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The structure of the database has been welldefined
and arrangements have been made in all
participating countries to collect and to validate
data. The quality-assurance process is in place and
has proven to be efficient on the first set of data provided.
An updated version of the database, which
now contains more than 400 records, is provided to
participants every year. Two meetings of the project
steering body were held during 2012 with a view to
establishing the basis for increased use of the database
for probabilistic risk assessments (PRAs).
The ICDE Project
The International Common-cause Data Exchange
(ICDE) Project collects and analyses operating data
related to common-cause failures (CCF) that have the
potential to affect several systems, including safety
systems. The project has been in operation since
1998, and was extended with a new agreement covering
2008-2011. It was also agreed in 2011 to start a
new project phase which will run from 2011 to 2014.
The ICDE Project comprises complete, partial and
incipient common-cause failure events. It currently
covers the key components of the main safety systems,
such as centrifugal pumps, diesel generators,
motor-operated valves, power-operated relief valves,
safety relief valves, check valves, control-rod drive
mechanisms, reactor protection system circuit breakers,
batteries and transmitters. These components
have been selected because several probabilistic
safety assessments have identified them as major risk
contributors in the case of common-cause failures.
Qualitative insights from data will help reduce the
number of CCF events that are risk contributors, and
member countries use the data for their national risk
analyses. Additional activities in the area of quantification
are under discussion. Reports have been produced
for pumps, diesel generators, motor-operated
valves, safety and relief valves, check valves and
batteries. Data exchange for switchgear and breakers
and reactor-level measurement was completed.
In 2012, a report on “Collection and Analysis of
Common-cause Failures of Centrifugal Pumps” was
completed and approved to be issued as a CSNI
report. A total of 353 ICDE events spanning a period
from 1975 through 2009 were examined with respect
to failure modes, degree of impairment, failure
symptoms, failure causes and technical fault aspects.
One of the report’s conclusions suggests that maintenance
and test activities are significantly more
effective for preventing complete failures in “failure
to run” events than in “failure to start” events. Thus,
maintenance and test activities should specifically
focus on the prevention of “failure to start” events.
A report on “Collection and Analysis of Commoncause
Failures of Control Rod Drive Assemblies
(CRDA)” was also completed in 2012 and approved for
distribution as a CSNI report. Some 169 ICDE events
spanning a period from 1980 through 2003 were
examined with respect to root cause, coupling factor,
observed population size, corrective action, the
degree of failure, affected subsystem and detection
method. Most of these failures were caused by core
or fuel assembly deformations due to irradiation,
thermal, mechanical and hydraulic loading, and
their mutual interaction. Communication of operating
experience with CCF phenomena is important
to ensure that plants can implement the appropriate
defences and controls to prevent significant impacts
on plant safety.
RADIOACTIVE WASTE MANAGEMENT
The CPD
The NEA Co-operative Programme for the Exchange
of Scientific and Technical Information Concerning
Nuclear Installation Decommissioning Projects
(CPD) is a joint undertaking functioning under an
agreement among 23 organisations in 12 NEA member
countries, one non-member economy and the
European Commission, actively executing or planning
the decommissioning of nuclear facilities. The
objective of the CPD is to acquire and to share information
from operational experience in the decommissioning
of nuclear installations that is useful for
future projects. It has operated under Article 5 of the
NEA Statute since its inception in 1985, and a revised
agreement among participants came into force on
1 January 2009 for a five-year period.
The information exchange also ensures that best
international practice is made widely available and
encourages the application of safe, environmentally
friendly and cost-effective methods in all decommissioning
projects. It is based on biannual meetings of
the Technical Advisory Group (TAG), during which
the site of one of the participating projects is visited,
and positive and less positive examples of decommissioning
experience are openly exchanged for
the benefit of all. Currently 59 projects under active
decommissioning (35 reactors and 24 fuel facilities)
are included in the information exchange. In 2012,
four additional decommissioning projects were
accepted: Waste storage facility #56 at Cadarache,
CEA, France; the Fukushima Daiichi nuclear power
plant, TEPCO, Japan; Brunsbüttel nuclear power
plant, KKB, Vattenfall Europe Nuclear Energy GmbH,
Germany; and the MR/FRT Research Reactors, NRC,
Kurchatov Institute, Russia.
Although part of the information exchanged
within the CPD is confidential and restricted to programme
participants, experience of general interest
gained under the programme’s auspices is released
for broader use. In this context, the CPD Task Group
on Site Remediation and Restoration continues to
review the experience, approaches and techniques
for nuclear site restoration.
The TDB Project
The Thermochemical Database (TDB) Project was
initiated in 1984 by the NEA Radioactive Waste
Management Committee to fulfil the need for a
high-quality database for modelling purposes in the
safety assessments of radioactive waste repositories.
The project’s current mandate runs to January 2013,
following a one-year extension decided by the TDB
Management Board. Sixteen organisations from
13 countries participate.
NEA Annual Report 2012
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