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March 2005
Nuclear and Industrial Safety Agency (NISA)
1. Actions Taken by the Accident Investigation Committee and NISA
Aug. 10, 2004 (the day following the day the accident occurred)
The Accident
Investigation Committee was established. Under the Committee’s
direction NISA investigated the cause of the secondary
system pipe rupture at Unit 3 of the Mihama Nuclear Power Plant.
Sept. 27, 2004
The interim report was prepared, and the Minister gave KEPCO a strict
reprimand and ordered the company to comply with the technical standard.
Oct. 2004 to Feb. 2005
NISA conducted additional hearings on each concerned to find the
causes of the accident and the measures for preventing the recurrence
of the accident.
Mar. 30, 2005
The Accident Investigation Committee held the 10th meeting, and
documented the final report. (Two meetings were held in Fukui City.)
2. Causes of the Accident
The direct cause of the accident is that the pipe thinning due to
erosion and corrosion was overlooked for many years because the pipe
in question was mistakenly missing from the inspection list. Further
investigations revealed that the root causes of the accident were the
poor maintenance management and insufficient quality assurance systems
of KEPCO, with the background of the KEPCO’s declined safety culture.
- Both KEPCO and Mitsubishi Heavy Industries, Inc. (MHI) neglected
their duties to check the inspection lists and to establish good
communication.
>>They failed to correct the mistakes in the inspection list that was
initially created by MHI.
-
KEPCO's improper management of subcontractors >> The item in question
had been mistakenly left out from the inspection list.
-
KEPCO's biased attitude toward process operations >> At some point,
noncompliance with technical standards was accepted as normal.
3. Responsibility of KEPCO and Preventive Measures
(1) It is a serious problem that KEPCO’s operation and management of a
nuclear power plant is inappropriate in terms of legal liability and
external responsibility (improper management of subcontractors), and
that their management system is incapable of grasping and rectifying
the actual conditions of sites. It is an urgent necessity to improve
their maintenance and management capability and to transform their
subcontractor management system into a thorough, efficient system. In
addition, continued efforts are essential to improve the corporate
culture and the sense of values regarding safety.
(2) Based on the points above, KEPCO submitted to NISA the “Report on
Preventive Measures” on March 1 and the “Action Plan” on March 25,
2005.
(3) By performing strict nuclear safety inspections, NISA keeps watch
on and leads KEPCO to verify whether preventive measures based on the
commitments by the president of KEPCO (assignment of personnel to
safety-related tasks, investments, etc.) have been properly
implemented, and whether the quality assurance system and the
corporate culture have fundamentally improved.
4. Responsibility of Mitsubishi Heavy Industries and Preventive
Measures
(1) The improper maintenance management is the result of a lack of
self-discipline as a major manufacturer that plays a vital role in
plant construction and maintenance. This has undermined public
confidence in not only MHI, but also overall nuclear safety.
(2) Based on the points indicated, MHI prepared the “Report on
Preventive Measures” and the “Additional report,” and submitted them
to NISA on March 1 and March 23, 2005, respectively.
(3) NISA calls on MHI to reflect on its past conduct, and keeps close
watch to verify that preventive measures and their improvement
activities are properly implemented. NISA expects that MHI will be
aware of the company’s standing as the only PWR (Pressurized Water
Reactor) manufacturer in Japan and will take all possible measures to
ensure safety (for example, sharing new knowledge of and information
on PWR plants with electric utilities).
5. Responsibility and Countermeasures of the Government (NISA)
(1) Regulations about the pipe wall thickness
It was acknowledged that one of the causes of the inappropriate
maintenance management is that NISA left the practical method of the
pipe wall thickness management to each company.
>> The ministerial ordinances were revised in December 2004, and NISA
issued a guideline as a government standard in February 2005.
(2) Regulations for the quality assurance of each company
As new safety regulations went into effect in October 2003, NISA
started inspections and directed to each company to conduct autonomous
maintenance management and quality assurance activities.
>> Based on the lessons learned from the accident, NISA makes
continuous improvements of inspection methods and strongly requires
all licensees to conduct maintenance management and quality assurance
activities in a strict, thorough manner.
6. Measures for Other Related Issues
(1) Aging management of nuclear power plants
The thinning of pipes is an important phenomenon of deterioration
through aging. NISA requests licensees to define the pipe thickness
management properly in aging management, and to establish a policy of
necessary management, and then to implement these. NISA also monitors
and evaluates the status of implementation of measures and policies.
>> NISA encourages the improvement of aging management in line with the
standards, reasonable inspection methods, policies, etc., that the
Committee for Aging Management will compile around July or August
2005.
(2) Initial actions after an accident
Although it is important to prevent the occurrence of an accident as a
matter of course, the initial actions that should be taken are equally
important in the sense of risk management to restrain or minimize the
spread of damage after an accident.
>> NISA improves and reinforces the initial action system and
procedures by coordinating with authorities regarding emergency
actions, emergency radiation medical treatment, etc., and by
establishing an emergency initial action manual.
(3) Labor safety
The Mihama accident should be examined from the standpoint of labor
accident prevention, and preventive measures should be enhanced.
>> It is requested that KEPCO takes measures in such a way as to
introduce a labor safety and sanitation management system in a
consistent manner.
>> NISA implements consistent measures and policies by coordinating
closely with the Ministry of Health, Labour and Welfare, which is in
charge of labor safety.
(4) Measures for social and local effects of an accident
The Mihama accident produced various social and local effects: the
local residents lost their sense of security in relation to the
nuclear power plant, harmful rumors spread and produced a serious
impact on economic activities, and so forth.
>> NISA plays an important role in strengthening the safety regulation
system, providing accurate information quickly, providing support in
the form of road work for transportation in an emergency, etc. In
addition, NISA makes continuous efforts to evaluate and analyze social
and local effects, and to implement effective measures for accidents
and disasters.
Reference:
Summary of preventive measures prepared by The Kansai Electric Power
Co., Inc. and Mitsubishi Heavy Industries Inc.
1. Preventive measures by KEPCO
(1) The president declared, “My and our company’s mission is to ensure
safety.” Under this declaration, five fundamental action policies were
announced:
- We will give the highest priority to safety.
We will introduce whatever resources are necessary to ensure safety. We will make continuous improvements to maintenance management, and
construct cooperative relationships with manufacturers and cooperating
companies. We will make an effort to regain the public confidence of local residents. We will objectively evaluate our safety-related activities and
disseminate information on those activities.
(2) Based on these five policies, short-term tasks (face-to-face
discussions between the management and workers at sites to improve the
safety culture, reinforcement of personnel working at power plants,
etc.) to be tackled early in 2005, and mid-term tasks (review of all
periodic inspection processes) to be addressed after 2005 were
presented.
2. Preventive measures by MHI
(1) Strengthening of maintenance functions to cope with aging
The “Mitsubishi Maintenance Committee” was established to promote
overall maintenance activities conducted throughout the Mitsubishi
Group. This committee meets twice a year to ensure that proper
maintenance activities can be conducted on a long-term basis.
(2) Company-wide improvements based on the lessons learned
The “In-house Nuclear Power Reform Committee” was established in
December 2004. It will start conducting systematic, company-wide
improvement activities within this year.
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