SCALE Validation Experience Using an Expanded Isotopic Assay Database for Spent Nuclear Fuel
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
The availability of measured isotopic assay data to validate computer code predictions of spent fuel compositions applied in burnup-credit criticality calculations is an essential component for bias and uncertainty determination in safety and licensing analyses. In recent years, as many countries move closer to implementing or expanding the use of burnup credit in criticality safety for licensing, there has been growing interest in acquiring additional high-quality assay data. The well-known open sources of assay data are viewed as potentially limiting for validating depletion calculations for burnup credit due to the relatively small number of isotopes measured (primarily actinides with relatively few fission products), sometimes large measurement uncertainties, incomplete documentation, and the limited burnup and enrichment range of the fuel samples. Oak Ridge National Laboratory (ORNL) recently initiated an extensive isotopic validation study that includes most of the public data archived in the Organization for Economic Cooperation and Development/Nuclear Energy Agency (OECD/NEA) electronic database, SFCOMPO, and new datasets obtained through participation in commercial experimental programs. To date, ORNL has analyzed approximately 120 different spent fuel samples from pressurized-water reactors that span a wide enrichment and burnup range and represent a broad class of assembly designs. The validation studies, completed using SCALE 5.1, are being used to support a technical basis for expanded implementation of burnup credit for spent fuel storage facilities, and other spent fuel analyses including radiation source term, dose assessment, decay heat, and waste repository safety analyses. This paper summarizes the isotopic assay data selected for this study, presents validation results obtained with SCALE 5.1, and discusses some of the challenges and experience associated with evaluating the results. Preliminary results obtained using SCALE 6 and ENDF/B-VII cross sections libraries are also briefly summarized. Oak Ridge National Laboratory (ORNL) has been performing spent-fuel isotopic validation studies using the depletion analysis methods in the SCALE [1] code system for the past 20 years. These studies involve comparisons of calculated inventories against measured isotopic composition data obtained from destructive radiochemical analysis of commercial spent nuclear fuel samples. The results of these benchmark studies are used to quantify the bias and uncertainties associated with isotopic calculations and ultimately determine appropriate margins for uncertainty that can be applied in safety-related analyses such as burnup credit in criticality calculations, decay heat analysis, and source terms. Previous studies using several versions of SCALE and nuclear data libraries have been published in multiple validation reports [2-6] that evaluate selected experimental data obtained largely from public sources. A study was recently initiated at ORNL with the objectives of updating and expanding the validation calculations using a comprehensive database of experimental isotopic assay data that includes isotopic composition data obtained from both publicly available sources and international commercial programs. As part of the study, an extensive isotopic database of nearly 120 measured spent fuel samples with an expanded range of initial enrichments and burnup values compared to previously analyzed data was reviewed and analyzed. The calculations were performed using two-dimensional (2-D) assembly models and a consistent set of modeling assumptions using the SCALE 5.1 code system and ENDF/B-V 44-group cross section library. As part of the current study, detailed benchmark modeling information and measurement data are being documented in a format that is readily usable for validating depletion and decay codes. The work is being extended to include analysis results using SCALE 6 and the ENDF/B-VII 238-group cross section library. This paper describes the isotopic composition data evaluated in this study and highlights the preliminary findings to date.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1026715
- Resource Relation:
- Conference: International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing, and Disposition, Cordoba (Spain), 27-30 Oct 2009
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
97 MATHEMATICS AND COMPUTING
07 ISOTOPE AND RADIATION SOURCES
ACTINIDES
BURNUP
COMPUTER CODES
CRITICALITY
CROSS SECTIONS
DECAY
FISSION
IMPLEMENTATION
INVENTORIES
LICENSING
NUCLEAR FUELS
RADIATION SOURCES
RADIOCHEMICAL ANALYSIS
REPROCESSING
SAFETY
SOURCE TERMS
SPENT FUEL STORAGE
SPENT FUELS
VALIDATION
WASTES
Nuclear Criticality Safety Program (NCSP)
Measured Isotopic Assay Availability
Validation Calculations
Experimental Isotopic Assay Database
Benchmark Modeling Information
Measurement
SCALE 6
ENDF/B-VII 238-Group Cross Section Library
Isotopic Composition Data Evaluation
Preliminary Findings
Organization for Economic Cooperation and Development/Nuclear Energy Agency (OECD/NEA)