TY - GEN

T1 - Specification for Phase VII Benchmark UO2 Fuel: Study of spent fuel compositions for long-term disposal

AU - Wagner, John

PY - 2008/11

Y1 - 2008/11

N2 - The concept of taking credit for a reduction in reactivity due to fuel burnup is commonly referred to as burnup credit. The reduction in reactivity that occurs with fuel burnup is due to the change in concentration (net reduction) of fissile nuclides and the production of actinide and fission- product neutron absorbers. After spent nuclear fuel (SNF) is discharged from a reactor, the reactivity continues to vary as a function of time due to the decay of unstable isotopes.
Burnup credit analyses for storage and transport consider timeframes that are extremely short (typically less than 100 years), as compared to the timeframe of interest to long-term disposal (e.g., 10,000 years after closure in the US). This benchmark proposes to study the ability of relevant computer codes and associated nuclear data to predict spent fuel isotopic compositions and corresponding keff values in a cask configuration over the time duration relevant to SNF disposal. It is recognized that the benefits of this proposed benchmark are largely confined to revealing differences in nuclear data for decay constants (half-lives, branching fractions), which are widely considered to be well-known. However, the results of this exercise may serve to reveal differences in international nuclear data sets and/or improve understanding and confidence in our ability to predict keff and source terms for timeframes relevant to long-term disposal of SNF.
The benchmark is divided into two sets of calculations:
Decay calculations for provided PWR UO2 discharged fuel compositions Criticality (keff) calculations for a representative cask model
Participants are requested to perform decay calculations, using the provided PWR fuel compositions as a starting point, and criticality calculations for the PWR fuel in the OECD cask model for 30 post-irradiation time steps, out to 1,000,000 years. Decay calculations will be performed for nuclides that are relevant to burnup credit and to public dose from nuclear waste repositories. Although it is acknowledged that the physical condition of the fuel will change over such a long time period, there is interest in the change in isotopic compositions over this duration, as well as interest in the relative behavior of keff over this duration. Analysis of the results will involve comparison of participant’s isotopic compositions and keff values as a function of time.

AB - The concept of taking credit for a reduction in reactivity due to fuel burnup is commonly referred to as burnup credit. The reduction in reactivity that occurs with fuel burnup is due to the change in concentration (net reduction) of fissile nuclides and the production of actinide and fission- product neutron absorbers. After spent nuclear fuel (SNF) is discharged from a reactor, the reactivity continues to vary as a function of time due to the decay of unstable isotopes.
Burnup credit analyses for storage and transport consider timeframes that are extremely short (typically less than 100 years), as compared to the timeframe of interest to long-term disposal (e.g., 10,000 years after closure in the US). This benchmark proposes to study the ability of relevant computer codes and associated nuclear data to predict spent fuel isotopic compositions and corresponding keff values in a cask configuration over the time duration relevant to SNF disposal. It is recognized that the benefits of this proposed benchmark are largely confined to revealing differences in nuclear data for decay constants (half-lives, branching fractions), which are widely considered to be well-known. However, the results of this exercise may serve to reveal differences in international nuclear data sets and/or improve understanding and confidence in our ability to predict keff and source terms for timeframes relevant to long-term disposal of SNF.
The benchmark is divided into two sets of calculations:
Decay calculations for provided PWR UO2 discharged fuel compositions Criticality (keff) calculations for a representative cask model
Participants are requested to perform decay calculations, using the provided PWR fuel compositions as a starting point, and criticality calculations for the PWR fuel in the OECD cask model for 30 post-irradiation time steps, out to 1,000,000 years. Decay calculations will be performed for nuclides that are relevant to burnup credit and to public dose from nuclear waste repositories. Although it is acknowledged that the physical condition of the fuel will change over such a long time period, there is interest in the change in isotopic compositions over this duration, as well as interest in the relative behavior of keff over this duration. Analysis of the results will involve comparison of participant’s isotopic compositions and keff values as a function of time.

UR - https://www.oecd-nea.org/science/wpncs/buc/specifications/phase-VII/Phase-VII_BenchmarkSpecification_REV01.pdf

M3 - Other contribution

ER -