of quake-induced ground
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deformation, and fire protection / prevention.The three parties believe that it is thenuclear industry’s duty to approach these matters as its own issues to address, rather
than waiting for the outcome of government deliberations.The parties are committed
to:(1) Amassing engineering insight from around the world to further enhance the antiquake safety and reliability of nuclear power stations, and(2) Providing and offering explanation to various information so as to help local
residents and the rest of the Japanese population establish better understanding.
The symposium has attracted participation applications from local residents, local
governments, national government, mass media, universities, electric powercompanies and manufacturers in Japan in the number that far surpasses initialprojection.Over ten countries have also registered their interest in participation.Thisreflects the high level of expectations and interest in the symposium.
<Symposium outlines>ａ．Period: February 26 (Tue) – 27 (Wed), 2008
ｂ．Venue: “Bunka Hall” of “Kashiwazaki Sangyo Bunka
Kaikan” (KashiwazakiCity, NiigataPrefecture)ｃ．Program:
1) Opening, welcome address, keynote address, special lecture2) Session 1:Integrity Evaluation of Equipment Affected by the Earthquake3) Session 2:Earthquake Induced Ground Deformation – Its Impact and Safety
Significance4) Session 3:Emergency Preparedness and Fire Protection5) Concluding session, closing
END

Japan Nuclear Technology Institute
Rev.0
February 19, 2008

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Outcome and status of reactor opening and in-core inspections at the Kashiwazaki Kariwa Nuclear Power Station
UnitOperation status
at the time of theearthquake

Reactor opening and in-core inspections
August 2007(*)

September

OctoberNovemberDecember

January 2008

February

At the time of the earthquake, Unit 1 was in outage. The reactor was opened, and fuel transfer (reactor core --> spent fuel storage pool) had already been completed.
->No abnormality such as damage, deformation and dislodgment was identified.

Unit 1Outage

Phase 1
Phase 2

Unit 2Startup

Reactor opening-> An inspection identified the deformation of the legs (for temporary placement)
and guide pins for the steam-water separate, kept in the temporary equipment storage pool (September 27).
->No abnormality such as damage, deformation and dislodgment was identified.

->No abnormality such as damage, deformation and dislodgment was identified.
->No abnormality such as damage, deformation

Fuel transferand dislodgment was identified.

In-core inspection Phase 1 & 2Unit 3

In operation

In-core inspection Phase 3
No abnormality such as damage, deformation and dislodgment was identified.<No abnormality such as damage, deformation and dislodgment was identified.<-Unit 4

In operation
No abnormality such as damage, deformation and dislodgment was identified. <No abnormality such as damage, deformation and dislodgment was identified. <-Unit 5

Outage-> Shutdown of the refueling machine’s automatic operation
during fuel transfer due to abnormal loading (November 11)-> Displacement of a wedge for the jet pump (No.1)(November 29)-> No abnormality such as damage, deformationand dislodgment was identified.

Unit 6Outage-> Inability to retrieve 2 control rods (November 23, 25)[Unrelated to the Chuetsu-oki Earthquake]→No abnormality such as damage, deformation and dislodgment
was identified.
No abnormality such as damage, deformation and dislodgment was identified.←→Detection of drain water from the reactor well liners (October 8)→Inability to retrieve 1 control rod (October 18) [Unrelated to the Chuetsu-oki Earthquake]

Unit 7

In operation→No abnormality such as damage, deformation and dislodgment was identified.
→No abnormality such as damage, deformation and dislodgment

was identified.
【Phase 1】（Inspection of the upper reactor）：In order to check inside of the reactor core, first conduct visual inspection of the overall reactor core by an underwater camera from above, followed by inspection of an area covering from the reactor
pressure vessel flange to the upper grid plate.
【Phase 2】（Inspection of the mid-reactor (reactor core)：Conduct visual inspection of the area covering from the upper grid plate to the core support plate and the outer circumference of the core shround (annulus) usnig and underwater camera. Also inspect the dryer
and separator that are taken out of the core.
【Phase 3】（Inspection of the bottom reactor）：Inspect the area covering from the core support plate to the bottom of the reactor after moving control rods and fuel supports that interfere with the inspection.