The present project aims to provide the γ-ray source spectrum (the gamma energies and their intensities) for a nuclear fuel, given its physical dimensions, its enrichment and the detailed knowledge of the burnup history. In a nuclear reactor, the nuclide concentrations within the nuclear fuel change due to nuclear transmutation caused by neutron irradiation and due to the radioactive decay during and after the irradiation. This alteration in the fuel composition is simulated in this project with a burnup-mode simulation using the reactor physics code Serpent 2. A second Serpent 2 photon-mode simulation follows as to evaluate the γ-radiation spectrum from the respective nuclides produced in the first simulation. Finally, the γ-ray mass attenuation coefficients for selected energies are evaluated by combining the fuel elemental concentrations with the corresponding mass attenuation coefficients for fresh fuel based on NIST XCOM database. To facilitate the repeated evaluation of the γ-ray source spectrum, a custom-made MATLAB® function, GetEmissions, that initiates the Serpent 2 simulations was created. This function utilizes the user input data, which are the fuel dimensions, the fuel enrichment and the burnup history, as to automatically create an input for the Serpent 2 code. Afterwards, it executes burnup and photon simulations, and finally extracts the data sought for, which are the emitted by the fuel γ-ray energies and their intensities (γ-ray source spectrum). In addition, for the given fuel characteristics, the function provides the mass attenuation coefficient for a selected γ-ray passing the fuel. Using the GetEmissions function, the gamma spectra from ten nuclear burnup history cases representing a scan through low and high burnup and short, medium and long cooling times are calculated. The resulting top ten gamma energies are listed by absolute intensity, and information about the mother nuclide and the decay is provided.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-377868 |
| Date | January 2019 |
| Creators | Anastasiadis, Anastasios |
| Publisher | Uppsala universitet, Tillämpad kärnfysik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | FYSAST ; FYSPROJ1122 |
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