In the past, criticality analysis of pressurized water reactor (PWR) fuel stored in racks and casks has assumed that the fuel is fresh with the maximum allowable initial enrichment. If credit is allowed for fuel burnup in the design of casks that are used in the transport of spent light water reactor fuel to a repository, the increase in payload can lead to a significant reduction in the cost of transport and a potential reduction in the risk to the public. A portion of the work has been performed at Oak Ridge National Laboratory (ORNL) in support of the U.S.
Present regulatory practices provide as much burnup credit flexibility as can be currently
expected. Further progress is achievable by incorporating the negative reactivity effects of a
subset of neutron-absorbing fission-product isotopes, and by optimizing the procedural approach
for establishing the burnup characteristics of the spent fuel to be loaded in burnup-creditdesigned
storage and transportation systems. This report describes progress toward developing a
From 1998 to 2004, a series of critical experiments referred to as the fission product (FP) experimental program was performed at the Commissariat à l'Energie Atomique Valduc research facility. The experiments were designed by Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and funded by AREVA NC and IRSN within the French program supporting development of a technical basis for burnup credit validation.
In the United States, burnup credit has been used in the criticality safety evaluation for storage pools at
pressurized water reactors (PWRs) and considerable work has been performed to lay the foundation for use of
burnup credit in dry storage and transport cask applications and permanent disposal applications. Many of the
technical issues related to the basic physics phenomena and parameters of importance are similar in each of these
applications. However, the nuclear fuel cycle in the United States has never been fully integrated and the
Although there are many reactor system benchmarks in the literature, they mostly
concentrate on the reactor system in isolation with only a few considering the fuel cycle.
However, there is currently increased emphasis on the performance of reactor systems
linked to their associated fuel cycle (Generation-IV for example). The published
international benchmark studies which relate to burn-up depletion calculations are
restricted to specific aspects of the fuel cycle:
Taking into account of the loss of reactivity of fuels at the end of their irradiation is known under the
term burnup credit (BUC). It is a question of dimensioning in a less penalizing way the devices of transport,
storage or of processing with respect to the risk of criticality. In the context of nuclear criticality safety a better
realism cannot be obtained at the price of conservatism. As a result the regulator requires measurements make it
possible to validate the adequacy between real fuels and the design assumptions. The sophistication of the
This report proposes and documents a computational benchmark for the estimation of the
additional reactivity margin available in spent nuclear fuel (SNF) from fission products and minor
actinides in a burnup-credit storage/transport environment, relative to SNF compositions
containing only the major actinides. The benchmark problem/configuration is a generic burnupcredit
cask designed to hold 68 boiling water reactor (BWR) spent nuclear fuel assemblies. The
purpose of this computational benchmark is to provide a reference configuration for the
This report has been prepared to support technical discussion of and planning for future
research supporting implementation of burnup credit for boiling-water reactor (BWR) spent fuel
storage in spent fuel pools and storage and transport cask applications. The review and
discussion in this report are based on knowledge and experience gained from work performed
in the United States and other countries, including experience with burnup credit for
pressurized-water reactor (PWR) spent fuel. Relevant physics and analysis phenomena are
The development of radioactive waste repositories involves consideration of how the waste and the
engineered barrier systems will evolve, as well as the interactions between these and, often relatively
complex, natural systems. The timescales that must be considered are much longer than the timescales
that can be studied in the laboratory or during site characterisation. These and other factors can lead to
various types of uncertainty (on scenarios, models and parameters) in the assessment of long-term,
To solve the still open question of high-level radioactive waste disposal, the countries having made the greatest progress in this
field usually choose to carry out comparing selection procedures including broad involvement of the public. This is a central
result of the “RepoSafe”symposium which took place from November 6 to 9, 2007, in Braunschweig. Within the scope of
this symposium, internationally leading experts, invited by the Federal Office for Radiation Protection (BfS) and Gesellschaft
As outlined in the overall program for high-level waste (HLW) management in Japan, defined by the Atomic Energy Commission (AEC), HWL separated from spent nuclear fuel during reprocessing will be immobilized in a glass matrix and stored for a period of 30 to 50 years to allow cooling; it will then be disposed of in a stable deep geological formation.
