[en] This paper reports recent regulatory progress in the development of a UK regulatory position for assessing licensees' plant safety cases which apply the use of burnup credit for criticality applications. This has been prompted by an increasing awareness amongst UK nuclear operators of the possible advantages in the use of burnup credit. (author)

[en] The Armenian NPP Spent Fuel Dry Storage (SFDS) facility of NUHOMS-56 project was constructed for storing the spent fuel assemblies remained in reactor pools after NPP shutdown in 1989. The criticality value was taken as for the fresh fuel assemblies and was required as 0.95. Basic criticality analysis assumptions should demonstrate the nuclear safety during all operations for normal, abnormal and accidental situations, and was based on fresh fuel elements. No credit was taken from burnup, which is conservative since only burned fuel will be stored. The licensing requirements were established by the ANRA with respect to the nuclear safety criticality limits set in IAEA rules and USNRC 10CFR codes. (author)

[en] This paper describes the impact of horizontal burnup profile on the criticality of spent fuel assembly. All calculations were made for WWER-440 fuel assembly with enrichment 3.6w% of U²³⁵ and burnup up to 60 MWd/kgU. (author)

[en] In 1999, the United States Nuclear Regulatory Commission (U.S. NRC) initiated a research program to support the development of technical bases and guidance that would facilitate the implementation of burnup credit into licensing activities for transport and dry cask storage. This paper reviews the following major areas of investigation: (1) specification of axial burnup profiles, (2) assumption on cooling time, (3) allowance for assemblies with fixed and removable neutron absorbers, (4) the need for a burnup margin for fuel with initial enrichments over 4 wt %, and (5) evaluation of experimental data. Recommendations resulting from the research program are presented. (author)

[en] The paper presents dummy calculations of effective neutron multiplication factor for dual purpose CONSTOR RBMK-1500 cask. This cask is designed for interim dry storage (and transportation) of 102 spent nuclear fuel half-assemblies. It was assumed in the calculations that internal basket tubes are consolidated. In this case 156 half-assemblies could be placed in the cask. K_eff was calculated for different fuel initial enrichments and for various cases when: a) only actinides; b) actinides plus fission products (FP) are taken into account. Obtained results have showed that if burnup credit is taken into account even if basket tubes are consolidated, k_eff values are less then allowable value 0.95. (author)

[en] The United States Department of Energy's Office of Civilian Radioactive Waste Management has developed a risk-informed, performance based methodology for disposal criticality analyses. The methodology is documented in the Disposal Criticality Analysis Methodology Topical Report, YMP/TR-004Q (YMP 2000). The methodology includes taking credit for the burnup of irradiated commercial light water reactor fuel in criticality analyses, i.e., burnup credit. This paper summarizes the ongoing and planned future burnup credit activities associated with the methodology. (author)

[en] NPP Krzko is going to increase the capacity of the spent fuel storage pool by replacement of the existing racks with high-density racks. The design, rack manufacturing and installation has been awarded to the Framatome ANP GmbH. Burnup credit methodology, which has been already approved by the Slovenian Nuclear Safety Administration in previous licensing of existing racks, will be again implemented in the licensing process with the recent methodology improvements. Specific steps of the criticality analysis and representative results are presented in the paper showing also the current national practice of the burnup credit implementation. (author)

[en] The aim of this study is to provide recommendations on the nuclear data and new evaluations for the main BUC fission products. The information given by integral experiments allows to select the best evaluation amongst the most recent one: JEF2.2, JENDL3.2, ENDFB6.7 and BROND2.2. When the evaluations do not follow the trends given by integral experiments, specific modifications of the existing evaluation consistent with the differential measurements are proposed in the thermal and resolved range. A rigorous fit of available differential experiments using the integral information has not been performed in this study. A quick overview of the measurements (generally the thermal capture cross-section at 0.0253 eV and the resonance parameters of the first large resonance) has allowed us to find simple solutions to correct the cross-section. (author)

[en] The vertical and horizontal change of the fuel burnup may have essential influence on the multiplication factor of storage systems. This phenomenon is examined for WWER fuel on the example of a compact storage pool. The axial and horizontal burnup profiles are taken from detailed calculations based on real operational history. The actinides only as well as actinides + fission products approach are examined. The results of the WWER burnup credit benchmark CB3+ investigating the end effect is also presented. (author)

[en] One of the most important issues in a burnup credit criticality safety analysis of a spent fuel management system of interest is the determination of the end effect due to the axial burnup distribution. In the paper on hand the impact of the initial enrichment of the fuel on the end effect of PWR axial burnup profiles is analyzed. It is shown that the end effect tends to increase with decreasing initial enrichment. For low initial enrichments, however, this tendency may be outweighed by the fact, that the higher the burnup is and the lower the initial enrichment is, the lower is the decline of the reactivity with increasing burnup. The impact of the initial enrichment of the fuel on the end effect is analyzed for a wet storage system assumed to be loaded with Westinghouse 16x16-21 Standard fuel assemblies. The analysis is made for normal operation conditions assuming the storage racks to be flooded with unborated water. No cooling time credit is taken. (author)