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credit criticality, criticality excursions analyses and
uncertainty analyses for criticality safety assessments,
and work on the evaluation of assay data of
spent nuclear fuel.
The WPNCS is also responsible for co-ordinating
activities of the International Criticality Safety
Benchmark Evaluation Project (ICSBEP) and the Spent
Fuel Isotopic Composition Database (SFCOMPO). In
2012, the NEA started a major restructuring effort
of the SFCOMPO database. This database aims at
providing functional access to all available experimental
assay data and, in the longer run, to the fully
evaluated assay data sets, essential for the validation
of depletion codes and, by extension, for many
criticality safety assessments of waste management
and disposal operations.
In addition, ongoing studies related to burn-up
credit, the safety approach that accounts for the
reduction in reactivity of spent nuclear fuel due
to the change in its composition after irradiation,
have recently revisited the case of spent fuel assemblies
from boiling water reactors in follow-up to the
Fukushima accident. Other benchmark activities
which concern the rigorous treatment of uncertainties
in different criticality safety assessment methodologies
are underway.
The activities of the Expert Group on Advanced
Monte Carlo Techniques were restarted. The group
is focusing on developing best practices and recommendations
for the good transfer of Monte Carlo
technologies to criticality safety practitioners.
Material science
Substantial progress was made on three out of five
state-of-the-art reports on multi-scale modelling of
fuel and cladding materials:
• an assessment of the possibilities and limits of
numerical methods applied to multi-scale modelling
of materials and the means to link them;
• a critical review of recent progress and bottlenecks
for future development of fuels;
• an assessment of the use of a multi-scale modelling
approach to describe the changes induced
by irradiations in structural nuclear materials.
The completion of two other reports is now
rescheduled for 2013: an assessment of primary
radiation damage characterisation and the limitations
of the Norgett Robinson and Torrens (NRT)-
dpa standard to propose a new parameter to better
describe radiation damage; and a validation and
benchmark of multi-scale modelling methods.
An international workshop on innovative accident
tolerant fuels for LWRs was held in December.
As part of R&D efforts to enhance the safety of current
Generation II/III plants in the post-Fukushima
context, this workshop aimed at sharing information
on innovative solutions to increase grace time
in severe accident conditions initiated by prolonged
loss of cooling and/or heat sink. A precise work programme
for this activity will be developed in 2013.
Integral experiments for minor actinide
management
The main objectives of this activity are to assess
the availability of minor actinide nuclear data, to
evaluate the target accuracies of these data in applications
such as transmutation in light water, fast
and accelerator-driven subcritical reactors, and, if
appropriate, to make recommendations on additional
differential and integral experiments needed
to meet the target accuracies. A review of existing
nuclear data and integral experiments for minor
actinide management has been performed, as well
as an assessment of the accuracy of the available
data. A discussion of the need for further measurements
is ongoing, with the final report due to be
issued in 2013.
Knowledge preservation
In order to assist member countries in the development
of new nuclear facilities, and in the context
of marked change in the composition of their skills
base as a generation of highly experienced nuclear
scientists and engineers retires, the NEA Nuclear
Science Committee launched, some years ago, a
programme establishing well-structured and highly
accessible databases to preserve and evaluate information
from reactor physics (IRPhE), criticality safety
(ICSBEP), shielding (SINBAD), fuel performance (IFPE)
and isotopic composition of spent fuel (SFCOMPO).
The maintenance and updating of these databases
are performed in close collaboration with the NEA
Data Bank.
The contents of the above-mentioned databases
were as follows in 2012:
• the IRPhE handbook included 56 series of reactor
physics experiments performed at 32 reactor
facilities;
• the ICSBEP handbook included 4 708 critical or
subcritical configurations;
• the SINBAD database contained 46 radiation
shielding, 31 fusion neutronic shielding and
23 accelerator shielding experiments;
• the IFPE database contained information on
1 452 rods/samples from various sources, comprising
BWR, AGR, PHWR, PWR and VVER reactor
systems;
• the SFCOMPO database contained 246 samples
from 14 commercial reactors and is being restructured
to improve user access to the data.
Contact:
Jim Gulliford
Head, Nuclear Science Section
+33 (0)1 45 24 10 72
jim.gulliford@oecd.org
NEA Annual Report 2012
29