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Issues for Effective Implementation of Burnup Credit
Issues for Effective Implementation of Burnup Credit
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
Regulatory Status of Burnup Credit for Spent-Fuel Storage and Transport Casks
Regulatory Status of Burnup Credit for Spent-Fuel Storage and Transport Casks
Cross-Checking of the Operator Data Used for Burn Up Measurements
Cross-Checking of the Operator Data Used for Burn Up Measurements
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
Sensitivity and Uncertainty Analysis of Commercial Reactor Criticals for Burnup Credit
Sensitivity and Uncertainty Analysis of Commercial Reactor Criticals for Burnup Credit
This paper provides insights into the neutronic similarities between a representative high-capacity rail-transport cask containing typical pressurized water reactor (PWR) spent nuclear fuel assemblies and critical reactor state-points, referred to as commercial reactor critical (CRC) state-points. Forty CRC state-points from five PWRs were analyzed, and the characteristics of CRC state-points that may be applicable for validation of burnup-credit criticality safety calculations for spent fuel transport/storage/disposal systems were identified.
Review of Yucca mountain Disposal Criticality Studies
Review of Yucca mountain Disposal Criticality Studies
Review of Results for the OECD/NEA Phase VII Benchmark: Study of Spent Fuel Compositions for Long-Term Disposal
Review of Results for the OECD/NEA Phase VII Benchmark: Study of Spent Fuel Compositions for Long-Term Disposal
Actinide-Only Burnup Credit for Pressurized Water Reactor Spent Nuclear Fuel - I: Methodology Overview
Actinide-Only Burnup Credit for Pressurized Water Reactor Spent Nuclear Fuel - I: Methodology Overview
A conservative methodology is presented that would allow taking credit for burnup in the criticality safety analysis of spent nuclear fuel (SNF) packages. The method is based on the assumption that the isotopic concentration in the SNF and cross sections of each isotope for which credit is taken must be supported by validation experiments. The method allows credit for the changes in the 234U, 235U, 236U, 238U, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, and 241Am concentration with burnup. No credit for fission product neutron absorbers is taken. The methodology consists of five major steps:
Actinide-Only Burnup Credit for Pressurized Water Reactor Spent Nuclear Fuel - III: Bounding Treatment of Spatial Burnup Distributions
Actinide-Only Burnup Credit for Pressurized Water Reactor Spent Nuclear Fuel - III: Bounding Treatment of Spatial Burnup Distributions
A flat, uniform axial burnup assumption, preferred for its computational simplicity, does not always conservatively estimate the pressurized water reactor spent-fuel-cask multiplication factors. Rather, the reactivity effect of the significantly underburned fuel ends, usually referred to as the "end effect," can be properly treated by explicit modeling of the axial burnup distribution based on limiting axial burnup profiles.
Actinide-Only Burnup Credit for Pressurized Water Reactor Spent Nuclear Fuel - II: Validation
Actinide-Only Burnup Credit for Pressurized Water Reactor Spent Nuclear Fuel - II: Validation
The calculation of isotopic concentrations in spent nuclear fuel (SNF) assemblies and the subcritical multiplication factor of SNF packages are two of the essential requirements of the actinide-only burnup credit methodology. To justify the accuracy of the computed values, the code systems used to perform the calculations must be validated. Here, the techniques used for actinide-only burnup credit isotopic and criticality validation are presented and demonstrated.
Use of Reactor-Follow Data to Determine Biases and Uncertainties for PWR spent Nuclear Fuel
Use of Reactor-Follow Data to Determine Biases and Uncertainties for PWR spent Nuclear Fuel
Modeling BWR Spent-Fuel Isotopics with SAS2H and CASMO-3
Modeling BWR Spent-Fuel Isotopics with SAS2H and CASMO-3
Effects of Integral Burnable Absorbers on PWR Spent Nuclear Fuel
Effects of Integral Burnable Absorbers on PWR Spent Nuclear Fuel
Spent Fuel Burnup Credit in Casks: An NRC Perspective
Spent Fuel Burnup Credit in Casks: An NRC Perspective
Until now, the Nuclear Regulatory Commission's (NRC) approval of criticality safety evaluations for spent fuel in transport and storage casks has been based on analyzing the fuel as though it were fresh and without burnable poisons. The well-known nuclide composition of fresh fuel has provided a straightforward and bounding approach for showing that spent fuel systems will remain subcritical under normal and accident conditions. Burnup credit refers to the approval of criticality safety evaluations that consider the decrease in fuel reactivity caused by. irradiation in the reactor.
Selection of Reactor Criticals as Benchmarks for Spent Nuclear Fuels
Selection of Reactor Criticals as Benchmarks for Spent Nuclear Fuels
An Empirical Approach to Bounding the Axial Reactivity Effects of PWR Spent Nuclear Fuel
An Empirical Approach to Bounding the Axial Reactivity Effects of PWR Spent Nuclear Fuel
One of the significant issues yet to be resolved for using
burnup credit ~BUC! for spent nuclear fuel ~SNF! is establishing
a set of depletion parameters that produce an adequately conservative
representation of the fuel’s isotopic inventory. Depletion
parameters ~such as local power, fuel temperature, moderator temperature,
burnable poison rod history, and soluble boron concentration!
affect the isotopic inventory of fuel that is depleted in a
pressurized water reactor ~PWR!. However, obtaining the detailed
Nondestructive Assay of Nuclear Low-Enriched Uranium Spent Fuels for Burnup Credit Application
Nondestructive Assay of Nuclear Low-Enriched Uranium Spent Fuels for Burnup Credit Application
Criticality safety analysis devoted to spent-fuel storage and transportation has to be conservative in order to be sure no accident will ever happen. In the spent-fuel storage field, the assumption of freshness has been used to achieve the conservative aspect of criticality safety procedures. Nevertheless, after being irradiated in a reactor core, the fuel elements have obviously lost part of their original reactivity. The concept of taking into account this reactivity loss in criticality safety analysis is known as burnup credit.
Investigation of the Effect of Fixed Absorbers on the Reactivity of PWR Spent Nuclear Fuel for Burnup Credit
Investigation of the Effect of Fixed Absorbers on the Reactivity of PWR Spent Nuclear Fuel for Burnup Credit
The effect of fixed absorbers on the reactivity of pressurized water reactor (PWR) spent nuclear fuel (SNF) in support of burnup-credit criticality safety analyses is examined. A fuel assembly burned in conjunction with fixed absorbers may have a higher reactivity for a given burnup than an assembly that has not used fixed absorbers. As a result, guidance on burnup credit, issued by the U.S. Nuclear Regulatory Commission's Spent Fuel Project Office, recommends restricting the use of burnup credit to assemblies that have not used burnable absorbers.
From Integral Experiments to Nuclear Data Improvement
From Integral Experiments to Nuclear Data Improvement
Target accuracy on LWR neutronics parameters is 2 to 5 times lower than the a priori uncertainty (1σ)
due to nuclear data. This paper summarizes the experimental facilities and the integral measurements that are required
for code qualification. The rigorous use of integral information through trend analysis method is described. Trends
on JEF2 data from Keff measurements and P.I.Es are presented. These trends were accounted for in the new JEFF3
evaluations. The role of fundamental experiments, such as worth measurement of separated isotopes, is emphasized.
Advances in Applications of Burnup Credit to Enhance Spent Fuel Transportation, Storage, Reprocessing and Disposition-Proceedings of a Technical Meeting held in London, 29 August-2 September 2006
Advances in Applications of Burnup Credit to Enhance Spent Fuel Transportation, Storage, Reprocessing and Disposition-Proceedings of a Technical Meeting held in London, 29 August-2 September 2006
This publication records the proceedings of a technical meeting organized by the IAEA and
held in London 29 August–2 September 2005 with sixty participants from 18 countries. As
indicated in the title, the objective of this meeting was to provide a forum for exchange of
technical information on spent fuel burnup credit applications and thereby compile state-ofthe-
art information on technical advances related to spent fuel transportation, storage,
reprocessing and disposition.